Solar Hydrogen’s Role for a Sustainable Future

Lecture Notes in Energy 74 Tanay Sıdkı Uyar Editor Accelerating the Transition to a 100% Renewable Energy Era Lecture Notes in Energy Volume 74 Lecture Notes in Energy (LNE) is a series that reports on new developments in the study of energy: from science and engineering to the analysis of energy policy. The series’ scope includes but is not limited to, renewable and green energy, nuclear, fossil fuels and carbon capture, energy systems, energy storage and harvesting, batteries and fuel cells, power systems, energy efficiency, energy in buildings, energy policy, as well as energy-related topics in economics, management and transportation. Books published in LNE are original and timely and bridge between advanced textbooks and the forefront of research. Readers of LNE include postgraduate students and non-specialist researchers wishing to gain an accessible introduction to a field of research as well as professionals and researchers with a need for an up-to-date reference book on a well-defined topic. The series publishes single- and multi-authored volumes as well as advanced textbooks. **Indexed in Scopus and EI Compendex** The Springer Energy board welcomes your book proposal. Please get in touch with the series via Anthony Doyle, Executive Editor, Springer ([email protected]). More information about this series at http://www.springer.com/series/8874 Tanay Sıdkı Uyar Editor Accelerating the Transition to a 100% Renewable Energy Era 123 Editor Tanay Sıdkı Uyar Energy Section Department of Mechanical Engineering Marmara University Istanbul, Turkey ISSN 2195-1284 ISSN 2195-1292 (electronic) Lecture Notes in Energy ISBN 978-3-030-40737-7 ISBN 978-3-030-40738-4 (eBook) https://doi.org/10.1007/978-3-030-40738-4 © Springer Nature Switzerland AG 2020 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. 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This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland Preface Coronavirus, COVID-1, is a virus that is too small to be seen. In a few months, it almost stopped all life on Earth. Not only did it stop the daily life, but in a short period of time it crossed all borders and oceans drawn by human beings quickly, reaching and infecting millions of people in 185 countries in almost over the world. Its circulation on Earth continues, and it is not yet clear up to where it will continue and when it will stop. 343,608 people have died from the coronavirus, COVID-19, outbreak as of May 24, 2020. Worse still, nobody knows what will happen tomorrow and beyond. No one can say anything concrete. Mankind has not been able to stop this epidemic for months with all its historical knowledge, and economic and technological capabilities. Far from stopping, it tries to reduce losses and increase the number of lives it can save. Governments are racing in the fight against this virus crisis by undertaking the task of designing social experiences, economic powers, management approaches and priorities of the social relations they rely on, and measures and recovery packages with the slogan of “PROBLEM GLOBAL, SOLUTION NATIONAL”. Despite the unknown future, these efforts and these packages have already reached a scale that will shape and restructure societies and economies in the coming years. However, mankind is not a stranger to this type of epidemics. Humanity has faced many epidemic diseases and disasters throughout its history. When it became unsustainable due to the suffering caused by local or regional crises, it evolved to new social forms or disappeared locally, depending on the level of uneven development and productive forces and the severity of pain. The fact that epidemics throughout the history of humanity have reached global dimensions in our era and are not limited to nations, local geographies, or even continents clearly reveals that the solution of the crisis today requires a global solidarity. v vi Preface The ongoing crisis has made global connections more visible, strengthened the vision of a more flexible society at national and regional levels, as well as once again clearly revealed the great differences between countries’ conditions and capacities. For this reason, international cooperation is required to overcome the crisis and the struggle against the crisis should be at the level of global common dependency and responsibility. It is an imperative rather than a necessity to direct global investments wherever they are needed, including the most vulnerable countries and communities. The extent and progress of the crisis require solidarity on a global scale, but it requires the bold implementation of the measures to determine the causes of the crisis without delay and eliminate them without wasting time. Today, we cannot dissociate the cause of the coronavirus epidemic, which threatens the entire planet, and took and continues to take hundreds of thousands of lives, from the consequences of the climate crisis. Global climate change caused by the plundering and looting of the natural values at the level of an uncontrolled war against nature in the second half of the twentieth century and afterward in an attempt to overcome its challenges by using advanced technology with an inexhaustible ambition for profit led to the global crises such as coronavirus. And it seems that crises caused by corona and similar viruses are neither the first nor the last. The climate crisis and its consequences affect the entire planet, causing unlimited losses, especially loss of life, economies collapse, and epidemic diseases that cannot be dealt with and threaten the future of humanity. Extreme atmospheric events, hurricanes, tornados, irregularity of precipitation regimes, floods, drought and desertification, melting glaciers and rising seas, large forest fires that could not be extinguished, destroyed ecosystems, drying lakes, lost water resources, polluted air, water, soil, all occur more frequently as the phenomena dragging the humanity to its end. Air pollution caused by fossil fuels, especially coal-fired power plants, spreads over hundreds of kilometers. People living here easily get lung and other chronic diseases and are the first target in epidemics. The use of coal, oil, and natural gas in the transportation, industry and housing sectors, both changes the global climate and the air pollution it creates causes the death of millions of people every year. Coronavirus, on the other hand, kills patients suffering from chronic diseases (cancer, tuberculosis, heart, and lung diseases) caused by using fossil fuel, without the opportunity to use medication. It is obvious that vaccination studies will last at least 1 year, due to inadequate number of tests in the initial process early diagnosis hasn’t been possible and in the countries where preventive medicine is ignored the fight against the virus will extend the time and increase the losses. Preface vii If the necessary lessons are not taken and the causes cannot be eliminated by doing what is necessary, such crises will continue until they destroy the living species in the universe with an increasing severity. Increasing loss of life is disruptive, and pressure on communities and economies will require comprehensive strategies to eliminate causes. A broader perspective is needed that sees energy, society, economy, and the environment as part of a unique, integrated system. The steps taken within the scope of the fight against the crisis, the investments made, and the public resources spent should provide more than a rescue operation for the existing socio-economic structures. Now, more than ever, public policies and investment decisions must be compatible with a vision of sustainable and fair future, free from political concerns. In the context of combating the epidemic, incentives and improvement measures should encourage economic development and job creation, promote social equality and prosperity, and put the world on a climate-safe path. The governments should resort to a renewable-energy-based energy transformation to bring a series of solutions at this difficult moment. Decentralized technologies enable citizens and communities to participate more in energy decisions with transformative social implications. More importantly, it offers a proven approach to remote healthcare in energy-poor communities and adds a key element to the crisis response process. Burning fossil fuels (coal, natural gas, and petroleum) in the atmosphere, which are the main causes of chronic diseases, should be stopped and transition to 100% renewable energy should take place as a permanent solution for the elimination of epidemics and for keeping people and other living creatures free from outbreaks. The energy transformation process should be accelerated to help revitalize renewable technologies and industries and create new jobs. What should be done to stop the carbon emissions, which has become a vital necessity for humans and nature, should be applied immediately without any excuses and “but’s”. Air is a nature element that makes life possible and sustainable. Water that makes life possible is a product that cannot be obtained in any way other than what nature offers. Soil, which gives plants life and can be cultivated, is the product of a process corresponding to tens of thousands of years. Forests that enable the universe to breathe and provide the rain to the universe as a natural event are the products of hundreds of thousands of years. Fossil forests are world heritage formations that enable us to discover natural history. The formation of fossils is a process that takes millions of years and makes it possible through the scientific studies to have information about the climate and plant species related to the geological times. These natural values should never be consumed for any reason. They should continue their existence in their natural environment and should be used based on sustainability of life in the way the nature offers. viii Preface We, as the promoters of transition to 100% renewable energy who worked together to produce this book, are trying to define the problems of conventional energy production and consumption, to find solutions that can be implemented and to develop related technologies and methodologies for effective long-term mitigation of the problems and protection of our unique common living space on Earth. Permanent solution to prevent people from catching epidemics is to stop combustion of fossil fuels (coal, natural gas, and oil) in the atmosphere, which is the main cause of chronic diseases. We need to develop and implement Local Green Deal’s in cities and National Green Deal’s in countries to make Global Green Deal a reality. Istanbul, Turkey Tanay Sıdkı Uyar Contents Accelerating the Transition to 100% Renewable Era. But How? Exergy Rationality in the Built Environment . . . . . . . . . . . . . . . . . . . . . Birol Kılkış 1 Role of IRENA for Global Transition to 100% Renewable Energy . . . . Elisa Asmelash, Gayathri Prakash, Ricardo Gorini and Dolf Gielen 51 The Renewable City: The Future of Low-Carbon Living . . . . . . . . . . . . Peter Droege 73 Assessment of Prerequisites and Impacts of a Renewable-Based Electricity Supply in Austria by 2030 . . . . . . . . . . . . . . . . . . . . . . . . . . . Gustav Resch, Gerhard Totschnig, Demet Suna, Franziska Schöniger, Jasper Geipel and Lukas Liebmann 99 History and Recent State of TIMES Optimization Energy Models and Their Applications for a Transition Towards Clean Energies . . . . . 113 Kathleen Vaillancourt, Olivier Bahn and Nadia El Maghraoui Electricity Grids for 100% Renewable Energy: Challenges and Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 Eberhard Waffenschmidt, Majid Nayeripour, Silvan Rummeny and Christian Brosig The Sustainable Energy Transition Cities and Local Governments in Focus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 Maryke van Staden The Pathway to 100% Renewable Energy—A Vision . . . . . . . . . . . . . . 169 Rian van Staden, Filippo Boselli and Anna Leidreiter ix x Contents Clean Energy Manufacturing: Renewable Energy Technology Benchmarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 Debra Sandor, David Keyser, Margaret Mann, Jill Engel-Cox, Samantha Reese, Kelsey Horowitz, Eric Lantz, Jon Weers, Billy Roberts, Stacy Buchanan, Doug Arent, Brian Walker and Robert Dixon Development and Thermodynamic Analysis of a 100% Renewable Energy Driven Electrical Vehicle Charging Station with Sustainable Energy Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 Abdulla Al Wahedi and Yusuf Bicer Community Wind Under the Auctions Model: A Critical Appraisal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 Stefan Gsänger and Timo Karl 100% Renewable Energy Generation with Integrated Solar Energy Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 Ayhan Atiz and Mehmet Karakilcik The Role of Hydrogen in Global Transition to 100% Renewable Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 Haris Ishaq and Ibrahim Dincer Solar Hydrogen’s Role for a Sustainable Future . . . . . . . . . . . . . . . . . . 309 Canan Acar Design and Analysis of a New Environmentally Benign Ammonia-Based Solar Thermochemical Integrated Plant . . . . . . . . . . . 333 Yunus Emre Yüksel, Fatih Yilmaz and Murat Ozturk An Overview of Hydrogen Production from Biogas . . . . . . . . . . . . . . . . 355 Yagmur Nalbant and C. Ozgur Colpan Underground Large-Scale Hydrogen Storage . . . . . . . . . . . . . . . . . . . . . 375 Hatice Karakilcik and Mehmet Karakilcik Biomass and Its Thermochemical Conversion: Can It Be a Road Map for Transition to 100% Renewable Energy? . . . . . . . . . . . . . . . . . . . . . 393 Atakan Ongen, Emine Elmaslar Özbaş, Hüseyin Kurtuluş Ozcan, Serdar Aydın and Nazlıcan Karabağ Role of Energy Storage in 100% Renewable Urban Areas . . . . . . . . . . . 411 Halime Paksoy, Nurten Şahan and Burcu Koçak Efficient Use of Energy in Buildings—New Smart Trends . . . . . . . . . . . 439 Hasan Heperkan, Büşra Selenay Önal and Tanay Sıdkı Uyar Contents xi Energy System Analysis, Simulation and Modelling Practices in Turkey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485 Egemen Sulukan, Tanay Sıdkı Uyar, Doğancan Beşikci, Doğuş Özkan and Alperen Sarı Residential Island Nano-grid for 100% Renewable Clean Energy . . . . . 507 John O. Borland Solar Chimneys: Technology and Their Role for Transition to 100% Renewable Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529 Dogan Eryener Towards a Low-Carbon Energy World: Some Pilot Projects in China, Europe and the United States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551 Wolfgang Palz Nomenclature, Acronyms and Abbreviations Nomenclature A A A A a, b ALT C c c c, d, e, g, h Ceq Chp CO2 CO2base Comp. COP COPEX CR D E_ E E E Eact,a Eact,c Area of wind turbine (m2) Area (m2) Solar panel irradiation area (m2) Surface area (m2) Constants of the heat pump COP versus temperature function (Eq. 37) Residence time in the atmosphere years Installed Capacity (kW) Specific heat capacity (J/kg °C) Unit emissions factor of a fuel (kg CO2/kW-h) Constant in Eqs. 33–35 Equipment Life-Cycle Cost-Design Temperature Difference Factor (€
K/kW-h) Heat Pump Life-Cycle Cost-Design Temperature Difference Factor (€/K
kW-h) Carbon dioxide emission (kg of CO2) Base (Reference) emission (kg of CO2) Compound Coefficient of performance Exergy-based coefficient of performance Composite Rationality Index District Pipe Inner Diameter (m) Energy flow rate (kW) Actual voltage of cell (V) Electrical energy (load) (kW-h) Energy (kJ) Activation overpotential at anode (V) Activation overpotential at cathode (V) xiii xiv Econc EDR ELC EM EMR Eohmic ex Ex _ Ex _Exdest _ D Ex _ d Ex _Ex Ex F FC GWP h H HSDI I Id In J Joa Joc L LH m _ m m_ N N n ODI ODP P PC PEF PER PEXR Ps Q_ Nomenclature, Acronyms and Abbreviations Concentration overpotential (V) Ratio of carbon CO2 emissions difference to the base emission, dimensionless Exergy-Levelized Unit Cost (€/m2 based on REMM) Composite embodiment cost (€) Exergy embodiment recovery, years (See Fig. 22) Ohmic overpotential (V) Specific exergy (kJ/kg) Exergy (kW) Exergy rate (kW) Exergy destruction (kW) Exergy destruction rate (kW) Exergy destruction rate (kW) Exergy rate (kW) Specific exergy (kJ/kg) Faraday constant (C/mol) Selling price of the solar panel (€) Global warming potential Enthalpy Specific enthalpy (kJ/kg) Human (Sustainable) Development Index Solar radiation (W/m2) Direct normal irradiation (W/m2) Net solar insolation normal to solar receiver surface (W/m2) Current density (A/m2) Anodic exchange current density (A/m2) Cathodic exchange current density (A/m2) One-way District circuit distance (m) Vlower heating value (kJ/kg) Mass (kg) Mass flow (kg/s) Mass flow rate (kg/s) Molar flow rate (mole/s) Number Number of moles Composite Ozone Depletion Index Ozone Depleting Potential Pressure (kPa) Unit power cost of a solar energy system (€/kWpeak) Primary energy factor Primary energy ratio (Reciprocal of PEF) Exergy-based primary energy ratio Power demand for pump stations (kW) Heat (w) Nomenclature, Acronyms and Abbreviations Q_ Q, QH R r RCO2 Re rms s s, t, u Sc S_ gen T TI U V V V w W W W_ x X Y DPS Heat rate (kW) Thermal energy (load) (kW-h) Gas constant (kJ/kmol K) Radius solar pond (m) Reduction Potential Ratio Reynolds number Root-mean-square (electricity) Specific entropy (kJ/kg K) Coefficients in Eq. 2 Solar constant (1366 W/m2) Entropy generation rate (kW/K) Temperature (°C or K) Transformation index Heat transfer coefficient (W/m2K) Velocity (m/s) Volumetric Flow (m2/h) Wind speed (m/s) Correction factor for COPEX in Eq. 4, 0.85  w  1.0 Power (W) Weight of a panel (kg) Work rate (kW) Length (m) Power Split The ratio of the temperature changes of the Stratosphere and Troposphere Power demand of the pump stations per unit pipe length (kW/m) Greek Letters a; b; d; c a g g gI gII gT gW q q k kmem rmem Atoms of C, H, N and O Symmetry factor Efficiency Energy efficiency First-law efficiency Second-law efficiency Power transmission and distribution efficiency Wind turbine-to-electricity first-law efficiency Density Density of air Stoichiometric constant Membrane water content Membrane conductivity (1/X cm) xv xvi D u / / w wR DCO2 RCO2 E Nomenclature, Acronyms and Abbreviations Difference Betz limit Golden ratio Fuel exergy to energy ratio Exergy efficiency Rational exergy management efficiency Avoidable CO2 emissions (kg CO2/kW-h heat) Total CO2 emissions (Direct and avoidable) (kg CO2/kW-h heat) Unit exergy (kW/kW) Subscripts 0 0 a a act app ar base BESS bt c c ch comp con D dem des e E el en ev EVTC ex exc f F f FC G Ambient conditions Reference state Anode Indoor air Activation Useful application (Temperature) Air Base Battery Energy Storage System Bottom Cathode Cooling Chemical Compressor Condenser Destruction Demand Destroyed Break-even Electric Electrolyser Energy Evaporator Evacuated tube solar collectors Exergy Exchanger Energy source, fuel Fan Fuel Fuel cell Generator Nomenclature, Acronyms and Abbreviations g H HSZ in in, out int l, m lm loss min, max net o o o, ref opt p P PEM PEV ph pump PV R rcv ret, sup s s SOC sp st sur sys T T tot u up w w, wt wf WT X, EX Geothermal Thermal (Heat) Heat storage zone Inlet Inlet and outlet connections of a hydronic circuit Integrated Local power plant, distant power plant, respectively Logarithmic Thermal losses Minimum, maximum Net power Air Standard state Reference Optimum Product Pump Proton exchange membrane Plug-in Electrical Vehicle Physical Pumping Photovoltaic Reservoir, return Receiver Return, supply Solar Sun State of Charge Solar pond Storage Surface System Power transmission, total, overall Turbine Total Useful Upper Water Wind, Wind Turbine Working fluid Wind turbine Exergy, exergetic xvii xviii Nomenclature, Acronyms and Abbreviations Acronyms and Abbreviations Abs ABS, ADS AC, DC BESS CHP Con COP Cu–Cl DE, 4DE DHW ECBCS EEA EES EIA EPA EU EVTC EXT FC Gen GSHP HE HEX HPT HRV HSZ HVAC IEA LHV LNG LowEx LPG LPT LVDC mCHP NCZ nZEXB OECD ORC OTEC P PEM Absorber Absorption, Adsorption Cycle Alternating Current, Direct Current Battery Energy Storage System Combined heat and power (Cogeneration) Condenser Coefficient of performance Copper chlorine District Energy System, 4th Generation District Energy System Domestic Hot Water Energy Conservation in Buildings and Community Systems Program European Environment Agency Engineering equation solver Energy Information Administration (US) Environmental Protection Agency European Union Evacuated tube solar collector Heat loss extraction Fuel cell Generator Ground-source heat pump Heat exchanger, or Hydrogen economy Heat exchanger High pressure turbine Heat-recovery ventilation Heat storage zone Heating, ventilating and air-conditioning (of buildings) International Energy Agency Lower heating value Liquified natural gas Low exergy (building) Liquified petroleum gas Low pressure turbine Low-voltage DC power Micro CHP (Electrical power capacity <50 kW) Non-convective zone Net-zero exergy building The Organization for Economic Co-operation and Development Organic Rankine cycle Ocean thermal energy conversion Pump Proton exchanger membrane Nomenclature, Acronyms and Abbreviations PEMFC PEV PV PV, PVT REMM SEAC SHF SOC SOE SP SPT ST SWWCP TES TP UCZ US WEF WGSR Proton exchange membrane fuel cell Plug-in electrical vehicle Photovoltaic Photo voltaic, Photo-voltaic-heat Rational exergy management model Single effect absorption cooling Solar heliostat field State of charge Solid oxide electrolyser Solar pond Solar power tower Solar tower Solar-wind-wave composite platform Thermal energy storage Temperature-peaking Upper convective zone United States World Economic Forum Water gas shift reactor xix List of Figures Accelerating the Transition to 100% Renewable Era. But How? Exergy Rationality in the Built Environment Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 14 Fig. 15 Fig. 16 Global energy consumption by sector (IEA 2018). (Building sector includes construction phase) . . . . . . . . . . . . . . . . Renewables for heating and cooling in Europe (EU 2016) . . . . . . US total energy consumption by sector, 1950–2017. Vertical axis shows consumption in quadrillion btu (EIA 2018) . . . . . . . . Correlation between stratosphere and troposphere temperatures, 2018 (Kilkis 2019a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Variation of CO2 concentration during the nine months (Kilkis 2019a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Irreversible cycle of ozone depletion and global warming from the built environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The decrease in refrigerant leakages (Cowan et al. 2009) . . . . . . . Retraction of ozone layer and atmospheric temperatures (EPA 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wind turbine operated heat pump has GWP,ODP, and DCO2 emissions (Kilkis 2019; Kilkis et al. 2017) . . . . . . . . . . . . . . . . . . Exergy flow diagram for the grid -operated heat pump (CASE 1) in heating mode, which is shown in Fig. 9 . . . . . . . . . . . . . . . . . . Coupling between emissions and development (Kilkis 2019) . . . . Triple improvement of HSDI, CO2 emission reduction, and wR (Kilkis 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The need for an integrated approach for cleaner cities. Derived from: (EEA 2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . District energy system with solar PVT plant (Kilkis 2019) . . . . . . Solar energy is not a complete solution alone. It depends on how we use it . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exergy rationale in geothermal energy (Kilkis 2019a) . . . . . . . . . 2 3 3 4 5 6 7 8 9 11 12 13 14 15 17 18 xxi xxii Fig. 17 Fig. 18 Fig. 19 Fig. 20 Fig. 21 Fig. 22 Fig. 23 Fig. 24 Fig. 25 Fig. 26 Fig. 27 Fig. 28 Fig. 29 Fig. 30 Fig. 31 Fig. 32 Fig. 33 Fig. 34 Fig. 35 Fig. 36 Fig. 37 Fig. 38 Fig. 39 Fig. 40 Fig. 41 Fig. 42 Fig. 43 List of Figures The number of countries with renewable energy regulatory policies by sector (REN 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . Sectoral breakdown of energy consumption-based global CO2 emissions (IEA 2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Net exergy gain is negative in a condensing boiler. . . . . . . . . . . . US electricity consumption in residential and commercial buildings (OECD/IEA 2018). . . . . . . . . . . . . . . . . . . . . . . . . . . . . Five wind-to-heat methods. The reference case is a coal-fired boiler or stove (Kilkis 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Four tiers of the holistic district energy model with LowEX renewables (Kilkis 2019b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A net-zero energy building is not necessarily a net-zero Exergy building . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NZEXD and NZEXB in 100%-renewable build environment . . . . Afyon geothermal energy district heating system layout (Şahin C and Gürler 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Geothermal energy, ORC, and heat pump in a district (Kilkis 2019a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Direct geothermal district heating . . . . . . . . . . . . . . . . . . . . . . . . . Geothermal power with ORC . . . . . . . . . . . . . . . . . . . . . . . . . . . . Break-even temperature for heating or power (Eq. 37) (Kilkis 2019a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wind to hydrogen for space heating with fuel cell . . . . . . . . . . . . Integration of wind and solar for heat and power in a hydrogen building (Kilkis 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Existing hydrogen network in the Netherlands (Kilkis 2020, Polar Teknoloji) . . . . . . . . . . . . . . . . . . . . . . . . . . . All DC-solar-active hydrogen hybrid net-zero/positive exergy building . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FPC with Tf = 638.8 K, Tret = 288 K, Tsup = 333 K, Tref= 283 K. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Simple solar PV system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conventional solar PVT system without circulating pump losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Holistic model for a conventional PVT system (Kilkis 2019) . . . . Contradiction between PV power output and thermal power output (Kilkis 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A case study, Tsup= 293 K (Kilkis 2019). The maximum improves only 4 W . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Feasible regions for PVT technology . . . . . . . . . . . . . . . . . . . . . . Payback periods with project size and geography . . . . . . . . . . . . . nZEXB in the mediterranean with roof PVT and PVT Façade brick . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100% renewable farm and greenhouse (Çolak et al. 2013) . . . . . . 19 19 21 23 24 26 27 29 30 31 31 31 33 34 35 36 36 37 38 38 39 40 40 41 41 42 43 List of Figures Fig. 44 Fig. 45 Fig. 46 Off-shore 100% renewable power plant with H2S gas from the black sea bed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Jet fuel but 100% renewable (Kılkış et al. 2019) . . . . . . . . . . . . . A 100% renewables system of systems approach with hydrogen economy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii 44 45 47 Role of IRENA for Global Transition to 100% Renewable Energy Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Needs and opportunities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Summary of recent trends and required levels of selected indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Innovations taking place in the electricity supply chain . . . . . . . . REmap offers a pathway for a well-below 2 °C climate target, towards 1.5 °C. Notes (1) Taking into account 2015–2017 emissions on top of the budget provided in IPCC (2018) (Table 2.2—with no uncertainties and excluding additional Earth system feedbacks); (2) Budgets exclude industrial process emissions of 90 Gt; for this study, the assumption is that CO2 emissions from land use, land-use change and forestry (LULUCF) fall from 3.3 Gt in 2015 to zero by mid-century. LULUCF subsequently becomes a net absorber of CO2 over the remainder of the 21st century, and, as a result, cumulative CO2 emissions from LULUCF between 2015 and 2100 are close to zero; (3) Current trajectory shows the recent historical trend line, assuming the continuation of the annual average growth in energy-related CO2 emissions from the last five years (2013–2018) of 1.3% compound annual growth up to 2050; (4) Emissions budgets represent the total emissions that can be added into the atmosphere for the period 2015–2100 to stay below 2 or 1.5 °C at different confidence levels (50 or 67%) according to the IPCC (2018) report . . . . . . . . . . . . . . . . . . . . . . . Renewables and energy efficiency, boosted by substantial electrification, can provide over 90% of the necessary reductions in energy-related carbon emissions. Note “Renewables” implies deployment of renewable technologies in the power sector (wind, solar PV, etc.,) and end-use direct applications (solar thermal, geothermal, biomass). “Energy efficiency” contains efficiency measures deployed in end-use applications in industry, buildings and transport sectors (e.g., improving insulation of buildings or installing more efficient appliances and equipment). “Electrification” denotes electrification of heat and transport applications, such as deploying heat pumps and EVs . . . . . . . . . . The global energy supply must become more efficient and more renewables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 55 57 59 60 61 xxiv List of Figures Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Wind and solar power dominate growth in renewable-based generation. Note In electricity consumption, 24% in 2016 and 86% in 2050 is sourced from renewable sources. CSP refers to concentrated solar power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power sector key indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electricity becomes the main energy source by 2050. Note For electricity use, 24% in 2016 and 86% in 2050 comes from renewable sources; for district heating, this share is 9% and 77%, respectively. DH refers to district heat . . . . . . . . Transport sector key indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . Buildings sector key indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . Industry sector key indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 63 64 64 65 66 The Renewable City: The Future of Low-Carbon Living Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. Fig. Fig. Fig. 14 15 16 17 Fig. 18 Josh’s House, Perth. © Josh Byrne, Perth 2014 . . . . . . . . . . . . . . B10 Active House, Stuttgart by Werner Sobek. © Zooey Braun, Stuttgart 2014 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Freiham-Nord Masterplan, as part of Munich’s 100% renewable energy city concept. © Anis Radzi (2018) . . . . . . . . . . . . . . . . . . Active-city House, Frankfurt by HHS Architects. © Anis Radzi (2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sample IESP cash flow for net zero energy districts. © Rocky Mountain Institute 2018 . . . . . . . . . . . . . . . . . . . . . . . . Robinsons place Dumaguete, Manila. © ABS-CBN News 2018 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veteran Freiburg Solar Settlement, Vauban, Germany. © plusenergiehaus.de 2012 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Renovation of Halle Pajol by Jourda Architectes, Paris. © apur.org 2017 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IBA Wilhelmsburg. © IBA-Hamburg 2014 . . . . . . . . . . . . . . . . . Renewable Wilhelmsburg. © IBA-Hamburg 2014 . . . . . . . . . . . . Kalkbreite housing cooperative by Müller Sigrist Architekten. © Martin Stollenwerk 2018 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ortoloco community events. © Ortoloco 2018 . . . . . . . . . . . . . . . WGV living lab. © CRC Low-Carbon living laboratory 2018. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RENeW Nexus. © Curtin University 2018 . . . . . . . . . . . . . . . . . . Solar installation in Gaza. © Jersualem Post. . . . . . . . . . . . . . . . . Village solar installation. © Greenpeace . . . . . . . . . . . . . . . . . . . . The potential for regions to become energy self-sufficient is illustrated in the Lake Constance Alpine-Rhine Region in Central Europe. © Droege/oekom . . . . . . . . . . . . . . . . . . . . . . . Energetic refurbishment of apartment buildings in Germany. © Jens Wolf/DPA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 78 79 80 81 82 83 83 84 85 86 87 88 88 92 92 93 94 List of Figures Fig. 19 Fig. 20 Land potential for tree planting and additional carbon stroage potential in Leicester, UK. © Davies et al. (2011) . . . . . . . . . . . . The Soft House, Hamburg. © Sheila Kennedy, MIT . . . . . . . . . . xxv 95 95 Assessment of Prerequisites and Impacts of a Renewable-Based Electricity Supply in Austria by 2030 Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Model coupling between Green-X (left) and HiREPS (right) . . . . Breakdown of the future development of renewable energy generation by construction period (left) and technology (right) according to the developed OE core scenario (source Green-X) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electricity price trend scenarios (left) and breakdown of the resulting demand for electricity from renewable electricity plants by construction period and technology according to the developed OE core scenarios (low, medium and high electricity prices) for the years 2021–2030 (right) (Sources OE Expert Advisory Council (2018) (left) and Green-X (right)) . . . . . . . . . . Development over time of the residual load according to scenario “Extrema-LimitHydro-2030” (+shows deficit, −shows surplus) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Flexibility needs at distinct time periods according to the scenario “Extrema-LimitHydro-2030” . . . . . . . . . . . . . . . . . 103 103 106 108 109 Electricity Grids for 100% Renewable Energy: Challenges and Solutions Fig. Fig. Fig. Fig. 1 2 3 4 Fig. 5 Fig. 6 Comparison of PV and CHP for one year . . . . . . . . . . . . . . . . . . Comparison of PV and CHP for beginning of October. . . . . . . . . Comparison of HP and CHP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . General structure of an energy cell (below) in a Cellular Energy System (above) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exemplary structure and interconnection of a cellular energy system (CES) including electricity, gas and heat grid from the transmission to the distribution level . . . . . . . . . . . . . . . Tasks and responsibilities of the energy cell management system (ECM). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 136 137 140 143 144 Clean Energy Manufacturing: Renewable Energy Technology Benchmarks Fig. 1 Clean energy manufacturing supply chain links. Items in bold are included in the benchmark analysis . . . . . . . . . . . . . . . . . . . . 196 xxvi Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 List of Figures Direct manufacturing value added retention for four clean energy technology supply chains, 2014. The colored bars (right axis) indicate the total clean energy manufacturing value added for each economy; the clean energy manufacturing value added retained within each economy (direct value added as a share of production revenue) is indicated by the gray bars (left axis). See methodology report for data quality discussion . . . . . . . . . . . . . . . Balance of trade in select clean energy technology end products and across c-Si PV module supply chain, 2014 (Millions USD 2014). The bars show the clean energy technology end product imports as negative values and the exports as positive values. The balance of trade is noted to the right of the bar. Interactive trade flow charts can be accessed at ManufacturingCleanEnergy. org/Benchmark. Tradedata are not dissaggregated for the specific clean energy technologies studied. For wind components, only data for wind generator sets (which consist of a nacelle packaged with blades) were available. Trade data for Li-ion battery cells were not dissaggregated by end use. See methodology report for data quality discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Benchmarked clean energy technology end product trade flows. Charts shows 2016 trade flows among benchmarked economies for wind gensets (nacelle and blades), PV modules, LIB cells, and LED packages in US$(2014). Note that for the trade data, Denmark has been included due to its importance in wind component manufacturing. An interactive version of the chart is available at http://www.manufacturingcleanenergy.org/ benchmark/wind.php . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Production and demand for four clean energy technology end products, 2014. Note LED chip (subcomponent), rather than LED package (end product) data reported, due to lack of economy-specific LED package production data, 2014. The bars indicate the production and market demand (consumption). See methodology report for data quality discussion . . . . . . . . . . . . . . . Production and production capacity utilization for four clean energy technology end products by economy. Note LED chip (subcomponent), rather than LED package (end product) data reported, due to lack of economy-specific LED package production data. 2014. Each bar shows the production revenue for the end product (darker shade) and the production value of unused manufacturing capacity (lighter shade) based on the lower horizontal scale. The line and numerical value show the capacity utilization rate based on the upper horizontal scale. See methodology report for data quality discussion . . . . . . . . . . . . . . . 200 201 202 203 204 List of Figures xxvii Development and Thermodynamic Analysis of a 100% Renewable Energy Driven Electrical Vehicle Charging Station with Sustainable Energy Storage Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 The proposed system diagram for plug-in electric vehicle charging station working on 100% renewable energy . . . . . . . . . . Energy efficiencies of the subsystems and components within the integrated charging station . . . . . . . . . . . . . . . . . . . . . . Exergy efficiencies of the subsystems and components within the integrated charging station . . . . . . . . . . . . . . . . . . . . . . The effect of reference pressure on the air separation exergy efficiency and exergy destruction . . . . . . . . . . . . . . . . . . . . . . . . . The effects of reference temperature on the air separation and ammonia production systems . . . . . . . . . . . . . . . . . . . . . . . . . The effects of reference temperature on the fuel cells and overall system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The effects of operation temperature of H2 fuel cell on the fuel cell work production, exergy destruction and exergy efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The changes of total power input and output from PV system and exergy destruction based on solar irradiance . . . . . . . . . . . . . The changes of total power output from wind turbine and exergy efficiency based on wind velocity . . . . . . . . . . . . . . . . . . . . . . . . . 217 224 224 226 227 227 228 228 229 Community Wind Under the Auctions Model: A Critical Appraisal Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Three main elements of community power . . . . . . . . . . . . Highest price awarded. Source Authors’ calculations, Bundesnetzagentur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Auctions evaluation by community wind players . . . . . . . Entry into the business of self-supply with renewable energies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Switch to new business areas . . . . . . . . . . . . . . . . . . . . . . Entry into the business of electromobility . . . . . . . . . . . . . Satisfaction with the NRW state government . . . . . . . . . . ...... 238 ...... ...... 244 249 . . . . . . . . 250 251 252 252 .. .. 260 265 .. .. .. 266 267 267 . . . . . . . . . . . . . . . . 100% Renewable Energy Generation with Integrated Solar Energy Systems Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Solar pond integrated with ORC . . . . . . . . . . . . . . . . . . . . . . . . Total solar energy on horizontal surface for Adana . . . . . . . . . Distribution of solar energy from surface to bottom of the SP in different months (Karakilcik at al. 2006) . . . . . . . . . . . . . . . Generated electricity in the ORC for four months . . . . . . . . . . The energy efficiency of ORC for four months . . . . . . . . . . . . xxviii Fig. 6 Fig. 7 Fig. 8 Fig. 9 List of Figures Solar pond integrated with EVTCs and ORC (Atiz et al. 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The daily solar energy variations for the EVTCs . . . . . . . . . . . Daily energy distributions of the solar energy on the SP . . . . . The produced electricity and thermal energy in the evaporator for a day . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. .. 269 271 272 .. 