Papers by Luca Evangelisti
Sustainability, 2014
This contribution aims at investigating the possibility to cloak a spherical object from an acous... more This contribution aims at investigating the possibility to cloak a spherical object from an acoustic wave by applying the scattering cancellation approach. In electromagnetism, the scattering problem is treated using the Mie expansion technique, through which the scattered field by a spherical object can be represented as a superposition of TE and TM spherical harmonics. It is possible to extend this concept to the acoustic field by defining an analogous approach; the pressure field, generated by an elastic wave impinging on a spherical object, can be expressed applying the Mie expansion technique, as well. In acoustics, to achieve scattering suppression at a given frequency, the constitutive parameters to control are density and compressibility. By varying these parameter values, it is possible to define an engineered material with anomalous properties, which cannot be found in nature, able to reduce the scattering cross-section (SCS) from a spherical object. We propose a study about the effectiveness of the SCS reduction from an elastic sphere coated with a properly-designed acoustic metamaterial. The sensitivity of the SCS to parameter variations is analyzed for different coating thicknesses and sphere dimensions. Our analysis is supported by both the analytical modelling of the structure and numerical simulations. OPEN ACCESS Sustainability 2014, 6 4417
Applied Mechanics and Materials, 2015
ABSTRACT The study of the building energy performance is based on simplified procedures that esti... more ABSTRACT The study of the building energy performance is based on simplified procedures that estimates the energy demand using monthly values of environmental parameters. It is well known that it is possible to use advanced dynamic softwares able to analyze the real building’s behavior along time. For this reason in this study a historical building energy retrofit has been performed through a dynamic software considering the influence of different kind of windowed elements on the annual energy demand. Four simulations, taking into account transparent elements characterized by progressively improved properties of thermal transmittance and solar gain factor, have been performed. The results obtained have been analyzed and compared.
Applied Mechanics and Materials, 2015
ABSTRACT World population is steadily increasing and it is estimated to reach 9 billion in 2050. ... more ABSTRACT World population is steadily increasing and it is estimated to reach 9 billion in 2050. Moreover, 72% of people live in big cities and the buildings energy requirement is growing, reaching the 45% of the total energy amount. This paper presents of a building energy efficient properly designed to realize a solar-powered house that is cost-effective, energy-efficient, and attractive. The study applied a methodology which is able to identify the best building plant configuration under a technical, economical and environmental point of view. It has been demonstrated that the proposed plant allows to reduce the fossil fuels consumption compared to a plant conventionally employed, with a proportional reduction of the greenhouse gas emissions of about 30% per year.
Sustainability, 2015
The increase of people living in large cities and the expansion of new urban areas are keys to de... more The increase of people living in large cities and the expansion of new urban areas are keys to defining new sustainable models. It is estimated that about 70% of the EU population lives in urban areas, and it is expected to reach 80% by 2030. Consequently, it is important to find a new concept of buildings that can reduce the total energy consumption. The Solar Decathlon is an international university competition, born in 2002, created by the U.S. State Energy Department (DOE). Students are challenged to design and operate a full-scale, innovative and sustainable house able to exploit solar radiation as its sole energy source. The objective of the competition is to promote research and education in sustainable architecture and solar energy fields. This paper presents an overview on the contribution of LIFT (Interdisciplinary Laboratory of Technical Physics of Roma Tre University) to the winning project of the Solar Decathlon Europe 2014 competition: The RhOME for denCity. This project consists of a building properly designed to produce a solar-powered house that is cost-effective, energy-efficient, and attractive.
Applied Mechanics and Materials, 2015
ABSTRACT Every day, in every city, many buses are moving, carrying a lot of citizens. During the ... more ABSTRACT Every day, in every city, many buses are moving, carrying a lot of citizens. During the year, especially during the summer, buses become uncomfortable places because of both environmental and internal conditions. Due to the rising of the mobility needs, time that people spend in vehicles has strongly grown. Moreover, also the thermal environment in urban buses changes greatly, in fact passengers onboard are exposed to local heating and/or cooling due to vertical temperature gradients, radiant asymmetry and local unexpected airflow. This study aims to optimize the energy performance of a bus envelope, identifying practical solutions. The analysis was carried out numerically, considering a hot day during July and passengers on board during the 24 hours per day.
Applied Mechanics and Materials, 2015
ABSTRACT This study aims to assess the influence of greenery shading and transparent surfaces on ... more ABSTRACT This study aims to assess the influence of greenery shading and transparent surfaces on historical building’s energy demand under a retrofit point of view. To achieve this goal, the energy requirement of the whole building has been considered. In order to improve buildings energy efficiency several simulations have been performed. In particular, the effects of some interventions related to different windowed elements, characterized by progressively improved thermal properties, have been taken into account.
