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Sergio Sibilio - One of the best experts on this subject based on the ideXlab platform.
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Impact of solar field design and back-up technology on dynamic performance of a solar hybrid heating network integrated with a seasonal borehole thermal energy storage serving a small-scale residential district including plug-in electric vehicles
Renewable Energy, 2020Co-Authors: Antonio Rosato, Michelangelo Scorpio, Giovanni Ciampi, Antonio Ciervo, Francesco Guarino, Sergio SibilioAbstract:Abstract A solar hybrid district heating network integrated with a seasonal borehole thermal energy storage is dynamically simulated and analyzed over a 5-year period. The system is devoted to satisfying the space heating and domestic hot water requirements of a small-scale district consisting of 6 typical Italian single-family houses, located in Naples, with home charging of 6 plug-in electric vehicles. Eight different plant schemes differing in terms of solar field configuration and/or back-up system used for compensating the intermittency of solar source are investigated. Two different configurations of solar field are analyzed: the first one with solar thermal collectors only and the second one integrating solar thermal collectors and photovoltaic panels coupled with a battery storage; three different alternative auxiliary Units are considered: natural gas-fired boiler, natural gas-fueled internal combustion engine-based micro-Cogeneration Unit and wood pellet boiler. An additional operating scheme is also proposed to better exploit the solar energy for domestic hot water production. The primary energy consumption, the carbon dioxide emissions and the operating costs of the proposed plant configurations are evaluated based on simulation results and then compared with those associated to a conventional decentralized heating system in order to assess the main energy, environmental and economic benefits/drawbacks.
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Performance of Different Back-up Technologies for Micro-Scale Solar Hybrid District Heating Systems with Long-term Thermal Energy Storage
Energy Procedia, 2018Co-Authors: Antonio Rosato, Giovanni Ciampi, Antonio Ciervo, Sergio SibilioAbstract:Abstract In this paper the performance of a solar heating network devoted to satisfying the heating demand of a micro-scale district composed of 6 typical single-family houses and 3 typical schools under the climatic conditions of Naples (south of Italy) is investigated by means of the dynamic simulation software TRNSYS over a 5-year period. The proposed system is composed of a solar collectors array, a short-term thermal energy storage, a long-term double U-pipe vertical borehole thermal energy storage and a heat distribution network. Three different technologies are investigated as back-up devices to be included in the district heating system: (i) a natural gas-fired boiler, (ii) a vapor-compression electric heat pump and (iii) a natural gas-fuelled internal combustion engine-based micro-Cogeneration Unit. The simulation results are compared with those associated to a conventional heating system in terms of primary energy consumption, operating costs as well as simple pay-back period in order to identify the best option in terms of back-up system and assess the potential energy and economic benefits associated to each technology.
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experimental analysis of a micro trigeneration system composed of a micro cogenerator coupled with an electric chiller
Applied Thermal Engineering, 2014Co-Authors: Giovanni Ciampi, Michelangelo Scorpio, Antonio Rosato, Sergio SibilioAbstract:Abstract Micro-trigeneration is one of the most promising technologies allowing the simultaneous production of electricity, heat and cooling on a small-scale basis, with a potential contribution to significant primary energy saving and greenhouse gas emission reduction if compared with the conventional separate energy production. The on-site performance of a micro-trigeneration plant serving the Built Environment Control Laboratory of Second University of Naples (south of Italy) during summer were measured and analyzed; the system was composed of a 6.0 kW natural gas-fueled reciprocating internal combustion engine-based micro-Cogeneration Unit feeding a 7.5 kW electric air-cooled water chiller. The experimental data were compared with the performance of conventional systems based on separate energy production in order to assess the feasibility of the proposed system; the comparison was performed according to the Italian scenario by estimating the potential savings in terms of primary energy consumption, operating costs and carbon dioxide equivalent emissions.