272 The Role of Hydrogen in Global Transition to 100% Renewable Energy Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. Fig. Fig. Fig. 8 9 10 11 Fig. 12 Fig. 13 Fig. 14 Fig. 15 Fig. 16 Fig. 17 Fig. 18 Energy consumption comparison of traditional and renewable energy sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of lower heating values of different fuels . . . . . . . . . Global demand of pure hydrogen (data from Agency IE 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3S approach for renewable energy-based hydrogen production systems (Dincer and Acar 2015) . . . . . . . . . . . . . . . . . . . . . . . . . . Future predictions for renewable energy-based hydrogen production (data from U.S. Department of Energy. https://www. energy.gov/eere/fuelcells/doe-technical-targets-hydrogenproduction-electrolysis) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydrogen production and utilization for the global transition to 100% renewable energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solar thermal energy based thermochemical copper-chlorine (Cu–Cl) cycle for hydrogen production system . . . . . . . . . . . . . . . Photoelectrochemical hydrogen production . . . . . . . . . . . . . . . . . . Solar photovoltaic based hydrogen production system . . . . . . . . . Wind energy-based hydrogen production system . . . . . . . . . . . . . Ocean thermal energy conversion-based hydrogen production system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Geothermal energy-based hydrogen production system . . . . . . . . . Biomass gasification based hydrogen production system . . . . . . . Wind energy-based system for electricity, heat and hydrogen production. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Effect of current density on fuel cell overpotential . . . . . . . . . . . . Wind speed effect on the wind turbine power and exergy destruction rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wind speed effect on the system efficiency during high wind speed and H2 flowrate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Current density effect on the fuel cell efficiencies . . . . . . . . . . . . . 277 278 279 281 282 283 290 291 292 293 293 294 295 297 302 303 303 304 List of Figures xxix Solar Hydrogen’s Role for a Sustainable Future Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Hydrogen’s role towards renewabilization and decarbonization of energy systems for a sustainable future . . . . . . . . . . . . . . . . . . GHG emissions of the selected hydrogen production options . . . . Resource use comparison of the selected hydrogen production options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fossil fuel use comparison results of the selected hydrogen production options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Water use comparison results of the selected hydrogen production options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydrogen production costs of the selected hydrogen production options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energy and exergy efficiencies of the selected hydrogen production options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Normalized performance rankings of the selected hydrogen production options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313 321 322 323 324 325 326 327 Design and Analysis of a New Environmentally Benign Ammonia-Based Solar Thermochemical Integrated Plant Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Schematic illustration of the investigated plant . . . . . . . . . . . . . . . Effect of dead state temperature on the whole system energetic efficiency at charging, storing and discharging time . . . . . . . . . . . Effect of dead state temperature on the whole system exergetic performance at charging, storing and discharging time . . . . . . . . . Impact of dead state temperature on the useful outlets rates from integrated plant at charging, storing and discharging time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Effect of solar radiation on the whole plant energetic performance at charging, storing and discharging time . . . . . . . . . Effect of solar radiation on the whole plant exergetic performance at charging, storing and discharging time . . . . . . . . . Impact of solar radiation on the useful outputs rates from integrated plant at charging, storing and discharging time . . . . . . Impact of pinch point temperature of ammonia synthesis reactor on the whole plant energetic performance at charging, storing and discharging time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Effect of pinch point temperature of ammonia synthesis reactor on the whole system exergetic performance at charging, storing and discharging time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Effect of pinch point temperature of ammonia synthesis reactor on the useful outlets rates from integrated plant at charging, storing and discharging time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 346 347 347 348 348 349 350 350 351 xxx List of Figures An Overview of Hydrogen Production from Biogas Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Main steps of hydrogen production from biogas (Adapted from Minh et al. 2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Schematic diagram of steam reforming process including reactants and products. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Schematic diagram of partial oxidation reforming process including reactants and products . . . . . . . . . . . . . . . . . . . . . . . . . . Schematic diagram of auto-thermal reforming process including reactants and products. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Schematic diagram of dry reforming process including reactants and products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Schematic diagram of dry oxidation reforming process including reactants and products. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of conventional and membrane reactors (Adapted from Marcoberardino et al. (2018)) . . . . . . . . . . . . . . . . Schematic diagram of the operating principle of the membrane system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydrogen transport mechanism through dense Pd-based membrane: (1) external diffusion, (2) adsorption, (3) dissociation, (4) diffusion, (5) recombination, (6) desorption, (7) external diffusion (Adapted from Gallucci et al. 2017) . . . . . . 358 359 360 361 362 363 366 367 367 Underground Large-Scale Hydrogen Storage Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Hydrogen storage technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . Storage density of hydrogen under certain pressure and temperature conditions (http://www.ilkdresden.de/en/service/ research-and-development-rd/detail/hydrogen-test-area-at-ilkdresden/) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Geological time of the salt dome (Beckman et al. 1995) . . . . . . . Variation with depths of liquid and gas storage facilities in the world (http://www.kbbnet.de/en/, http://energy.gov/eere/ fuelcells/hydrogen-storage) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Construction of a salt cavern storage facility. a Initial borehole b solution mining and cavern formation in process c final solution-mined cavern (Stone et al. 2009). . . . . . . . . . . . . . . . . . . 378 380 383 384 386 Biomass and Its Thermochemical Conversion: Can It Be a Road Map for Transition to 100% Renewable Energy? Fig. 1 Indicators of renewable energy in power, heating and transportation in 2017 and 2018 (Murdock et al. 2019) . . . . . . . . 397 List of Figures xxxi Role of Energy Storage in 100% Renewable Urban Areas Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 14 Energy storage technologies classification according to energy transformations used (Konuklu et al. 2018) . . . . . . . . . . . . . . . . . Water tank operation modes; a External heat exchanger, b Mantle heat exchanger, c Immersed coil heat exchanger (Nash et al. 2017) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Packed-bed storage tank with packing material (Koçak and Paksoy 2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . UTES systems (Ochs et al. 2008) . . . . . . . . . . . . . . . . . . . . . . . . . Temperature change during heating/cooling of a solid and heat effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PCM categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Closed (left) and open (right) sorption storage systems (Krese et al. 2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energy storage for power applications (Argyrou et al. 2018) . . . . Central solar heating plant with seasonal heat storage in Hamburg, Germany (Schmidt et al. 2004) . . . . . . . . . . . . . . . . Design configuration of a CSHPSS in Hamburg and Friedrichshafen, Germany (Schmidt et al. 2004) . . . . . . . . . . . . . . Large hot water storage (construction and final state) combined with solar thermal district heating “Am Ackerman-Bogen” in Munih Germany (IEA-ETSAP and IRENA 2013) . . . . . . . . . . Seasonal storage in Eggenstein-Leopoldshafen, Germany (Ochs et al. 2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . System diagram of Andasol power plant with 2-tank molten salt storage system (Aringhoff et al. 2002) . . . . . . . . . . . . . . . . . . . . . a Mixture of PCM plaster, b Applying of PCM plaster to the wall (Kusama and Ishidoya 2017) . . . . . . . . . . . . . . . . . . . 413 415 416 417 418 418 421 421 429 430 430 431 431 433 Efficient Use of Energy in Buildings—New Smart Trends . . . . . . . . . . . Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Distribution of primary energy production by resources, 145,3 million of TOE (https://www.enerji.gov.tr/tr-TR/EIGMRaporları) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Breakdown by sector energy consumption of Turkey, 145,3 million of TOE. (https://www.enerji.gov.tr/tr-TR/EIGMRaporları) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Distribution of Turkey electricity generation by source (http://www.teias.gov.tr) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Distribution of electricity consumption by sector in Turkey (http://www.teias.gov.tr) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . World primary energy production 2018 (International Energy Agency, World Energy Outlook 2018) . . . . . . . . . . . . . . . . . . . .. 442 .. 442 .. 443 .. 444 .. 444 xxxii Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 14 Fig. 15 Fig. 16 Fig. 17 Fig. 18 Fig. 19 Fig. 20 Fig. 21 Fig. 22 Fig. 23 Fig. 24 Fig. 25 Fig. 26 Fig. 27 Fig. 28 Fig. 29 List of Figures Development of energy efficiency of buildings in Germany (Erhorn and Erhorn-Kluttig 2012) . . . . . . . . . . . . . . . . . . . . . . . . . Cost—optimal point for a specified country (Wittchen and Thomsen 2012) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energy class certificate (http://www.enerjikimlikbelgesi.com/) . . . Characteristic relations between zones . . . . . . . . . . . . . . . . . . . . . Electrical network analogy for the calculations (Voss and Musall 2012) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Components of the mechanical system (DIN V 18599:2007) . . . . HAP software (https://www.carrier.com/commercial/en/us/ software/hvac-system-design/hourly-analysis-program/) . . . . . . . . Energy plus (https://energyplus.net/) . . . . . . . . . . . . . . . . . . . . . . . Heat pump (https://midori.com.tr/isi-pompasi/isi-pompasi-nedir. html) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Combined heat and power (https://centraxgt.com/) . . . . . . . . . . . . Renewable energy (Özkara 2018) . . . . . . . . . . . . . . . . . . . . . . . . . Annual additions of renewable power capacity, by technology and the total, 2012–2018 (Renewables 2019) . . . . . . . . . . . . . . . . Estimated renewable energy share of global electricity production, end of 2018 (Renewables 2019) . . . . . . . . . . . . . . . . . Estimated Renewable Energy Share of Global Electricity Investments, End 2018 (Renewables 2019). . . . . . . . . . . . . . . . . . Estimated shares of bioenergy in the total final energy consumption, overall and by end-use sector, 2017 (Renewables 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Geotermal power capacity global additions, share by country 2018 (Renewables 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hyropower global capacity, shares of top 10 countries and rest of world 2018 (Renewables 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . Solar PV global capacity additions, share of top 10 countries and rest of world 2018 (Renewables 2019) . . . . . . . . . . . . . . . . . . . . . CSP thermal energy storage global capacity and annular additions, 2008–2018 (Renewables 2019) . . . . . . . . . . . . . . . . . . . Wind power global capacity and annular additions, 2008–2018 (Renewables 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solar water heating collectors global capacity, 2008–2018 (Renewables 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solar water heating collector additions, top 20 countries for capacity added, 2008 (Renewables 2019) . . . . . . . . . . . . . . . . Condensing boiler systems (http://boilerhut.co.uk/) . . . . . . . . . . . . The IoT architecture model (Khajenasiri et al. 2017) . . . . . . . . . . 446 448 449 452 453 453 454 456 458 461 463 464 465 465 466 467 467 468 468 469 469 470 470 472 List of Figures Fig. Fig. Fig. Fig. Fig. 30 31 32 33 34 Fig. 35 Fig. 36 Fig. 37 Automation in the houses (Jourdan 2010). . . . . . . . . . . . . . . . . . . Commerzbank headquarters building (Yilmaz 2006) . . . . . . . . . . Overall view of the Grand Bazaar . . . . . . . . . . . . . . . . . . . . . . . . External units of the split air conditioners reflect a bad view . . . . A water source heat pump system with cooling towers and a boiler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alternative solution utilizing sea water . . . . . . . . . . . . . . . . . . . . . Layout of the intermediate chill water loop between the Marmara Sea and the Grand Bazaar (red line) . . . . . . . . . . . . . . . . . . . . . . . Alternative solution utilizing cooling towers . . . . . . . . . . . . . . . . . xxxiii 473 474 475 475 476 477 478 478 Energy System Analysis, Simulation and Modelling Practices in Turkey Fig. 1 Fig. 2 Fig. 3 Reference energy system of the residential sector in Turkey (Mutluel and Sulukan 2017) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Generalized RES of Turkey energy system (Sulukan et al. 2017) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CO2 emission projections between 1990 and 2025 (Sağlam et al. 2017b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494 496 500 Residential Island Nano-grid for 100% Renewable Clean Energy . . . . . Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Global carbon emissions from 1960 to 2018 . . . . . . . . . . . . . . . . Zero-NEM (negative-NEM) of − 323 kWh/month for residential home in Aiea, HI in 2018 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hawaiian electric duck curve due to mid-day rooftop solar PV backfeed to the grid (www.HECO.com) . . . . . . . . . . . . . . . . . . . . TOU rates from SDG&E and Hawaiian electric with peak rates during peak demand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Decline in rooftop solar-PV permits on Oahu, HI by − 84% . . . . Monthly HECO residential utility bill from Jan 2012 to Dec 2019 for pre-solar and solar phase 1–4 . . . . . . . . . . . . . . . . . . . . . Pre and post comparison for CSS solar-PV + battery storage system with a PPA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of a peak summer day to b winter day energy usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of summer high and low to winter daily energy usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Daily peak hot water thermal storage temperature from Aug 2016 to May 2019 showing full day target of 165 °F and effects of 1, 2 and 3 solar thermal panels . . . . . . . . . . . . . . . . . . . . . . . . Daily solar-PV generation peak from June 2016 to April 2019 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Breakdown of multiple home energy sources from 2012 to 2019 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508 509 510 510 511 513 514 514 515 516 517 519 xxxiv Fig. 13 Fig. 14 Fig. 15 Fig. 16 Fig. 17 Fig. 18 Fig. 19 Fig. 20 Fig. 21 Fig. 22 List of Figures Detail breakdown in multiple home energy sources from 2016 to 2019 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Daily cost of electricity analysis for multiple energy sources . . . . ROI savings analysis with a 10 year battery life . . . . . . . . . . . . . . Actual cost savings for CSS rooftop solar-PV + multi-storage residence in Aiea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Smart home energy management system showing inverter communication control of solar PV-generation, battery charging/ discharging and grid-buy in response to demand consumption . . . Future weather forecasting using smart SkyCam with local satellite/radar weather imaging and daily accuweather.com UV index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PV.WATTS simulations results for 27 panel rooftop solar-PV with 3 stringers based on panel tilt angle 10°–90° and direction East–South–West . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . East/West facing solar irradiation measurements . . . . . . . . . . . . . . Daily grid-buy electricity curves over a 2 week period showing the effects of overnight EV charging for a Tesla-75 using level 2 charging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NEM customer adding EV charging level 1 for Chev Bolt in Nov 2017 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 520 520 521 522 523 523 525 526 527 527 Solar Chimneys: Technology and Their Role for Transition to 100% Renewable Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 1 Fig. 2 Fig. 3 Fig. Fig. Fig. Fig. 4 5 6 7 Fig. 8 Fig. 9 Fig. 10 First large-scale solar updraft tower demonstration, Manzanares, Spain, 1982. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Schematic of a conventional and transpired solar collector updraft tower respectively . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solar chimney application for cooling, ventilation and heating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A solar updraft a compressed habitat, Vienna . . . . . . . . . . . . . . . . A proposal for urban use of solar updraft towers . . . . . . . . . . . . . A solar updraft tower for air cleaning in cities . . . . . . . . . . . . . . . A hybrid solar updraft tower experimental test unit in Trakya University, Edirne, Turkey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hybrid compost waste heat solar chimney power plant . . . . . . . . A hybrid solar updraft tower test unit in Trakya University, Edirne, which combines updraft and downdraft mechanisms in a single structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A solar updraft tower combined with geothermal, photovoltaic panels and downdraft towers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531 536 539 542 543 544 546 547 548 549 List of Boxes Role of IRENA for Global Transition to 100% Renewable Energy Box 1: Box 2: Practical Options for Global Energy Decarbonisation . . . . . . . . . . Best Practice Example—Sweden: 100% Renewable Electricity by 2040 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 66 xxxv Accelerating the Transition to 100% Renewable Era. But How? Exergy Rationality in the Built Environment Birol Kılkış 1 Introduction According to the 2018 IEA Key World Energy Statistics Report, the share of buildings in energy consumption has lately exceeded the individual shares of industry and transport (IEA 2018). IEA Statistics are all based on the quantity balances of energy and do not consider the quality balances of energy consumption in buildings with the quality of energy used in industry and transport. Their energy balance flow sheets, energy atlases, and main trade gas flow charts are based on the energy quantity based on the First Law of Thermodynamics. On the other hand, according to the Second Law of Thermodynamics, renewable energy resources generally have lower energy quality (Exergy) compared to fossil fuels and thereby present a better fit to the quality demands of the built environment, which also demand low quality of energy like for heating and cooling. This establishes a better-quality match and balance between renewable energy sources and the demands on the built environment side. Such a better-quality balance results in a much lesser amount of exergy destruction, where exergy destruction leads to additional but avoidable CO2 emissions. Unless international energy statistics transform to the Second Law, renewables may not be able to prove their competence, especially in the built environment. Therefore, in the quest of increasing the share of renewables towards 100% for decarbonization, deceleration of global warming, and minimizing ozone depletion, buildings are both the prime concern and the success potential for decarbonization with renewables. The new Horizon Europe (HE) program for the financing period 2021–2027 represents an important opportunity for the energy sector (RHC 2019). Committing 15 billion EUR for the Climate, Energy, and Transport Cluster, renewable heating and B. Kılkış (B) European Technology and Innovation Platform Renewable Heating and Cooling (RHC), Brussels, Belgium e-mail: [email protected] © Springer Nature Switzerland AG 2020 T. S. Uyar (ed.), Accelerating the Transition to a 100% Renewable Energy Era, Lecture Notes in Energy 74, https://doi.org/10.1007/978-3-030-40738-4_1 1 2 B. Kılkış cooling is an essential part of the energy transition, while heating and cooling represent 47% of the EU’s energy consumption. Yet, only 18% of heating in Europe is currently based on renewable energy sources. Figure 2 shows the current contribution breakdown of renewables (EU 2016). The rest primarily belongs to gas, coal, and oil. In terms of fossil fuel use, almost half of the EU’s buildings have individual boilers installed before 1992, with an efficiency of 60% or less. 22% of individual gas boilers, 34% of direct electric heaters, 47% of oil boilers and 58% of coal boilers are older than their technical lifetime. This finding points to an important and timely opportunity from the techno-economical point of view such that transition to renewables may be coupled with the transition from conventional heating and cooling equipment to renewable-compatible and renewable-friendly systems and equipment for buildings for the better-quality match. In Fig. 2, nuclear has been repositioned by the Author from renewables, because nuclear is neither renewable nor fossil in the classical meaning, but may be considered to be a low-carbon fuel, if large amounts of CO2 embodiment taking place during their construction, nuclear fuel production, and nuclear waste disposal and storage are entirely ignored-which is often the case in the public domain. Extending the scope to a global scale, renewable energy supplied approximately 10.3% of total global energy consumption for heating in 2015. Another 16.4% was supplied by traditional biomass, predominantly for cooking and heating in the developing world (REN 2019). Despite additional bio-heat, geothermal direct use, and solar thermal capacities were added, growth has been quite slow. Energy demand for cooling is also growing rapidly worldwide. Figure 3 shows that commercial and residential buildings in total have been a major consumer also in the USA since 1950, in excess of transportation and eventually their consumption exceeded industry slightly. Although the carbon footprint and global warming are proportioned to buildings in almost the same ratio given in Figs. 1 and 2, the main mechanism leading to the current global crisis is not well understood. Without understanding the root causes of the global crisis, the utilization of renewable energy sources directly with conventional equipment and systems in the built environment will not be successful. Therefore, it is a prerequisite for understanding the deeply interconnected global warming and ozone depletion for a sustainable transition to 100% renewables (Fig. 3). Fig. 1 Global energy consumption by sector (IEA 2018). (Building sector includes construction phase) 3 RENEWABLES Accelerating the Transition to 100% Renewable … Fig. 3 US total energy consumption by sector, 1950–2017. Vertical axis shows consumption in quadrillion btu (EIA 2018) BUILDINGS Fig. 2 Renewables for heating and cooling in Europe (EU 2016) 2 The Global Crisis-What Is Happening in the Atmosphere? Today, the standard practice of evaluation and rating of ‘high performance’, ‘sustainable’, and ‘green’ buildings simply rely on the First Law of Thermodynamics and simple economy. Although their HVAC systems seem to be quite ‘efficient’ and green, new metrics, which are based on the Second-Law, namely exergy rationality metrics, show that these heating, ventilating, air-conditioning, and refrigeration practices are not rational and environmentally benign unless they are redesigned and re-equipped accordingly. Otherwise, ozone depletion and global warming will remain to accelerate. First, it must be understood what is happening in the atmosphere and look much deeper into the global warming issue than what the industry is claiming. Until today, ozone depletion potential (ODP) and global warming potential (GWP) of the refrigerants used in many applications were treated separately. In fact, global 4 B. Kılkış warming taking place in the lower layers of the atmosphere simultaneously reduces the heat transfer like a thermal blanket to the stratosphere and further cools the ozone layer. This accelerates ozone depletion because the ozone layer gets less dense with decreasing temperatures. Increasing humidity in the atmosphere due to man-made cooling towers etc. is also contributing to this adverse mechanism. In this respect, the latest atmospheric findings clearly show that there is almost a perfect correlation between ODP and GWP in terms of monthly changes in troposphere and stratosphere temperatures which are the indicators of CO2 concentration and the ozone hole. Figure 4 reveals thermal and time symmetries for the Northern hemisphere (NASA 2019): 1. On the Temperature Scale, 2. On the Time Scale. According to Fig. 4, the ratio of the temperature changes of Stratosphere and Troposphere at a given month, Y is equal to π (Kilkis 2019a): GWP ODP Fig. 4 Correlation between stratosphere and troposphere temperatures, 2018 (Kilkis 2019a) Accelerating the Transition to 100% Renewable … Y = |% Temperature Change in Stratosphere| ≈π |% Temperature Change in Troposphere| 5 (1) The Y ratio gives the first clue about the direct dependence of ozone depletion on CO2 concentration, or in other words, the GWP changes: on an annual basis while global temperature increases, ozone layer temperature decreases in a mirror image fashion. For example, the maximum global temperature occurs on the same day of July when the ozone layer is the coldest. Following this occurrence, the ozone hole becomes the largest after following a thermal lag of about two months (September). When the stratosphere temperature rises again in December, the ozone hole diameter becomes minimum (almost nil). Consequently, the maximum CO2 concentration over the months in a year (2018), which is shown in Fig. 5 also coincides with the GWP curve given in Fig. 4. These findings lead to a new ODP and GWP correlation, including CO2 emissions behavior. By a series of mathematical elaborations, the following composite formula was developed for refrigerants only, which transforms ODP into ODI in terms of the GWP value of a given refrigerant. The atmospheric residence time, ALT in years is also factored in (Kilkis 2019b): sGW P t × ODI = (1 − ODP)  ALT 1 u {s = 0.1, t = 0.03, u = 0.01, ODP < 1} (2) Table 1 shows that even the best available less-ozone-harmful refrigerant, namely CO2 with 0 ODP and 1 GWP has a non-zero ODI, because of its long residence time in the atmosphere. F gas has zero ODP, very high GWP, and less residence time. Therefore its ODI is higher than CO2 gas. Fig. 5 Variation of CO2 concentration during the nine months (Kilkis 2019a) 6 B. Kılkış Table 1 Actual ozone depletion effect of F-Gas and CO2 Gas (Kilkis 2019a) Refrigerant ODP GWP ALT ODI R744 (CO2 ) 0 1 120 yr. 0.115 R227ea (F Gas) 0 3500 30 yr. 0.132 An Irreversible Cycle Figure 6 shows a closed-loop cycle about the effects of building heating and cooling on global warming and ozone depletion. Today most of the heating is achieved by heating systems using fossil fuels. These systems emit CO2 , which causes global warming. CO2 triggers more ozone depletion. Larger ozone hole permits more harmful rays such that global warming is accelerated and ice sheets are melted. More water vapor resulting from this melting process causes more global warming due to its greenhouse effect. Global warming means more cooling demand, by which cooling equipment currently relies on electric power generated mainly by fossil fuels, causing more CO2 . The only positive impact of global warming with CO2 emissions is less heating demand. However, because overall cooling loads involve latent cooling need (Humidity), their increasing impact on global warming and ozone depletion surpasses the reduced demand for heating. In cooling, ODI, CO2 , outdoor temperature, electricity demand increases while the chiller performance, COP decrease. This vicious cycle Fig. 6 Irreversible cycle of ozone depletion and global warming from the built environment Accelerating the Transition to 100% Renewable … 7 may only be broken by renewables on-site. The irreversibility circle for heating in Fig. 6 exemplifies how renewables may help to reduce the global crisis: • Replace fossil fuels from building heating by various waste and renewable energy sources, • This replacement will also support the ozone layer. • Eliminate refrigerant leaks and/or eliminate harmful refrigerants by using captured CO2 or by using hydrogen fuel cells, generated by water electrolysis with renewable energy sources, • Eliminate fossil fuels from electric power plants by with solar and wind power plants, • Reduce heating and cooling needs and transform to nearly-zero exergy buildings such that a better exergy balance is established between renewables and buildings. This will minimize exergy destructions and therefore avoidable CO2 emissions. On the other hand, Fig. 7 (Cowan et al. 2009) prooves that the cycle shown in Fig. 6 is indeed irreversible, because ozone-depleting refrigerant leakage ratios, LR are very slowly decreasing, according to a wide data scatter. This rate is even slower according to the least-squares fit by the Author of this Chapter. The small decrease in leakage rates is overwhelmed by the ever-increasing cooling loads. Figure 8 helps to explain the most recent climatic and environmental disasters in terms of the difference between the unit exergy changes, ε between the stratosphere and troposphere (by a factor of about 7), which form a thermal shear between both layers. This temperature shear is coming closer to the earth, resulting in severe floods, and more frequent and stronger tornadoes, which happen today at locations of previously unheard of around the globe. LR Least Squares Fit Fig. 7 The decrease in refrigerant leakages (Cowan et al. 2009) 8 B. Kılkış Fig. 8 Retraction of ozone layer and atmospheric temperatures (EPA 2019) How Renewable Energy Sources are Innocent? Just to use renewables at the energy source for decarbonization efforts is not enough. How we use them, where we use them, and in which order is quite important. Figure 9 shows a wind energy system, where part of the electric power is used in driving a ground-source heat pump. The conventional compressor of the heat pump contains a refrigerant, which inevitably leaks continuously with a known ozone-depletion potential, ODP. Although the wind turbine does not release CO2 (except manufacturing and installation embodiments), the cooling cycle of refrigeration at the same time releases waste heat to the atmosphere and in some large applications cooling towers are used, which have GWP. Although the entire system seems to be perfectly green, renewable, and environmentally sustainable, it is not, because it contributes to ozone depletion and global warming due to the fact that wind energy is not used in the best application and with the best equipment, which should be totally atmosphere-friendly. In order to increase the COP of the heat pump, heating or cooling load temperatures must be transformed to moderate levels. If this is a retrofit project and existing HVAC equipment will be kept, they may be optimally oversized instead of replacing them with low-exergy equipment. This needs to be balanced between additional pump or fan power demand, which may result in grid power need versus partial oversizing of the heat pump with higher COP (Kilkis 2000). Accelerating the Transition to 100% Renewable … 9 Fig. 9 Wind turbine operated heat pump has GWP, ODP, and CO2 emissions (Kilkis 2019; Kilkis et al. 2017) This example shows that for 100% renewable targets, the following measures need to be taken: • Track the renewable source (s) along the chain of emissions, demand, and energy transfer, • Develop atmosphere-friendly energy conversion systems and equipment, • Implement more renewable energy compatible applications like nearly-zero Exergy, or LowExergy (LowEx) buildings and similar applications, • Observe exergy balance between pumping and heat (and or cold) transferred in district energy (DE) system, • Minimize unit exergy destructions in the complete chain from supply to demand and waste. In this respect minimize the number of transformations from one form of power to another form of heat or vice versa. The same also holds for energy storage. Store energy in its original. Unit exergy destructions, εdes due to mismatches cause avoidable CO2 emissions, which are related to the exergy-based COP of the ground-source heat pump, namely COPEX. 10 B. Kılkış    T1  εdes = 1 −  {Heating or Cooling} T2 (3) COPEX (see Eq. 6) depends on how well the heat pump supply is suited to the heating or cooling demand. εdes is the unit exergy according to the ideal Carnot cycle between T 1 and T 2 . εdes = 1 − wCOPEX {0.85 ≤ w ≤ 1.0} (4) CO2 = 0.27εdes kg CO2 /kW - h of heat {Avoidable} (5) In Eq. 4, w is the adjustment factor for non-ambient exergy inputs, like a limited amount of waste heat, available in a building mostly originating from a fossil fuel expense, rather than wind or solar energy. This factor is about 0.85 in building applications like HRV applications in which the indoor supply air is further peaked by a boiler downstream. If there is no temperature peaking, then w is one. Equation 5 is based on converting any given εdes value to its CO2 emissions equivalent based on a standardized value calculated for a natural gas boiler with an average First-Law efficiency of 0.85 in the field and the unit exergy of natural gas (0.87 kW/kW), and unit CO2 emissions coefficient of natural gas (0.2 kg CO2 /kWh):   1 0.2 kg CO2 /kWh = 0.27 kg CO2 /kWh per unit εdes 0.85 kW/kW 0.87 COPEX = ψR εdem {Exergy destroyed upstream} εsup  εdss ψR = 1 − {Exergy destroyed downstream} εstrp ψR = (6) (7) (8) In Eqs. 7 and 8, ψ R is the Rational Exergy Management Model (REMM) efficiency, which watches the balance between the quality of energy among supply and demand points in the built environment. It must approach 1 in exergy-rational applications for minimum CO2 emissions. For any heat pump application alone, with COP > 1, ψ R needs to be multiplied by COP. The EU target for electrification with heat pumps for heating and cooling is not exergy-rational if a natural gas-fired thermal power plant combusting natural gas at T f = 2235 K and the grid electricity supplied is used by a heat pump with a COP of 3 for radiant floor heating at supply and return temperatures of 330 K and 320 K, respectively. For CASE 1 shown in Fig. 9 corresponds to grid power input from a thermal power plant COPEX is far less than one due to large exergy destructions (see Fig. 10). In the same token, ψ R , which is responsible for CO2 emissions is quite small. In a fully exergy-rational (COPEX → 1), composite renewable energy system Accelerating the Transition to 100% Renewable … 11 Fig. 10 Exergy flow diagram for the grid -operated heat pump (CASE 1) in heating mode, which is shown in Fig. 9 for Fig. 9, COP must approach to (1/ψ R ) = 28.6, quite unpractical. 283 K is the reference temperature, T ref . (1−320/330) × 3 = 0.1 {see Eq. 7, COP is 3} ψR = (1−283/2235)) {see Eq. 6) COPEX = ψR = 0.1 The virtual, Carnot-Cycle based source temperatures for solar and wind energies, T f are determined by Eqs. 6 and 9. ηw is the efficiency of the wind turbine. In = Sc  1− Tref Tf  0.95 (9) 0.95 W/W corresponds to the unit exergy at the surface of the sun (5778 K) relative to a reference temperature of 283 K on Earth if there was not any atmosphere. If I n is equal to the solar constant (outside the atmosphere) T f is 5778 K (Radiation from the sun taking place in a medium of nearly vacuum). In the real case of I n < S c , Eq. 9 applies for T f . (In the atmosphere). Tf = Tref (1 − ηw ) (10) From Eq. 10, the magnitude of the unit exergy, εsup of the wind turbine becomes equal to ηw . Then, CASE 2, which is wind turbine-operated heat pump shown in Fig. 9, may be solved, if the mechanical efficiency of the wind- to-electricity efficiency of the wind turbine, ηw is known. It is assumed that wind turbine-generated electricity is used to drive the heat pump. If ηw is 0.4, for example, then T f from Eq. 10 is 472 K. After replacing 2235 K with this value in Fig. 9, ψ R and COPEX become 0.23. CO2 (due to unit exergy unbalance between the kinetic energy of wind and heat (or cold) supplied by the heat pump) decreases to 0.1 kg CO2 /kWh of heat because εdes1 reduces to 0.3 kWh/kWh. This is a 2.6 times reduction from CASE 1. It may seem awkward to have a CO2 emission responsibility. In fact, this is an avoidable emissions responsibility, that is avoidable to a large extent by selecting a larger-capacity wind turbine, with higher efficiency, a higher COP of the heat pump 12 B. Kılkış and thus generating surplus electricity for other useful applications with higher unit exergy demand compared to heating or cooling only. These results and comments give us the fundamental drivers and points to take care of towards transitioning to 100% renewables. 3 Exergy and Renewables to the Rescue Decoupling economic development from CO2 emissions is the most critical challenge of the global crisis (Fig. 11). While both power and heat are required for economic growth and wealthy urbanization, CO2 emissions follow a parallel trend. 20 + 20 + 20 goals of EU, namely a 20% increase in energy savings, utilization of renewable energy sources, and efficiency, respectively each may reduce the increasing rate of CO2 emissions but cannot decouple it from economic growth. HSDI is the Human (Sustainable) Development Index defined by UNDP. Economic growth turns into Sustainable Development once decoupling is achieved by exergy rationality allowing natural sinking to take over. The compound CO2 emissions, including the effect of exergy destruction, is given in Eqs. 11a and 11b. There are two components, namely direct emissions, and avoidable emissions, of which the latter can be avoided by reducing exergy destructions (Kilkis 2011). Fig. 11 Coupling between emissions and development (Kilkis 2019) Accelerating the Transition to 100% Renewable … 13 (11a) (11b) With an increasing trend of transitioning to renewables, biogas, biofuel add-ons, and other technologies are already serving the second 20% target but at a slow pace. The third 20% target, namely efficiency, is also improving. For example, combined heat and power (CHP), condensing boilers, etc. are already approaching their theoretical limits, leaving not much room for improvement (Fig. 12). The first 20% target is also on the right track, with smart grids, DC underground lines, and energy-saving measures. Yet, the proposed fourth 20% parameter, namely ψ R remains unresolved and unknown, even though it has a large room for improvement. With existing technology and by simply changing the mindset from the FirstLaw to the Second-Law, this value may improve up to 80% and even more simply by Fig. 12 Triple improvement of HSDI, CO2 emission reduction, and ψ R (Kilkis 2019) 14 B. Kılkış ψR Fig. 13 The need for an integrated approach for cleaner cities. Derived from: (EEA 2018) innovative combinations of equipment in a circular economy approach. For example, the most polluted ten cities in Europe may be improved by increasing ψ R (see Fig. 13). An increase in ψ R , not only reduces the (1-ψ R ) term but, due to a decrease in exergy destructions, thermal and electrical power demands decrease as well as CO2 emissions. Thus, triple decarbonization is obtained (Fig. 12). In Eq. 11b and Fig. 11, three decarbonization goals need to be supplemented hereby with a fourth goal, namely exergy rationality, ψ R . Equation 11b clearly shows that CO2 emissions may be substantially reduced if ψ R is increased from 0.35 to a technically achievable value above 0.80. Even if the target for 100% renewables is achieved by solar heat, wind energy, solar PV farms, etc., such that the first term in the square brackets and the very last term are eliminated, CO2 may not be zero unless the renewables are utilized with the goal of ψ R → 1, which leads to the condition, namely EDR → 1. EDR is the Ratio of Emissions Difference: EDR = 1 − [CO2 /CO2 baxe ] (12) The term CO2base , which is 0.63 kg CO2 /kWh is the standard emission rate corresponding to 0.5 kWh thermal and 0.5 kWh electrical loads, c values of 0.2 kg CO2 /kWh for natural gas. 0.85 is a typical condensing boiler efficiency, and 0.35 is the power generation and transmission efficiency. Recommendations The above discussions reveal that the 2nd Law provides further insight and ability to decarbonize in a widely realistic and sustainable way, beyond where the 1st Law stops. In the quest of 100% renewables, as shown in Table 1, ψ R may simply transform all EU directive metrics. For cold processes where application temperatures are below T ref , (T ref /T s ) term in all equations is inverted (Table 2). ⎛ PESEX = ⎝1 − ⎞ 1 CHPEη Re fEη + CHPH η REFH η ×  2−ψR ref 2−ψR  ⎠ × 100 (13) Accelerating the Transition to 100% Renewable … 15 Table 2 Sample transfer functions for EU directives (Kilkis 2017) Sample EU terms 1st Law 2nd Law Comments Performance coefficient COP COPEX Multiply COP by ψ R Primary energy ratio PER PEXR (Inverse of PEF) Multiply PER by ψR Primary energy factor PEF PEFX PEF/ψ R . Apply separately to electric and heat Primary energy savings PES PES aEX Cogeneration applications. Equation 13. ψ Rref is 0.2 Ton-oil equivalent Mtoe MtoEX Multiply Mtoe by ψ RF a CHPEη and CHPHη are the partial electric and thermal power efficiencies, respectively. Their denominators are their reference values Exergy-Based Mtoe: Do not compare solar heat and oil: MtoEX =  1− Tref Tf 0.881  × Mtoe = ψRF × Mtoe (14) Here, ψ RF is indexed to the unit exergy of crude oil, εF , namely 0.881 W/W. 4 Case Study A solar PVT plant serves a Fourth-Generation district energy system (4DE). PVT plant generates both power and heat. Power is partially used to drive the circulation pumps in the district piping. Thermal power may be converted to cold by individual absorption (ABS) and or adsorption (ADS) units on customer site, on-demand. The rest of the generated power is distributed in the grid for electrical demand of different types and purposes, including mass transit. Figure 14 shows the basics of the system. The common mistake in the design and operation of such systems is the ignorance of the unit exergy difference between electrical and thermal powers. Among all ancillaries, which demand power circulation pumps need to be carefully optimized such that thermal exergy provided to the district, E XH in Eq. 15 must exceed the exergy demand of the pumps, ignoring other parasitic losses and ancillary demand. EXH > EXP (D, L) Fig. 14 District energy system with solar PVT plant (Kilkis 2019) (15) 16 B. Kılkış The term E XP is a function of the pipe diameter, D and the distance between the PVT plant and the district, L. For the limiting case of Eq. 15 and the given installed thermal capacity, C of the PVT plant, providing heat to the district between 330 and 320 K, serving radiant panels for heating and at the same time serving heat at 60 °C for DHW against Legionella risk.  