The Norwegian Centre for offshore wind energy (NORCOWE)

The Norwegian Centre for Offshore Wind Energy (NORCOWE) Peter Mosby Haugan Geophysical Institute, University of Bergen and Nansen Environmental and Remote Sensing Center [email protected] Kristin Guldbrandsen Frøysa Christian Michelsen Research AS Bergen, Norway Finn Gunnar Nielsen Statoil and Geophysical Institute, University of Bergen Bergen, Norway Abstract——NORCOWE is an industry-led consortium including research institutes and universities which address key challenges for development of offshore wind. These include understanding marine boundary layer properties for improving industry standards and developing control and maintenance procedures which reduce costs. Keywords; Offshore technology, renewable energy, wind energy, offshore wind, air-sea interaction I. INTRODUCTION The world’’s need for more and clean energy is closely related to the population growth and an improved standard of living. But meeting these growing energy needs in a sustainable and affordable way is not an easy task. It cannot be achieved by a single source of energy alone. Harnessing the power from wind is a proven technology that has been used for centuries and one that can make a significant contribution in modern times to meet our growing energy needs. Worldwide, the installed wind power capacity has been growing steadily during recent years, even in the midst of the financial crisis. According to [1] the growth in global installed wind power in 2011 was 21%. By the end of 2011, the accumulated installed wind power globally was 238 GW (in comparison the total installed hydro power in Norway is about 30GW). Moreover, the growth is not limited to Europe: China is now the world leader both with respect to installed capacity and rate of installing wind power. However, a majority of the installed wind power plants are on land, while less than 2 % are installed offshore. With higher and more consistent wind speeds, moving more power production offshore could unlock a huge potential in meeting energy demands. Europe has been the leading region for offshore wind power, but other markets with large coastlines such as the USA are considering this option for their energy mix. Most notably, Japan has recently turned its attention to offshore wind after the Fukoshima nuclear power accident. With deep waters, close to large power markets, offshore wind, and in particular floating offshore wind, could be an attractive option. Very recently, the South Korean government 978-1-4577-2091-8/12/$26.00 ©2011 IEEE announced it will invest in offshore wind, implementing a 100 MW demonstration phase in 2014 and 400 MW in 2016 as steps towards a 2.5 GW offshore wind farm. II. MOVING OFFSHORE So why move the wind power offshore? There are several reasons: Wind power on land requires space, which is a scarce resource in densely populated areas. Developing wind power at an industrial scale requires large turbines, and large wind farms. The visual impact and noise are key problems which make large wind farms on land less desirable. During the last 25 years, state of art size of wind turbines has increased by a factor 100; from 50 kW to 5 MW. Transporting and installing such big units in remote areas on land is a challenging task. However the marine industry has long experience in handling large items. There are also significantly less conflicts related to use of acreage offshore than on land, although possible conflicts with for example fishing activities, shipping routes and bird migration routes must be considered carefully during wind farm design. The energy density in the wind is proportional to the third power of the wind velocity. Thus with a more steady and higher average wind velocity offshore than on land a significantly improved power production can be expected. A striking example of this is Statoil’’s Hywind demonstration project; even if this is a test unit, the capacity factor in 2011 was 50% while the average value for Norwegian wind turbines in 2011 (0.51 GW installed capacity) was 31%. Hywind is pictured in Fig. 1 and its geographical location is indicated in Fig. 2. There is a vast amount of wind energy available offshore, the technically available resources vary widely depending upon the limitations related to water depth and distances to shore and electrical infrastructure used. But even conservative estimates, see e.g. [2] concludes that the technical potential is several times the present worldwide electrical power production. The Marine Board of the European Science Foundation states the vision that [3]:”” By 2050 Europe could source up to 50% of its III. CHALLENGES However great the benefits, there are significant challenges in developing large scale offshore wind power which need to be overcome. To design and operate large offshore wind farms, we need to understand the interaction between the wind field in the atmospheric boundary layer and wind turbines, both as individual turbines and turbine –– turbine interaction via the wake and even interaction between wind farms. The oil and gas industry has had focus on extreme events. For wind power, the normal conditions are more important than the extreme from an energy yield point of view. In the operational phase also the mentioned interaction phenomena have to be addressed to achieve an optimum power off-take from each turbine. There is limited offshore