Applied Mechanics and Materials, 2015
ABSTRACT World population is steadily increasing and it is estimated to reach 9 billion in 2050. ... more ABSTRACT World population is steadily increasing and it is estimated to reach 9 billion in 2050. Moreover, 72% of people live in big cities and the buildings energy requirement is growing, reaching the 45% of the total energy amount. This paper presents of a building energy efficient properly designed to realize a solar-powered house that is cost-effective, energy-efficient, and attractive. The study applied a methodology which is able to identify the best building plant configuration under a technical, economical and environmental point of view. It has been demonstrated that the proposed plant allows to reduce the fossil fuels consumption compared to a plant conventionally employed, with a proportional reduction of the greenhouse gas emissions of about 30% per year.
Energy and Buildings, 2015
ABSTRACT International standards, in particular the Italian one, evaluate buildings energy perfor... more ABSTRACT International standards, in particular the Italian one, evaluate buildings energy performance assuming steady-state working conditions: currently, the study of the energy performance of buildings is based on a simplified calculation that estimates the energy demand using monthly or seasonal average outdoor temperatures. For this reason we have conducted a comparative analysis of the energy performances of an old building using a semi-stationary software and a dynamic one. The studied building is placed in the peripheral part of an historical city located in the center of Italy. We have performed three simulations considering transparent elements characterized by progressively improved properties of thermal trans-mittance and solar gain factor. A comparison between the outputs of the two codes, in order to highlight the different ways of evaluating the energy contributions to annual energy demand, has been performed. Finally, the models were validated by means of an in-situ measurement campaign using a heat flow meter – in order to measure the thermal transmittance of the opaque walls – and a thermographic camera. This modus operandi allowed us to appreciate how the use of a dynamic software is essential to deal with the inertial properties of the structure and to calculate in an accurate way the annual energy demand.
Energy Procedia, 2014
This study represents a new way for an innovative method of thermo-mechanical design for all buil... more This study represents a new way for an innovative method of thermo-mechanical design for all buildings (new and historical), with the purpose to assess the feasibility of innovative plants from a technical, economic and environmentally point of view. The thermal loads, starting from the analysis of consumers' parameters, were calculated via TRNSYS and the results were processed using RETScreen. With the latter a comparison between a conventional plant and one based on innovative technologies was carried out.
Sustainability, 2014
This contribution aims at investigating the possibility to cloak a spherical object from an acous... more This contribution aims at investigating the possibility to cloak a spherical object from an acoustic wave by applying the scattering cancellation approach. In electromagnetism, the scattering problem is treated using the Mie expansion technique, through which the scattered field by a spherical object can be represented as a superposition of TE and TM spherical harmonics. It is possible to extend this concept to the acoustic field by defining an analogous approach; the pressure field, generated by an elastic wave impinging on a spherical object, can be expressed applying the Mie expansion technique, as well. In acoustics, to achieve scattering suppression at a given frequency, the constitutive parameters to control are density and compressibility. By varying these parameter values, it is possible to define an engineered material with anomalous properties, which cannot be found in nature, able to reduce the scattering cross-section (SCS) from a spherical object. We propose a study about the effectiveness of the SCS reduction from an elastic sphere coated with a properly-designed acoustic metamaterial. The sensitivity of the SCS to parameter variations is analyzed for different coating thicknesses and sphere dimensions. Our analysis is supported by both the analytical modelling of the structure and numerical simulations. OPEN ACCESS Sustainability 2014, 6 4417
Sustainability, 2014
Most of the world's population lives in urban areas and in inefficient buildings under the energy... more Most of the world's population lives in urban areas and in inefficient buildings under the energy point of view. Starting from these assumptions, there is the need to identify methodologies and innovations able to improve social development and the quality of life of people living in cities. Smart cities can be a viable solution. The methodology traditionally adopted to evaluate building energy efficiency starts from the structure's energy demands analysis and the demands reduction evaluation. Consequently, the energy savings is assessed through a cascade of interventions. Regarding the building envelope, the first intervention is usually related to the reduction of the thermal transmittance value, but there is also the need to emphasize the building energy savings through other parameters, such as the solar gain factor and dye solar absorbance coefficients. In this contribution, a standard building has been modeled by means of the well-known dynamic software, TRNSYS. This study shows a parametrical analysis through which it is possible to evaluate the effect of each single intervention and, consequently, its influence on the building energy demand. Through this analysis, an intervention chart has been carried out, aiming to assess the intervention efficiency starting from the percentage variation of energy demands.