EXH 320 K =C 1− 340 K  = 0.059C If for example, the power demand of the installed pump stations, is Ps is 15% of the thermal capacity, C, COP of the district energy system between the plant supply and district demand points looks quite favorable: COP = C C = 6.7 = Ps 0.15C (16) But COPEX tells a different story if the average PV efficiency is 0.15: COPEX = 0.059C[W/W] = 0.41 0.15C[0.95W/W] 0.95 W/W is the unit exergy of electricity. From Eq. 7, ψ R is 0.061 and the corresponding, avoidable CO2 emissions responsibility may be calculated from Eqs. 4, 5, and 6, which is 0.16 kg CO2 /kWh of heat delivered to the district. Therefore, although the solar energy source is 100% renewable, the CO2 emission responsibility is not zero and this solar system is not 100% renewable. In order to improve the exergy performance of the system, pipe diameter may be increased to reduce pumping power demand per meter of pipe, PS at an expense of more cost and embodied CO2 for the pipe material. The maximum one-way distance between the plant and the district L, namely L max is related to exergy (Kilkis 2019). Consequently, the PVT systems should ideally be located within the district. However, this condition concludes that every building, in this case, should have their own PVT panel on their roofs and facades. This eliminates district thermal power distribution exergy destructions and solar energy utilization rate shall approach 100%. Lmax < EXH PS (0.95) (17) Topics presented so far quantifies the need for the transition to the Second-Law of Thermodynamics to effectively investigate the means and measures of transition to 100% renewables. In this respect, renewables should be utilized by paying attention to the following: • The right quality of renewable supply, • To the right (exergy-balanced) application(s), • At the right order of utilization in the right cascade, Accelerating the Transition to 100% Renewable … 17 • At the right time, • At the right location, and • With proper storage without changing the form of energy, i.e. power to heat. 5 Barriers to 100% Renewables Despite the need and the great potential of renewables, especially in the built environment for decarbonization and replacing the use of fossil fuels, the progress in renewable energy uptake, especially in heating and cooling, is quite slow against several barriers. The main barriers that yet to be removed for faster market penetration and globally wider use are: 1. Mistakes in the Name of 100% Renewables and Decarbonization Following the renewable chain from the supply point, many ‘renewable‘ applications involve conventional systems and equipment, which are not exergy-compatible. Some of them need supplementary electric power from the grid, which is responsible for CO2 emissions and even ODI. Many systems and equipment also involve GWP, like in Fig. 15. Equation 18 may approximate the equivalent CO2 emission of the equipment, if their refrigerant types (GWP), annual charge amounts, R and annual leakage ratios, LR are known. Fig. 15 Solar energy is not a complete solution alone. It depends on how we use it 18 B. Kılkış Fig. 16 Exergy rationale in geothermal energy (Kilkis 2019a) CO2 ∼ =  GW P 1   LR × R {kg CO2 /year indexed to CO2 refrigerant} 100 (18) Equation 18 assumes that new refrigerants have nearly zero ODP. If the refrigerant properties are, R = 0.4 kg, LR = 10%, GWP = 1200, then, CO2 emission equivalency is approximately 48 kg CO2 /year, although the energy source is purely solar. This figure does not include additional emissions when supplementary grid power is used. When electricity generation from low-exergy heat is considered, because power has a higher unit exergy, this idea will not work unless the 1st Law is also accounted for. Figure 16 shows two alternatives: 1-power generation with Organic Rankine Cycle (ORC) with 8% 1st Law efficiency (ηORC ), 2. direct utilization of heat at 80 °C (533 K). Alternative 1 has ODI responsibility and Alternative 2 releases CO2 emissions unless re-injected to the ground. In Alternative 1, the exergy output, E XE is 0.08 kW/kW. In Alternative 2, E XH is higher: 0.2 kW/kW. Therefore, depending on the geothermal temperature, it may be better to keep the heat as heat. Again, although the energy source is purely renewable (geothermal), the end result is not 100% free from harmful emissions. Their harmful emissions responsibility must also be compared. These examples show that exergy is a game maker despite many describe it as a game-changer: it changes the game but also shows the proper strategies for 100% renewables. 2. Insufficient Legislation Although 128 countries have power regulatory incentives and mandates according to Fig. 17, only 29 countries have incentives or mandates for renewables in heating and cooling policies. Similarly, only 17 countries have adopted targets towards 2050 for zero CO2 (REN 2019). 3. Insufficient Understanding of CO2 Emissions CO2 emissions are considered only in terms of its direct component without compounding with the avoidable component due to exergy destructions. Buildings already have the largest share of direct CO2 emissions, which is shown in Fig. 18. Depending mainly on fossil fuels, their ψ R value does not exceed 0.10. For example, if a natural-gas condensing boiler is used only for space heating, ψ R is just about 0.06. The rest of the available exergy is destroyed. The result is a high avoidable CO2 emission rate, even more than direct emission. When compounded with the already Accelerating the Transition to 100% Renewable … 19 Fig. 17 The number of countries with renewable energy regulatory policies by sector (REN 2019) Fig. 18 Sectoral breakdown of energy consumption-based global CO2 emissions (IEA 2018) biggest share in the direct emissions, buildings become the most responsible sector, which further increases with the world population and modern urbanization. 4. Lack of Complete Interpretation of Renewable Power and Heat Thermodynamics All ratings and economic feasibility of renewable power (electricity) are based on the quantity of energy utilized from renewables in the built environment. This is the First Law of Thermodynamics. This law does not question downstream of the power generation about where this renewable energy is used and how it is used in terms of quality of energy both on supply and demand sides. This is the subject matter of the Second Law. Electric power has indeed the highest quality of energy (Exergy) and must be allocated to quality-balanced demands deserving such high quality. For example, if the electric power generated from a wind turbine is directly used to heat 20 B. Kılkış a building by electric resistance heaters, the First Law efficiency of using the electric power in heating is almost 100% but the rationality in this process according to the Second Law is only around 5%. This means a large portion of the execution potential of several useful applications is irreversibly destroyed and the wind turbine electricity becomes almost useless. More importantly, the exergy destructions directly translate to CO2 emissions responsibility, because somewhere else some other fuel spending is needed to be used to make-up this exergy loss. Therefore, without reference to the Second Law, the real virtues and potential hidden environmental risks of renewables may not be holistically understood. This is a serious barrier especially on the global warming emissions responsibility because although the wind power is almost free of CO2 and other harmful emissions, the same green energy source becomes grey if it is not sufficiently well evaluated in terms of quality downstream of power generation. This will be discussed in more detail in the following sections. 5. Fossil Fuel and Gas Craze Lately, the thirst for fossil fuels is becoming a craze, which is mainly fueled by international political interests. The same also holds true for nuclear energy. The situation is so critical that many countries are facing serious conflicts and sanctions. Some countries like Turkey have become a transitway on both land and sea, so much that the fossil fuel (Natural Gas) pipelines are almost becoming a gas highway extending thousands of kilometers. The Mediterranean Sea has become a focal conflict for natural gas exploration. For every cubic meter of natural gas surfaced from deep-sea wells, the emission potential of CO2 is about 5 kg. This is a great conflict between explorations and decarbonization efforts. Relatively low fossil fuel prices (They do not include environmental and global warming costs with all its consequences like floods, hurricanes, etc.) mask the global warming emergency and reduce the economic feasibility of renewables, although their prices are dramatically dropping. In this manner, for example, no one remembers to generate hydrogen with renewables and store, transport and use it. This seems to many people a myth or luxury. On the contrary we do not have the luxury of exploring, extracting, and using fossil fuels. This argument also holds true for nuclear energy. 6. Deliberate Ignorance of the Second Law The Second Law, which deals with the quality of energy (Exergy) is considered to be a game-changer and treated in most cases as a threat to the economy and industry. The industry is not alone in this kind of resistance to the rationality of energy use. For example, World Energy Statistics Report does not refer at all to exergy (IEA 2018). Energy Efficiency Indicators released so far deal with only the quantity of energy (IEA 2018). In the EU there is only one concerned scientist group that proclaims the importance of exergy: The only European initiative about the inclusion of exergy in EU energy analyses is published by Science Europe (Science Europe 2016). In quote: Educators, researchers, policymakers, stakeholders, and citizens are urged to consider energy and natural resources on the basis of exergy, and in doing so understand that: Accelerating the Transition to 100% Renewable … 21 Fig. 19 Net exergy gain is negative in a condensing boiler • exergy measures energy and resource quality; • exergy-destruction foot-printing improves industrial efficiency; • exergy offers a common international energy-efficiency metric; • Optimal use of limited mineral resources by the application of exergy rarity; • and exergy should be integrated into policy, law and everyday practice. This proclamation shows how important it is to factor in exergy for 100% renewable transition. Many HVAC systems and equipment known and sold as energy-efficient and green are not energy rational at all. Two examples are given below: a. Condensing boiler: Condensing boilers are unfair alternatives to renewables due to their very high First Law efficiency up to 97% peak. However, Figure 19 shows that actually, they consume natural gas by 23% more CO2 responsibility compared to a conventional boiler. Therefore, an exergy rationality metric is essential like ψ R for comparison purposes. First, they reduce the combustion temperature in order for condensation. Then, they need a heat exchanger and a small additional (or oversized) fan. b. Waste Heat Recovery: It is claimed that waste heat recovery from the exhaust ventilation air in buildings is highly efficient and cost-effective by referring to the First Law. Without considering the unit exergy difference between the electricity consumed by extra fan power in order to overcome the waste-heat exchanger pressure drop, and the thermal exergy recovered the COP indeed seems to be quite preferable, but COPEX value is much less than 1. A typical data is given in Table 3. The solution could be a better optimization of the heat exchanger and to utilize more efficient fans and electric motors with variable frequency drive in order to optimize the operation from an exergy point of view (Kilkis 2020). 7. The Economy is not Everything We are paying for the quantity of energy but we are using only the quality of energy Prof. Peter Novak, ASHRAE 22 B. Kılkış Table 3 Typical data for heat recovery ventilation Solar panels are simply sold with e/m2 or e/kWpeak price based on the 1st Law, which does not make much sense since the type and the function of solar systems are much different. How much quality of energy they deliver is not asked. A cheap FPC only generates hot water with low exergy, a more expensive PV panel generates electric power with high exergy but wastes the remaining heat collected, a PVT system, generates both heat and power with higher exergy than the others, at a higher cost. Total efficiency is not a simple addition of power and heat, because of their different unit exergy. 1 kW of heat and 1 kW of cold also have different exergy. In order to avoid this confusion, Exergy-Levelized Cost, ELC has been developed, combining exergy rationality, price, PC, embodied costs, EM, panel area, A, and weight, W (Kilkis 2019).  ELC = PC+EM (Wp ) Itest Ap [εsup E ηE +εsup H ηH ] ψR Ap  {Euro/kWEXpeak /m2 } (19) W p is panel weight (kg), PC is in Euros. EM is in Euros/kg. Subscripts E and H stand for electric and thermal outputs respectively. ELC corresponds to design (test) conditions. 8. Irrational Exergy Allocation US allocation of electricity for residential and commercial sectors in 2008 is shown in Fig. 20. In the residential sector, space heating, cooling, and DHW are responsible for 42.5% of the total consumption. This is a large waste of exergy, because most of the demand, including some of the cooling, may be achieved by non-electric systems with waste or solar thermal. At least a solar trigeneration system could be used for Accelerating the Transition to 100% Renewable … Residential 23 Commercial Fig. 20 US electricity consumption in residential and commercial buildings (OECD/IEA 2018) minimum exergy destructions. Even if renewable electricity is generated first, on-site or near-site, the exergy question pends whether it is the best way to use it for heating. In commercial buildings, HVAC demand is about 40%, of which many of them may be satisfied by non-electric systems. This is a problem of misallocation of energy sources at the wrong applications in the wrong order. 6 Is Renewable Electricity Good for Heat? Not so: Electricity Was not Created for Heating The use of high-exergy electricity for low-exergy applications is a chronic habit, which causes large exergy destructions. For example, China has recently developed a strategy about heating with wind electricity in her Northern provinces. Indeed, in cold climates, heating demand high but wind potential is abundant. This seems a good idea but the use of wind energy in space heating is a serious exergy misallocation. The problem is compounded by the low urbanization density and it is rather difficult to implement district energy systems and to rely on waste heat of near-by factories. On the contrary, in hot climates, electricity demand for cooling is increasing due to global warming and heat island effect, especially in dense urban settlements. In either case, extreme climates mean longer heating seasons with dispersed demand or longer cooling seasons with intense demand. The more the heating or cooling energy demand is, the more are the CO2 emissions from conventional HVAC systems in buildings. Therefore, for cleaner air and less global warming, transformation into renewable energy systems gains prime urgency. These targets must be achieved by a holistic approach with the most exergy-rational objective. For example, almost 95% of the electrical energy may be transformed into many useful applications. However, if wind energy is first transformed into heat and used only for heating, a large loss of opportunities about remaining potential uses are lost (Irreversible loss of quality). This causes additional but avoidable CO2 emissions. Figure 21 shows five methods of wind-to-heat strategy and hydrogen economy on a city level (Kilkis 2019). Method 24 B. Kılkış 1 REFERENCE 2 3 4 5 Fig. 21 Five wind-to-heat methods. The reference case is a coal-fired boiler or stove (Kilkis 2019) 1 is direct resistance heating with wind electricity. Method 2 is heating (or cooling) with a ground-source heat pump, driven by wind electricity. Method 3 is hydrogen production by electrolyzing water and then storing and using in a fuel cell for both heat and power again. The system may be interconnected with grid power. In this case, GWP exists. Method 4 is hydrogen- biogas fueled combined heat and power (CHP). Cooling is possible by adding an absorption system. Ultimate utilization of wind power is a hydrogen city, which is Method 5. Table 4 subjects their sustainability to 12 metrics. PEF = 1/PER (20) PER = COP = ηI ηW T (21) TI = ηi ψR (1 − ODI ) (22) Accelerating the Transition to 100% Renewable … 25 Table 4 Results of the performance metric data for five alternatives (Kilkis 2019) Metric Fossil fuel Wind Coal Electric Reference Renewable methods Hydrogen Boiler Stovea 1 2 3 4 5 0.60 0.35 (0.45)b (0.45) 0.38 0.40 0.55 1 ηI (or ηWT ) 2 ηII 0.0378 0.0122 0.016 0.56 0.27 0.29 0.47 3 PEF – – 1 1 1 1 0.90c 4 PER 0.60 0.35 0.45 1.12 0.38 0.40 0.55 5 COP 0.60 0.35 0.45 4 0.38 0.40 0.55 6 COPEX 0.0378 0.022 0.016 0.56 0.27 0.29 0.47 7 ΨR 0.063 0.063 0.035d 0.14 0.72e 0.72f 0.85 8 CO2 0.83 1.43 0g 0 0 0 0 9 0.78 1.34 0.80 0.71 0.232 0.24 0.12 10 CO2  CO2 1.61 2.77 0.80 0.71 0.232 0.24 0.12 11 ODI 0.115 0.115 0.14 0.135 0 0.023 0.015h 12 TI i 0.0336 0.0196 0.0135 0.121 0.2736 0.280 0.460 NOTES for Table 4 a Assuming that the same type of coal is used b Typical electro-mechanical wind turbine efficiency c Due to hydrogen and DC power district network losses d This is a value, which is lower than a boiler case e Excluding PV system contribution f Without the ORC type of bottoming cycle g Excluding embodied CO emissions 2 h With industrial CO capture and use for refrigerating cycles 2 i TI is the transformation index, which combines the First and Second Laws and represents harmful emissions by ODI. See Eq. 22 ηII = ψR ηl = COPEX (23) 7 Sustainable Solutions for 100% Renewables This section identifies ten steps for a sustainable future with 100% renewables, based mainly on the Second Law. These ten steps are explained below. Step 1. Holistic Approach for Sustainable Build Environment Today, we should not only speak about sustainable buildings but sustainable and smart cities for 100% renewables. A smart city is not just a city of smart automation controls, smart transport, driverless buses, and electric cars, etc. A smart city is a complex combination of individual buildings that generate, share, and utilize the 26 B. Kılkış Fig. 22 Four tiers of the holistic district energy model with LowEX renewables (Kilkis 2019b) energy with the maximum use of the quality of energy as well as the minimum use of the quantity of energy, while the environment is sustained. For example, the city of Delft is planning to rent the suitable roof areas of townhouses to install photovoltaic (PV) and photo-voltaic-thermal (PVT) panels to generate, share and utilize solar energy collectively at city-wide and grid-wide, not only in terms of power but also the heat of different forms. Therefore, we cannot speak any more about an individual building but a collection of buildings. The term collective is a keyword for future cities and buildings. Therefore, one needs to analyze buildings with a holistic approach integrated with the built environment at large with all its upstream and downstream. In such an approach, energy/exergy and water nexus, by using the Rational Exergy Management Model will be successful. Figure 22 shows such a holistic view of a district energy system in four tiers, starting from the renewable energy sources, which is the first ring of the exergy flow and ending at individual buildings, which are also prosumers, coupled with heat pumps of optimum capacity achieved by optimally insulating the building and oversizing the heating or cooling equipment to improve the COP of heat pumps (Kilkis 2019b). EMR is the payback period for the embodiments of renewable energy systems and equipment by their energy and CO2 savings during operation. If a heat pump is necessary for upgrading the supply temperature, T f to be compatible with the conventional equipment, an optimum T f may be determined, which comprises partial oversizing of both the heat pump and the equipment. By ignoring the incremental changes in the power demands of pumps (or fans), Eq. 24 is used, where C eq and C hp are the life-cycle cost-design operating temperature factors. T a is the dry-bulb indoor air temperature (Kilkis 2000). The negative term is for cooling.  Topt = ± Ceq + Ta Chp Step 2. Decide Whether Net-Zero Energy or Net-Zero Exergy Comes First (24) Accelerating the Transition to 100% Renewable … 27 In the quest of reaching the goals of the recent Paris Agreement for reducing CO2 emissions, net-zero energy buildings (NZEB) and net positive-energy (NPEB) buildings are becoming common (IEA 2018). Although universally accepted several definitions for NZEB have been published, there are other issues to be resolved (US DOE 2015). A major issue that has not been addressed in the building and energy sector is the fact that with the increasing share of renewable energy resources and systems in the built environment at different exergy levels, their exergy differences and the need for exergy balance between the supply (resource) and the demand points (built environment, such as buildings) need to be identified and their importance in optimum and net-positive solutions have to be acknowledged (Kilkis 2011). In this respect, the shortcomings of the First- Law are demonstrated in the following two examples. Example The Net Zero Exergy Building (NZEXB) definition becomes more important than the NZEB definition while renewable energy systems become more diversified and connected to the district. The temperatures of the heat received from and supplied to a district system by a presuming building or the cold service received from the district and supplied to the district must be taken into account, exergy-wise. For example, in Fig. 23, an exergy exchange deficit occurs if the presuming building delivers 30 °C water from its solar FPC system to the district but receives 40 °C water from the district in the same quantity over a given period of time. A similar deficit occurs for cooling because exchange temperatures of the chilled water supply and return between the district and the prosumer building are different. This building is a net-zero energy building while it exchanges both electrical and thermal energy in equal quantities. Fig. 23 A net-zero energy building is not necessarily a net-zero Exergy building 28 B. Kılkış If for example, on an annual basis, the building receives 10,000 kWh of AC electrical energy with RMS of 5% and provides 10,000 kWh AC electrical energy with RMS of 10%. There is an electric power quality difference in terms of RMS. In the same period, the building receives 15,000 kWh of heat from the district (supply) at an average temperature of 353 K (80 °C) and provides heat of 15,000 kWh to the district (return) at an average temperature of 343 K (70 °C). In terms of the ideal Carnot Cycle, thermal exergy exchanges are: Exsup = (1 − 283/353) · 15000 = 2974.5kWh, Exxet = (1 − 283/343) · 15000 = 2623.9 kWh. Obviously, although the net energy (Quantity) exchange is the same, there is net annual exergy (Quality) exchange deficit of 350.6 kWh. A similar condition holds true for the cooling season. Obviously, this building is not a net-zero-exergy building, because the supply and return exergies are not equal. Consequently, the district should be equipped with exergy meters rather than calorimeters in order to establish a fair distribution of charges among the energy and power supplier (district), subscribers and prosumers in the district. This is especially important for-low exergy districts and buildings utilizing low-exergy sources. Step 3. Implement New Metrics Leading to 100% Renewables So far, exergy is mentioned and used only at a scale of a building, which defines only a low-exergy building. The following definitions were developed in order to expand the concept to district and city levels. NZCB: Net-zero carbon building is a building, which on an annual basis has an EDR of 1. nZCB: Near-zero carbon building is a building, which on an annual basis has an EDR equal or greater than 0.80, but less than one. NZEXB: Net-zero Exergy Building is a building, which on an annual basis, exchanges the same total exergy of heat and power with the local district energy system. The exergy of power and different thermal energies are calculated separately on the ideal Carnot Cycle and then summed. nZEXB: Nearly- zero Exergy Building is an individual building or compound connected to the district, which on an annual basis provides at least 80% of the total exergy of heat and power to the district as the total exergy of heat and power received from the district. LoWEXB: Low-Exergy Building is a building, which can satisfy its heating loads with low exergy sources at about 40 °C and sensible cooling loads at about 15–18 °C. NPEXB: Net-positive Exergy Building is a building, which on an annual basis, supplies a surplus of total exergy of heat and power to the local district energy system to the total exergy of heat and power received from the district energy system. NZEXDa : Net-zero Exergy District is a district, which has its own (local) centralized and/or distributed energy (Sub-stations) system, which on an annual basis, supplies the same total exergy of heat and power to the local district energy system Accelerating the Transition to 100% Renewable … 29 Fig. 24 NZEXD and NZEXB in 100%-renewable build environment NZEXB 4DE NXEXD as the total exergy of heat and power received from them. This is generally known to be the 4th Generation District Energy System or beyond (> 4DE). Figure 24 shows the physical relation between NZEXD and NZEXB. MtoEX: Another major universal flaw and energy-related literature is the use of Mtoe (Megaton of oil equivalent), which is a First-Law definition for a given quantity of energy. Crude oil has a standardized adiabatic flame temperature, about 2373 K and the unit exergy, εsup is 0.881 W/W in terms of the ideal Carnot cycle. Its exergy, E X is 10.25 MW-h for an energy amount, Q of 11.63 MW-h for one ton of crude oil. Now consider 11.63 MW-h of hot water supplied by solar energy at 50 °C (εsup = 0.124 W/W). According to Mtoe definition, this amount is exactly 1 Mtoe. In contrary to this misleading equivalency, 11.63 MW-h of 50 °C water has only 1.44 MW-h exergy (0.124 W/W × 11.63 MW-h), which is equivalent to only 0.14 ton of oil (1.44/10.25). Evidently, the exergy equivalency of solar heat and crude oil does not exist. Step 4. Decarbonization With the Second-Law Referring to Fig. 11 and Eq. 11b, five major parameters may be identified for improving the overall efficiency and CO2 emissions. These are: 1. 2. 3. 4. 5. Type of fuel or renewable energy source Equipment and plant efficiency (First-Law) Exergy Rationality, defined by ψ R . Plant and grid power transmission efficiency, transformer losses, etc. Power loads. Step 5. Avoid Mistakes in Renewable District Energy Systems District energy systems can be of the best instruments towards 100% renewables because they allow optimally clustered and exergy-rational hybridization of renewable energy systems. Furthermore, central heating and cooling through a district network are generally more efficient. But this latter statement may not hold true from the exergy point of view. Therefore, a careful exergy rationality analysis is in order. Geothermal district heating is one of them. Geothermal District Heating: In the City of Afyon geothermal energy at a wellhead temperature of 96 °C (369 K) is used for district heating (Şahin C and Gürler 2019). According to Fig. 25, the re-injection temperature is 48 °C (321 K). The wellhead flow rate is such that 6 MW of thermal power is available. Before utilization 30 B. Kılkış Fig. 25 Afyon geothermal energy district heating system layout (Şahin C and Gürler 2019) of the heat, the geothermal brine is kept in an open-air pool for cooling down the supply heat to 90 °C (363 K), because the piping material used in the district network cannot withstand higher temperatures. This causes exergy destruction of at least 0.45 MW to the atmosphere with large amounts of CO2 , which has a global warming potential (GWP). GWP also translates to ODP (Eq. 3). Evaporation further reduces the available geothermal power and increases the GWP. District loop pumping station requires 2 MW of electric power. The result is a low COPEX value, which in this case is 0.202 if the system is treated to be a simple heat pump. On contrary, the COP value is 2.77, which is high enough to mislead that the system is efficient enough despite Ψ R is only 0.313, which means that large amounts of exergy destructions take place in the system, which reflects avoidable but unaccounted CO2 emissions by the First Law. How the system may be improved for minimum exergy destructions and better utilization of the geothermal energy towards 100% renewables, another study of the Author analyzed ORC and ground-source heat pump combination, which is shown in Fig. 26. In order to make the situation more exergy-critical, a lower well-head temperature (exergy) of 80 °C was chosen. Net exergy is the sum of electrical output and the thermal output minus the sum of exergy demand of circulation pumps and the cooling fan. EXT = EXE + EXH − EXP − EXF COPEX = EXT (EXP + EXF ) (25) (26) The power is split between the building and a ground-source heat pump, X providing comfort heat (or cold). If X is equal to zero, then this is the all-electric case, if X is equal to one, then this is an all-heat case. Calculations for ψ R by using Figs. 27 and 28 show that at such a low source temperature it is slightly more rational to Accelerating the Transition to 100% Renewable … 31 Fig. 26 Geothermal energy, ORC, and heat pump in a district (Kilkis 2019a) Fig. 27 Direct geothermal district heating Tf Tapp Fig. 28 Geothermal power with ORC Tf 32 B. Kılkış use geothermal heat directly. 353 K is the geothermal source temperature, T f at the wellhead. For biogas or natural gas, this temperature is the Adiabatic Flame Temperature, AFT. T ref is the average environment temperature, which may be taken to be the average global temperature of about 14 °C (290 K) (Universe Today 2019). For cold processes where the temperatures are below T ref , the term (T ref /T app ) is inversed. REMM shows that direct geothermal heating is slightly more exergyrational than just ORC power generation in this case. This requires a composite index for the quantity and quality of energy in a system of systems, namely Composite Rationality Index, C R :  ψR =  K 1− 333 353 K K 1− 283 353 K  1− εdes =1−  ψR = 1 − εsup 1−   = 0.286  283 333  283 353 = 0.243 CR = ηI × ψR or, (27a) CR = COP × ψR (27b) For the geothermal district heating-only case, if the efficiency ηI is 0.65, then C R is 0.185. If the COP of the ORC system is 0.10, then C R is 0.024. Consequently, the reduction potential ratio R of avoidable CO2 from the carbon stock may also be calculated (Kilkis et al. 2017): (2 − CR )ORC = 1.2 (2 − CR )District R= (28) This result shows that ORC and district cases have similar exergy rationality, a closer look and proper selection at low supply temperature save about 20% from avoidable CO2 emissions. For the economic analysis, the exergy rationality cost, C EX may be proportionated to the number of exergy destructions is used for economic analysis destructions. Here, c is the average unit cost attributable to exergy destructions, including climatic disasters. The following exergy-based equations were derived for the specific purpose of the analysis.  εdes εs CEX = c (29) EXE = ηORC (1 − X ) (30) ηORC = a + bT1 (31)  EXH T3 = XCOP 1 − T4  COP = g + h(TR − T3 ) (32) (33) Accelerating the Transition to 100% Renewable … 33 Fig. 29 Break-even temperature for heating or power (Eq. 37) (Kilkis 2019a) Xopt = EXP = c + dX 2 (34)   −f EXF = eηORC (35) COP − ηorc {0 ≤ X ≤ 1} 2d (36) If COP, ηORC , and d are 4, 0.1, and 3 respectively, then X opt is 0.65. Although the First-Law, in this case, gives the same X opt with a positive energy quantity, the exergy is negative, meaning that the system is not rational yet towards 100% renewables. Figure 29 shows that there are two regions regarding the optimum solution in terms of the break-even temperature, T e . If the geothermal source temperature is higher than T e , then ORC system is preferable if waste heat is utilized. Otherwise, the system must be an all-heat system (X = 1). Equation 37 solves T e . Te =  COP 1 − b T3 T4  −a (37) X opt shows that COP, ηORC and coefficient d of the power demand of pumps and fans are the major players in the success of the renewable energy system. Often the pump and fan exergy demand are ignored but sometimes included in energy analysis. According to Eq. 37, T e gets more relaxed with an increase in a and b, which improves the ORC efficiency thus ORC becomes more favorable. If, COP increases then T e increases in favor of the heat-only case. It must also be noted that both the ORC unit and the heat pump emit ozonedepleting chemicals (ODC) and this must be kept in mind in questioning how ORC systems are environment-friendly when coupled with geothermal energy and heat pumps. Geothermal energy sources also emit chemicals and H2 S gas besides CO2 . 34 B. Kılkış Unless these non-condensable gases are completely retrieved, the environmental benefits need to be seriously questioned. Step 6. Accelerate the Transition with Exergy Futurism Table 4 about renewables for heating in terms of wind energy, for example, shows that the ultimate solution is to transform renewable energy sources into a hydrogen economy (HE) on a grand scale. The first step in accelerating such a target is to design passive hydrogen buildings with on-site, active hydrogen and renewable energy components. Then these hydrogen buildings may be connected to a hydrogen grid, which is fed by a central plant, composed of all available renewable and waste energy resources and systems. Then passive hydrogen buildings become active hydrogen buildings, which exchange energy and water, completing an energy/exergy/water nexus (Prosumer). According to Fig. 30, a hydrogen house with its own active minihydrogen economy, its Ψ R is 0.72. With the partial contribution of PV cells, Ψ R value reaches 0.85. Then the corresponding CO2 emission is only 0.166 kg CO2 /kWh of heating excluding PV system contribution. This is almost a ten-fold CO2 emission reduction potential, compared to a coal-fired boiler case. Figure 31 shows the Hydrogen house. CO2 = (0) + 0.83 × (1 − 0.80) = 0.166 kg CO2 /kWh of heating. {Without PV System} CO2 = (0) + 0.83 × (1 − 0.85) = 0.12 kg CO2 /kWh of heating. {With PV system contribution}  313 K   283 K  1− 333 K + 1− 303 K  283 K  ψR = 1− = 0.72 1− 515 K According to Eq. 10, the virtual Carnot-Cycle equivalent supply temperature, T f of the wind turbine is 515 K for an average First-Law efficiency, ηI of 0.45: Tf = Tref 283 K = = 515 K. (1 − ηI ) (1−0.45) Step 7. Transform to Hydrogen Cities Fig. 30 Wind to hydrogen for space heating with fuel cell Tf = 515 K ELECTRICITY 333 K εdes1 313 K HEAT 283 K εdes2 303 K Accelerating the Transition to 100% Renewable … 35 ηW = 0.45 Fig. 31 Integration of wind and solar for heat and power in a hydrogen building (Kilkis 2019) This step is the grand solution for the long-run strategies for renewable energy systems. A system of hydrogen homes, which are prosumers be blended into hydrogen cities for maximum exergy rationality, in terms of ψ R value, which may reach 0.95 with carefully optimized designs. Hydrogen is distributed in the district with pipes, which consume much less power than hydronic thermal distribution. Existing natural-gas pipelines may be upgraded for medium-pressure hydrogen transport. Figure 32 shows the already existing hydrogen network in the Netherlands. For heating purposes, fuel cells or micro CHP units (smaller than 50 kW power capacity) are installed onsite. The success of the hydrogen economy depends on the development of new and retrofit hydrogen energy buildings. Figure 33 shows the active hydrogen house concept, which exchanges hydrogen and power with the grid and water with the municipal water network. Impact of Hydrogen on the Ozone Layer: There are claims that hydrogen fuel could widen the ozone layer due to leakages of the process chain and utilization (Jacobson 2008). In spite of these claims, there is a scientific consensus that the CO2 equivalence of hydrogen is 4.3 megaton of CO2 per 1 megaton emission of hydrogen over a 100-year time horizon. The plausible range between 0 and 9.8 express 95% confidence. On this basis, although the impact of hydrogen emissions on the global climate is very unlikely to be zero and it is very likely that it will be small. If a 36 B. Kılkış PERCENT OF H2 PIPELINES Netherlands 237 km 15% Belgium 613 km 40% France 303 km 20% Germany 376 km 25% Fig. 32 Existing hydrogen network in the Netherlands (Kilkis 2020, Polar Teknoloji) Fig. 33 All DC-solar-active hydrogen hybrid net-zero/positive exergy building Accelerating the Transition to 100% Renewable … 37 1% leakage for the entire hydrogen system is considered, then the global warming consequences are indeed very likely to be small. However, the ODI of hydrogen gas leakage is not zero and is roughly one-fifth of CO2 . ODI H2 = ODI CO2 = 0.115/5 = 0.023. Hydrogen cities with small ODI with an associated small GWP and 1% leakage seems to be the best alternative for storing and utilizing wind energy along with other renewables. Active Hydrogen Home: Figure 33 shows an active hybrid house connected to the hydrogen grid. This building is an active hydrogen house because it generates electric power on-site with solar PVT and exchanges it with the grid. Its on-board fuel cell converts grid hydrogen to both heat and power. It stores hydrogen gas (not shown) and also water. An electrically operated GSHP heat or cools by radiant panels. ABS or ADS system may also be used for cooling. Step 8. Make The Right Choice In Solar Energy- FPC, PV, or PVT? There are several ways to harness solar energy, depending upon what the main demand is. The simplest is a solar flat plate collector, which only generates hot water in summer. Solar Flat-Plate Collector (FPC): An FPC delivers only heat between supply and return temperatures, T sup and T ret , respectively. Figure 34 shows that exergy is destroyed between T f -T out (εdes1 ) and T sup -T ref (εdes2 ). Major exergy destruction (εdes1 ) is upstream of the useful work because no electricity or any other useful work with higher-exergy is generated. In this case, the Rational Exergy Management Model (REMM), gives the rationality metric by, ψ R.   ret 1 − TTsup εH W = 0.24 ψR = = εs 0.557 Solar PV: PV cells generate only power at a higher exergy level. This is shown by the Exergy Flow Bar in Fig. 35. Starting from the frame temperature of the PV panel, T E , major exergy destruction takes place downstream of the useful application. If for the same solar insolation level, the PV panel frame temperature, T E is 353 K, then Fig. 34 FPC with T f = 638.8 K, T ret = 288 K, T sup = 333 K, T ref = 283 K 38 B. Kılkış Fig. 35 Simple solar PV system ψ R will be 0.64. ψR = 1 −   1 − 283 εdes 353 = 0.64 =1− εsolar 0.56 Conventional Solar PVT: Whether exergy is destroyed upstream or downstream of the useful work, a substantial portion of the available solar exergy is destroyed. However, when PV and FPC systems are coupled, exergy destruction decreases with two smaller exergy destruction points left. The effect of active cooling of the PV cells is revealed in Fig. 36 by a lower T E (330 K). However, T sup needs to be low for effective PV cooling (313 K). For T ret = 303 K:  313 K   283 K  1− 330 K + 1− 303 K εdes1 + εdes2   =1− = 0.79 ψR = 1 − 283 K εsolar 1− 638.8 K Fig. 36 Conventional solar PVT system without circulating pump losses Accelerating the Transition to 100% Renewable … 39 For actively cooling a PVT, a coolant fluid is circulated in the panel and its hydraulic ancillaries by a pump or fan. This parasitic loss is mapped to the exergy flow bar by T E ’.  