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influence of climatic conditions and control logic on nox and co emissions of a micro Cogeneration Unit serving an italian residential building
Applied Thermal Engineering, 2014Co-Authors: Giovanni Angrisani, Antonio Rosato, Sergio Sibilio, Carlo Roselli, Maurizio Sasso, Andrea UnichAbstract:Abstract The increasing diffusion of micro-Cogeneration systems is raising the need for studying their environmental impact in order to assess their sustainability. The adoption of the systems for the combined production of heat and power may provide a significant reduction of global impact in terms of carbon dioxide emissions with respect to the separate production of electricity and heat. However, a comprehensive environmental evaluation of this technology should take into account as well the impact due to the presence of plants spread over the territory that could increase the local pollution, in particular due to nitrogen oxides and carbon monoxide, and thus could worsen the local air quality. In this paper the nitrogen oxides and carbon monoxide emissions of a residential building-integrated micro-Cogeneration system were evaluated; a 6.0 kWel natural gas fuelled internal combustion engine-based micro-Cogeneration Unit was coupled with a multi-family house compliant with the transmittance values suggested by the Italian Law. The analyses were carried out by using the whole building simulation software TRNSYS upon varying the city where the building is located (four Italian cities representative of different climatic regions were considered) as well as the control logic of Cogeneration device (electric and thermal load-following strategies). The simulated performance of the proposed system was compared with those of a conventional system composed of a natural gas-fired boiler (for thermal energy production) and a power plant mix connected to the central electric grid (for electricity production) in order to assess the suitability of the Cogeneration-based system in reducing the local emissions.
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dynamic performance assessment of a residential building integrated Cogeneration system under different boundary conditions part i energy analysis
Energy Conversion and Management, 2014Co-Authors: Antonio Rosato, Sergio Sibilio, Michelangelo ScorpioAbstract:Abstract This work examines the energy performance of a residential building-integrated micro-Cogeneration system during the winter season by means of a whole building simulation software; a 6.0 kWel natural gas-fuelled internal combustion engine-based Cogeneration Unit was coupled with a multi-family house composed of three floors, compliant with the thermal transmittances of both walls and windows equated to the threshold values suggested by the Italian Law. The main purpose of the paper is to compare the proposed system with a conventional system composed of a natural gas-fired boiler (for thermal energy production) and a power plant mix connected to the Italian central grid (for electric energy production) in order to assess the potential energy saving under various operating scenarios. The simulations were performed by considering the multi-family house located into four different Italian cities (Palermo, Napoli, Roma and Milano) representative of different climatic regions of Italy in order to estimate the influence of climatic conditions; a parametric analysis was also performed with the aim to evaluate the sensitivity of the energy flows when varying the volume of the combined storage tank; taking into consideration that the economic viability of the Cogeneration Unit strongly depends also on the value of the co-produced electricity, the system performance was also evaluated by considering two different electric demand profiles (with and without the electric consumption associated to the overnight charging of an electric vehicle); the operation of the micro-Cogeneration device was estimated under both electric and thermal load-following control strategies. The analyses showed that, in comparison to the conventional system, the proposed system allows for a relevant reduction of primary energy consumption under thermal load-following logic; significant effects of climatic conditions, tank volume, as well as electric demand profile on the simulation results were highlighted. In the companion paper (Part II: Environmental and economic analyses) the performance of the proposed system was analyzed and compared with those of the reference system from both environmental and economic point of views.
Antonio Rosato - One of the best experts on this subject based on the ideXlab platform.