acreage in shallow water with good wind conditions, thus the industry is moving further from shore into deeper water and a more hostile environment. This puts stricter requirements to the reliability of the wind turbines than has been industry practice up to now. We need more robust wind turbine generators with fewer parts that are designed for the offshore environment. The trend is to make the turbines bigger and bigger. Larger turbine diameters in turn imply more challenging interaction with the atmospheric boundary layer and other turbines. Many recent multi MW turbines have a weight per MW that is higher than for smaller turbines. If this trend is not changed the size and costs of the support structures will be a severe challenge. Figure 1. Hywind before deployment. Hywind is an experimental floating wind turbine with 2.3 MW rated power. Photo credit Statoil. electricity need from Marine Renewable Energy. This would have a profound impact on the European economy and European citizens. It would contribute to energy supply and security, reduce CO2 emissions and their impact on the oceans, improve the overall state of the environment, improve quality of life, create jobs in a range of innovative sectors and herald a new era of environmentally sustainable development.”” In marine renewable energy the Marine Board mainly includes energy from offshore wind, waves, tides and ocean currents. Among the marine renewable energy sources, offshore wind has the greatest potential. The European Wind Energy Association [4] expects that by 2020 and 2030 the installed offshore wind power will amount to 40 GW and 150 GW respectively. This is to be compared to the 4 GW of installed offshore wind power today. The 40 GW in 2020 is mainly reflecting the ambitions of UK and Germany. Why does Europe have such ambitions within offshore wind? The keywords are: The need for more energy, it will contribute to security of energy supply, it will create a new industrial sector with significant job creation, and it is a key factor in achieving the ambitions set for reductions in CO2 emission. The German car industry had in 2009 about 740 000 employees. According to [5], the German wind industry had about 96 000 of a total of 367 000 employees in the renewable sector in 2010. The lifecycle greenhouse gas emissions for offshore wind power is in the range 9 –– 14 gram CO2eq/kWh as compared to electricity produced from conventional coal and gas fired power plants that has average lifecycle emissions of 1000 gram CO2eq/kWh and 500 gram CO2eq/kWh respectively [2]. Efficient installation of heavy equipment in hostile environment is a known task for the oil and gas industry. But new challenges are faced in offshore wind industry; heavy lifts Figure 2. Operational wind farms (red stars) and planned windfarms (yellow areas) in the North Sea. The location of Hywind is indicated by a green cross. are not only a few, the offshore wind installations require hundreds of such operations to be performed within a limited time window. Here advanced logistics, advanced weather forecasts and understanding of the operations involved become essential issues that will challenge the traditional offshore marine operators. Even if the reliability of the future turbines is improved, there will still be need for accessing the turbines. Present methods for access are developed for sheltered water and not suited for open sea. Here new and improved methods are under development, but still much work remains before safe access can be obtained in typical wave conditions during the winter months. Common to many of the tasks above is that there needs to be semi or full scale prototype testing before the technology can be implemented on an industrial level. Within EU several such prototyping and testing initiatives are proposed; e.g. the European Wind Initiative, EWI. Such prototypes need large funding that calls for international cooperation and coordination. Such coordination may slow the decision process and involve problems related to IP rights. Several more challenges could be mentioned, but there is one that is common to all the R&D work on offshore wind: We have to bring down the cost of energy. Thus we have to improve the present solutions, look for radical new solutions and not least build competence. Lack of competence may put severe restrictions to the capability of reaching the ambitious goals set for the offshore wind development. IV. THE NORCOWE CONSORTIUM AND ITS APPROACH The Norwegian centre for offshore wind energy (NORCOWE) is a centre for environment-friendly energy partly funded by the Norwegian government through a competitive grant from the Norwegian Research Council, partly by industry and partly by the participating research organisations. The industry has majority in the board. The industry partners are Agder Energi AS, Aker Solutions AS, Lyse Produksjon AS, National Oilwell Norway AS, Origo Solutions AS, Statkraft Development AS, Statoil AS, StormGeo AS and Vestavind Offshore AS. The research partners are Christian Michelsen Research (host), Uni Research, University of Agder, University of Bergen, University of Stavanger and Aalborg University. While this is a national Norwegian centre, a Danish partner (Aalborg University) is included in the consortium, thereby capitalizing on the recognized Danish lead in wind technology. Other international connections are established