TE 1− Tf    TE · (1 − c) = 1 − Tf (38) The term c is the ratio of the parasitic power exergy demand to the PV output. If c is 0.05, then, T E ’ is 336 K, meaning a decrease in the ψ R from 0.87 to 0.79. Such a decrease like 10% requires a major reduction or elimination of pumping need. Due to the interrupted nature of solar energy, an external thermal storage system (TES) is necessary. In order to understand the mechanism better, a holistic model was developed, which is shown in Fig. 37. This figure shows how much the overall PVT system is complicated with five interconnected tiers, namely the PVT panel itself (Tier 1) the fluid circulation system (Tier 2), a thermal storage system with its own ancillaries (Tier 3), temperature peaking system (Tier 4) and load demand points in the building (Tier 5). The net total exergy output, E XT of such a composition is given in Eq. 39. E XE is the power exergy output, E XH is the thermal exergy output, E XP1 is the power exergy demand of the primary fluid circulation system, and E XTES is the exergy destruction due to heat loss of the thermal storage system to its environment. The insulation level may be another subject of optimization, which is excluded in this model. The symbol E XTP stands for the exergy required for temperature peaking by the unit TP in Tier 4, if necessary, on the demand side. All electrical systems in Tiers 1 to 5 operate on DC electricity without conversion to AC, thus eliminates inverter (IN) losses. All tiers depend upon the volumetric fluid (or gas) flow rate, V̇ , which must be dynamically controlled and optimized for maximum E XT (EU 2016). The exergy demand for fluid circulation for PV cooling is crucial such that the exergy Fig. 37 Holistic model for a conventional PVT system (Kilkis 2019) 40 B. Kılkış gain by preserving PV efficiency may sometimes be less than the exergy demand of the pump. (39) (40) Figures 38 and 39 show that the maximum total exergy output E XT (74.5 W) is less than the output E XPV that a PV system alone could provide (97 W) (EU 2016). Performance metrics for different solar panels are summarized in Table 1, Fig. 38 Contradiction between PV power output and thermal power output (Kilkis 2019) Fig. 39 A case study, T sup = 293 K (Kilkis 2019). The maximum improves only 4W Accelerating the Transition to 100% Renewable … 41 which shows that, if the primary goal is to decarbonize the heating sector, then the obvious choice will be advanced PVT for small applications but for large-scale district applications, the Hydrogen City option is preferable for 2050 targets (Figs. 40, 41, Table 5). Fig. 40 Feasible regions for PVT technology Fig. 41 Payback periods with project size and geography Table 5 REMM efficiency and total exergy output of different solar panels REMM efficiency FPC PV PVTa Advanced PVT ΨR 0.24 0.64 0.79 0.88b Total exergy per unit solar input, εT 0.09 W/W 0.20 W/W 0.26 W/W 0.35 W/W a Excludes the power exergy demand of the PVT-dedicated circulation pump. Sometimes the net exergy output may be negative b Operated with embedded heat pipes [] 42 B. Kılkış Fig. 42 nZEXB in the mediterranean with roof PVT and PVT Façade brick Passive Hydrogen House: A net-zero exergy solar house for hot and humid climates, doable with existing technology is shown in Fig. 42. This house has the roof and façade-mounted advanced, pumpless PVT panels with heat pipes (Kilkis et al. 2019). Recommendations A Roadmap for Electrification with 100% Renewables For the highest level of sustainable success and for truly minimizing CO2 emissions, the following recommendations are presented. • • • • • • Apply hydrogen economy also to the agricultural and transport sector, Until then the best choice is hydrogen economy with fuel cells, The next step is hydrogen economy with CHP, supported by ORC and biogas, Support RD for high-efficiency ORC for bottoming-cycle CHP, Never use electricity by direct resistance heating, Defer the use of heat pumps until COP increases and buildings are low-exergy type, • If heat pumps need to be used, then support them by solar PV. In milder climates and warmer provinces, PVT systems may be used, • If office buildings, schools, etc. need cooling and humidity control even in Northern climates at a certain period of the year, adsorption-cycle chillers may be used. This requires optimum sizing of the wind and other renewable energy systems, • Use CO2 instead of ozone-depleting refrigerants, Accelerating the Transition to 100% Renewable … 43 • CO2 from coal-fired plants must be captured and used/marketed for refrigerant replacements. Indeed, CO2 is the most viable and safe refrigerant, especially in heating. Therefore, this option becomes especially attractive for the Northern provinces, • First upgrade buildings to low-exergy and energy-conserving type, • Improve the efficiency of fuel cells and develop cheaper ones without rare-earth elements, • Blend wind energy with solar, biogas, and geothermal, • If feasible collaborate with industrial waste heat, • Retrofit natural-gas systems with hydrogen, • Develop optimization programs to optimize the wind power to heat options for given climatic conditions, building typology, load demands, available infrastructure, and size of the number of buildings. Even the building heights matter for minimum emissions. • The waste heat of power plants must be used in district energy systems. • If the cogeneration system is preferred over fuel cells, then the bottoming cycle for additional power generation must be used. • In the transition process of electrification and heating into a hydrogen economy, existing coal and lignite power plants must capture H2 S gas and convert it to hydrogen for use. • Later, convert district energy systems into hydrogen piping. In order to accomplish that conversion, the piping network must be designed so that they may be convertible to a large extent with less need for upgrading and infrastructure modifications. • For better multi-variable optimization and system-of-a system-type of approach, new rating parameters must be developed and implemented, like the ones presented herein. Step 9. Consider Other Sectors 100% Renewable Farm: Besides large-scale solar and wind energy installations, renewable energy systems should be integrated with smaller-scale applications in agriculture and animal farms. Figure 43 shows a 100% renewable system, involving, Fig. 43 100% renewable farm and greenhouse (Çolak et al. 2013) 44 B. Kılkış solar, wind and ground heat, where PVT panels are coupled with wind turbines. Renewable electricity drives irrigation pumps. In this case, ψ R is almost 1 (electricityto-electricity). Another part of the electricity drives a GSHP for root-zone heating or for greenhouse cooling. Thermal storage both in heat and cold forms is available. PVT panels are cooled by the well water, but not so much that irrigation is not compromised. Computer-controlled, variable-speed pumps are used. Step 10. Use Alternative Fossil Fuels Wisely-If You Absolutely Need Them. Fig. 44 Off-shore 100% renewable power plant with H2 S gas from the black sea bed Accelerating the Transition to 100% Renewable … 45 100% Black Sea Off-Shore Power: Fig. 44 shows an off-shore, 100% renewable energy system on a converted old oil drilling platform, which processes the H2 S gas to hydrogen (Kilkis 2019). This design encompasses wave, wind, and solar (PVT) energy systems with ORC bottoming cycle using PVT heat with compressed energy storage. The system converts H2 S to H2 . On the land, part of the hydrogen may be further processed to regular jet fuel with 100% renewables, if H2 obtained from 100% renewables and wastes: (2n + 1)H2 + nCO = Cn H(2n+2) + n H2 O (41) The hydrogen gas input to this process is sourced from two different sources, namely by direct electrolysis of (sea) water using electricity obtained from renewables at a solar, wind, wave energy off-shore compound platform (SWWCP) in Fig. 44 and from the drilling system of the same SWWCP system tapping the hydrogen sulfide (H2 S) gas deposits, which is abundant in the Black Sea Bed. The following chemical process is used (WEF 2019): 2COS + O2 = 2CO + SO2 (42) Carbonyl sulfide (COS) is found in many industrial process streams, such as those associated with petroleum refineries and coal gasification plants. Carbon disulfide (CS2 ) is a greenhouse gas. This chemical is used to form CO and dry sulfur dioxide (SO2 ) (WEF 2019). Thus, an added value is generated while greenhouse gas emissions are sequestered from the industry (Fig. 45). 2CS2 + 5O2 = 2CO + 4SO2 Fig. 45 Jet fuel but 100% renewable (Kılkış et al. 2019) (43) 46 B. Kılkış CO + H2 S = H2 + COS (44) 8 Conclusions Exergy is both a game-changer and a game maker in the name of the 2nd Law. It first changes almost all games in the built environment, by pointing out that global warming, ozone depletion, climatic disasters are the prime responsibilities of humanmade systems and equipment in the built environment. Many every-day applications have been shown hereby that they generate even more avoidable CO2 emissions than direct emissions, which we can observe and calculate with the 1st Law. Maybe this unawareness makes exergy an unwanted term by many, despite the fact that it also shows ways and means to avoid exergy blunders, which are exemplified here. If a 100% renewables target needs to be achieved in a decoupled format of sustainable development and harmful emissions, exergy is the only rational way. If we have any hope of keeping climate change within safe boundaries, global emissions need to fall to zero within the next three decades. That was the message of the Intergovernmental Panel on Climate Change in 2018. So just how far have we got to go? So far only seventeen nations and 34 major companies are planning to or have already set targets to reach net-zero (WEF 2019). That is how far we can go with the 1st Law techniques, at the face value of 100% renewables target. This chapter has shown that with quantified discussions and examples, that why the 2nd law is a game maker. In order to put the 2nd Law in sustainable actions before 2050, district energy systems must be implemented beyond their 4th generation (> 4DE) (Kilkis 2016). This approach starts with LowEx buildings (Kılkış 2012) and lowexergy systems and equipment (ECBCS, Annex 37. Heating and cooling with a focus on increased energy efficiency and comfort-project summary report. http://www.ieaebc.org/Data/publications/EBC_Annex_37_PSR.pdf. Last visited: 15 Aug 2019). In fact, the quest for utilizing wind and solar energy for heat or cold is not new, but the right way with maximum COPEX value is the key metric for optimum and rational solutions (Kilkis 1999; Kilkis 2017). COPEX in every component of a system of systems type of approach must approach 1 for approaching 100% renewables target. Today it is estimated that this value averages around 0.25. Equations 4, 5, and 6 show that total CO2 emissions depend on it. The future will look bright only if all elements of decarbonization, which are exemplified in this Chapter towards 100% renewables are collected and hybridized optimally around a hydrogen economy system with energy/exergy/water nexus, shown in Fig. 46 (Kılkış and Kılkış 2018; Kılkış and Kılkış 2019). Accelerating the Transition to 100% Renewable … 47 Fig. 46 A 100% renewables system of systems approach with hydrogen economy References Çolak L, Kılkış B, Yaltay CE, Dalarslan M (2013) Solar assisted pumping by a PHVT system in rural regions, 2013 ISES solar world congress. Elsevier, Energy Procedia Cowan D, Gartshore J, Chaer I, Francis C, Maidment G (2009) IOR. Real zero- reducing refrigerant emissions and leakage-feedback from the IOR project, Proc Inst R 2009–10, pp 7–1 to 7–16 EU (2016) Communication from the commission to the European parliament, The council, The European economic and social committee and the committee of the regions. 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In: 14th National sanitary engineering congress, TESKON, 17–20 April 2019, Izmir, Geothermal Energy Seminar Proceedings, pp 229-237 US DOE EERE (2015) A common definition for zero energy buildings, Prepared for the U.S. Department of energy by the national institute of building sciences, 22 p, Sept 2015 WEF (2019) Zero by 2050: How the world’s economy has planned to battle climate change. https://www.weforum.org/agenda/2019/07/zero-emissions-target-climate-change-impact/? fbclid=IwAR3bdOqyXZn0V8R9tRnrH2uYWeSICYRfwK8hjn5wxMmtJr4F4JkWL96fmFg. Last visited: 15 Aug 2019 Role of IRENA for Global Transition to 100% Renewable Energy Elisa Asmelash, Gayathri Prakash, Ricardo Gorini and Dolf Gielen Abstract The global energy transformation is more than a simple transformation of the energy sector—it is a multi-faceted transformation of our societies and economies. The transition towards a decarbonised global energy system can be realised much more cost-efficiently than previously thought due in part to the rapidly falling costs of renewable energy technologies. This chapter highlights the urgent need for an accelerated energy transition to 2050. Since the signing of the Paris Agreement in 2015 and despite the growth of renewable energy technologies, energy-related CO2 emissions have risen by around 4%. In this context, the next years and decades are critical and the revisions of the NDCs in 2020 in combination with Long-term Strategies must yield a convincing outcome for an energy transition that puts the world on a global pathway to reduced emissions. Technologies for these systems are available today, are deployable and cost-competitive at a large scale and there are quite a lot of studies exploring 100% RE scenarios, indicating that it is clearly topic of growing interest. On this context, the analysis—part of International Renewable Energy Agency’s (IRENA) latest global energy transformation roadmap details an energy transition pathway for the global energy-system to meet the Paris Agreement of “well-below 2 °C”. By 2050, renewable energy in the power sector could reach 86%, while representing two-third of total primary energy supply mix. The pace of energy transition can be ramped up by several inter-related factors, ranging from technologies to socio-economics, to institutional drivers and different forms of finance. Keywords Energy transition · Renewables · Decarbonisation · Sustainable development and energy policy E. Asmelash (B) · G. Prakash (B) · R. Gorini · D. Gielen International Renewable Energy Agency (IRENA), Innovation and Technology Centre (IITC), Willy-Brandt-Allee 20, 53113 Bonn, Germany e-mail: [email protected] G. Prakash e-mail: [email protected] © Springer Nature Switzerland AG 2020 T. S. Uyar (ed.), Accelerating the Transition to a 100% Renewable Energy Era, Lecture Notes in Energy 74, https://doi.org/10.1007/978-3-030-40738-4_2 51 52 E. Asmelash et al. 1 Why 100% RE Systems 1.1 Rationale and Drivers The Intergovernmental Panel on Climate Change (IPCC) Special Report on Global Warming of 1.5 °C (SR1.5), estimates that human activities have already caused approximately 1.0 °C of global warming above pre-industrial levels. Unless significant counter measures are taken, global warming would not be limited to/stabilise at 1.5 °C between 2030 and 2052 (IPCC Special Report on Global Warming of 1.5 °C 2018). Pathways limiting global warming to 1.5 °C require rapid and extensive transitions in all sectors (i.e., energy, agriculture, urban infrastructure and buildings, transportation, and industrial systems). These system transitions are unique in terms of scale and more pronounced in terms of speed and they require cross-sector emissions reductions, a wide portfolio of mitigation options and a significant increase in investments. In addition, efforts to limit warming to 1.5 °C are closely linked to sustainable development, which balances social well-being, economic prosperity and environmental protection. Reducing energy-related CO2 emissions is the heart of the energy transition. Rapidly shifting the world away from the consumption of fossil fuels causing climate change toward cleaner, renewable forms of energy is key if the world is to reach the agreed-upon climate goals. There are many drivers behind this transformation. Firstly, falling costs of renewable energy (RE), which have continued to decline rapidly. As an example, electricity costs from utility scale solar photovoltaic (PV) projects since 2010 has been remarkable—between 2010 and 2018 the global weighted-average levelized cost of energy (LCOE) of solar PV declined to 77%. With the right regulatory and institutional frameworks in place, recent record low auction prices for solar PV in Dubai, Mexico, Peru, Chile, Abu Dhabi and Saudi Arabia have shown that an LCOE of USD 0.03/kWh is possible in a wide variety of national contexts (IRENA Renewable Power Generation Costs in 2018 2019). Similarly, in Europe, offshore wind can now compete at market prices, while in the US, non-hydroelectric renewable energy resources such as solar PV and wind are expected to be the fastest growing source of electricity generation in the next two years. Secondly, air quality improvements. Air pollution is a major public health crisis, mainly caused by unregulated, inefficient and polluting energy sources, namely fossil fuels. The switch to clean renewable energy sources would bring a greater prosperity, improving the air quality in cities, preserving and protecting the environment. Thirdly, reduction of carbon emissions. The transformation of the global energy system needs to accelerate substantially to meet the objectives of the Paris Agreement, which aim to keep the rise in average global temperatures “well below” 2 °C and ideally to limit warming to 1.5 °C in the present century, compared to pre-industrial levels. Role of IRENA for Global Transition to 100% Renewable Energy 53 Finally, transforming the global energy system will also improve energy security and enhance affordable and universal energy access. For countries heavily dependent on imported fossil fuels energy security is a significant issue, and renewables can provide an alternative by increasing the diversity of energy sources through local generation and thus contribute to the flexibility of the system and resistance to shocks. Similarly, energy access is an area of great inequality and renewable energy technologies can be adopted and applied in the rural areas where the national grid has not yet been extended through rural electrification, energy community projects, as well as through distributed renewable energy resources (DER). Also, The United Nations Sustainable Development Goals (SDGs), adopted in 2015, provide a framework for assessing links between global warming of 1.5 °C or 2 °C and development goals including poverty eradication and reducing inequalities (IPCC, 2018). SDG 7, which calls for ensuring “access to affordable, reliable, sustainable and modern energy for all” by 2030, has a strong connection with the majority of SDGs, illustrating how energy is central to fostering the pathways necessary to keep the world well below 2 °C of warming and meet a wide range of SDG targets. The decarbonisation of the energy sector and the reduction of carbon emissions to limit climate change is at the heart of IRENA’s energy transition series, which examines and provides accelerated and feasible low carbon technology deployment pathway towards a sustainable and clean energy future (IRENA Transforming the energy system and holding the line on the rise of global temperatures 2019) (Fig. 1). 1.2 Mixed Progress in the Energy Transition Despite clear evidence of human-caused climate change, support for the Paris Agreement on climate change, and the prevalence of clean, economical and sustainable energy options, the world is still not on track and efforts and progress are still well below the levels needed. Indeed, the world is starting from a baseline that it is still far away from what is needed for the decarbonisation of the energy sector. Recent trends are also not encouraging, as they show slow progress and slow improvements towards the final objective. The Fig. 2 summarises the need for acceleration by looking at five key indicators, namely: (i) renewable energy share in power generation; (ii) total final energy consumption per capita; (iii) share of electricity in final energy consumption; (iv) emissions per capita; and (v) energy intensity improvement rate. Some indicators do not show positive trends. In the period from 2010 and 2016, the share of renewable energy in final energy consumption stayed at roughly the same levels, electrification of final uses of energy has mostly stagnated, global CO2 emissions from the energy sector increased by almost 13% and estimates indicate that emissions continued to rise and may have reached a new record high of 34.3 Gt CO2 in 2018 (Carbon Brief Analysis: Fossil-Fuel Emissions in 2018 Increasing at Fastest 54 E. Asmelash et al. Fig. 1 Needs and opportunities Rate for Seven Years 2018). In addition, investment in renewable energy declined in 2017 after several years of growth (IEA World Energy Investment 2018). Despite an increase in investment in energy efficiency, the combined investment in renewable energy and energy efficiency showed a slight reduction of 3% in 2017, compared to the previous year. That is unfortunate in a world where a strong acceleration in investments in energy efficiency and renewable energy is needed. Partly because of that decline and partly due to a modest increase in fossil fuel investment, the share of investment in fossil fuels in the energy supply increased in 2017 (IEA World Energy Investment 2018). However, despite the very slow progress, there are two positive trends. First, in the power sector, the share of renewable energy in electricity generation has been increasing steadily. Renewable electricity generation share increased from around 20% to nearly 24% from 2010 to 2016 (or 3.1% per year on average) (IRENA Hydrogen from Renewable Power: Technology Outlook for the Energy Transition 2018). An estimate for 2018 indicates a further increase to 26%. The second positive sign is the consistent improvement in the energy intensity of GDP. Role of IRENA for Global Transition to 100% Renewable Energy 55 Fig. 2 Summary of recent trends and required levels of selected indicators 1.3 What Exactly is 100% Renewable Energy: Implications for Supply and Demand Sectors There are quite a lot of studies exploring 100% RE scenarios, indicating that it is clearly a topic of growing interest. However, there seems to be some confusion between 100% RE in energy supply mix and 100% RE in power generation mix, which are indeed very different concepts. Having 100% RE in energy supply mix implies the complete phase out of fossil fuels in the complete energy sector (including power, transport, buildings, industry) and the creation of an energy system that runs entirely on renewable energy sources. On the other hand, 100% RE in power means that the entire generation of electricity will be covered by renewable energy sources, while fossil fuels could only be used as back-up in extreme circumstances or even not used with emerging low-carbon technologies such as hydrogen and other flexibility measures like energy storage. Given the above, IRENA sees possibilities for many more countries with 100% RE power in the coming decades but for many countries 100% RE energy is unlikely for economic and technical reasons. In fact, according to IRENA’s latest global REmap analysis, renewable energy in the power sector could reach levels towards 100%, representing 86% of the total power generation by 2050, while renewable energy in 56 E. Asmelash et al. total primary energy supply would be lower and represent 67% of the total supply (IRENA Global Energy Transformation 2019). The transition towards a 100% RE power system is not smooth and does not come without any challenges, and some technical and political uncertainties also remain on how closed power systems with dominant variable renewable energy shares would operate. On the technical point of view, inflexible power system is among the most frequently mentioned barriers, as it reduces the grid capacity available for renewables and therefore causes frequent curtailment of renewable energy. Moreover, for the electricity sector, higher penetration of variable renewables requires a number of changes in the way systems are developed and operated. However, barriers and obstacles delaying or impeding target setting for 100% renewable energy and policy development for implementation are not only technical but also of a political/economic nature and are mainly related to policy, market design and business models, which all need to be redesigned to accommodate higher levels of VRE. Figure 3 illustrates the main innovations taking place in the electricity supply chain to overcome technical and political/economic challenges. Indeed, there is no one-size-fits-all approach to achieving 100% renewable energy, and that targets and enabling frameworks need to be adjusted to local circumstances. In general, reaching a 100% renewable energy system will require further analysis and dialogue on what is needed on national as well as sub-national level regarding target setting, policies and planning (IRENA Towards 100% Renewable Energy: Status, Trends and Lessons Learned 2019). 2 How to Achieve 100% Renewable Energy System: IRENA’s Pathway for Global Transition to Renewable Powered Future 2.1 IRENA’s Energy Transition Study The global energy transformation is more than a simple transformation of the energy sector—it is a multi-faceted transformation of our societies and economies. As such, the direction and future shape of a Paris Agreement compatible energy system will be determined by several inter-related factors, ranging from technologies to socioeconomics, to institutional drivers and different financial instruments. The findings in this section are based on latest analysis conducted by the International Renewable Energy Agency (IRENA)’s “Global Energy Transformation— A Roadmap to 2050”, which details an energy transition pathway for the global energy-system to meet the Paris Agreement aim of “well-below 2 °C”. Role of IRENA for Global Transition to 100% Renewable Energy Fig. 3 Innovations taking place in the electricity supply chain Box 1: Practical Options for Global Energy Decarbonisation IRENA’s renewable energy roadmap, or REmap approach 1 and analysis, includes several key steps: • Identifying the current plans for global energy development as a baseline scenario (or Reference Case) as far as 2050. This presents a scenario based on governments’ current energy plans and other planned targets and policies, including climate commitments made since 2015 in Nationally Determined Contributions under the Paris Agreement. 57 58 E. Asmelash et al. • Assessing the additional potential for scaling up or optimising low-carbon technologies and approaches, including renewable energy, energy efficiency and electrification, while also considering the role of other technologies. • Developing a realistic, practical energy transformation scenario, referred to as the “REmap Case”. This calls for considerably faster deployment of low-carbon technologies, based largely on renewable energy and energy efficiency, resulting in a transformation in energy use to keep the rise in global temperatures this century well below 2°C and closer to 1.5°C compared to pre-industrial levels. The scenario focuses primarily on cutting energyrelated carbon-dioxide (CO2 ) emissions, which make up around two-thirds of global greenhouse gas emissions. • Analysing the costs, benefits and investment needs of low-carbon technologies worldwide to achieve the envisaged energy transformation. • Note: The findings in this chapter consider policy targets and developments until April 2019. Any new policy changes and targets announced since then are not considered in the analysis and therefore could influence the findings. • For more on the global roadmap and its underlying analysis, see https:// www.irena.org/remap. The gap between aspiration and reality in tackling climate change continues to be significant, as highlighted by the Intergovernmental Panel on Climate Change (IPCC) special report on the impacts of global warming of 1.5 °C (IPCC Special Report on Global Warming of 1.5 °C 2018). Rising CO2 emissions, an uneven distribution of efforts among countries and short-sighted fossil fuel investments all increase the risks of the world going further off course. The urgency of action to combat climate change—and the impacts of the policies needed to get the world back on track— need to be fully grasped by decision makers, consumers and businesses. IRENA’s energy transition study shows that global fossil fuel production under current and planned polices of the Reference Case will peak between 2030 and 2035; whereas for a pathway aligned with the Paris Agreement goals, the peak would need to occur in 2020. In 2017 and 2018 energy-related CO2 emissions rose, driven largely by increased use of fossil fuels; on average, energy-related CO2 emissions have risen around 1.3% annually over the last five years (Carbon Brief Analysis: Fossil-Fuel Emissions in 2018 Increasing at Fastest Rate for Seven Years 2018). If governments’ longterm plans, including their Nationally Determined Contributions (NDCs), were followed, annual energy-related CO2 emissions will decline only slightly by 2050, and will put the world on track for at least 2.6 °C of warming by mid-century, and higher warming after. Based on a carbon budget from the latest IPCC special report on the impacts of global warming of 1.5 °C (IPCC Special Report on Global Warming of 1.5 °C 2018), the Reference Case indicates that, under current and 1 https://irena.org/remap. Role of IRENA for Global Transition to 100% Renewable Energy 59 planned policies, the world will exhaust its energy related CO2 emissions budget in 10–18 years To set the world on a pathway towards meeting the aims of the Paris Agreement, energy-related CO2 emissions would need to be scaled back by at least an additional 400 gigatonnes (Gt) by 2050 compared to the Reference Case; in other words, annual emissions would need to be reduced by around 3.5% per year from now until 2050 and continue afterwards. Energy-related emissions would need to peak in 2020 and decline thereafter. By 2050 energy-related emissions would need to decline by 70% compared to today’s levels. While the REmap analysis is focused only on energy-related CO2 emissions, additional efforts are needed to reduce emissions in non-energy use (such as using bioenergy and hydrogen feedstocks); industrial process emissions; and efforts outside of the energy sector to reduce CO2 emissions in agriculture and forestry (Fig. 4). IRENA’s REmap Case presented in this chapter outlines an aggressive, yet technically feasible and economically beneficial, route for accelerated climate action. It shows that the accelerated deployment of renewables, combined with deep electrification and increased energy efficiency, can achieve over 90% of the energyrelated CO2 emissions reductions needed by 2050 to reach the well-below 2 °C Fig. 4 REmap offers a pathway for a well-below 2 °C climate target, towards 1.5 °C. Notes (1) Taking into account 2015–2017 emissions on top of the budget provided in IPCC (2018) (Table 2.2— with no uncertainties and excluding additional Earth system feedbacks); (2) Budgets exclude industrial process emissions of 90 Gt; for this study, the assumption is that CO2 emissions from land use, land-use change and forestry (LULUCF) fall from 3.3 Gt in 2015 to zero by mid-century. LULUCF subsequently becomes a net absorber of CO2 over the remainder of the 21st century, and, as a result, cumulative CO2 emissions from LULUCF between 2015 and 2100 are close to zero; (3) Current trajectory shows the recent historical trend line, assuming the continuation of the annual average growth in energy-related CO2 emissions from the last five years (2013–2018) of 1.3% compound annual growth up to 2050; (4) Emissions budgets represent the total emissions that can be added into the atmosphere for the period 2015–2100 to stay below 2 or 1.5 °C at different confidence levels (50 or 67%) according to the IPCC (2018) report 60 E. Asmelash et al. Fig. 5 Renewables and energy efficiency, boosted by substantial electrification, can provide over 90% of the necessary reductions in energy-related carbon emissions. Note “Renewables” implies deployment of renewable technologies in the power sector (wind, solar PV, etc.,) and end-use direct applications (solar thermal, geothermal, biomass). “Energy efficiency” contains efficiency measures deployed in end-use applications in industry, buildings and transport sectors (e.g., improving insulation of buildings or installing more efficient appliances and equipment). “Electrification” denotes electrification of heat and transport applications, such as deploying heat pumps and EVs aim of the Paris Agreement.2 Electrification with renewable power is key, together making up 60% of the mitigation potential; if the additional reductions from direct use of renewables are considered, the share increases to 75%. When adding energy efficiency, that share increases to over 90% (Fig. 5). Going forward, the share of renewable energy should rise from around 14% of total primary energy supply (TPES) in 2016 to around 65% in 2050 (Fig. 6). Under the IRENA REmap Case3 renewable energy use would nearly quadruple, from 81 exajoule (EJ) in 2016 to 350 EJ in 2050. TPES would also have to fall slightly below 2016 levels, despite significant population and economic growth. In the period from 2010 to 2016, global primary energy demand grew 1.1% per year. In the Reference case, this is reduced to 0.6% per year to 2050, whereas in REmap the energy demand growth turns negative and results in a decline of 0.2% per year to 2050 (IRENA Global Energy Transformation 2019) (Fig. 6). 2 According to the IPCC, 67% 2 °C up to 1.326 Gt; the REmap case, with 827 Gt by 2050 is well below the 2 °C pathway, and towards the 50% 1.5 °C. More information about the carbon budget, and assumptions for non-energy greenhouse gas emissions, is included in the full report available online at www.irena.org. 3 This analyses the deployment of low-carbon technologies, largely based on renewable energy and energy efficiency, to generate a transformation of the global energy system which for the purpose of the REmap analysis has the goal of limiting the rise in global temperature to below 2 °C above pre-industrial levels by the end of the century (with a 66% probability). For more information about the REmap approach and methodology, please visit www.irena.org/remap/methodology. Role of IRENA for Global Transition to 100% Renewable Energy 61 Fig. 6 The global energy supply must become more efficient and more renewables 2.2 Pathway for the Electricity Sector: Towards 100% Renewables Power Delivering the energy transition at the pace and scale needed would require the almost complete decarbonisation of the electricity sector by 2050. This can largely be achieved by using renewables, increasing energy efficiency and making power systems more flexible. Under the REmap Case, electricity consumption in end-use sectors would increase 130% by 2050, to over 55 000 TWh, compared to 2016. By 2050, the share of renewable energy in generation would be 86%, up from an estimated 26% in 2018. Meanwhile, the carbon intensity of electricity generation would decline by 90%. By 2050, variable renewable energy, mainly wind and solar PV, would account for three-fifth of total global electricity generation rising from their current shares of 7% and 3%, to 35% and 25% respectively (Fig. 7). These sources would lead the way for the transformation of the electricity sector, rising from around 564 GW of wind capacity and 480 GW of solar PV in 2018 to over 6 000 GW and 8 500 GW by 2050, respectively. In addition, strong growth in geothermal, bioenergy and hydropower would be seen as well (Fig. 7). Investment in new renewable power capacity would increase to over USD 650 billion per year over the period to 2050. Transforming the power system to produce around an 86% share for renewable power would require investments in infrastructure and energy flexibility of another USD 350 billion per year (a total of USD 12 trillion for the period 2016–2050). In all, investment in decarbonisation of the power system will need to reach an average of nearly USD 1 trillion per year to 2050. Over the period between 2016 and 2050, investments in renewable power generation capacity would total USD 23 trillion in the REmap Case, more than double the investment requirements in the Reference Case of USD 11 trillion. Three-fourths of the additional investments are required to deploy variable renewables, mainly wind and solar PV (Fig. 8). 62 E. Asmelash et al. Fig. 7 Wind and solar power dominate growth in renewable-based generation. Note In electricity consumption, 24% in 2016 and 86% in 2050 is sourced from renewable sources. CSP refers to concentrated solar power 2.3 Electricity: The Central Energy Carrier The most important synergy of the global energy transformation comes from the combination of increasing low-cost renewable power technologies and the wider adoption of electric technologies for end-use applications in transport and heat. Electrification of end-use sectors utilising renewable power would lead the transition. The renewable energy and electrification synergy alone can provide two-thirds of the emissions reductions needed to set the world on a pathway to meeting the goals of the Paris Agreement. Overall, the share of electricity in final energy would need to increase from just 20% today to almost 50% by 2050. On sectorial level, the share of electricity consumed in industry and buildings would double. In transport it would need to increase from just 1% today to over 40% by 2050 (Fig. 9). The transport sector sees the largest transformation. As performance improves and battery costs fall, sales of electric vehicles, electric buses and electric two- and three-wheelers are growing. By the end of 2018, over 5 million light electric cars Role of IRENA for Global Transition to 100% Renewable Energy 63 Fig. 8 Power sector key indicators were on the road (IEA Global EV Outlook 2018). Under the REmap Case, the number would increase to over 1 billion by 2050. (That number could double if it includes all types of electric two- and three-wheelers). To achieve this, most of the passenger vehicles sold from about 2040 on would need to be electric. Under the REmap Case, while over half the stock of passenger vehicles would be electric by 2050, closer to 64 E. Asmelash et al. Fig. 9 Electricity becomes the main energy source by 2050. Note For electricity use, 24% in 2016 and 86% in 2050 comes from renewable sources; for district heating, this share is 9% and 77%, respectively. DH refers to district heat 75% of passenger car activity (passenger-kilometres) would be provided by electric vehicles (Fig. 10). Electricity demand in the building sector is projected to increase by 80% by 2050. The increase occurs despite improvements in appliance efficiency because of strong growth in electricity demand (particularly in emerging economies) and Fig. 10 Transport sector key indicators Role of IRENA for Global Transition to 100% Renewable Energy 65 Fig. 11 Buildings sector key indicators increases in the electrification of heating and cooling. The REmap Case considers deployment of highly efficient appliances, including smart home systems with advanced controls for lighting and air conditioning, improved heating systems and air conditioners, better insulation, replacement of gas boilers by heat pumps and other efficient boilers, and retrofitting of old and new buildings to make them more energy efficient. Developing and deploying renewable heating and cooling solutions for buildings, urban development projects and industries is also key. Heat pumps achieve energy efficiencies three to five times higher than fossil-fuelled boilers and can be powered by renewable electricity. Under the REmap Case, the number of heat pump units in operation would increase from around 20 million in 2016 to around 253 million units in 2050. They would supply 27% of the heat demand in the buildings sector (Fig. 11). Under the energy transition, electricity would meet more than 40% of industry’s energy needs by 2050. By 2050, 80 million heat pumps would also be installed to meet similar low-temperature heat needs, more than 80 times the number in use today (Fig. 12). Direct electrification in these sectors can be challenging for certain uses, however, unless renewable-based power can be further converted and stored via other energy carriers. One such promising energy carrier is hydrogen (IRENA Hydrogen from Renewable Power: Technology Outlook for the Energy Transition 2018). The production of hydrogen by splitting water into hydrogen and oxygen using electricity could be significantly increased. As an energy carrier, hydrogen made from renewables could be seen as complementary to electricity since it offers a way to transport renewable energy over long distances. It has the technical potential to channel renewable electricity to subsectors in which decarbonisation is otherwise difficult. The REmap Case shows that by 2050 hydrogen has the potential to supply nearly 29 EJ of global energy demand, two-thirds of which would come from renewable sources. 