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Impact of solar field design and back-up technology on dynamic performance of a solar hybrid heating network integrated with a seasonal borehole thermal energy storage serving a small-scale residential district including plug-in electric vehicles
Renewable Energy, 2020Co-Authors: Antonio Rosato, Michelangelo Scorpio, Giovanni Ciampi, Antonio Ciervo, Francesco Guarino, Sergio SibilioAbstract:Abstract A solar hybrid district heating network integrated with a seasonal borehole thermal energy storage is dynamically simulated and analyzed over a 5-year period. The system is devoted to satisfying the space heating and domestic hot water requirements of a small-scale district consisting of 6 typical Italian single-family houses, located in Naples, with home charging of 6 plug-in electric vehicles. Eight different plant schemes differing in terms of solar field configuration and/or back-up system used for compensating the intermittency of solar source are investigated. Two different configurations of solar field are analyzed: the first one with solar thermal collectors only and the second one integrating solar thermal collectors and photovoltaic panels coupled with a battery storage; three different alternative auxiliary Units are considered: natural gas-fired boiler, natural gas-fueled internal combustion engine-based micro-Cogeneration Unit and wood pellet boiler. An additional operating scheme is also proposed to better exploit the solar energy for domestic hot water production. The primary energy consumption, the carbon dioxide emissions and the operating costs of the proposed plant configurations are evaluated based on simulation results and then compared with those associated to a conventional decentralized heating system in order to assess the main energy, environmental and economic benefits/drawbacks.
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Performance of Different Back-up Technologies for Micro-Scale Solar Hybrid District Heating Systems with Long-term Thermal Energy Storage
Energy Procedia, 2018Co-Authors: Antonio Rosato, Giovanni Ciampi, Antonio Ciervo, Sergio SibilioAbstract:Abstract In this paper the performance of a solar heating network devoted to satisfying the heating demand of a micro-scale district composed of 6 typical single-family houses and 3 typical schools under the climatic conditions of Naples (south of Italy) is investigated by means of the dynamic simulation software TRNSYS over a 5-year period. The proposed system is composed of a solar collectors array, a short-term thermal energy storage, a long-term double U-pipe vertical borehole thermal energy storage and a heat distribution network. Three different technologies are investigated as back-up devices to be included in the district heating system: (i) a natural gas-fired boiler, (ii) a vapor-compression electric heat pump and (iii) a natural gas-fuelled internal combustion engine-based micro-Cogeneration Unit. The simulation results are compared with those associated to a conventional heating system in terms of primary energy consumption, operating costs as well as simple pay-back period in order to identify the best option in terms of back-up system and assess the potential energy and economic benefits associated to each technology.
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experimental analysis of a micro trigeneration system composed of a micro cogenerator coupled with an electric chiller
Applied Thermal Engineering, 2014Co-Authors: Giovanni Ciampi, Michelangelo Scorpio, Antonio Rosato, Sergio SibilioAbstract:Abstract Micro-trigeneration is one of the most promising technologies allowing the simultaneous production of electricity, heat and cooling on a small-scale basis, with a potential contribution to significant primary energy saving and greenhouse gas emission reduction if compared with the conventional separate energy production. The on-site performance of a micro-trigeneration plant serving the Built Environment Control Laboratory of Second University of Naples (south of Italy) during summer were measured and analyzed; the system was composed of a 6.0 kW natural gas-fueled reciprocating internal combustion engine-based micro-Cogeneration Unit feeding a 7.5 kW electric air-cooled water chiller. The experimental data were compared with the performance of conventional systems based on separate energy production in order to assess the feasibility of the proposed system; the comparison was performed according to the Italian scenario by estimating the potential savings in terms of primary energy consumption, operating costs and carbon dioxide equivalent emissions.