in particular in Europe, but also to the US. International industry partners are also welcome. Within Norway there is also collaboration with NOWITECH, another centre for environment-friendly energy focussing on offshore wind technology. NORCOWE contributes to the needed improvements, investigates radical and creative solutions and not least contributes to building competence necessary to grow the industry addressing key challenges mentioned above. The NORCOWE work packages focus on wind and ocean conditions, innovative concepts, offshore deployment and operation, wind farm optimisation, education, environmental impact assessment, test facilities and infrastructure. NORCOWE brings together very different research groups and competence centres which had not been working much together before the establishment of the centre. Norway hosts proud traditions and excellent research groups in marine climate and meteorology rooted in traditions from Vilhelm Bjerknes and his co-workers and followers, as well as recognized offshore technology competence developed for the oil and gas industry. Combining these two largely separate competence clusters with each other and with Danish wind energy experience mainly from land, is the key approach of NORCOWE. The centre has now been in full operation for more than two years. In the following we show some examples of activities ranging from geophysical studies of exploitable wind resources and boundary layer physics to marine operations. The annual report from 2011 [6] and other reports available at www.norcowe.no give more information on these and other aspects. A. Wind resources Wind resources far offshore are expected to be more stable and less geographically varying than onshore. However, the precise geographical distribution of harvestable wind energy is not well known. Detailed studies in NORCOWE based on models and observations have shown that effects of coastal topography may extend more than 100 km offshore. The vertical wind profile is needed to assess the performance of large, tall future turbines versus standard turbines of today. In a 30 year perspective also scenarios for climate change should be considered in addition to natural climate variability. Fig. 3 shows one example of a product that has been produced by downscaling from a stretched, global atmosphere model. The wind power potential is here estimated at 100 m height. It can be seen that the wind climate of the North Atlantic influences the North Sea and Norwegian Sea so that the northern North Sea has a higher potential than the southern parts. Close to the coast, Scotland and selected parts of the Norwegian coast show high potential. Present development Figure 3. Distribution of analysed full load hours per year based on meteorological observations and models for the period 1972-2001. Black line is 3750 hours. The power curve from a Repower 5M turbine is used to weight the 6 hourly wind speed. Figure courtesy Idar Barstad, Uni Research. plans (Fig. 2) center on the southwestern North Sea where the water depth is relatively shallow. However, if technology for floating turbines like Hywind can be developed, the higher energy regions in the northern North Sea can also be exploited. Several other analysis products are developed and used for assessing exploitable wind energy in different offshore areas. B. Marine atmospheric boundary layer Most of the understanding that we have of the atmospheric (planetary) boundary layer comes from studies over land where wind blows over a fixed surface. Much fewer observations exist from the marine realm where matters are complicated by the wavy and moving surface. Momentum transfer from wind to waves and currents takes part, although in special cases also waves (swell) can generate wind. The lack of larger scale topography offshore however, is expected to homogenize conditions and reduce turbulence compared to onshore hilly terrain in strong winds. These factors are favorable for exploitation of offshore wind energy. An important issue for large wind turbines is the vertical profile of mean wind and its variability. Measurements and model experiments performed in NORCOWE (Fig. 4) show that especially rather close to the coast, the occurrence of stable to very stable atmospheric stratification situations in the spring and early summer, implies that the hub-height of tall wind turbines may be above the surface layer in 15-20 % of the time. This implies that the standards used today for calculating energy outputs and fatigue loads are not valid. It is therefore recommended that new standards are made to reflect what the actual atmosphere looks like over open ocean conditions. NORCOWE research can help develop such standards. Figure 5. Measurements in atmosphere and ocean. Illustration credit Aanderaa Data Instruments. NORCOWE is also making its own marine boundary layer, wave and surface ocean condition measurements with a range of instrumentation including scanning LIDAR and floating measurement buoys, Fig. 5. For more information see www.norcowe.no. C. Marine operations The city of Stavanger is a main hub for the offshore oil and gas industry in Norway. University of Stavanger and other partners in NORCOWE have considerable experience and background from marine operations in connection with development and production of petroleum. In particular for issues like design of fixed and floating