66 E. Asmelash et al. Fig. 12 Industry sector key indicators Box 2: Best Practice Example—Sweden: 100% Renewable Electricity by 2040 IRENA is establishing a dialogue of best practice and is advising on innovative solutions to aid the development of national 100% renewable electricity strategies for Sweden (IRENA Innovative solutions for 100% renewable power in Sweden 2020). In 2016, the Swedish government concluded an agreement on Sweden’s long-term energy policy. The agreement consists of a roadmap for a transformation of the energy system including a target to reach 100% renewable electricity production by 2040. In order to achieve such an ambitious target, a new Climate Act entered into force in 2018, as part of a climate policy framework imposing on current and future governments the obligation to pursue a climate policy in line with its climate goals, present a climate report every year and develop a climate policy action plan every four years to monitor progress. There are several instruments driving the overall renewable energy transformation. Firstly, the carbon tax. Initially introduced at USD 30/ton CO2 , the tax on fossil fuels based on carbon content has increased to USD 140/ton CO2 at current levels. Secondly, mandatory renewable energy quota system. This aims at further increase the share of renewables in the electricity system, as it requires consumers to cancel renewable electricity certificates in proportion to their consumption. The certificates are generated by producers of renewable electricity from new plants and sold in an open market. Since the carbon tax was implemented, the economy has grown by 75% while the country’s emissions declined by 26%. Renewable energy technologies already contribute more than half (54%) of Swedish energy use, and hydropower is the largest renewable electricity source in Sweden, followed by wind and biomass. Hydropower generation in recent years has varied between Role of IRENA for Global Transition to 100% Renewable Energy 67 62 and 78 TWh, and renewable energy has contributed 60–75% of electricity consumption. As the country moves towards 100% RE, no increase in hydropower generation is expected, and owners have decided to close two nuclear reactors by 2020. Since 2000, wind power has increased from 240 MW to 6 520 MW in 2017, passed 10% of generation and is projected to double by 2021. To promote implementation, the government in 2015 appointed a co-ordinator of Fossil Free Sweden. The initiative is open to all relevant stakeholders in Sweden, and more than 350 actors have signed up for the initiative. So far, a set of roadmaps for the development of different carbon-intensive industries has been produced. Although other challenges remain, such as decarbonising the transport sector, the success of carbon pricing provides an example for other countries of how to develop a competitive market for bioenergy and for other renewable energy technologies. 3 Actions Needed Now to Transform to 100% Renewable Energy System This chapter makes clear that an energy transition is urgently required, and that developing 100% renewable energy systems is a key cornerstone in this process. Technologies for these systems are available today, are deployable at a large scale quickly and are cost-competitive. The Paris Agreement was signed in 2015. Since then energy-related CO2 emissions have risen by around 4%. The coming years are critical: there is a need for a leap in national collective ambition levels. The revisions of the NDCs in 2020 in combination with Long-term Strategies must yield a convincing outcome for an energy transition that puts the world on a global pathway to reduced emissions, despite differing views on the mitigation measures needed and the rapid evolution of renewable technologies • The power sector needs to be transformed to accommodate growing shares of variable renewables. • Digitalisation is a key enabler to amplify the energy transformation. • Accelerating the electrification of the transport and heating sectors is crucial for the next stage of energy transformation. • Hydrogen produced from renewable electricity could help to reduce fossil-fuel reliance. • Supply chains are key to meet growing demand for sustainable bioenergy. • Decarbonising the global energy system requires swift and decisive policy action. Table 1 summarises some of the key decisive actions that are needed now for fostering the transition to 100% renewable powered future. Build no new coal power plants and accelerate the decommissioning of exis ng coal capacity. Promote ac ons towards circular economy (material recycling, waste management, improvements in materials efficiency and structural changes such as reusing and recycling). Promote community-based finance that can help lower the overall cost of borrowing for the transi on, while simultaneously facilita ng the involvement of society in the transi on. Iden fy and map renewable energy resources and Align the financial system needs with broader develop a por olio of financeable projects over the sustainability and energy transi on requirements. medium and long terms. Set up a pla orm providing comprehensive, easily accessible and prac cal informa on, tools and guidance to assist in the development of bankable renewable energy projects. All stakeholders will need new management and governance skills to enhance transparency, accountability and enforcement of clean energy policies. Finance/markets/business models Society Cogni ve shi (continued) Use informa on communica on technology and digitalisa on, along with demand side management, to reduce peak electricity demand, lower the need to invest in power capacity, and reduce opera onal costs. Promote" Do it Ourselves” approaches with adequate traning and educa on programmes targe ng both consumers and ci zens involved in energy communi es to prac vely involve in energy transi on. Promote financing schemes for accelera ng Consumers can evolve from passive energy deployment of renewables and energy efficiency users, to ac ve stakeholders engaged in the measures for energy demand and supply projects. development of new social prac ces around energy use. Planning/regula on/opera on Establish long-term energy planning strategies that aligns both climate and energy needs, considering ac on plans in the power sector and in each end-use sectors (couple with the SDGs and the NDCs). Promote holis c policies design approach involving coordina on among various energy and environmental ministries. Co-operate with and strengthen interna onal programmes (such as IRENA, the IEA, and its Technology Collabora on Programmes and Mission Innova on) to define a joint agenda for se ng long term energy strategies and renewable technology innova on. Investment shi Energy Planning shi Key ac ons needed now towards 100% renewable energy future Ins tu on/ R&D/Innova on Policy shi Table 1 Actions now 68 E. Asmelash et al. Deploy cost-reflec ve tariff structures by properly readjus ng the balance between volumetric charges (USD/kWh), fixed charges (e.g., USD/meter-month) and, where applicable, demand charges (USD/kW). Consider establishing community energy authori es with the sole purpose of suppor ng community energy projects through providing advisory services and funding opportuni es. By facilita ng stakeholder engagement and increasing public awareness, authori es could significantly accelerate their development. Establish carbon pricing, together with the elimina on of fossil fuel subsidies, not only provide important signals to the market in favor of decarbonisa on of the economy, but can also generate significant addi onal revenue flows. Create stable and predictable market condi ons for investment in clean energy to facilitate the realloca on of capital toward low-carbon solu ons and to minimise the spectre of stranded assets and avoid long-term lock-in into a carbon intensive energy system. Redesign power markets to enable the op mal investments for systems with high levels of VRE and enable sector coupling. (continued) Create a dedicated pla orms and networks of experts as well as groups for exchanging knowledge and exper se for the discussion and exchange of renewable energy and DER best prac ces and benchmarks at a global level. Promote equitable distribu on of economic benefits and costs. Promote ini a ves that provide addi onal income (i.e. lease to land owners, crea ng jobs during project installa on and opera on) and clean energy for its members, also redirec ng funds into educa onal visits to renewable plants (i.e. wind and solar) for social understanding and acceptance. Adapt regula ons and aid in the development of an Facilitate compe ve environments in which ac ve market to allow energy consumers to par cipate reduc on in the cost of energy is both rewarded in ancillary service markets. through the right to deliver new projects and supported through the provision of targeted public research and development (R&D) funding. Create and promote educa on and training policies, including an assessment of the occupa onal pa erns and skill profiles in rising and declining industries, and how workers might most successfully be retrained. Raise awareness and understanding of the poten al of DER, not only for direct users, but also for the society as a whole to foster wiser behavioural changes. Revise tariff structures and price regula ons. Support Poten al stranded assets should be internalised in regulatory and pricing policies including the right to overall risks assessment. generate and sell electricity, tariff regula on and gridarrival policies. Adjust regula ons to increase space and me granularity of system opera on and pricing. Ac vely engage communi es in the design, construc on, opera on and maintenance phase of the projects in order to increase community buy-in and enhance sustainability. Create a central goal of a just transi on policy must be to create structures that enable individuals, communi es and regions that have been trapped in a fossil fuel energy system to par cipate in the benefits of the transi on. Align public policies with private sector ini a ves. Set up specific funds for innova on and innova ve financing and investments mechanisms for the implementa on of DER technical solu ons. These include, inter alia: combo loans, crowdfunding pla orms, financing solu ons in partnership with mul lateral agencies, and blended finance schemes. Promote systemic innova on by crea ng a regulatory environment that enables smarter energy systems through digitalisa on (eg., ar ficial intelligence, the Internet of Things, blockchain), to promote the coupling of sectors through greater electrifica on and to embrace decentralisa on trends. This innova on needs to be expanded beyond technology and into markets, regula ons, new opera onal prac ces in the power sector and new business models. Combine energy efficiency and renewable energy measures (for example, public sector policies that integrate renewable technologies in the renova on of public buildings). Table 1 (continued) Role of IRENA for Global Transition to 100% Renewable Energy 69 Deploy microgrids to improve resilience of the grid and energy access rate with renewable sources. Deploy super grids to strengthen the interconnec ons among countries within a region. Mainstreaming gender perspec ves through audits and awareness training, gender targets and quotas, be er work-life balance, crea ng networks and suppor ng mentorship and transparent workplace prac ces. Cooperate with grid opera rs to schedule charging of EVs and ba eries during offpeak hours Accelerate modal shi from passenger cars to public transport (electric railways or trams or electric buses). Sources IRENA Global Energy Transformation: A Roadmap to 2050 (2019), IRENA Innovation Landscape for a Renewable-Powered Future: Solutions to Integrate Variable Renewables (2019), IRENA, IEA and REN21 Renewable Energy Policies in a Time of Transition (2018), IRENA Climate Change and Renewable Energy: National Policies and the Role of Communities, Cities and Regions (2019), IRENA Renewable Energy: A Gender Perspective (2019) Concentrate RD&D efforts to assist sectors that lack commercially available decarbonisa on solu ons. Relevant sectors include energy intensive industries (iron, steel and cement produc on) and transport (freight, avia on and shipping). Set up a stable and suppor ve policy framework for emerging technologies such as hydrogen. Create business models that focus on mobility services rather than car ownership – such as car sharing, Uber and autonomous vehicles – could transform the way private and public mobility operates. Promote ins tu onal investors (pension funds, insurance companies, endowments and sovereign wealth funds) and growth of new capital market instruments, such as green bonds, through which investors can more easily invest in the energy transi on. Priori ze to improve flexiblity of power system (with Promote innova ve business models that enhance flexible supply, storage, demand response, power-to- the system’s flexibility and incen vise X, electric vehicles, digital and informa on and deployment of renewable technologies. Examples communcia on technologies include virtual power plants, innova ve forms of technologies, etc.,). Update grid codes. power purchase agreements, pla orm business models such as peer-to-peer trading, and business models that enhance demand side response. Encourage the development of Planners, regulators and operators must develop new interna onally harmonised technical skills and competences. standards and quality control standards to facilitate cross-border trade and exchange of innova ve technologies. Table 1 (continued) 70 E. Asmelash et al. Role of IRENA for Global Transition to 100% Renewable Energy 71 References Carbon Brief Analysis: Fossil-Fuel Emissions in 2018 Increasing at Fastest Rate for Seven Years (2018) IEA Global EV Outlook 2018 (2018) International Energy Agency (IEA), Paris IEA World Energy Investment 2018 (2018) International Energy Agency (IEA), Paris IPCC Special Report on Global Warming of 1.5 °C (2018) IPCC, Geneva IRENA Climate Change and Renewable Energy: National Policies and the Role of Communities, Cities and Regions (2019) Report to the G20 Climate Sustainability Working Group (CSWG) International Renewable Energy Agency, Abu Dhabi IRENA Global Energy Transformation: A Roadmap to 2050 (2019 edition) (2019) International Renewable Energy Agency, Abu Dhabi IRENA Hydrogen from Renewable Power: Technology Outlook for the Energy Transition (2018) International Renewable Energy Agency (IRENA), Abu Dhabi IRENA, IEA and REN21 Renewable Energy Policies in a Time of Transition (2018) IRENA, OECD/IEA and REN21 IRENA Innovation Landscape for a Renewable-Powered Future: Solutions to Integrate Variable Renewables (2019) International Renewable Energy Agency, Abu Dhabi IRENA Renewable Energy: A Gender Perspective (2019) IRENA, Abu Dhabi IRENA Renewable Power Generation Costs in 2018 (2019) International Renewable Energy Agency, Abu Dhabi IRENA Towards 100% Renewable Energy: Status, Trends and Lessons Learned (2019) International Renewable Energy Agency, Abu Dhabi IRENA Innovative solutions for 100% renewable power in Sweden (2020) International Renewable Energy Agency, Abu Dhabi IRENA Transforming the energy system and holding the line on the rise of global temperatures (2019) International Renewable Energy Agency, Abu Dhabi The Renewable City: The Future of Low-Carbon Living The Istanbul Protocol Peter Droege Abstract This Protocol is dedicated to the city of Istanbul and its civic achievements, and the liberation of all cities and humankind from fossil and nuclear energy, in a world that is harmonious, peaceful, connected, democratic, bound- and boundaryless, ubiquitously demilitarised and united in the quest to pursue the United Nations Sustainable Development Goals, in order to jointly confront and avert the imminent self-immolation of humankind by anthropogenic global heating. This paper was originally formulated for and commissioned by the Cooperative Research Centre for Low-Carbon Living, Australia, and borrows from my edited book, Urban Energy Transition—Renewable Strategies for Cities and Regions. It is an homage to best and next practice in renewable city building, and an expression of hope for a future, sic. There is a great potential contribution to be made to transforming how we think about our immediate living environment and general place in the world—and the opportunities posed by lowering carbon emissions (‘carbon’ here always used as short for carbon dioxide equivalent greenhouse gas emissions: not all GHGs actually contain carbon) embodied in the production of and generated in powering, heating and cooling our residential environments, work spaces and the built environment in general. Commercial energy is to a large extent applied in the building and transport sectors, hence the focus on urban living in shifting the energy paradigm is both astute and profound. Energy renewability, embodiment, efficiency and sufficiency continue to form a magic quadrangle from which to draw instruction for action. Embodiment in particular presents an important growth perspective: as low-carbon living (LCL) gives way to what I would like to call ultralow-carbon life (ULCL) it is essential to lower the quantities of ‘carbon’—greenhouse gases—in the atmosphere to keep the well-tempered greenhouse from sliding into a hothouse state. This paper is also an urgent call to heed the need for rapid proliferation of LCL principles and projects, and their mobilization across the built environment production system. It is a call to build an open market for this by creating the required regulatory and policy frameworks, and to remove all the overt and hidden ways in which fossil content is subsidized. This is no longer just urgent but has now become P. Droege (B) Liechtenstein Institute for Strategic Development, Vaduz, Liechtenstein e-mail: [email protected] © Springer Nature Switzerland AG 2020 T. S. Uyar (ed.), Accelerating the Transition to a 100% Renewable Energy Era, Lecture Notes in Energy 74, https://doi.org/10.1007/978-3-030-40738-4_3 73 74 P. Droege manifestly overdue, as a result of political delays and incumbent industry inertia. And given the importance, even primacy of cities and urban areas in global human settlements, the Renewable City—urban environments, economies, movements and systems entirely relying of renewable energy resources—is now an essential precondition to any hope to stabilize the global climate. The future of low carbon living lies in ultra-low carbon cycle balance, and, consequently, highly carbon retentive cities and regions. Or better yet: a truly carbon negative built and cultural environment, one that removes, sequesters, stores and binds greenhouse gas already in the atmosphere. This cannot be enough: a massive regenerative action agenda needs to ensue to attempt at ‘global gardening’, the un-development and re-nurturing of Earth’s biosphere. 1 Introduction Humans can be brilliant in short-term, even medium-term planning by individuals or small groups, but modern humankind has proven spectacularly ill-equipped in devising and exerting conscious and constructive, collective, long-term agendas. The delays in critical action over the past generation—in full view of the risks—meant that today, seemingly paradoxically ‘100% renewable is no longer enough’ and ‘the zero emissions target is too high’. In recognising and meeting this challenge lies the very meaning and future of low-carbon living. We now know what some of us have long suspected: the UNFCCC targets and frameworks were always far too loose and narrow, and the IPCC projections scientifically naive—influenced by both political pressure and wishful thinking. They implied that there was a ‘carbon budget’ to work with, foolishly disregarding even the possibility that it had already been long blown by the time this very image of a ‘carbon budget’ was implanted. Many in today’s climate-aware community understand this now. Another long and stubbornly held myth concerned the mechanical systems thinking that led to linear projections and simple-minded graphs showing how lowered emissions would directly correspond to lowered temperatures by the global climate and carbon systems. Everyone bought into and promoted these comforting illusions, built into popular ‘inconvenient truth’ presentations and reports as convenient emotional escape hatches by major and minor climate celebrities: from Al Gore to Prince Charles, and from Sir Nicholas Stern to the last carbon compensation and offset scheme operator riding the airline passenger guilt wave. The unnerving notion of trading inside a great carbon bubble was made safe by the sober notion of ‘the budget’. The shocking truth is: that budget was already blown back on June 10 1986 when James E. Hanson, another reluctant purveyor of the magic carbon budget myth, correctly testified before a US Senate committee that we will find ourselves in the very hot water that we are in now, although neither the long-blown budget nor the feedback problem were not then and are not now quite acknowledged. The Renewable City: The Future of Low-Carbon Living 75 2 100% Is not Enough—and 0 Is Too High The most positive future to aspire to is a massive propagation of LCL developments, innovations and findings, in buildings, neighbourhoods and communities—and perhaps most importantly and challengingly the existing building stock. Elevating the retrofitting and refurbishment of the energy wasting building and plant stock to a national priority and making it the very foundation of building, construction and planning regulations is fundamental. It pales only in comparison to the equal second priority of decarbonising its energy source, and to dramatically shift away from coal, oil and gas, and retire the dying nuclear industry. The carbon budget myth has given a wide berth to the widespread complacency that is the most tragic hallmark of modern society. As a result the equal third and equally urgent challenge lies in endowing the built and (agri-)cultural environment with the ability to also withdraw copious amounts of excess GHGs from the atmosphere and bind them in soils and materials, support biodiversity and sustainably manage increasingly scarce water resources. Sustainability principles, once quaint aberrations in a landcape of business-asusual have emerged as urgent survivability measures, without all really noticing it yet: relying on renewable energy, ending the combustion of fossil resources, transforming carnivorous food culture and industrial agriculture, lowering atmospheric GHGs and binding them in soils and materials, shrinking lifestyle footprints, revolutionising water management, and shoring up biodiversity are essential elements in ULCl actions and demands for the built environment. Ultra low carbon life means that target horizons shrink to 2020 and aims emerge as 150%—rather than 80–100%— emission reductions. The built, agri/cultural and natural environments together must achieve the net absorption of atmospheric CO2 and other greenhouse gases. 3 From Low Carbon Comfort to Ultra Low Carbon—Historical Context—Paths Out of a Very Predictable Predicament Earth is not a spaceship, contrary to the seminal sustainable development expression and literary image Spaceship Earth launched in the 19th century and popularised in the 1960s (George 1879; Ward 1966; Boulding 1966; Fuller 1968). It is a fairly ancient planet of 4.5 billion years on a fixed orbit—and yet it presently is also on a rapid journey in its climatic behaviour. Its degree of habitability is transforming in front of our very eyes: it is becoming a different kind of planet. For anyone who thought that she or he might not be so special: the perhaps mockingly named Anthropocene is an unusual moment in this planet’s biospheric and human evolution. It would be a very unique moment if Earth were to morph from Goldilocks habitability into what would be a very difficult planet to colonise with enormous technological and financial resources, let alone with the actually quite limited means at our disposal. 76 P. Droege Interested in interplanetary travel? Instead of racing for eight months through space to get to Mars, we need to do nothing, continue business as usual and wait for only a few more years to arrive at a wholly new and ferociously alien world: Terra 2 would feel a bit like Venus. This transformation does not come easy, and is being exerted by a century of concerted geo-engineering effort in the form of fossil energy injection, fossil carbon release and other means of transforming land, water, inherited populations, systematically eliminating biodiversity and resilience. We don’t know what this planet will look like, or how long its final transformation would take. We hope we can halt it, that it still depends on how effective current and immediately future measures are and will be to halt the slide into the unknown. Halting the current mutation will take a massive change of exactly the kind presented in this forum as pioneering and lab like projects, but as a basic requirement for going on, not just an aspirational goal. Some astrophysicists like Carl Sagan or Stephen Hawking have long mused about the worst-case possibility of a finally stable terrestrial surface temperature of 250 °C, rather than the present 15, when the stunning temperature-maintaining phenomenon of a living Earth would have been boiled off. 4 Low Carbon—Existing Context—Actions for a Sustainable Predicament Halting this slide is the new meaning of Sustainability, which has always been about Survivability. The rising number of innovations provide the methods and projects for this platform—part of a sustainable development trajectory that is fast becoming a global paradigm. It is the core, the seed of overdue emergency action agenda. The initiatives presented in this paper all propose to highlight the many extraordinary successes and advances in the proliferation of renewable energy have been made: the powerful feed-in tariffs; the rise of 100% renewable buildings, communities and regions; the broad march of solar and wind into many countries’ power mixes; the revolution of national policies to embrace energy transitions; and the rise of renewable energy investment—which has long become the dominant mode in annual capital expenditures in new power generation capacity world-wide. A renewable city supports, thrives on closer cooperation between the city, its hinterland, the state and beyond. It relies on intelligent renewable energy networks that monitor a constellation of decentralised renewable energy plants and generators at varying scales. It will need improvements and extensions to existing energy supply infrastructures to improve integration, connection and most importantly, increase accessibility to different types of renewable energy. Favourable and compatible spatial planning policies and guidelines at the urban, regional, federal, and even EU levels will be sought to achieve equitable, safe and reliable flows and access to such energy sources. The Renewable City: The Future of Low-Carbon Living 77 The following ten groups of important initiatives offer views into a sizeable and growing pool of constructive and tested practice that is to be transformed into mainstream. Presented are cases, themes and topics that epitomise the transformation from the Fossil to the Renewable City. What used to be an aspiration goal now has become an existential necessity. 5 Current and Emerging Approaches to Low Carbon Living 5.1 Renewable Nuclei: Active Homes Low Carbon Sustainable Building: Josh’s House, Perth, Australia Carbon Positive Building: B10 Active House, Stuttgart, Germany Model buildings are powerful ways to develop, study, demonstrate and inspire about the deployment of buildings providing their own energy from local renewable sources and to share excess power with neighbours or the grid. Two buildings from opposite ends of the world highlight two very different approaches. Josh’s House in Fremantle is a large and lived-in demonstration family home with garden, and ‘Werner’s House’ in Stuttgart is a model research exhibition of the future: a modes sized, modular, prefabricated unit for bungalow style or stacked apartment deployment. They perhaps also highlight differences in our attitudes about life and culture, and the production of the built environment (Figs. 1, 2). Josh’s House is a residential ‘living lab’ near Fremantle demonstrating that high performance, energy positive housing is accessible now as a mainstream market offering. Completed mid-2013, the 10 Star NatHERS rated home was originally fitted with a 3 kW solar PV system, a gas boosted solar hot water system and conventional energy efficient appliances. Monitoring of the operational energy requirements of the home demonstrated that energy usage was less than half of the local Fig. 1 Josh’s House, Perth. © Josh Byrne, Perth 2014 78 P. Droege Fig. 2 B10 Active House, Stuttgart by Werner Sobek. © Zooey Braun, Stuttgart 2014 average and power generation was double to that consumed. The subsequent inclusion of a grid connected battery system enabled 81% self-reliance in solar power whilst continuing to export surplus to the grid. The house also includes a range of sustainable water management features such as rainwater harvesting, greywater reuse and water sensitive landscaping, resulting in a 90% reduction in mains water usage. The latest upgrade is the inclusion of an electric vehicle (EV) for family transport, along with an electric heat pump hot water system and an induction stove, enabling disconnection from the gas supply. The solar system has been upgraded to 6.4 kW of PV with a 5 kW inverter to meet the additional energy loads and remain energy positive. All aspect of this project have been extensively documented on video and factsheets, with these resources made openly available through the project website (www.joshshouse.com.au) along with live performance data. The principles of how to build this house and its power and water systems have been used in the scaled-up projects below that enable the research team to examine the opportunities provided by shared infrastructure (Josh Byrne). B10 is ‘Werner (Sobek)’s House’ built by a prefabricated home manufacturer in Stuttgart’s Weissenhof Siedlung. The techniques and the innovations developed and tested range from the building’s design, production and assembly to the harvesting, storage and targeted local distribution of energy from renewable sources. B10 was completely prefabricated, with all building elements modularised for wastefree disassembly and reuse, based on an rigorous approach to industrial production combined with a high degree of customization. The building’s timber structure is lightweight and entirely recyclable, just as the façade and other features. Surplus energy harvested by PV panels and solar heat is either stored in B10 or passed on to a neighboring historical monument. Energy distribution is managed by an intelligent automation system specifically developed for B10. B10 generates 200% of its energy consumption: the premise is that the process of rebuilding and upgrading existing neighbourhoods is far too slow and therefore new infill buildings should be designed and built as generators and batteries to serve conventional neighbourhoods. This is a prototype supported by the German government, designed to boost existing The Renewable City: The Future of Low-Carbon Living 79 neighbourhoods’ renewable energy supply: B10 provides power to the neighbouring Weissenh of Museum, a Le Corbusier designed building (adapted from Sobek 2018). 6 Renewable Cities and Quarters City Energy Transitions: 100% Renewable Plans for Frankfurt and Munich, Germany Active City-House for the Renewable Metropolis: Active City House, Frankfurt, Germany The 100% renewable energy region movement is a growing force in Germany. Cities, too increasingly wish to control their energy destiny. Several German metropolitan cities adopt the regenerative resolve and initiative shown by the smaller 100% renewable villages and districts. The efforts by large metropolitan cities like Frankfurt am Main and Munich in combining bi-partisan political support, strategic planning and partnerships across sectors and administrative boundaries, raise the share of renewable energy, boost energy savings, and enable the testing of innovative energy infrastructure technologies. Critical were the urban planning and sustainable building frameworks these cities have put in place to guide their shaping of a 100% renewable city (Figs. 3, 4). The urban planning centred approaches by the metropolitan cities of Frankfurt and Munich in Germany to achieve 100% renewable energy reveal the dynamics of the broader 100% renewable movement, its impact on villages, towns, cities and regions, and its relation to advancing the urban sustainability agenda. A welldeveloped system of governance for the deployment of renewable energy systems (RES) has evolved at several spatial planning levels in Germany, giving rise to a rich energy relevant domain of spatial considerations for city planners, urban designers and architects in the design of RES infrastructure for metropolitan areas that are based Fig. 3 Freiham-Nord Masterplan, as part of Munich’s 100% renewable energy city concept. © Anis Radzi (2018) 80 P. Droege Fig. 4 Active-city House, Frankfurt by HHS Architects. © Anis Radzi (2018) entirely on local and regional sources. Successful examples in both cities illustrate how respective energy concepts are achieved, overcoming a range of specific regulatory, technical and methodological challenges. Frankfurt, to date, has the largest number of energy-efficient high-rise buildings in Germany with >1500 apartments, and >300,000 m2 of surface area built to a passive house standard, including schools, day nurseries, and sports halls (Stadt Frankfurt am Main, 2013). Growth in energy efficient building has been propelled by municipal obligations that require passive houses to be built on city land or land purchased from the city. It has also been boosted by the city’s “Green Building Frankfurt” prize, which is awarded to architects, planners, and construction firms for building innovative sustainable green structures. By requiring design submissions to comply with strict energy standards, the built results have brought great improvements to the quality and energetic performance of entire city quarters. The “Aktiv-Stadthaus” is a cooperative apartment block designed by HHS Architects and developed by Frankfurt’s own municipal housing agency. Built in 2016 on a former inner-city parking lot, the “plus energy” building covers the entire electricity demand of 74 apartments through a building-integrated PV roof and facade system coupled with an on-site energy storage facility. The infill development has transformed the image of the inner-city area as a place for high-quality, sustainable living. As a “power-and-storage” station, the block has demonstrated that urban buildings can help ease the ability of the city to cover its energy needs with renewable energy sources. And by using the locally-generated and partially-stored PV current in the block to power electric vehicles for shared use by residents, the development has contributed to raising their mobility and interaction with the city (adapted from Radzi 2018). The Renewable City: The Future of Low-Carbon Living 81 7 Replicable Renewable Energy Districts Net-Zero Energy Districts: An Integrative Business Model for US cities Renewable Malls: Transforming Shopping Centres Into Flexible, Decarbonized Urban Energy Assets The Rocky Mountain Institute has developed an integrative business model for developing net-zero energy (NZE) or ultra-low energy districts in a way that is attractive to the district developer, parcel developer, and tenants, as well as beneficial to the local electric grid and neighboring community. While many elements are broadly replicable, this business case was first modeled specifically for the developer of a proposed 180-acre, 6 million square feet mixed-use NZE development located on a former industrial site in a midsize US city. The RMI uses the term net-zero energy to describe the general concept where the energy consumption of a building or multiple buildings is offset by renewable energy on an annual basis and should not be taken as implying alignment to any one specific, more granular, definition (Fig. 5). Urban systems de-carbonization is achievable if supported by measures for energy efficiency and integration of renewable energy sources (RES). In this context, a key role can be played by shopping malls. They are usually identified as “icons of consumer society,” but they also have a huge energy retrofitting potential. Moreover, they can have an active role in the future smart grid, connecting buildings and energy Fig. 5 Sample IESP cash flow for net zero energy districts. © Rocky Mountain Institute 2018 82 P. Droege Fig. 6 Robinsons place Dumaguete, Manila. © ABS-CBN News 2018 infrastructures. Photovoltaic (PV) and energy storage systems (ESS) play a fundamental role in exploiting such potential, and can very quickly become a cost effective solution contributing to emissions reduction, as demonstrated in the presented case study. Considering the short economic perspective of investors, the capital expenditure associated with retrofitting could be a barrier, and the evaluation of suitable economic indicator of primary importance to choose among several retrofitting strategies. Despite the fact that overall legislative frameworks and regulations do not promote shopping centers as key energy and social infrastructures to achieve ambitious targets in the ongoing urban transformation, energy-efficient shopping malls massively using RES and ESS can actually become the backbone of the city of tomorrow (Fig. 6). 8 The Sun’s Urban Energy Systems PV City: Effective Approaches to Integrated Urban Solar Power Solar City: The Urban Fabric as Solar Power Plant: Amsterdam, London, Paris, New York, Seoul, Tokyo Photovoltaic (PV) energy systems are on their way to becoming the cheapest form of electricity production in most countries. They have reached a cost level that makes PV competitive in several market segments: the cost of generating electricity from PV has reached parity with retail electricity prices, i.e., socket parity. PV is also particularly suited for the integration into existing and new infrastructure, for example, in buildings, canopies, sound barriers, and the like. For this reason, solar PV represents a key technology for prosumers at the building, district, and city level (Figs. 7, 8). In the 2016 draft of the recast of the RES and electricity EU directives, the concept of self-consumers is pushed as a driving force toward decarbonization of the electricity and heating sector at the city level associated with the creation of local energy communities and collective self-consumption as an emerging business model (Moser 2018). The Renewable City: The Future of Low-Carbon Living 83 Fig. 7 Veteran Freiburg Solar Settlement, Vauban, Germany. © plusenergiehaus.de 2012 Fig. 8 Renovation of Halle Pajol by Jourda Architectes, Paris. © apur.org 2017 The degree of urbanisation has made the decarbonisation of cities and urban areas a paramount importance. The implementation challenge is particularly poignant in the urban energy services sector, where conventional infrastructure-scale solutions deepen climate injustice. Conventional infrastructure-scale energy production components (i.e., fossil fuel powered power plants) must be contrasted with the “solar city,” where the urban fabric is reconstituted as a platform for decentralized production of solar electricity at a scale that advances the twin aims of sustainability and justice, yielding the economic, social, and environmental implications of urban decarbonization. The issuing of solar bonds and other financing means has been modeled to show that a city of the size and nature of New York, studied along with Amsterdam, London, Munich, Seoul and Tokyo, could be financed with a 10–12 year investment maturity horizon. The city has a potential solar energy to power conversion capacity—calculated on reasonably available roof areas only—of nine GWp or 11 TWh per year, providing about a quarter of its annual power consumption on average: Manhattan: 6%, the Bronx 31%, Brookly, 35%, Queens, 42% and Staten Island 48% (Byrne 2018). 