Sustainability, 2014
This study aims to highlight the importance of thermal inertia in buildings. Nowadays, it is poss... more This study aims to highlight the importance of thermal inertia in buildings. Nowadays, it is possible to use energy analysis software to simulate the building energy performance. Considering Italian standards, these analyses are based on the UNI TS 11300 that defines the procedures for the national implementation of the UNI EN ISO 13790. These standards require an energy analysis under steady-state condition, underestimating the thermal inertia of the building. In order to understand the inertial behavior of walls, a cubic Test-Cell was modelled through the dynamic calculation code TRNSYS and three different wall types were tested. Different stratigraphies, characterized by the same thermal transmittance value, composed by massive elements and insulating layers in different order, were simulated. Through TRNSYS, it was possible to define maximum surface temperatures and to calculate thermal lag between maximum values, both external and internal. Moreover, the attenuation between external surface temperatures and internal ones during summer (July) was calculated. Finally, the comparison between Test-Cell's annual energy demands, performed by using a commercial code based on the Italian standard UNITS 11300 and the dynamic code, TRNSYS, was carried out.
Energy Procedia, 2014
Nowadays many people use public transports in urban centers. Consequently, every day a lot of bus... more Nowadays many people use public transports in urban centers. Consequently, every day a lot of buses move within cities, trying to ensure the best service to citizens. During the year buses become crowded places and using an air conditioning system in constant operation, it tries to ensure a certain condition of comfort for the passengers on board. The aim of this study is to analyze and optimize the energy performance of a bus shell, identifying practical solutions have not yet been adopted in order to reduce the impact of air conditioning on bus' consumption and, therefore, on air pollution. For this reason it was decided to conduct a thermal analysis of a bus for public transport, in order to understand the behavior of the bus shell and to deduce possible optimization measures that have not yet been made until now. The analysis was carried out considering the hottest day of July and the coldest day of January, considering the operating conditions based on the most common graphics TGM (Average Daily Traffic) able to define the concentration of traffic city during the 24 hours per day. The study was done using the dynamic simulation software TRNSYS. With this software it was possible to recreate faithfully the structure of the bus and the external environmental conditions, assessing the impact of different technical solutions for an improvement of internal conditions and a reduction of the cooling capacity required. As the presence of passengers on public transport are considered like a "benefit" during the winter, the analysis is started with the identification of a summer solution and the subsequent evaluation of this solution for the winter time. The aim of this study was to optimize the bus shell and select the most appropriate solutions. Regarding the transparent surfaces it has been given importance to factors such as the thermal transmittance and the solar gain factor (g-value). Aware of the influence given by the solar radiation on the energy loads, bus energy performance were simulated also considering different types of paintwork with high reflectance.
Energy Procedia, 2014
Currently, the study of the energy performance of buildings is based on a simplified calculation ... more Currently, the study of the energy performance of buildings is based on a simplified calculation that estimates the thermal loads using monthly or seasonal average outdoor temperatures. In addition, the employed software require technical data such as the specific heat capacity of materials, but at the same time they are not able to properly consider the thermal inertia of buildings. The more precise evaluation allows to assess the correct interventions for energy requalification under a smart cities perspective. This study was performed considering a stationary software (Aermec MC11300) and a dynamic software (TRNSYS). Three simulations considering transparent elements characterized by progressively improved properties of thermal transmittance and solar gain factor have been performed. It has been performed a comparison between the outputs of the two software in order to highlight the different ways of evaluating the energy contributions on thermal loads. Finally, the models were validated by means of an in-situ measurement campaign using a heat flow meter -in order to measure the thermal transmittance of the opaque wallsand a thermographic camera. This modus operandi allowed to appreciate how the use of a dynamic software is more appropriate to deal with the inertial properties of the structure to calculate in a more detailed way the annual thermal loads and to obtain more information on individual heating zones.
Sustainability, 2014
Nowadays it is possible to employ several software packages to evaluate building's energy perform... more Nowadays it is possible to employ several software packages to evaluate building's energy performance, each of them based on a different calculation code, with different boundary conditions in terms of environmental temperature, solar radiation, wind velocity and relative humidity. In this contribution, a comparison between two calculation codes, taking into account different types of buildings, has been carried out. In particular, a semi-stationary calculation code and a dynamic one have been employed to determine energy demands of three different building's types: an old building, a house and a flat. Analyzing semi-stationary conditions (consequently simplified environmental conditions), a software which applies the UNI TS 11300 standard has been considered. This standard defines the procedures for the national implementation of the UNI EN ISO 13790. Furthermore, in order to consider the environmental conditions variation, a well-known dynamic software has been used.
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Papers by Luca Evangelisti