platforms subject to wind, waves and currents, a well as reliability, maintenance and asset management, NORCOWE draws heavily on this experience and competence base. Understanding and modelling the dynamics of floaters is a complex field of research where the offshore oil and gas activities form an invaluable basis for present efforts towards offshore wind. A recent development related to maintenance is research efforts towards heave compensation during installation and intervention on offshore wind turbines. Modeling, control and optimal design of hydraulically actuated manipulators are parts of this. The common theme of these studies has been tool point control since this has been identified as a key competence. Experimental facilities include two Stewart platforms, Fig. 6, which can be used together simulating realistic loads and conditions. Figure 4. Simulated marine boundary layer height in the area of the FINO1 German research platform in the southern North Sea. Courtesy of Olav Krogsæter, StormGeo. Figure 6. A NORCOWE Stewart platform in operation at University of Agder, in this case with LIDAR mounted on top, testing for offshore use. Photo credit CMR. V. PERSPECTIVE NEXT 5 YEARS It is easily realized that building up the industrial capacity to design, manufacture, install and operate all the wind turbines needed is a huge challenge, but also a great opportunity for existing as well as new industrial actors. Presently the cost of offshore wind power is too high; the cost has to come down. This must be achieved by using a number of means. The offshore wind industry is still young and much learning and development remains. Although Norway does not have any historical merits with respect to wind power, a lot of relevant competence is available from the marine industry and hydropower sector that can be utilized in realizing the European as well as global ambitions on offshore wind power during the next decades. The competence from 40 years in offshore oil and gas is of particular relevance, but needs to be refocused for use towards offshore wind. In the next five years coinciding with the duration of NORCOWE, we foresee a transition from technology qualification which is ongoing, through development of new industry standards which is just beginning, through to mass production and implementation, Fig. 7. A possible future link between offshore wind and petroleum is energy supply from wind to offshore oil and gas production, today mostly fuelled by gas turbines. Electricity supply from shore has been discussed at political level in Norway, but is costly. If there will be a requirement for renewable energy supply to offshore oil and gas production, offshore wind may be competitive. The domestic energy supply in Norway is well served by hydropower so the main role to be developed for Norwegian offshore wind industry, using selected coastal farms as stepping stone, may be as energy provider to northern Europe through a North Sea grid and as technology provider for deployments elsewhere. 2010 2011 2012 2013 2014 2015 2016 2017 2018 Several more challenges could be mentioned, but there is one that is common to all the R&D work on offshore wind: We have to bring down the cost of energy. Thus we have to improve the present solutions, look for radical new solutions and not at least build competence. Lack of competence may put severe restrictions to the capability of reaching the ambitious goals set for the offshore wind development. VI. NORCOWE has been established to address challenges of offshore wind by combining Norwegian meteorology, geophysics and offshore technology with Danish wind energy competence. While turbines fixed to the seafloor may be expected to be the major part of offshore wind deployment in years to come, NORCOWE also includes research on floating turbines. With efficient installation procedures, increased reliability and reduced maintenance costs and intelligent control of turbines based on measurements and production forecasts, offshore wind energy can be cost competitive. The development of standards and better understanding of offshore operating conditions for large turbines is expected to be crucial for development of this environment-friendly renewable energy source in the near future. ACKNOWLEDGMENT The authors would like to thank all involved in NORCOWE, personnel as well as sponsors, for their contributions to the development of the centre and thereby the basis for this paper. REFERENCES [1] [2] [3] Technology qual. Industry standard [4] Mass production [5] Figure 7. Timeline for NORCOWE and related industrial development. SUMMARY [6] The Global Wind Energy Council (GWEC) 2012. Global wind statistics 2011 Intergovernmental Panel on Climate Change (IPCC) 2011. Special Report on Renewable Energy Sources and Climate Change Mitigation (SRREN). The Marine Board of the European Science Foundation 2010. Marine Renewable Energy. Research Challenges and Opportunities for a new Energy Era in Europe. (http://www.marineboard.eu/) European Wind Energy Association (EWEA) 2011. Wind in Our Sails. The coming of Europe’’s offshore wind energy industry.(http://www.ewea.org/fileadmin/ewea_documents/documents/p ublications/reports/Offshore_report_web_01.pdf) German Ministry for the environment, Nature conservation and Nuclear safety (BMU) 2011. Renewable Energy Sources 2010. NORCOWE Annual Report 2011. Available at www.norcowe.no.