84 P. Droege 9 Large-Scale Urban Regeneration Programs and Systems Renewable Wilhelmsburg: recruiting the International Building Exhibition to fight climate change Implementing the Heating Sector Transition Integrated Urban Infrastructure: Energy Storage and Sector Coupling Germany has a long history of building exhibitions, beginning in 1901. A building exhibition is always more than a showcase for architecture: building exhibitions drive urban development (IBA Hamburg, 2009). Building exhibitions concentrate and coordinate private and public spending on construction in an area or region with specific problems, as well as specific opportunities. So, they represent a treasure trove of more than a hundred years’ experience when it comes to finding innovative solutions for the most pressing problems of urban community life. Many ideas still live on today. From 2007 through 2013 Hamburg hosted an international building exhibition (IBA) on Europe’s largest river island, Wilhelmsburg (Figs. 9, 10). It initiated 70 building and 14 social and cultural projects (IBA Hamburg, 2014) in order to demonstrate what is possible when an entire city district is remodeled according to social and environmental considerations. These projects were designed to show what the future of modern environment friendly town planning might be, and how cities could be remodeled in a climate-friendly or even climate-neutral way. Another advantage was that a neglected district of Hamburg with a negative image could be reinvented as a pioneer of energy-efficiency and social inclusion. To realize the “Future Concept Renewable Wilhelmsburg,” IBA specified four operational fields. First of these was the refurbishment of the existing building stock, second, ‘new buildings of energetic excellence’, third‚ ‘local district heating’, and fourth‚ ‘local renewable energies’ (Hellweg 2018). The heating sector represents one of the biggest challenges to achieving climate neutrality in regions with cold winters. Local municipalities will have an important Fig. 9 IBA Wilhelmsburg. © IBA-Hamburg 2014 The Renewable City: The Future of Low-Carbon Living 85 Fig. 10 Renewable Wilhelmsburg. © IBA-Hamburg 2014 role to play in this process. In Germany challenges arise with the transformation of the heating sector and the possibilities for action facing local municipalities. There are two main areas of action: the energy-efficiency retrofitting of existing buildings, and the transformation of district heating systems. With respect to the energy-efficiency refurbishment of building stock, it is important that cities and municipalities look at private, as well as public properties, and address concerns about historical preservation and social issues. District heating grids allow for the costefficient integration of renewable energy and waste heat sources; however, operating conditions, and in some cases network structures, must be modified accordingly (Sparber et al. 2018; Weiß et al. 2018). The generation and transmission processes of renewable energy still takes mainly part in rural and peri-urban areas—not yet in urban centers at sufficiently significant scale. Many technologies easily implemented in lower density districts such as wind, water or biogas production are not yet adopted for application in urban areas— one exception is solar power and thermal energy. But even solar electricity is more widely applied in lower density and rural areas although its application in urban areas matches the existing grid infrastructure well. In contrast to rural areas with grid integration problems energy infrastructure in urban centers is already well prepared for renewables integration. There are almost unlimited energy storage possibilities with enormous capabilities but also large differences. There is a fundamental necessity to combine and couple the different energy sectors for electricity, heat, cold, gas and transport. Only in coupling the energy sectors and using cheap and efficient energy storage options from one energy sector to solve challenges within another the energy transition process can be managed in an efficient way (Stadler and Sauer 2018). 86 P. Droege 10 Lifestyle-Embodiment of Low Carbon Living Kalkbreite Cooperative, Zurich, Switzerland Ortoloco, Zurich, Switzerland The Kalkbreite development, completed in 2014, stands for a class of communally designed and operated, internally networked, cooperatively owned inner-urban flexspaces: core living spaces with common, flexibly rentable support spaces for meeting, working, living and accommodating guests. Genossenschaft Kalkbreite is a cooperative of 850 members comprising neighbourhood residents, tenants, and several local associations. It is responsible for the management of the Kalkbreite development, a large-scale mixed-use urban project located in Zurich-Aussersihl, Switzerland. The project was constructed based on the principle of creating and leasing affordable residential and commercial spaces, combining living, working and culture, integrating a mix of social groups and shared facilities, and promoting sustainable development. All of which had to be in line with the objectives of the so-called 2000-W Society. The principles sustain vibrant urban life within one neighbourhood block (Figs. 11, 12). The building is organised around internal network spaces. The cooperative works well with Zurich wide agricultural cooperatives like Ortoloco. This is one of several urban and regional agricultural cooperatives serving the metro-city of Zurich. These own and lease agricultural space and operate it on biological and agroforestry principles. Reducing food miles and global consumption Ortoloco and a series of other similar cooperatives are good match and expression of emergeing lifestyles that serve city dwellers that become vested in and support through shared cultivation, harvesting, storage, distribution and consumption largely based on city dwelling communities within bicycling distance. Ortoloco is a self-managed vegetable cooperative based in Dietikon, Zurich. As a joint initiative of farmers and consumers, Ortoloco leases 1.4 hectares of arable land from organic farm Fondlihof in the Limmat Valley of Zurich to create their own Fig. 11 Kalkbreite housing cooperative by Müller Sigrist Architekten. © Martin Stollenwerk 2018 The Renewable City: The Future of Low-Carbon Living 87 Fig. 12 Ortoloco community events. © Ortoloco 2018 community vegetable farm. Over 60 types of vegetables and a variety of edible wild herbs are harvested weekly, distributed and consumed by members of the cooperative. The cooperative operates on the principle of producing quality local food, ensuring fair working conditions, and maintaining sustainable production methods. Members of the cooperative participate in making important decisions, and are involved in the operation of the farm. This means that costs, risks, and profits are shared. The cultivation of vegetables takes place according to the directives of Bio Suisse, a Swiss certification for organic produce. The range of produce available to consumers change according to the seasons, and is distributed through established food “depots” and consumed weekly though vegetable bags subscribed for at least one year by members from Zurich, Dietikon and surrounding areas. Ortoloco was inspired by the book Neustart Schweiz, which described a vision for a local economic model that ensured a community a wide range of services such as a bakery, dairy, and kindergarten amongst others, all of which were managed by local citizens. Individuals involved are expected to lend their specific skills to the neighbourhood. Whole neighborhoods instead of individual households would jointly organize projects, especially in the development of local food supplies. 11 Fremantle as Renewable Laboratory From White Gum Valley (WGV) to Smart City Renew Nexus Ten House Living Lab Study The objective of the 10 House Living Labs project was to understand which factors influence house performance, as previous research has shown that houses designed to be energy and water efficient often do not perform as intended. While the design is important to minimise resource consumption, the way houses are used can have an equal effect on performance (Figs. 13, 14). 88 P. Droege Fig. 13 WGV living lab. © CRC Low-Carbon living laboratory 2018 Fig. 14 RENeW Nexus. © Curtin University 2018 The project consisted of a longitudinal study of ten detached suburban family homes located in the City of Fremantle. While these houses had a mix of demographics and building designs, they all presented energy or water efficient features, such as solar panels, solar hot water and rainwater tanks. The houses also presented elements of climate sensible design. The ten houses had their electricity, water, gas, solar energy generation, rainwater use and internal temperature monitored for two years. The first year of data collection was used to establish a baseline in terms of occupant behaviours and practices and to evaluate the homes from a design perspective. During the second year, a behaviour change program was implemented, providing each household with a series of tailored tools designed to increase their awareness and facilitate a reduction of water and energy while enabling occupants to maintain a high-quality lifestyle. This project demonstrated that while the energy efficient houses perform better than standard Australian dwellings, they do not operate to their full potential. Overall house performance is attributed not only to construction quality, maintenance and technology but also to everyday house operation. The latter is driven by occupant practices, which are reproduced sequentially as part of an established routine. The results of the 10 House Living Labs project were used to develop the concept of the The Renewable City: The Future of Low-Carbon Living 89 Home System of Practice, which explains occupant dynamics within a home and enables the creation of innovative technologies to improve resource efficiency while fulfilling occupants’ needs. Mainstreaming Zero Energy Homes This national project is working with major land developers and builders to deliver a series of Net Zero Energy Homes (ZEH) in residential display villages around Australia with the aim of better understanding cost and market perception barriers to this offering whilst increasing engagement amongst industry players. A key stage of the project includes collaborative design charrettes with builders to ascertain the steps required to get their ‘base design’ to ZEH status whilst tracking cost and trade capacity implications. The second stage involves surveying visitors to the display homes to understand the level of interest in the design and technologies underpinning the ZEH performance, versus interest in other house features. These activities are being captured in a series of videos and industry reports for wide dissemination. To date, ZEH display homes have been built in Townsville (Queensland), and Melbourne (Victoria), and others are underway in Perth (WA) and Canberra (ACT). Findings from the design and building of the ZEH homes are that major energy efficiency gains were obtained mainly from additional insulation, glazing upgrades and energy efficient appliances (hot water systems and air conditioners in particular). In addition, only a relatively small sized PV system (4 kW) is required to cover the net needs of a typical Australian household provided that the building envelope is designed appropriately for the climate and the appliances are energy efficient. WGV Living Lab WGV is a 2.2 ha medium density, 100 dwelling residential infill development located in the City of Fremantle. Led by the WA State Government’s land development agency LandCorp, WGV demonstrates design excellence on many levels by incorporating diverse building typologies (detached houses and apartments), climate sensitive considerations, solar energy generation and storage, innovative water management and creative urban greening strategies. The project has received international certification as a ‘One Planet Living’ community. Researchers are following the WGV development process from construction through to occupancy, using a ‘learn-by-doing’ approach to research where innovations are tested in real-life settings with the aim of informing policy and industry outcomes. Research activities include the monitoring of different dwelling types to assess design performance, as well as the impact of technology choice and occupant behaviour on energy use and carbon emissions. The project is also exploring the inter-relationships between developers, local government, builders and purchasers, low carbon aspirations and outcomes, and how these can be better aligned. As of late 2018, WGV is approximately 60% completed and occupied. Monitoring is underway across the development and data is being utilised by residents, researchers and industry. Learnings from the WGV project are being shared with industry and government through tours, speaking events and technical publications. 90 P. Droege A 10 part web-based video series called ‘Density by Design’ (www.densitybydesign. com.au) documents the WGV Living Lab story in detail as a means of sharing the project journey and research outcomes to a broad audience. WGV is demonstrating that low carbon residential developments are technically feasible and commercially viable in today’s market with ‘As Built’ modelling and early building performance data indicating that WGV will meet its design goal of being a Net Zero Energy precinct. What’s more, the collaboration between industry and researchers, which has been enabled by the CRC for Low Carbon Living, has led to a ground-breaking trial for shared solar power and battery storage technology on strata-titled developments. Beyond WGV Project is examining how to extend WGV innovations in scale across a brownfield redevelopment land in Fremantle. The area is the focus of research by both the CRCs for Water Sensitive Cities and Low Carbon Living. There is an opportunity to prototype a precinct scale sustainable neighbourhood across the whole precinct. The vision is to incorporate a range of innovations such as community batteries, water sensitive urban design, and a potential Trackless Tram transit system linking the precinct to the city centre in Fremantle. ‘Beyon WGV’ will seek to remove major barriers to new energy and water solutions for future redevelopments in the Knutsford precinct. This presents the real world challenge for decisions about establishing a business case and alterative governance model for these alternative systems. Further, investigations to date suggest that there are also no major technical barriers to the installation of renewable energy and water systems at a precinct scale, the major challenges sit in the areas of (a) developing alternative/integrated water and energy infrastructure that can align with uncertainties of multiple land owners and incremental development patterns; (b) engaging the stakeholders including business and citizens over the long term; (c) keeping the vision of what is being created, focused for 20–50 years; (d) developing appropriate governance and business models to support the rollout; and (e) in relation to the above marrying with the Local and State Government decision making frameworks and planning systems. This researchers are also in discussion with City of Fremantle and LandCorp about how to manage the urban renewal process over the long term to realize the vision of Knutsford as a leading sustainable development precinct. RENeW Nexus The RENeW Nexus project is supported and funded by the Australian Government through the Smart Cities and Suburbs Program. The program aims to help local governments and communities use smart technology and increase the accessibility and use of public data so that cities, suburbs and towns become more liveable, productive and sustainable and urban service delivery becomes more efficient and effective. The project sponsor is Curtin University, and project partners include Murdoch University, City of Fremantle, Landcorp, Power Ledger, Western Power, Synergy, energyOS, CISCO and Data 61/CSIRO. The project has begun to explore the theory The Renewable City: The Future of Low-Carbon Living 91 that the value of solar energy can benefit the grid and community through peer-to-peer trading across the grid. Further, the value of water can be captured if potable water can be supplemented by utilising rainwater and greywater through the subsurface aquifer to other household and landscape systems. For both solar energy and water systems the focus is on peer-to-peer trading across the power grid or within a micro grid environment, and through a water balance across the aquifer in a development, or storage facilities in an established urban development. This is a distributed system where the transaction layer is blockchain based, and can be deployed with smart metering capability to create a dynamically connected smart city environment. The first trial of this system is being carried out in the City of Fremantle and includes the energy grid provider and retailer, a water provider and retailer, the City, a state developer and most importantly citizens as prosumers and consumers of energy and water. Data analytics will determine trading logic and suitable conditions that are required, stakeholder satisfaction, utilisation of assets and efficiency gains achieved through peer to peer trading. The project trial will also allow for demonstration of the proposed distributed energy and water ledger that will be implemented at East Village at Knutsford. This project is enabling research and data analysis to support and inform the transition to a new energy and water network. 12 Climate Design for Social Justice Solar for Gaza—Low Conflict Living As An Existential Human Right: Gaza Sustainable Neighbourhood Design in Developing Countries Peaceful cooperation is a precondition for being able to effectively counter the causes of climate change, and successfully adapt to its effects. Solar for Gaza (S4G) was developed in the spirit of the ClimateforPeace.org campaign, a global call for the cessation of armed conflict in order to address one of the world’s greatest common enemies: manmade global warming and growing fossil and nuclear energy risks. Solar for Gaza emerged in response to Israel’s Gaza Strip bombings between December 27, 2008 and January 18, 2009—officially known as Operation Cast Lead—when a group of architectural students in Liechtenstein took up a long tradition of “engagement design,” seeking to support academic and civic efforts in Israel and Gaza to address—from afar—the suffering of ordinary people caught in a seemingly permanent and tightening cycle of violence. Sketched out a Gaza and its wider region entirely based and prospering on renewable energy. It specified geographical, social, economic, technical, organizational and political factors supporting the incorporation of renewable energy into various phases of relief, recovery and regeneration (Figs. 15, 16). It was also advanced as embedded in an inspired regional initiative—Solar for Gaza and Sderot—in a collaboration between the Arava Institute for Environmental Studies, the Institute for Global Leadership at Tufts University and the Chair for Sustainable Spatial Development at the University of Liechtenstein (adapted from Droege et al. 2018b). 92 P. Droege Fig. 15 Solar installation in Gaza. © Jersualem Post Fig. 16 Village solar installation. © Greenpeace Considering that almost 90% of global urbanization is projected to occur in countries of the developing world, many with substantial social justice, equity and poverty challenges, cities’ growth in these countries will both have a significant impact on global GHG emissions, seriously threatening any effort to reduce them—and deepen their dependence on debt inducing fossil and/or nuclear energy dependency. Energy consumption is mainly determined by the building and transport sectors, but is also influenced by other issues that urban growth has to face: rising demand for food and greater demand for potable water, combined with changing rainfall patterns and depletion of aquifers. To cope with all these challenges, a paradigm shift is required, that is, a different urban design approach that affects the urban form, texture, and land use, and the way the basic urban services, such as energy, water, food, and waste treatment, are designed and provided, with a holistic view. A sustainable neighborhood design process in tropical climates is discussed, outlining the importance of adopting a systems perspective and considering infrastructure interconnections (adapted from Butera 2018). The Renewable City: The Future of Low-Carbon Living 93 13 Modelling Renewable Resource and Value Flows STAR—Mapping regional negative carbon performance—Renewable energy selfsufficiency and positive income streams: Lake Constance Alpine-Rhine Region, Switzerland-Liechtentein-Austria-Germany Value-Added and Employment Effects of Renewable Energies and the EnergyEfficiency Refurbishment of Existing Housing: Berlin, Germany The Space Time and Renewables (STAR) model has the ability to model and map on GIS platforms such time variable scenarios for regions, cities, towns, and neighborhoods. It was developed for the Lake Constance Alpine-Rhine Energy (LACE) Region to not only test when and how it can become entirely independent energetically, or whether it can sequester more atmospheric carbon than it emits, and how much financial value creation can be achieved—but also to demonstrate the model’s ability to test time sensitive scenarios for urban planning purposes. The LACE region not only has the potential to become carbon neutral, but even to become a CO2 sink that binds more carbon than it emits. The investments into the transformation process were assessed and juxtaposed with the fossil/nuclear energy savings (Figs. 17, 18). A shift of the systematic differential costs in time can be observed: initially the energy costs will rise, but in the longer term—from 2030 onwards—they will begin to fall dramatically. The savings gained from avoiding fossil and nuclear energy can be invested within the region to generate jobs and prosperity (adapted from Droege et al. 2018a). Fig. 17 The potential for regions to become energy self-sufficient is illustrated in the Lake Constance Alpine-Rhine Region in Central Europe. © Droege/oekom 94 P. Droege Fig. 18 Energetic refurbishment of apartment buildings in Germany. © Jens Wolf/DPA STAR used a methodological ‘plug-in’ for ascertaining the communal value capture coefficient. The Berlin based Institute for Ecological Economy Research developed a model to quantify the value added and employment effects generated by renewable energies at the local level, to fill the gap concerning the identification of local and regional economic effects of the energy transition. Discussions of climate protection and the energy sector transition are still dominated by cost considerations; however, decentralized efforts such as the expanded use of renewable energies at a communal level yielded new ‘value-added’ financial flows—from salaries, tax income and coporate revenue in the renewable energy planning, manufacture and servicing sectors. But energy-efficiency improvements to existing buildings, too, can have a positive economic impact with respect to local and regional value added and employment. For this the ‘renewables value added’ approach has been extended to account for the economic effects of energy-efficiency refurbishment of existing dwellings (from Heinbach et al. 2018). 14 Urban Carbon Sequestration The 4M Project: Increasing carbon sequestration and storage in city greenspaces, Leicester UK Low-Carbon Building Materials: The Soft House, Hamburg The 4M project used a spatial modelling approach to identify areas and landcover types in the city of Leicester, United Kingdom with the greatest potential for increased carbon storage. Davies et al. (2011) found that trees accounted for around 97% of the carbon stored in aboveground vegetation, and based on the spatial models, discovered treat potential for tree planting in residential and non-residential settings to increase aboveground carbon storage in the city, as well as to produce biomass that could be used to substitute for fossil fuels (Figs. 19, 20). The tree planting modelling assumed The Renewable City: The Future of Low-Carbon Living 95 Fig. 19 Land potential for tree planting and additional carbon stroage potential in Leicester, UK. © Davies et al. (2011) Fig. 20 The Soft House, Hamburg. © Sheila Kennedy, MIT planting of mixture of species already existing in the city, and the potential carbon sequestration over 25 years. This is compared to an alternate scenario where short rotation coppice is used to generate woody biofuel (Davies et al. 2011). The Soft House, designed by Kennedy and Violich Architecture, is an innovative work/live row housing project which demonstrates novel concepts in sustainable construction and domestic renewable energy generation. Located in Hamburg, Germany, it consists of four apartments units which uses a dynamic textile façade to harness sunlight, alongside solid wood construction. The energy-harvesting textile façade is responsive to movement of the sun, while inside the apartments transparent curtains 96 P. Droege allow the occupants to partition their domestic layout as needed. The curtains also help to regulate heat and warmth internally. The electricity generated by the external textile façade is fed directly into these LED embedded curtains, which thus is able to provide additional light inside the apartments. A dense wooden radiant floor linked to a geothermal source distributes cooling in the summer and heating in the winter. Each unit has a terrace space, a PV canopy, and a vertical convection atrium space that helps circulate air, brings daylight into the ground floor, and offers vertical views of the sky. The traditional all-wood construction adopted in The Soft House uses only wood dowel joints with no glues, nails, or screws, and is exposed as the interior finish. The solid spruce wood structure sequesters carbon. Spruce is said to absorb about as much carbon dioxide from the atmosphere as using reinforced concrete emits. The wood is also fully demountable for recycling at the end of the building’s life. The wood structure can be fabricated by local carpenters or small-scale manufacturers. This pilot project in sustainable construction illustrates the ability to create housing with reduced embodied material energy, that retains its soft natural character of the building material (Stauffer 2013). 15 Conclusion: Launching the Istanbul Protocol In conclusion: local, national and global proliferation of the principles underlying the documented initiatives has long become critical—without current policy, regulatory and market frameworks having been yet fully adjusted. To articulate the call for action, we propose the Istanbul Protocol: paradigms and principles to shift to cities and regions regenerated through renewable energy, individual and collective innovation. It is a call to the nation—and nations elsewhere—for states, cities and regions to rise and support fundamental transformation in its economy, institutions and governance to enable the systematic replacement of inherited energy systems with distributed renewable energy infrastructures fully founded on new technologies and community benefits. This is also of meaning to finding ways of regenerating and retrofitting existing neighbourhoods and their building stock. Acknowledgements This research analysis and compilation was funded by the CRC for Low Carbon Living Ltd supported by the Cooperative Research Centres program, an Australian Government initiative. Disclaimer Any opinions expressed in this document are those of the authors. They do not purport to reflect the opinions or views of the CRCLCL or its partners, agents or employees. The CRCLCL gives no warranty or assurance, and makes no representation as to the accuracy or reliability of any information or advice contained in this document, or that it is suitable for any intended use. The CRCLCL, its partners, agents and employees, disclaim any and all liability for any errors or omissions or in respect of anything or the consequences of anything done or omitted to be done in reliance upon the whole or any part of this document. The Renewable City: The Future of Low-Carbon Living 97 Peer Review Statement The CRCLCL recognises the value of knowledge exchange and the importance of objective peer review. It is committed to encouraging and supporting its research teams in this regard. The author(s) confirm(s) that this document has been reviewed and approved by the project’s steering committee and by its program leader. These reviewers evaluated its originality, methodology, rigour, compliance with ethical guidelines, conclusions against results conformity with the principles of the Australian Code for the Responsible Conduct of Research (NHMRC 2007), and provided constructive feedback which was considered and addressed by the authors. Contributors Primary other contributors: Anis Radzi, Peter Newman, Josh Byrne, Mike Mouritz, Greg Morrison, Kayla Fox-Reynolds - and the authors of the second edition of Droege, P. 2018 Urban energy transition: renewable strategies for cities and regions. Elsevier – listed below and referenced throughout this paper. © 2018 Elsevier. References Boulding KE (1966) The economics of the coming spaceship earth. In: Jarrett E (ed) Environmental quality in a growing economy. Resources for the Future/Johns Hopkins University Press, Baltimore, MD, pp 3–14 Butera FM (2018) Sustainable neighborhood design in tropical climates. In: Droege P (ed) Urban energy transition—renewable strategies for cities and regions. Elsevier Byrne J, Job T (2018) Utilizing the Urban fabric as the solar power plant of the future. In: Droege P (ed) Urban energy transition—renewable strategies for cities and regions. Elsevier Davies et al (2011) Mapping an urban ecosystem service: quantifying above-ground carbon storage at a city-wide scale. J Appl Ecol 48:1125–1134 Droege P, Dieter DG, Ariane R, Matthias S (2018) Building regenerative regions rapidly: the STAR energy model as regional planning tool. In: Droege P (ed) Urban energy transition—renewable strategies for cities and regions. Elsevier Droege PS, Teichman, Cody Valdes (2018) Solar for gaza: an energetic framework for renewable peace and prosperity for gaza and its greater region. In: Droege P (ed) Urban energy transition— renewable strategies for cities and regions. Elsevier Fuller B (1968) Operation manual for spaceship earth. Lars Muller George H (1879) Progress and poverty: an inquiry into the cause of industrial depressions and of increase of want with increase of wealth: the remedy. Robert Schalkenbach 1942 Edition Heinbach K, Bernd H, Steven S (2018) Value-added and employment effects of renewable energies and the energy-efficiency refurbishment of existing housing—case study: Berlin, Germany. In: Droege P (ed) Urban energy transition—renewable strategies for cities and regions. Elsevier Hellweg U (2018) Renewable Wilhelmsburg, Hamburg, Germany: using the international building exhibition to fight climate change. In: Droege P (ed) Urban energy transition—renewable strategies for cities and regions. Elsevier Moser D, Marco L, Laura M (2018) Photovoltaic city: effective approaches to integrated urban solar power. In: Droege P (ed) Urban energy transition—renewable strategies for cities and regions. Elsevier Radzi A (2018) The 100% renewable energy metropolis: governing the design of cities for renewable energy infrastructures. In: Droege P (ed) Urban energy transition—renewable strategies for cities and regions. Elsevier Sobek W (2018) Buildings as renewable power plants: active houses for the electric city. In: Droege P (ed) 2018 Urban energy transition—renewable strategies for cities and regions. Elsevier Sparber W, Roberto F, Chiara D (2018) Thermal city: comprehensive guide to the heating and cooling of Urban areas. In: Droege P (ed) Urban energy transition—renewable strategies for cities and regions. Elsevier 98 P. Droege Stadler I, Sauer M (2018) Urban energy storage and sector coupling. In: Droege P (ed) Urban energy transition—renewable strategies for cities and regions. Elsevier Stauffer NW (2013) Building façades that move, textiles that illuminate: A pathway to flexible, resilient architecture. http://energy.mit.edu/news/building-facades-that-move-textiles-thatilluminate/. Accessed 20 Oct 2018 Ward B (1966) Spaceship earth. Columbia University Press Weiß J, Elisa D, Bernd H (2018) Implementing the heating sector transition in our cities—challenges and problem-solving approaches based on the example of municipalities in Germany. In: Droege P (ed) Urban energy transition—renewable strategies for cities and regions. Elsevier Assessment of Prerequisites and Impacts of a Renewable-Based Electricity Supply in Austria by 2030 Gustav Resch, Gerhard Totschnig, Demet Suna, Franziska Schöniger, Jasper Geipel and Lukas Liebmann Abstract In the final version of the Climate and Energy Strategy, the Austrian Federal Government postulated an ambitious target for the domestic expansion of renewable energy sources (RES) in June 2018: The goal is to generate electricity by 2030 to the extent that the national total electricity consumption is covered 100% (at a yearly balance) from renewable energy sources. This chapter provides information on how the transformation to an Austrian electricity system based almost exclusively on renewable energy generation can function and look like from a technical and economic point of view. Apart from that, we shed light on some of the requirements to and impacts of achieving this transition: On the one hand, a comprehensive economic reassessment of the expansion of renewable electricity supply in Austria by 2030 and the corresponding investment and support expenditures is presented. Apart from economic impacts, we also shed light on the impacts concerning supply security that come along with the strong uptake of renewables, specifically due to the massive expansion of volatile electricity generation from variable renewables like wind, solar and run-of-river hydropower. In conclusion, it should be noted that although the #mission2030 goal for the expansion of renewable energies appears G. Resch (B) · F. Schöniger · J. Geipel · L. Liebmann Energy Economics Group, Institute of Energy Systems and Electrical Drives, Technische Universität Wien (TU Wien), Gusshausstrasse 25/370-3, A-1040, Vienna, Austria e-mail: [email protected] F. Schöniger e-mail: [email protected] J. Geipel e-mail: [email protected] L. Liebmann e-mail: [email protected] G. Totschnig · D. Suna Austrian Institute of Technology (AIT), Vienna, Austria e-mail: [email protected] D. Suna e-mail: [email protected] © Springer Nature Switzerland AG 2020 T. S. Uyar (ed.), Accelerating the Transition to a 100% Renewable Energy Era, Lecture Notes in Energy 74, https://doi.org/10.1007/978-3-030-40738-4_4 99 100 G. Resch et al. extremely ambitious, it can nevertheless be classifiable as feasible. Massive investments in renewable technologies would occur, causing only a moderate increase in electricity prices since support expenditures would remain at a politically and socially acceptable level. Concerning supply security, it can be stated that expected increase in consumption due to the development of new consumption poses major challenges for the entire energy system. The model analysis shows that these are however manageable, but it requires considerable effort and proactive action. Rapid political action is consequently needed in order to be able to follow the ambitious path in a timely manner so that the planned increases in the generation stock as well as in necessary flexibility provision are available both in the early years after 2020 and later. Keywords Renewable electricity generation · Austria · Investments · Support expenditures · Supply security · Flexibility needs 1 Introduction This chapter provides information on how the transformation to an Austrian electricity system based almost exclusively on renewable energy generation can function and look like from a technical and economic point of view. Apart from that, we shed light on some of the requirements to and impacts of achieving this transition. 1.1 Background and Policy Context In the final version of the Climate and Energy Strategy (BMNT 2018), the Austrian Federal Government postulated an ambitious target for the domestic expansion of renewable energy sources (RES) in June 2018: The goal is to generate electricity by 2030 to the extent that the national total electricity consumption is covered 100% (at a yearly balance) from renewable energy sources. In the previous years, a broad set of assessments have been undertaken in this thematic context: • In November 2015, the Association of Austrian Electricity Companies, namely Oesterreichs Energie (OE), published the electricity strategy “Empowering Austria”. It goes beyond the year 2020 and plans to increase electricity generation from renewable sources by 20 TWh by 2030 compared to the current renewable electricity generation (2015). According to this, production from hydropower, wind power and photovoltaics should increase by 6–8 TWh in 2030 and the stock of electricity produced from biomass CHP (2 TWh) would be secured. In 2030, the share of renewable energies in electricity generation should amount to 85%. • In April 2016, OE commissioned Ecofys and TU Wien to analyse which support systems for renewables would be the most cost-effective way to achieve the goals Assessment of Prerequisites and Impacts … 101 outlined in the electricity strategy. In doing so, it should take into account the feasible expansion potential in Austria, comply with European requirements and refer to trends in other member states of the European Union. From that point of view, an extensive evaluation and analysis of the expansion of renewable energies and the required investments and support expenditures was carried out (Tiedemann et al. 2017). In view of the current political circumstances, according to which an even stronger uptake of renewables is envisaged, a comprehensive economic reassessment of the expansion of renewable electricity supply in Austria by 2030 and the corresponding investment and support expenditures appears useful for the political debate. Apart from economic impacts, it appears of key relevance to shed light on the impacts concerning supply security that comes along with the strong uptake of renewables, specifically due to the massive expansion of volatile electricity generation from variable renewables like wind, solar and run-of-river hydropower. All this was done in the context of two studies commissioned by OE,1 aiming to support the implementation of the national integrated climate and energy strategy of the Federal Government (#mission2030) and the preparation of the energy security action plan. On the one hand, the study “Mission#Impact - Ökonomische Neubewertung des Ausbaus und des resultierenden Investitions - und Förderbedarfs erneuerbarer Energien in Österreich” (Resch et al. 2019) undertaken by TU Wien focusses on economic impacts and political needs. Complementary to that, on the other hand, the study “Versorgungssicherheit und Flexibilität bei 100% erneuerbarem Strom in Österreich im Jahr 2030 mit Hinblick auf 2050” (Suna et al. 2019) derived by AIT/TU Wien provides a first, comprehensive overview of the need for flexibility of the Austrian electricity system. Both studies focus on 2030 but provide an outlook beyond that (up to 2050). 2 Methodology and Key Assumptions Comprehensive model-based assessments of the electricity sector in Austria and its neighbors have been undertaken in the course of both studies. The techno-economic analyses are thereby based on a transparent presentation of the results as well as the underlying assumptions. The sources of the model assumptions are thematically relevant preliminary studies on the part of OE as well as existing databases at TU Wien and AIT—especially with regard to costs and the dynamically available deployment potentials of renewable energies in Austria. Individual elements, such as the detailed design of the support policies for renewable energies, have been adapted specifically for this study. 1 The authors gratefully acknowledge the financial and intellectual support provided by Oesterreichs Energie. For details on both studies we refer to https://oesterreichsenergie.at/the-world-ofelectricity.html. 102 G. Resch et al. 2.1 The Applied Modelling System The quantitative analyses carried out are based on the use of two complementary energy system models developed by TU Wien: • HiREPs: HiREPS is a power system simulation and optimisation model that allows for detailed assessments of the physical integration constraints of the power system. Thanks to a suitable grid representation also related limitations and/or requirements can be assessed. The model is used for the detailed modeling of the use of conventional energy sources and the effects of the coupling of electricity and heat generation by means of power-to-heat (P2H), the charging of electric vehicles and the necessary (pump) storage. The supply of renewable energy sources and the demand for electricity are included in the model as hourly (feed-in) profiles in accordance with the scenario specification. • Green-X: The Green-X simulation model identifies the required market incentives, funding needs and funding design, and provides a detailed analysis of how different energy policy instruments work. The model aims at indicating consequences of RES policy choices in a real-world energy policy context. In principle, it allows for conducting in-depth analyses of future RES deployment and corresponding costs, expenditures and benefits arising from the preconditioned policy choices on country, sector and technology level on a yearly basis, in the time span up to 2050. To maintain consistency, the models are coupled by an interface between detailed power system modeling on an hourly basis (HiREPs) and market research from today until 2030 and beyond (Green-X). Figure 1 gives an overview on the interplay of both models. Both models are operated with the same set of general input parameters, however in different spatial and temporal resolution. Green-X delivers a first picture of renewables deployment and related costs, expenditures and benefits on a yearly basis (2020–2050). The output of Green-X in terms of country- and technologyspecific RES capacities and generation in the electricity sector for selected years (2020, 2030, 2040, 2050) serves as input for the power-system analysis done with HiREPS. Subsequently, the HiREPS model analyses the interplay between supply, demand and storage in the electricity sector on an hourly basis for the given years. The output of HiREPS is then fed back into the RES investment model Green-X. In particular the feedback comprises the amount of RES that can be integrated into the grids, the electricity prices and corresponding market revenues (i.e. market values of the produced electricity of variable and dispatchable RES-E) of all assessed RES-E technologies for each assessed country. 3 Key Results and Findings This section is dedicated to shed light on key results and findings. We start with a brief recap of the modelled uptake of renewables in Austria’s electricity sector. Assessment of Prerequisites and Impacts … Solar PV Wind Yearly Ɵme resoluƟon (2006 -2050), years modelled: 2010 to 2040 103 LocaƟonal power plant database Green-X Transmission Grid • Energy/CO2-price development • Default (2010) technology costs • Energy demand development Financing condiƟons RES policy Hourly Ɵme resoluƟon (8760h), years modelled: 2030 & 2040 HiREPS Supply Demand ITERATION Non-economic barriers Dynamic cost-potenƟal curves, Policy interacƟon, Investment decision Storage • RES deployment • Dynamic cost development Common electricity market model (technological learning) 160,000 RES LRMC [€/MWh] 140,000 120,000 • Feedback on RES market values • Feedback on curtailment of RES • Feedback on electricity prices [MWh] 100,000 80,000 60,000 40,000 20,000 0 RES deployment 1 25 49 73 97 121 145 169 RES system costs 193 217 241 265 289 313 337 361 385 409 433 457 481 505 529 553 577 601 Power plant dispatch & commitment (electricity, heat, transport) RES support expenditures Assessment of benefits (CO2 & fossil fuel avoidance) RES investments Electricity prices Total system costs Transmission grid expansion Fig. 1 Model coupling between Green-X (left) and HiREPS (right) Next, economic impacts are illustrated, indicating the necessary investments and the support expenditures required to refinance the RES uptake. Finally, a closer look is taken at supply security, in particular at the required system flexibility that comes along with the strong expansion of volatile renewables like wind and solar (Fig. 2). Electricity generaƟon from RES (with technology details for new plant (post 2020)) and RES share -yearly, dynamic development Breakdown of RES electricity today (2016) & tomorrow (2030) 92,2% 90% 80 (OE core scenario**) Other RES*** Solid biomass (energy sector) Wind Photovoltaics Hydropower 70 72,6% 70% [TWh] 60 60% 50 50% 40 40% 30 Other RES 30% Solid biomass (electricity sector, with support) 20 Wind Photovoltaics 10 Hydropower RES power plant stock (installed up to 2020) 20% 10% RES share in gross electricity demand 0 0% 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 80 0,7 2,0 70 17,2 +30 TWh 60 [TWh] 80% [% -Share in gross electricity demand] 90 50 40 2,6 2,0 Basevalue 2016 13,5 5,4 1,1 30 20 41,5 47,7 10 0 Status Quo (2016) +30 TWh* (OE core scenario**) Outlookto2030 Remarks: *Net increase from 2016 to 2030 of RES focus technologies (Hydro, Wind, PV); **OE core scenario: ConsumpƟon increase to 88 TWh unƟl 2030 and achievement of Mission#2030 target; ***Other RES: Incl. Biogas, Sewage and Landfil gas, Industr. Use of Solid Biomass and Biowaste, Geothermal. Fig. 2 Breakdown of the future development of renewable energy generation by construction period (left) and technology (right) according to the developed OE core scenario (source Green-X) 104 G. Resch et al. 3.1 The Future Development of Renewable Electricity Supply At the outset, the need for renewables expansion up to the year 2030, which would go hand in hand with the increase in the share of renewables from today’s balance of 72.6% (2016 level according to Eurostat (2017)) to 100%2 by 2030. Due to the nature of the target setting, electricity demand is therefore a central parameter for determining the demand for renewables. If the electricity demand according to the OE core scenario increases from around 72.4 TWh (2018) to 88 TWh in 2030,3 taking into account the predefined exemptions, this implies an increase in renewable electricity production from the current (2016) 52.6 TWh to around 81.1 TWh in 2030. Taking into account a decline in electricity generation from other renewables (by about 1.5 TWh4 ), this results in a net increase of about 30 TWh in hydropower, wind energy and photovoltaics. This increase can be achieved, for example, by increasing hydropower by 6 TWh and by 12 TWh in wind energy and photovoltaics, as assumed in the present study and as illustrated by Fig. 2. 3.2 Investments and Support Expenditures In the underlying study (cf. Resch et al. 2019), an economic reassessment of the future expansion and the resulting investment and promotion needs of renewable energies in Austria was made. In concrete terms, relevant aspects of the implementation of 2 According to the Austrian Climate and Energy Strategy #mission2030 of June 2018 balancing and balancing energy, flexibility necessary for operation of the network as well as the provision of guaranteed power shall continue to be provided in accordance with the technical and economic feasibility to ensure security of supply will be provided. Consequently, balancing and balancing energy to stabilize grid operation should not be included in the calculation of the 100% renewable electricity supply. Furthermore, the generation of own power from fossil fuels in the production of goods should continue to be possible for reasons of resource efficiency—and this is therefore not included in the calculation of the share of renewable energy to achieve the target. 3 On closer analysis, the comparatively high demand growth according to the OE core scenario turns out to be extremely realistic, especially considering new consumption. The main reason here is the rapid increase in e-mobility, ie the replacement of combustion engines based on fossil fuels by modern electric drives. Such a development seems to serve the purpose of decarbonising the entire energy system and especially of the mobility sector, or from today’s point of view almost without alternative. The interlinking of electricity and transport alone therefore requires an increase in electricity demand of around 7 TWh in the period from 2016 to 2030. For the development of consumption in the other sectors, however, a conservative trend is continued in the core OE scenario—and accordingly, in general growth rates in line with history (6-year average). 4 Particularly for biogas and according to the model analysis also for industrial biomass utilization, a significant reduction in production compared to today is to be expected due partly to expiring subsidies and due to the assumed persistently low energy price level. This sum totals 1.5 TWh comparing electricity generation from other renewables (i.e., biogas, sewage gas, landfill gas, geothermal, biogenic fraction of household waste and industrial biomass use) in 2016 and 2030. Assessment of Prerequisites and Impacts … 105 the #mission2030 target for renewable energies in Austria’s electricity sector are examined. The investment needs induced by the expansion of renewables are significant (e 2.6 billion per year according to the core scenario) The massive expansion also requires significant investment in renewable energy technologies. In line with the net increase in hydropower, wind and PV power generation by around 30 TWh, on average over the coming demand yearly investments of around e 2.6 billion can be expected. The investment requirement correlates with the renewables ambition—if, for example, it increases from 30 to 35 TWh due to increased demand growth, this will increase the investment requirement to around e 3 billion and vice versa. According to the core scenario, the support requirement is within a range of e 0.4– 1.3 billion per year—depending on the general development of electricity prices The analyzed need for support shows the demand for renewables, which is relevant from the consumer’s point of view. In the case of floating market premiums (net) support represents the difference between the (competitively determined) price for electricity from a given RES technology and the market value of the injected electricity into the grid. Since the market value of renewable electricity reflects the revenue situation on the wholesale electricity market, the clear dependence on the general development of electricity prices is given here. As illustrated above in Fig. 3 (left), three trend scenarios were considered in the modeling. According to the middle trend scenario, where a moderate rise in electricity prices is postulated, to around e 50/MWh by 2030, the annual average support requirement for the coming decade is around e 929 million (see Fig. 3, right). (Significantly) lower electricity prices, as postulated in the low-price scenario, would require a substantial increase (about 36%) in support expenditures. The same applies to the high-price scenario—if electricity markets follow this trend, this would result in a reduction of support costs by a considerable 53% compared to the core scenario of medium prices. The need for support is sensitive to the level of ambition of the renewable expansion On the other hand, the level of ambition regarding the expansion of renewable energies proves to be decisive. If, for example, renewables need to be increased by only 25 instead of 30 TWh net by 2030 due to a lower increase in electricity consumption (compared to the OE core scenario), this would reduce the average support expenditure by around 11%. An analogous statement (with opposite sign) naturally also applies in the case of a stronger renewal expansion in comparison to the OE core scenario serving as a reference. Further sensitivities provide information about the influence of the design of the funding instruments Within the framework of the underlying study, other relevant aspects influencing the resulting funding requirements were also examined in detail: 106 G. Resch et al. Trend scenarios for wholesale electricity prices, (yearly average, development over me) Support expenditures (yearly, on average 2021-2030) Cost expression: real, EUR 2015 100 Low Central 1,300 1.263 1,200 122 Cost expression: real, EUR2015 Other RES High 90 Solid biomass (energy sector, with support) 1,100 80 1,000 70 [Millionen €] 900 60 [€/MWh] Wind 246 50 800 929 98 40 500 30 400 217 Hydropower 81 Power plant stock (installed up to 2020) 160 221 167 300 20 435 58 38 65 80 200 308 100 269 194 0 0 2015 PV large-scale (free field, etc.) 154 700 600 10 Decentral PV 150 2020 2025 2030 2035 2040 2045 +30 TWh, low prices +30 TWh, medium prices +30 TWh, high prices Fig. 3 Electricity price trend scenarios (left) and breakdown of the resulting demand for electricity from renewable electricity plants by construction period and technology according to the developed OE core scenarios (low, medium and high electricity prices) for the years 2021–2030 (right) (Sources OE Expert Advisory Council (2018) (left) and Green-X (right)) • Strategic auction bidding as an expected consequence of inadequate competition, according to the model calculations, resulted in an increase in support requirements of 9% on average compared to the respective comparison scenario, where perfect competition was assumed. • A shorter guaranteed duration of support in accordance with current practice in Austria, i.e. 13 years instead of the across Europe common practice (20 years), leads to a significant increase of the support expenditures in the coming decade. The average annual funding requirement in the period from 2021 to 2030 would, according to the model calculations, increase by around 10% compared to the OE core scenario. This is in part a bringing forward of funding amounts that would otherwise have incurred later. In view of the expected increase in electricity prices in later years, but also to ensure the operation of RES plants over a longer period, even in the case of low electricity prices, it seems highly advisable to extend the duration of support. 3.3 Supply Security and Flexibility Provision The high proportion of wind energy and photovoltaics leads to weather-related massive fluctuations in power supply. Flexibility is needed to compensate in the short term and to compensate for longer-term (seasonal) differences between production and consumption. Suitable options, which differ in their application due to various technical and economic parameters, are examined in the context of this study. Assessment of Prerequisites and Impacts … 107 On the one hand, the flexibility options considered are the flexible power plant technologies consisting of gas power plants and combined heat and power generation, which can adapt their generation to changing situations in the grid as needed. Furthermore, the storage technologies (pump) storage power plants, compressed air storage, lithium-ion batteries and power-to-gas are considered. Additionally, load management is also taken into account, covering power-to-heat, electromobility and industrial load management. Further flexibility options include cross-regional and crossborder exchange via the transmission grid and the option of reducing non-controllable renewable generation (wind and PV). Within the underlying study TU Wien’s HiREPS power and district heating model is used for calculating a broad set of scenarios spanning the 2030, 2040 and 2050 years as well as various aspects of flexibility needs and security of supply. The following presentation focuses on the most relevant case for security of supply: the scenario “Extrema-LimitHydro-2030”. In this scenario, extreme weather conditions, including the occurrence of a “dark calm”, as observable in the underlying meteorological data of 2006, in combination with low water levels in hydro reservoirs are assumed. The scenario provides information on whether the flexibility options available to Austria (in the future) can help to ensure a cost-efficient and secure electricity supply. In this scenario, network expansion in line with the APG master plan or the TYNDP by ENTSO-E, as well as a substantial expansion of storage power in Austria, remain valid as flexibility options. Determining the demand for flexibility In order to analyze the consequences of increasing volatility in electricity supply and possibly also in electricity demand, the combined analysis of the load and the volatile, i.e. the non-controllable, renewable electricity supply by means of the residual load factor is used. The residual load is defined as the electricity demand of the end customer minus the generation of electricity from volatile renewable energies (wind, PV and run-of-river power). Although the total annual electricity demand (in public power supply, excl. for example industrial auto-producers) of 81.5 TWh in 2030 is essentially covered by the generation of these three renewable sources in 2030, the simultaneous feed-in occurring in each hour in relation to the load leads to temporary generation gaps (positive residual load) or to temporary generation surpluses (negative residual load). As applicable from Fig. 4, indicating the development of the residual load over time for the given scenario, only in the rarest cases is the hourly balance produced a priori. The residual load thus shows that part of the load that has to be covered by the controllable power plants or other forms that provide flexibility. The need for flexibility is derived from the fluctuations in residual load. These fluctuations occur both in the short term and in the long term and generally require different solutions. In order to better distinguish the short and long-term need for flexibility, the need for flexibility is broken down into five periods and evaluated. The shortest period is one day, followed by one week, one month, one season, and the longest period is one year. However, the requirements of flexibility (day, week, month, season and year) that occur recurrently within certain time periods are not summable 108 G. Resch et al. 15 Residual load [GW] 10 5 0 -5 -10 1 169 337 505 673 841 1009 1177 1345 1513 1681 1849 2017 2185 2353 2521 2689 2857 3025 3193 3361 3529 3697 3865 4033 4201 4369 4537 4705 4873 5041 5209 5377 5545 5713 5881 6049 6217 6385 6553 6721 6889 7057 7225 7393 7561 7729 7897 8065 8233 8401 8569 8737 -15 Hour (per year) Fig. 4 Development over time of the residual load according to scenario “Extrema-LimitHydro2030” (+shows deficit, −shows surplus) but instead measure the variability of the residual load for the corresponding period. For example, the daily need for flexibility measures the hourly fluctuations in residual load within one day. It is calculated as the sum of the positive hourly deviations of the residual load from the respective daily mean value of the residual load. The result is then quantified as amount of energy per day. The summary of these positive daily differences for all 365 days of the year shows the total daily need for flexibility within one year. In contrast, this study determines the annual need for flexibility as the cumulative sum (over all hours of a year) of the positive deviations of the seasonal mean values of the residual load from the annual average of the residual load. The annual need for flexibility thus characterizes the seasonal differences in residual load, for example in the case of an oversupply in the summer half-year and a shortfall in winter. The calculations show that the Austrian power system of the future will be subject to strong dynamics in residual load and generation. It will be necessary to be responsive to the changes during system expansion and operation in order not to reach the limits of safe operation and thus security of supply. Remarkable is the strong increase of the negative residual load and the negative gradient (GW/h) of the residual load as a result of increasing temporary power surpluses. This is mainly due to the future high shares of volatile sources wind and PV in combination with a possibly dynamic load (where demand is responsive to price signals for e-car charge and power-toheat by using electric boilers and heat pumps). Furthermore, the natural seasonal fluctuations of these plants must be managed. Depending on the scenario chosen, the need for flexibility is around 4.8 TWh per year, for example in the case of daily flexibility, and the annual flexibility requirement is around 10 TWh (cf. Fig. 5). The coverage of the need for flexibility as well as the use of power plants depend on price developments at the European electricity markets and the availability of the various flexibility options. It should also be borne in mind that merely meeting the need for flexibility, i.e. balancing variability, is not enough to guarantee a secure electricity supply. Here it is important to maintain the overall perspective and thus to balance Flexibility needs [TWh] Assessment of Prerequisites and Impacts … 11 10 9 8 7 6 5 4 3 2 1 0 109 10.0 4.8 4.4 4.0 3.1 daily weekly monthly saesonal (half year) yearly (hourly fluctuaons in RL (daily fluctuaons in RL per (weekly fluctuaons in RL (monthly fluctuaons in RL (seasonal fluctuaons in per day) week) per month) per season) RL per year) Fig. 5 Flexibility needs at distinct time periods according to the scenario “Extrema-LimitHydro2030” the residual load, both in a positive and in a negative direction. For this purpose, further measures should be provided in a suitable form. Furthermore, the complete and on-schedule expansion of the (pump) storage power plants (construction of about 2,900 MW in the considered scenario) according to current OE power plant list until 2030 will not be sufficient to fully meet the need for flexibility in implementing the expansion targets for renewable electricity generation from their own resources. 4 Conclusions The politically desired and promoted massive expansion of renewable energy as well as the expected increase in consumption due to the development of new consumption poses major challenges for the entire energy system. The model analyses show that these are however manageable, but it requires considerable effort and proactive action. Active political action seems to be crucial in order to enable the planned expansion of renewable power station capacities by means of adequate framework conditions. This includes, for example, speeding up the implementation of power plant and pipeline projects in due time, as well as raising public awareness on the part of politicians regarding the necessary and useful measures for implementing the energy transition. To maintain system stability, the required network infrastructure must also be available. This implies the implementation of the grid expansion plans at the national level according to the APG master plan or at the European level according to TYNDP by ENTSO E. Since the international electricity exchange is and will be an important part of a cost-efficient electricity system, the timely recognition of energy policy developments in the neighboring countries, such as the solutions to the 110 G. Resch et al. German coal exit, is a necessary precondition for a sustainable long-term planning of the measures to maintain security of supply in Austria. Flexible power plants, such as (pumped) storage power plants and thermal power plants, gas or biomass operations, as well as possibly longer-term power-to-gas in combination with cross-border exchange, will form the main pillars of the Austrian system flexibility. In addition to sufficient transmission capacities, the respective, actual availability in the neighboring countries is decisive for the cross-border exchange of flexibility. In the modeling, the addition of up to 2,900 MW by 2030 to (pump) storage power plant capacity according to the OE power plant list in accordance with the renewable target of #mission2030 is assumed. In addition, however, thermal power plants are also required, which can make a significant contribution to security of supply, especially in critical times such as dark skies. However, the future level of CO2 prices probably plays a key role for their profitability. In the future, if electricity market revenues are not sufficient to ensure the continued existence of the required power plants or to allow new investments, alternative arrangements might be necessary to safeguard the availability of capacity reserves in critical hours and/or days. In conclusion, it should be noted that although the #mission2030 goal for the expansion of renewable energies appears extremely ambitious, it can nevertheless be classified as feasible. Massive investments in renewable technologies would occur, causing only a moderate increase in electricity prices since support expenditures would remain at a politically and socially acceptable level. Rapid political action is consequently needed in order to be able to follow the ambitious path in a timely manner so that the planned increases in the generation stock as well as in necessary flexibility provision are available both in the early years after 2020 and later. In the underlying studies, model analyses of the effects of the ambitious goals of the #mission2030 is carried out for the first time. They should thus serve as a starting point for further analyses that are necessary for a fact-based specification of the necessary conditions for the economic expansion and use of flexibility technologies in the energy system of the future. References Bundesministerium für Nachhaltigkeit und Tourismus (BMNT) (2018) #Mission2030 – Endfassung der österreichischen Energie- und Klimastrategie 2030. Bundesministerium für Nachhaltigkeit und Tourismus, Juni 2018. http://www.mission2030.bmnt.gv.at#Mission2020 Eurostat (2017). Online database from EUROSTAT on energy statistics, accessed in July 2018. OE Expert Council (2018): Expert judgement (status 6 September 2018) on future electricity price trends, derived by OE’s Advisory Board for the study Mission #Impact. Vienna, Austria, 2018. Resch G, Liebmann L, Schöniger F (2019) Mission #Impact - Ökonomische Neubewertung des Ausbaus und des resultierenden Investitions- und Förderbedarfs erneuerbarer Energien in Österreich (in German). A study by TU Wien, commissioned by Oesterreichs Energie. Vienna, Austria Suna Demet G, Totschnig C, Messner H, Aghaie J, Kathan W, Friedl G, Resch F Schöniger (2019) #MissionFlex – Versorgungssicherheit und Flexibilität 2030 (in German). A study by AIT and TU Wien, commissioned by Oesterreichs Energie. Vienna, Austria Assessment of Prerequisites and Impacts … 111 Tiedemann Silvana, Klessmann C, El-Laboudy T, Resch G, Totschnig G, Welisch M, Liebmann L, Hiesl A (2017) Fördersysteme für erneuerbare Energien in Österreich (Endbericht – in German). A study commissioned by Oesterreichs Energie, done by Ecofys and TU Wien. Berlin, Vienna History and Recent State of TIMES Optimization Energy Models and Their Applications for a Transition Towards Clean Energies Kathleen Vaillancourt, Olivier Bahn and Nadia El Maghraoui Abstract Mathematical models of energy-economy-environmental systems (E3) provide a rational framework for exploring the effects of energy and climate policies and support adequate decision-making. Numerous models have been developed over the years with different solution approaches, features, geographical scope and time resolution. There is no complete or ideal models but different models that answer different questions or similar questions with different perspectives. Developed since the early 1980s, the TIMES (The Integrated MARKAL-EFOM System) optimization models have contributed to support decision-making at various geographical scales from global to city levels. In this Chapter, we distinguish a set of national studies that performed TIMES model developments to study the energy transition and address the impacts of integrating high levels of renewable energies on the system. Each study follows a different approach with the sole purpose to optimize the energy used in order to reduce greenhouse gas (GHG) emissions. Examples of applications are provided to illustrate the rich potential of optimization models for assisting decision makers with climate change mitigation. In particular, a special attention is given to the electricity sector as electrification of end-uses and decarbonization of the electricity sector are consistent priorities of actions across studies. Keywords Optimisation · Energy system models · Energy transition · Climate mitigation · Renewable electricity K. Vaillancourt (B) ESMIA Consultants, Blainville, QC, Canada e-mail: [email protected] O. Bahn GERAD and Department of Decision Sciences, HEC Montréal, Montreal, QC, Canada N. E. Maghraoui GERAD and Polytechnique Montréal, Montreal, QC, Canada © Springer Nature Switzerland AG 2020 T. S. Uyar (ed.), Accelerating the Transition to a 100% Renewable Energy Era, Lecture Notes in Energy 74, https://doi.org/10.1007/978-3-030-40738-4_5 113 114 K. Vaillancourt et al. 1 Modelling the Energy Transition As part of the Paris Agreement, most countries committed to reduce their greenhouse gas (GHG) emissions with the ultimate goal of keeping the global temperature rise below 2 °C. Moreover, it is increasingly argued that the carbon neutrality of the global energy sector should be achieved in 2050 to maintain the temperature below 1.5 °C by 2100. Climate change mitigation is a very complex problem with many different combinations of possible solutions, which vary among sectors, among regions, and over time. In all cases, however, achieving these commitments requires important transformation of energy sectors. The complexity of the links between the different energy sectors, as well as between the energy sector and the rest of the economy suggests the use of a systemic approach. In this context, mathematical models of energy-economy-environmental systems (E3) provide a rational framework for exploring the effects of energy and climate policies and support adequate decision-making. Numerous models have been developed over the years with different solution approaches, structures, intrinsic features, levels of details, geographical scope and time resolution. There is no complete or ideal models but different models that answer different questions and/or similar questions but different perspectives. Optimization E3 models provide a rigorous analytical basis for defining decarbonization pathways that meet growing demands with progressive reductions in GHG emissions at a minimum cost. Among the optimization category of models is the TIMES (The Integrated MARKAL-EFOM System) model generator developed within a Technology Collaboration Programme of the International Energy Agency and used by a large number of organizations worldwide. This chapter focuses on recent state of TIMES optimization energy models and their applications for a transition towards clean energies. Section 2 provides a brief overview of the main classes of E3 models with their main characteristics and roles for studying the energy transition. Section 3 takes a closer look at the optimization TIMES approach. Most recent developments in various TIMES models used worldwide are summarized in Sect. 4. Following these model improvements, examples of applications to a transition toward clean energies are provided in Sect. 5, before concluding in Sect. 6. 2 A Simplified Classification of E3 Models For many years, several models covering energy, economy, and environment (E3 models) have been developed. However, each model may follow a different approach. In order to aid potential users of these models to find out which one is most suited for a certain purpose or situation, several studies have attempted to classify them using different criteria (Bahn et al. 2005; Beeck 1999; Boulanger and History and Recent State of TIMES Optimization … 115 Bréchet 2003; Morrison et al. 2015). The most common criteria used to differentiate between these models concerns their analytical approach, namely bottom-up, top-down and hybrid. Bottom-up models use a techno-economic approach representing the technologies of the energy sector in detail while top-down models use a macroeconomic approach based on an entire economic description (Bahn et al. 2005). However, these two approaches become decreasingly relevant to the emergence of hybrid models in which the two approaches have been merged (Vaillancourt 2010). In addition, due to the recent advances in both model categories (bottom-up and top-down), the distinction between these categories tends to be somewhat confused (Loulou et al. 2004). This review does not include integrated assessment models capturing the feedback between energy and climate systems. 2.1 Techno-Economic Models Bottom-up models represent in detail the so-called Reference Energy System (RES) for one or more regions, including energy exchanges between regions. Resources, current and emerging technologies (extraction, production, consumption) and forms of energy are explicitly characterized by their technical and economic attributes (efficiency, emission factors, etc.) (Vaillancourt 2010). Bottom-up models calculate the production of primary and secondary energy and also the consumption of total final energy in order to meet energy demands as well as eventual emission reduction constraints (Bahn 2018). Demands are based on socio-economic (rather than energy) assumptions and are expressed exogenously from actual needs in physical units (number of houses, industrial production, vehicle-kilometers, etc.). We distinguish two main types of techno-economic models namely optimization models and simulation models (Vaillancourt 2010): • Optimization models minimize the updated total cost of the system in order to meet final demands while respecting environmental constraints. They, therefore, calculate a partial equilibrium between energy supply and demand in a perfectly competitive market and determine the least costly technological combination to satisfy final energy demand, as well as the price of each form of energy. Policies are modelled through constraints on technologies, forms of energy or air pollutants. • Simulation models focus on the representation of consumer behaviour (individuals, industries). They contain information on the competitiveness of rival technologies. The technological choices are determined by investments. Thus, the market shares of different technologies are not always based on optimal choices. Policies are modelled through constraints on market share and technology diffusion processes. The principal limitation noted in bottom-up models lies in the fact that they do not represent the complete interactions that link the energy sector with the rest of the economy. Indeed, the optimal solution, in this case, corresponds to a partial economic equilibrium (Bahn 2018). 116 K. Vaillancourt et al. The first optimization models developed were MARKAL (MARKet Allocation) (Loulou et al. 2004), EFOM (The Energy Flow Optimization Model) and MESSAGE (Model for Energy Supply Strategy Alternatives and their General Environmental Impact) (IIASA 2019). They were developed during the 70s and 80s in order to optimize energy systems in the medium term. Improved versions were then combined in more recent models, in particular the TIMES model (Loulou et al. 2016). TIMES are reference analysis tools of the Energy Technology Systems Analysis Program (ETSAP 2019) of the International Energy Agency. POLES (Prospective Outlook on Long-term Energy Systems) is a simulation model used by the European Commission (2019a). Similarly, the US Department of Energy uses NEMS (National Energy Modelling System) for annual energy outlook production (EIA 2019). MAED (Model for Analysis of Energy Demand) is yet another simulation model used to assess future energy demands based on assumptions on medium to long-term scenarios of socio-economic and technological development of a country or region (IAEA 2006). 2.2 Macroeconomic Models Top-down models represent the whole economy; however, they describe energy technologies in an aggregated way. These models may represent more interactions that link the energy sector with the rest of the economy. The principal limitation noted in top-down models is that they do not represent precisely energy technologies (Bahn 2018). Two main types of macroeconomic models can be distinguished (Vaillancourt 2010): • General equilibrium models that have a neoclassical view of the economic system describing the global economy through the behaviour of economic agents. They consider the feedback between quantities and prices and calculate an equilibrium price in each market assumed to be in perfect competition. They are useful for analyzing major structural effects in terms of supply and demand as well as longterm effects. They are used to analyze impacts of international climate policies on national economies and to proceed to a simulation of international cooperation strategies. • Macro-econometric models are neo-Keynesian whose economy is demand-driven. They capture the medium-term dynamics of the national economic aggregates and its components. Prices vary with supply and partial market imbalances. They allow analyzing the global impact of climate policy on economic variables such as gross domestic product, employment and balance of trade. The EPPA (Emissions Prediction and Policy Analysis) model of the Massachusetts Institute of Technology (MIT 2019) and the GEM-E3 (General Equilibrium Model for Energy-Economy-Environment Interactions) model of the European Commission (2019b) are examples of general equilibrium models used to analyze impacts of climate change policies. On the other hand, the Oxford model also called GMM History and Recent State of TIMES Optimization … 117 (Global Macro-econometric Model) is an example of a macro-econometric model that has been developed to perform more disaggregated analyses of the energy sector (Oxford Economics 2019). There also exist input-output models based on national data tables that are used to study the intersectoral effects of short-term climate policy at the national level, such as the effects of carbon taxes. The META-Net economic modelling system is applied to find the impacts of carbon taxes on national energy systems (Nakata 2004). 2.3 Hybrid Models Hybrid models have been developed to better integrate macroeconomic factors into techno-economic models. For example, TIMES-MACRO (Loulou et al. 2016) is a technological model linked to macroeconomic modules. In another example, recent versions of GEM-E3 incorporate in their general equilibrium framework a technoeconomic description of electricity supply (Capros et al. 2013). Finally, the LongRange Energy Alternatives Planning System (LEAP) model combines different modelling approaches: techno-economic, simulation, macroeconomic and accounting techniques (Heaps 2008). 2.4 Comparison of Approaches It should be recalled that there is no ideal or complete model, but rather many models whose choice will depend on the type of issues to be analyzed or the type of decisions to be made: • Bottom-up models are used to identify an optimal configuration of energy systems. These models can assess the impact from a techno-economic point of view on the energy sector of energy and climate policies. They are also called energy system models. • Top-down models are used to address the impact of energy and climate policies on macroeconomic variables such as employment and gross national product. The main differences in characteristics, as well as the main role and limitations associated with these two categories of models, reside in their traditional forms. These differences are summarized in Table 1. We should note, however, that these distinctions are decreasingly noticeable with the development of hybrid models (Vaillancourt 2010). In addition, we should note that this is not a comprehensive list of distinct features, as models differ in many dimensions, not only following the bottom-up and top-down classification but within each class of models as well. Bottom-up models for instance are characterized by alternative structures, geographical scopes, time resolution and assumptions about the future. Some models have a specific sector detailed (e.g. the 118 K. Vaillancourt et al. Table 1 Characteristics and roles of the two main families of E3 models Category Bottom-up models Top-down models Database Explicit and detailed representation of energy forms and technologies in energy sectors Energy flows More general representation of energy supply and demand in the main economic sectors Monetary flows Approach Techno-economic approach where energy balance conditions (supply = demand) are maintained throughout the system in physical units A macroeconomic approach where economic feedback between the energy sector and other economic sectors are taken into account Balance Partial balance: energy sector General balance: entire economy Demand Driven by the demand for energy services, exogenously specified by the user The use of energy is defined as the result of economic equilibrium Type Optimization models Simulation models General equilibrium models Macro-econometric models Input-output models Examples EFOM, MAED, MARKAL, MESSAGE, NEMS, POLES, TIMES EPPA, GEM-E3, GMM, META-Net Hybrid approaches (examples) Bottom-up with link to macroeconomic: MARKAL-MACRO, CIMS TB with a bottom-up description of some energy sectors: recent versions of GEM-E3 Role Identify a configuration of energy systems and measure the technical and economic impacts of implementing policies Evaluate the impact of policies on the global economy and macroeconomic variables such as employment and gross domestic product Limit (traditional version) Limited to the energy sector for policy analysis Limited to a more general analysis of energy sector policies LEAP: mix of bottom-up and top-down modelling techniques Source Adapted from Vaillancourt (2010) electric sector), while others include a full representation of the whole energy system. They are also characterized by different solution approaches which imply different assumptions about the decision process over time: some assume a perfect foresight context where actors can anticipate future events while making optimal decisions today and some assume they are myopic where decisions are made on the basis of current conditions. History and Recent State of TIMES Optimization … 119 3 A Closer Look at the Optimization TIMES Approach We provide next more detail on the MARKAL/TIMES bottom-up approach, as the reminder of this paper will focus on developments and applications with TIMES models. 3.1 MARKAL Model MARKAL model is one of the first bottom-up energy models that have been developed since the early 1980s after the first oil crisis. It has been widely used subsequently to study energy security issues after the first oil crisis, followed by environmental problems such as acid rain and now climate change mitigation. It is cast as a dynamic mathematical model with perfect foresight. This implies in particular that investment decisions are made for each time period with perfect knowledge of future events. A period may, for example, be of a 5-year duration; the years of the same period are assumed to be identical. Including a wide range of energy technologies, the model distinguishes each of them by describing its technical and economic parameters. The model calculates energy balances within the energy system to provide energy services at an overall minimum cost. MARKAL calculates then a (partial) balance of energy markets, meaning that energy producers deliver exactly how much energy consumers are willing to buy. Contrary to earlier bottom-up energy models, demands for energy services are elastic to their own prices in MARKAL. This enables the model to maximize the total surplus of energy producers and consumers while facing certain constraints, and allows a more accurate computation of the balance between supply and demand (Boulanger and Bréchet 2003). However, assumptions of perfectly competitive markets may be relaxed by introducing specific assumptions, such as penetration limits for new energy technologies. 3.2 TIMES Model The evolution of MARKAL is the TIMES model that combines the two MARKAL and EFOM approaches. TIMES is currently used by more than 80 institutions across 70 countries. It corresponds to a dynamic partial equilibrium model to analyze energy markets. Similar to MARKAL, TIMES relies on linear programming to maximize the total surplus of energy producers and consumers, while respecting specific constraints. This is operationally done by minimizing the total discounted cost of the energy 120 K. Vaillancourt et al. systems used to meet useful energy demands. The two models also share a multiperiod, multi-regional, structure, to analyze a (potentially large) number of regions while capturing energy trade between them. But TIMES provides more flexibility to modellers, for instance through time periods of variable lengths, a flexible number of hierarchical time-slices, a more refine approach for representing vintage processes, or a flexible definition of energy processes (Loulou et al. 2016). Moreover, the timing of investment payments is much more detailed in TIMES and allows distinct (and more realistic) capital flows whether it relates to large infrastructure (e.g. a new hydro dam) or smaller technologies (e.g. a car). TIMES acknowledges as well that global and technology-specific discount rates are time-dependent and not constant over time. TIMES deals with the entire energy sector but can also apply to a single energy sub-sector (e.g. electricity or transport). To describe energy systems, the model uses inputs that represent inventories of equipment related to existing systems, but also the characteristics of (potential) future technologies. Similarly, TIMES represents current as well as future sources of primary energy supply. In addition to these inputs, the model also supports energy-environment policy analysis (Loulou et al. 2016). Furthermore, in order to explore future energy systems, in the long run, TIMES adopts a scenario approach. A scenario is based on a set of consistent assumptions. The model also recognizes that the demand for energy services is elastic in relation to its own prices. This makes possible the endogenous variation of demands in the policy scenarios relative to the baseline scenario, capturing behavioural changes and their impacts on the energy sector. 4 Recent Developments in TIMES Models Used Worldwide We distinguish a set of studies conducted in different countries that performed TIMES model developments to study the energy transition and address the impacts of integrating renewable energies on the system. Each study follows a different approach and methodology with the sole purpose to optimize the energy used in order to reduce greenhouse gas (GHG) emissions. Given the popularity of TIMES models for studying the energy transition, it was not possible to review all relevant methodological developments. For instance, the latest review report of the ETSAP (Vaillancourt 2018) includes over 200 references published during the 2014–2016 period only with developments and applications of more than 80 TIMES models. We have selected few examples of recent papers to illustrate the numerous possibilities of TIMES in terms of analysis of the energy transition and renewable penetration. Moreover, we have restricted the selection of papers with analysis of deep decarbonization scenarios and very high renewable penetration rates. Consequently, other interesting developments of TIMES models are not necessarily covered in this chapter, including better representation of consumer behaviour and of other global challenges such as access to water and food. History and Recent State of TIMES Optimization … 121 4.1 Refine the Representation of Specific Sub-systems Systems analysis is a central concept to the developments and applications of these models. System analysis is a problem-solving method that provides a better understanding of the behaviour of complex systems such as energy systems and serves as a basis for improved decision-making with access to better information. The core of the approach is to separate an overall complex system into various components or sub-systems with the most appropriate level of detail for adequately supporting the decision-making process that it is supposed to serve. A sub-system can be considered to be a specific sector in a specific region in a specific time period and its interactions with other sectors and the same sector in other regions and time periods. Policies and targets can apply the entire system, as well as to some or all of the sub-systems. Given the complexity of energy systems, the large amount of data required to represent them in many details, and the numerous assumptions required to assign values to highly uncertain technical or economic parameters over time, developing specific sub-systems in existing large scale optimization models to study the energy transition is a methodological contribution in itself. For example, Sgobbi et al. (2016) have developed a comprehensive hydrogen supply chain module in a multi-regional TIMES model for European countries to assess its role in climate mitigation scenarios with reduction targets up to 80% by 2050 compared with 1990 levels. They distinguished four types of hydrogen production technologies from various input fuels in centralized and distributed versions: gasification and pyrolysis, reforming, electrolysis and nuclear reactors. Hydrogen is also a by-product of advanced ammonia and chlorine production technologies. The capture hydrogen transport in liquid or gaseous forms from centralized facilities. As another example, Vaillancourt et al. (2019) conducted a study to explore the role of bioenergy in Quebec’s rapid transition to a low-carbon energy system through a TIMES model for Canada with a detailed representation of multiple bioenergy pathways. Model developments allow a comprehensive representation of supply chains with: (i) a large variety of feedstocks (crops, fatty residues, forest residues, agricultural residues, pulp and paper residues, dedicated crops of fast-growing trees, organic municipal waste, manure, sewage sludge, and landfill biogas), (ii) many conversion processes (fermentation, transesterification, combustion, gasification, hydrolysis, pyrolysis, anaerobic digestion, etc.), and (iii) numerous options for final usages of bioenergies. 4.2 Refine the Time Resolution Traditionally, TIMES model are solved for a limited number of time periods over the 2050 or 2100 horizons with a limited number of annual time slice (e.g. 2–4 seasons and 2–4 intraday periods). Given the flexibility of TIMES for defining the time resolution as well as improvements in computing capabilities, few authors have 122 K. Vaillancourt et al. tested the impacts of having a greater disaggregation of the annual time dimension for studying the decarbonization of the electricity sector. In Krakowski et al. (2016), a TIMES model was used to evaluate the penetration of renewable energy in the French electricity system ranging from 40% to 100%. The purpose of this study was to broaden the debate on whether such high renewable energy penetration rates were feasible. TIMES provides a realistic representation of electrical systems and plausible options for their long-term development. The model was completed with a thermodynamic description of electrical systems to assess their reliability. In addition, the 2012–2050 horizon has been divided into 13 annual periods. Each period was further divided into seven seasonal periods (six monthly periods plus one period representing a potential winter week), each seasonal period was divided into two typical days (working days and weekends) and each typical day has been subdivided into six periods including two periods for the night, two for the morning, one for the afternoon period and the sixth period for the maximum demand). Kannan and Turton (2011) developed the Swiss TIMES electrical system model (STEM-E) to generate insights on long-term development of the electricity sector under a cost-minimization framework. The main objectives were to analyze electricity generation at the hourly level taking into account the availability and operational constraints of the interconnected system elements, and elucidate the problems associated with the integration of intermittent renewable energy technologies. To achieve these objectives, STEM-E was calibrated on historical data from 2000 to 2009. Key inputs included past and future electricity demand, existing technology stocks, national and imported energy resources, technical and economic characteristics of future electricity and heat generation technologies. Another study done by Drouineau et al. (2015) used a TIMES model to analyze the capacity of the Reunion Island to reach its autonomy in electricity by 2030 with a fine resolution of time periods: each year was divided into two seasons, namely; the summer season and the sugar season and each day has been subdivided into eight time slices. The approach adopted focused on conducting a prospective study, which provides future production mixes under different scenarios. This approach has been associated with a quantitative assessment of the reliability of the power supply using two reliability indicators indicating that intermittent sources can strongly develop and thus worsen their reliability. 4.3 Linking TIMES with Other Models or Tools Another approach consists to link TIMES models to other models or analytical tools in order to capture additional dimensions of the problem to be solved and provide more complete solutions. A soft-link approach with a simulation model has been used by few authors as it provides a more realistic picture of technology stocks turnover than optimization models and sometimes include more details and have a finer time resolution (one-year History and Recent State of TIMES Optimization … 123 steps). Thellufsen et al. (2019) have analyzed cleaner solutions for district heating in Ireland in a future low-carbon system using the Irish TIMES model. To this end, EnergyPLAN was used to study in addition to the operation of the heating system, the feasibility of district heating compared individual heating solutions. EnergyPLAN allows time simulation of the heating system and therefore, it includes the operation of combined heat and power plants, boilers and storage facilities in relation to the electrical system, on a chronological basis on the year. Similarly, Vaillancourt et al. (2017) have used a multiregional TIMES model to explore deep decarbonization pathways for Canada in a soft-link framework with a simulation model that is calibrated with historical data from 1978 and enables projections to 2050 and beyond in one-year steps. The soft-links work iteratively in both directions where the simulation model provides projections of key macroeconomic drivers and service demands and decision variables from the optimization model are integrated back in the simulation model for further refinements to input variables. Another area where a soft-link approach with another model has proved to be particularly useful is the analysis of the optimal electricity generation mix with high penetration of renewables over time. Indeed, some electricity sector models provide a more precise representation of electric systems than TIMES namely regarding the optimal dispatch. Tigas et al. (2015) used a TIMES model by linking it to a probabilistic production simulation model (ProPSim) to study the decarbonization of the Greek electricity and transport systems by 2050. The ProPSim model calculates the residual charge duration curves, which are used to calculate the optimal extension of the dispatchable generation plants. This combination makes it possible to better manage the stochastic aspects related to the penetration of renewable energies. Welsch et al. (2014) have assessed the effects of soft-linking the Irish TIMES model with a well-known unit-commitment and dispatch model: PLEXOS. It allows simulating the electricity market with a more detailed temporal resolution, thus enabling to minimize the expected costs of the electricity dispatch. PLEXOS accounts for additional operational details such as minimum stable generation levels and operating reserve requirements. Finally, several attempts have been made for linking TIMES models to life-cycle analysis (LCA) tools. McDowall et al. (2018) aimed to flexibly link a LCA-based tool to a European TIMES model in order to determine how the inclusion of indirect emissions can change the optimal technological pathways for the decarbonization of the European energy system. The indirect CO2 emission factors associated with the construction of power sector technologies have been calculated by means of a hybrid LCA approach. The method consists of a disaggregation of an input-output table and its environmental extension based on data from life-cycle inventories, and the use of Environmentally-extended Input-Output (EEIO) analysis to calculate carbon emissions. It allows overcoming the main limitations of each approach, i.e. the high aggregation of EEIO models and the incomplete system boundaries in LCA. 124 K. Vaillancourt et al. 5 Applications to a Transition Toward Clean Energies Once more, it was not possible to review the numerous publications with applications of TIMES models to study the transition toward clean energies. Examples are provided below to illustrate the rich potential of optimization models for assisting decision makers with such a complex problem that is climate change mitigation. 5.1 Decarbonisation of the Energy System Multiple TIMES optimization models are used today to support the analysis of energy and climate policies all over the world. Geographical coverage varies from the global to the city level as does the spatial resolution within each model region (Vaillancourt 2018). Different models with different spatial resolution provides complimentary information for decision makers taking into account both internal regional differences and the global factors. Due to the large diversity of energy systems within a specific region or even a specific country, detailed national or multiregional approaches are necessary to study the energy transition while capturing the needs for investments in infrastructure for clean energy transport and distribution within the country or between neighbouring regions (Vaillancourt et al. 2017). These investments are not captured in global models with continents or multiple countries represented as single aggregated regions. However, limiting assumptions are required in such national models regarding the potential evolution of the international demand for energy resources under different levels of commitments for climate change mitigation in the various countries. Global models allow making more consistent and comprehensive assumptions regarding the evolution of international trade movements for energy commodities in such a mitigation context. As a global challenge, countries cannot be looked at in isolation when it comes to climate policies. Global models can also be used to study the international cooperation aspects, an important component of the global climate change agenda. This is a significant challenge for emerging countries as significant capital investments are required in order to transform the energy system without jeopardizing socio-economic growth. As a technology-rich model with a flexible definition of the time dimension, TIMES is also well suited to investigate the techno-economic trade-offs for meeting medium-term targets at the least cost while taking into account the need for meeting even more stringer targets for the long term. Many studies have proved to be especially useful to define optimal pathways for achieving ambitious GHG reductions, while contributing to the growth of the economy and minimizing the risk of technological locked-in (Solano-Rodríguez et al. 2018). Regardless of the geographical coverage or the time resolution, there are consistent observations across studies regarding priority actions for an optimal transition toward History and Recent State of TIMES Optimization … 125 a clean economy: energy efficiency improvements in all sectors, electrification of enduses (buildings, transports, industries, etc.), and decarbonisation of the electricity sector. Following these transformations, various additional mitigation options are considered to achieve deep decarbonisation levels when electrification is not possible. Their role in the energy system depend on the geographical context and the characteristics of regional energy systems. For example, the role for biomass and biofuels is largely depending on the availability of biomass resources. Vaillancourt et al. (2019) conducted a study to explore the role of bioenergy in a Canadian province in rapid transition to a low-carbon economy using a TIMES model for Canada. The model calculates the most optimal energy sector configuration that would reduce GHG emissions to meet the official target by 2030 compared with 1990 levels (37.5%) and beyond (40%). They found out that in order to achieve the desired levels of GHG reduction, the energy transition required should include a larger role for bioenergy in 2030 (from 6% in a reference case to 18% in the most stringent scenario. This requires the access to a large diversity of biomass feedstocks and many improvements in efficiencies and costs of conversion processes. Although very expensive, hydrogen could also play a role where others are limited and following technological development. For instance, Sgobbi et al. (2016) indicated that low-carbon hydrogen production technologies could become viable options for the transport and industry sectors as early as 2030 in a carbon mitigation context. Electrolysis technologies in particular provide flexibility to the system by absorbing electricity at times of high availability of intermittent sources. However, it is increasingly argued that the carbon neutrality of the global energy sector should be achieved in 2050 to maintain the temperature below 1.5 °C by 2100. Reaching the carbon neutrality goal will require the integration of the most advanced technology innovations for the most energy intensive industrial sectors (aluminum, iron & steel, cement, chemicals, etc.) as well as a closer look to net negative GHG options such as the use of bio-energy with carbon capture and storage (Selosse and Ricci 2014) with all the social perception challenges it raises. 5.2 Integration of Renewable Electricity and Heat Previous studies exploring deep decarbonization pathways showed that electrification of end-uses and decarbonization of the electricity sector were consistent priorities of actions for many countries. Consequently, any climate change mitigation plan requires a special attention to the electricity sector, in a systemic and dynamic view of the whole energy system given its complexity and regional diversity. Some studies have proved to be especially useful to describe optimal pathways for decarbonizing the electricity supply mix while taking into account the capacity of the grid to integrate a high share of intermittent renewables. For example, Amorim et al. (2014) have used a TIMES approach to analyze possibilities to fully decarbonize electricity generation in Portugal by 2050, in order 126 K. Vaillancourt et al. to contribute to a deep decarbonization of the Portuguese energy sector. To this end, two cases were considered: (1) the Portuguese generation sector is optimized as an isolated system, and (2) the latter is part of an integrated Iberian system (Portugal and Spain). The study illustrates the benefits of optimizing the integrated system, which yields reduced energy costs. These cost reductions are achieved through a larger exploitation of renewable energy sources (such as solar and wind energy) in the Portuguese generation sector, together with new interconnections between Portugal and Spain (at the end of the model horizon, 2050) to accommodate higher electricity exports to Spain. In a soft-link framework with a probabilistic production simulation model, Tigas et al. (2015) have analyzed the possibilities, for Greece, to reduce energy-related GHG emissions by 60–70% in 2050, from the 2005 level, in line with the European Union objective to abate its GHG emissions by 85% (in 2050, from the 2005 level). In particular, using the linked TIMES model, they have studied a scenario that envisions an almost 100% electricity generation from renewable energies. Besides, achieving an (almost) complete decarbonization of electricity generation would facilitate an intensive electrification of the transport sector that is currently responsible for a large amount of GHG emissions in Greece. However, this scenario implies higher overall energy costs compared to the situation where the TIMES model is free to choose least costly strategies to achieve the GHG reduction targets. In that case, besides decarbonizing to a large extent electricity generation, the optimal strategy also relies on the implementation of a number of targeted energy efficiency measures, and on a large-scale renewable energy system penetration in all end-use sectors. A detailed analysis of the electricity sector often requires a finer resolution than for other sectors. In this regard, Krakowski et al. (2016) have analyzed different levels of renewable energy penetration, ranging from 40 to 100% by 2050, in the French electricity generation sector considering seven seasons, a distinction between working days and weekends and six intraday periods. They have relied for their analysis on a TIMES model, together with indicators of the power system reliability. The latter is likely to deteriorate due to the penetration of renewable energy sources, even at moderate levels (40%). However, the use of flexibility options, such as demandresponse, shall help reduce the negative impacts of intermittent renewable energy systems. The authors conclude by highlighting the interest for decision-makers of such a study that would help them anticipate the aforementioned negative impacts. At present, the (French) Reunion Island’s electricity generation relies mainly on imported fuels, while it has significant potential for renewable energies. Drouineau et al. (2015) have used a TIMES approach, again together with indicators of the power system reliability, to assess from a techno-economic perspective whether Reunion Island could achieve electricity self-sufficiency by 2030. The authors conclude that self-sufficiency could indeed be achieved, by using in particular biomass (sugarcane, cane, and wood) but also intermittent energy sources. The latter would negatively impact the reliability of the power system. This effect could, however, be mitigated by imposing some legal limits on intermittent sources for instantaneous electricity production. History and Recent State of TIMES Optimization … 127 By linking a TIMES model with the unit-commitment and dispatch model PLEXOS, Welsch et al. (2014) could also study the evolution of the Irish electricity system in more details. They showed that long-term energy models can clearly underestimate the importance of flexibility in the electrical system if short-term operational requirements are not taken into account. The study highlighted some of the limitations of long-term energy systems models if they do not adequately take into account operational aspects. Energy strategies and policies may, otherwise, underestimate the costs of meeting climate change or energy security targets. Other aspects not included in traditional analysis using TIMES models can change optional solutions if added to the analytical framework. For instance, McDowall et al. (2018) have conducted a study, using a European TIMES model, to determine the extent to which the inclusion of indirect effects on GHG emissions (from a lifecycle assessment perspective) could change the optimal technological pathway for the decarbonization of the European energy systems (EU28 member states plus Norway, Iceland and Switzerland). Although indirect emissions account for only a small part of the total emissions (less than 10%), their inclusion would lead to changes in the optimal configuration of energy sectors. In particular, some renewable energy technologies (notably solar photovoltaic) become relatively less attractive. But these changes are more pronounced than the reduction in the attractiveness of renewable energy as a whole. Besides, McDowall et al. (2018) also concluded that renewable energy sources remain an essential element of the European decarbonization strategy. Finally, Thellufsen et al. (2019) have studied the impact of cleaner heating solutions, based on district heating from industrial waste heat and combined heat and power (CHP) plants, on achieving deep decarbonization (up to 80% reduction) in Ireland. They rely on an Irish TIMES model linked to EnergyPLAN, a model that enables to consider hourly operations of both heating and electricity systems. The study indicates that the district heating option is a more fuel-efficient solution than the individual heating one. In the Irish context, this increase in fuel efficiency yields more savings than the higher investment costs incurred by the district heating option. The authors conclude that district heating could play an important role in the transition towards clean energy systems. 6 A Need for Greater Transparency for Efficient Decision-Making Mathematical E3 models are particularly useful for exploring the transition toward clean energies and by providing decision makers with rigorous insights on deep decarbonization pathway options and long-term mitigation strategies. The TIMES optimization models in particular, developed within the ETSAP program of the International Energy Agency, have contributed to support decision-making all over the world at various geographical scales from global to city levels. 128 K. Vaillancourt et al. As large scale energy system models, they describe the energy sector with a complete list of energy forms, as well as different existing, improved and emerging technologies. They allow for detailed accounting of all energy flows within the energy sector from primary and secondary energy production to final energy consumption and useful energy demands. These models are typically projected to 2050 or even 2100, which makes it possible to study the structural changes within the energy sector. In addition, they provide important additional features compared with other types of energy system models, such as simulation models. By following a linear programming formalism, these models make it possible to determine a optimal configurations of the energy sector which makes it possible to satisfy the total demand for energy services at lower cost, by respecting GHG emission limits or renewable penetration targets. However, the use of such models to assist policy-makers with energy and climate policy design and implementation raises issues regarding the robustness of the solutions found by the optimization program, especially given the large number of assumptions are required to assign values to highly uncertain technical or economic parameters over time. The main critic addressed to optimization energy system models is indeed the “black box” aspect of the approach which affects the credibility of their outcomes and usefulness to support decision-making. Different approaches have been used by the TIMES modeller community to address uncertainty issues such as sensitivity analysis, parametric scenario analysis, Monte Carlo simulations, and stochastic programming. These approaches have partially contributed to show policy-makers and other stakeholders that large-scale optimization energy system models can provide robust insights for policy making despite the large number of assumptions embedded in model databases. Nevertheless, enhancing the credibility further will follow a better understanding of the links between input parameters and output results. The only possible solution to overcome this limitation involves more transparency regarding model inputs, a better dissemination of model roles and possibilities as well as a reinforced communication links between science and policy. References Amorim F, Pina A, Gerbelova H, Pereira da Silva P, Vasconcelos J, Martins V (2014) Electricity decarbonization pathways for 2050 in Portugal: a TIMES (The Integrated MARKAL-EFOM System) based approach in closed versus open systems modelling. 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Appl Energy 135: 600–615 Electricity Grids for 100% Renewable Energy: Challenges and Solutions Eberhard Waffenschmidt, Majid Nayeripour, Silvan Rummeny and Christian Brosig Abstract On the way to a 100% renewable energy system electrical power grids face a number of new challenges: Big centralized power plants are being replaced by small distributed generators operating on renewable energy. Especially wind and photovoltaic power generation add new uncertainties to the generation of power. The distributed generation results in a different and even reverse power flow. On the other hand, the distributed generators also offer new possibilities like local power supply in case of emergencies. The local generation may even be beneficial for the reliability of the power supply. New types of electrical loads are emerging, like electric vehicles, heat pumps and battery storages. They may soon lead to local grid overloads. But fortunately, most of them are controllable loads. Thus, they can beneficially contribute to using the uncertainly generated renewable power. However, this requires a holistic view on the total energy system including a coupling of all involved energy sectors. Therefore, this chapter first gives an overview of existing publications about the impact on the electric power grid by the energy sectors and their inter-coupling. Then, a cellular power grid structure is proposed and described, which takes advantage of the distributed structure of renewable energy generation. Finally, some aspects on clustering and controlling such a cellular grid structure are presented. 1 Introduction Eberhard Waffenschmidt The climate change is propagating faster than experts have ever forecasted. The main contribution is the burning of fossil carbon for energy purpose. Therefore, the worldwide energy system has to be changed as fast as possible to a 100% renewable E. Waffenschmidt (B) · M. Nayeripour · S. Rummeny · C. Brosig TH-Köln (Cologne University of Applied Science), Cologne, Germany e-mail: [email protected] M. Nayeripour Alexander von Humboldt-Stiftung, Bonn, Germany © Springer Nature Switzerland AG 2020 T. S. Uyar (ed.), Accelerating the Transition to a 100% Renewable Energy Era, Lecture Notes in Energy 74, https://doi.org/10.1007/978-3-030-40738-4_6 131 132 E. Waffenschmidt et al. energy system. This will be a nearly fully electrical power system, because the main contributors to renewable power are wind and solar power. On the way to such a system, especially electrical power grids face a number of new challenges: Big centralized power plants are being replaced by many small distributed generators operating on renewable energy. Especially wind and photovoltaic power generation adds new uncertainties in the generation of power. Electrical and other energy storages are necessary as soon as possible to match generation and demand. Also controllable loads (see below) will help with this issue. The distributed generation results in a different and even reverse power flow in the power lines and components. Especially distribution grids will behave totally different, because at sometimes they are used to collect power instead of distributing it. On the other hand, the distributed generators also offer new possibilities like local power supply in case of emergencies. The local generation may even be beneficial for the reliability of the power supply. These aspects require thinking of a different power grid structure, or at least a different organisation of the power grid. New types of electrical loads are emerging, like electric vehicles, heat pumps and battery storages. They may soon lead to local grid overloads. In many areas this is much rather an issue for the local distribution grid than for the transmission grid connecting regions. But fortunately, most of the emerging loads can be considered as controllable loads. Thus, they can even contribute to beneficially use the uncertainly generated renewable power. However, this requires a holistic view not only on the electric, but on the total energy system including a coupling of all involved energy sectors. Such sectors are distributed electrical generation, heat demand, charging of electric vehicles and gas supply. In addition, the control of power grids will change: The inertia of large generators will have to be replaced by virtual inertia. Primary control power is being taken over by fast controllable devices, especially batteries, and even completely new control structures without Primary and Secondary Control Power are proposed. Therefore, this chapter first gives an overview of existing publications dealing with the impact of the different energy sectors and their inter-coupling on the electric power grid. Then, a cellular power grid structure is proposed and described to take advantage of the distributed structure of renewable energy generation. Finally, some aspects on clustering and controlling such a cellular grid structure are presented. Electricity Grids for 100% Renewable Energy … 133 2 Effects on the Electrical Distribution Grids Due to Coupling of Energy Sectors Christian Brosig 2.1 Introduction The electrical energy system is only one part of the energy system to be decarbonized. Heating and mobility have a very high share of the overall energy consumption. In Germany today they account for 782 TWh and 728 TWh (Bundesministerium für Wirtschaft und Energie 2018), while the whole consumption of electrical energy is only 520 TWh (Arbeitsgemeinschaft Energiebilanzen 2018). For mobility it is clear, that decarbonisation will particularly be met with an electrification and there is also a trend in heating towards heat-pumps, as they are much more efficient than conventional heating devices. If we look at the proportional distribution of energy consumption in the three sectors, it is clear, that this will be a huge challenge for the electrical distribution grid. This part of the chapter gives an overview of upcoming technologies and how they will affect the electrical distribution grid. It focuses on: 1. Photovoltaics (PV) 2. Power-to-heat—heat-pumps (HP) and combined heat and power (CHP) 3. e-mobility. Power-to-gas is another emerging technology, which will be only marginally addressed. All results have been elaborated and gathered within the project ES-FLEX-Infra, funded by the European fund for regional development (EFRE). 2.2 Photovoltaics Georg Kerber describes the limit for the feed in of PV in low-voltage distribution grids in his PhD-thesis 2010 (Kerber 2010). Problems arise above all in suburban and rural areas. The 3% voltage change criterion of the VDEW Guideline (VDEAR-N 4105 2017) is a strongly limiting factor. Otherwise, adaptation measures such as reactive power control of inverters make between 60 and 90% of the PV power potential in low-voltage networks accessible, without serious adjustments (Kerber 2010). In urban areas, the PV potential on roof-tops often is not sufficient to imply problems for the grid. This is also shown in (Birk et al. 2018). 134 E. Waffenschmidt et al. 2.3 Power-to-Heat The discussion about power-to-heat is largely driven by the use of HP. Here, too, numerous papers on their effects on the low-voltage networks exist. Particularly to emphasize, through a very well-founded research, a clear structure and detailed models is described in Protopapadaki and Saelens (2017). The paper discusses the influence of HP on rural low-voltage grids in Belgium, using a thermal model of the houses, as well as a stochastic behaviour influence of the inhabitants. Without a buffer storage, the authors come to the conclusion that a degree of penetration of 20–30% can be achieved, whereby the cables are the limiting factor in their models. Voltage problems only occur at higher penetration rates (Protopapadaki and Saelens 2017). Navarro-Espinosa and Mancarella (2014) investigates the effects on suburban networks in Great Britain and refers to a series of sensitivity analyses. They find a degree of penetration of about 40% for air heat pumps and 50% for ground-source heat pumps. Here, too, thermal overloading of the cables at the outgoing end of the string is more problematic than voltage band violations (Navarro-Espinosa and Mancarella 2014). Problems with heat pumps are load peaks which occur and which depend on the ambient temperature. This stresses the network with a high simultaneity factor. Heat storages can help to compensate for peak loads. This has been demonstrated for example in Baeten et al. (2017) for the complete Belgian electrical network. The authors come to the result that the load peaks in the overall system can be reduced by about 11%, depending on the use of a storage (Baeten et al. 2017). The authors of Arnold et al. (2013) follow a different approach, which is to investigate the interaction of heat pumps, PV and CHP plants in a suburban low-voltage network. They assume that CHP plants are operated in a heat-driven way and thus flatten the exact peak load times of the heat pumps. Key findings are, that at 20% penetration of the heat pumps, the same additional penetration can be achieved with cogeneration units, which increase the minimum voltage in the network from 0.85 pu to 0.9 pu. PV has a neglectable compensating effect. For a suburban network in the Cologne area, (Kusch et al. 2015) comes to the conclusion that 45% of the degree of heat pump penetration is already possible without storage and with storage even 90.6%. However, it assumes an application of domestic demand side management (DSM) in all considerations, whose influence on the results is not explained in detail and thus difficult to assess. Shao et al. (2013) comes to far higher possible degrees of penetration in an urban low-voltage grid in Denmark. However, the authors of this study assume significantly lower installed power for the heat pumps used and use standard load profiles. This way, they neglect high simultaneity factors, which may appear in smaller grids. The control of heat pumps and battery electric vehicles (BEV) enables them to conclude in a feasibility of a 100% penetration of both technologies (Shao et al. 2013). Within the framework of smart-grids, heat pumps are said to have an enormous potential for flexibility. Fischer and Madani (2017) provide a well-founded overview Electricity Grids for 100% Renewable Energy … 135 of relevant publications on the topic and derives some recommendations. Applications range from the integration of renewable energy, over the reduction of energy costs to grid-compatible operating patterns in the virtual power plant. 2.4 E-Mobility The effects of e-mobility or BEV on the networks have already been worked out in a dissertation (Van Roy 2015), although the focus is on the coordination of local charging and integration in a building. In general, the different charging capacities must be considered separately. In the low-voltage grid, outputs of 2.3 kW (10 A), 3.68 kW (16 A, single-phase), 11.04 kW (16 A, three-phase) and in extreme cases 22.08 kW (32 A, three-phase) are usual. In addition, rapid charging stations are being discussed and are already being built at filling stations, which will be equipped with much higher charging capacities from 43 kW up to 135 kW. For a distribution network in Gothenburg, Sweden, (Babaei 2010) comes to the conclusion that in commercial and industrial applications up to 56% or 90% (with 2.3 or 3.68 kW charging power) of the BEV can be charged if a complete switch to emobility has been made. In residential areas the figure is 64 and 102% respectively. The authors assume a very high simultaneity. In the medium-voltage network the cables and in the low-voltage network the transformers are identified to be the weakest spots in the system (Babaei 2010). Marwitz and Klobasa (2016) analyses the effects on the basis of a rural lowvoltage network. Without controlled charging, at a penetration rate of 20% already, the first network overloads occur. They assume a higher charge power of 10.8 kVA and investigate three different charging controls, from the central, smart control, to a price signal control, right up to a decentralised autonomous charge control on the basis of the voltage measured on site. They identify the central control to be the most effective—it can handle the 20% penetration—and the price signal control—which leads to an unacceptable voltage drop at 20% penetration—as most stressing for the grid (Marwitz and Klobasa 2016). 2.5 Power-