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influence of climatic conditions and control logic on nox and co emissions of a micro Cogeneration Unit serving an italian residential building
Applied Thermal Engineering, 2014Co-Authors: Giovanni Angrisani, Antonio Rosato, Sergio Sibilio, Carlo Roselli, Maurizio Sasso, Andrea UnichAbstract:Abstract The increasing diffusion of micro-Cogeneration systems is raising the need for studying their environmental impact in order to assess their sustainability. The adoption of the systems for the combined production of heat and power may provide a significant reduction of global impact in terms of carbon dioxide emissions with respect to the separate production of electricity and heat. However, a comprehensive environmental evaluation of this technology should take into account as well the impact due to the presence of plants spread over the territory that could increase the local pollution, in particular due to nitrogen oxides and carbon monoxide, and thus could worsen the local air quality. In this paper the nitrogen oxides and carbon monoxide emissions of a residential building-integrated micro-Cogeneration system were evaluated; a 6.0 kWel natural gas fuelled internal combustion engine-based micro-Cogeneration Unit was coupled with a multi-family house compliant with the transmittance values suggested by the Italian Law. The analyses were carried out by using the whole building simulation software TRNSYS upon varying the city where the building is located (four Italian cities representative of different climatic regions were considered) as well as the control logic of Cogeneration device (electric and thermal load-following strategies). The simulated performance of the proposed system was compared with those of a conventional system composed of a natural gas-fired boiler (for thermal energy production) and a power plant mix connected to the central electric grid (for electricity production) in order to assess the suitability of the Cogeneration-based system in reducing the local emissions.
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dynamic performance assessment of a residential building integrated Cogeneration system under different boundary conditions part i energy analysis
Energy Conversion and Management, 2014Co-Authors: Antonio Rosato, Sergio Sibilio, Michelangelo ScorpioAbstract:Abstract This work examines the energy performance of a residential building-integrated micro-Cogeneration system during the winter season by means of a whole building simulation software; a 6.0 kWel natural gas-fuelled internal combustion engine-based Cogeneration Unit was coupled with a multi-family house composed of three floors, compliant with the thermal transmittances of both walls and windows equated to the threshold values suggested by the Italian Law. The main purpose of the paper is to compare the proposed system with a conventional system composed of a natural gas-fired boiler (for thermal energy production) and a power plant mix connected to the Italian central grid (for electric energy production) in order to assess the potential energy saving under various operating scenarios. The simulations were performed by considering the multi-family house located into four different Italian cities (Palermo, Napoli, Roma and Milano) representative of different climatic regions of Italy in order to estimate the influence of climatic conditions; a parametric analysis was also performed with the aim to evaluate the sensitivity of the energy flows when varying the volume of the combined storage tank; taking into consideration that the economic viability of the Cogeneration Unit strongly depends also on the value of the co-produced electricity, the system performance was also evaluated by considering two different electric demand profiles (with and without the electric consumption associated to the overnight charging of an electric vehicle); the operation of the micro-Cogeneration device was estimated under both electric and thermal load-following control strategies. The analyses showed that, in comparison to the conventional system, the proposed system allows for a relevant reduction of primary energy consumption under thermal load-following logic; significant effects of climatic conditions, tank volume, as well as electric demand profile on the simulation results were highlighted. In the companion paper (Part II: Environmental and economic analyses) the performance of the proposed system was analyzed and compared with those of the reference system from both environmental and economic point of views.
Giovanni Ciampi - One of the best experts on this subject based on the ideXlab platform.
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Impact of solar field design and back-up technology on dynamic performance of a solar hybrid heating network integrated with a seasonal borehole thermal energy storage serving a small-scale residential district including plug-in electric vehicles
Renewable Energy, 2020Co-Authors: Antonio Rosato, Michelangelo Scorpio, Giovanni Ciampi, Antonio Ciervo, Francesco Guarino, Sergio SibilioAbstract:Abstract A solar hybrid district heating network integrated with a seasonal borehole thermal energy storage is dynamically simulated and analyzed over a 5-year period. The system is devoted to satisfying the space heating and domestic hot water requirements of a small-scale district consisting of 6 typical Italian single-family houses, located in Naples, with home charging of 6 plug-in electric vehicles. Eight different plant schemes differing in terms of solar field configuration and/or back-up system used for compensating the intermittency of solar source are investigated. Two different configurations of solar field are analyzed: the first one with solar thermal collectors only and the second one integrating solar thermal collectors and photovoltaic panels coupled with a battery storage; three different alternative auxiliary Units are considered: natural gas-fired boiler, natural gas-fueled internal combustion engine-based micro-Cogeneration Unit and wood pellet boiler. An additional operating scheme is also proposed to better exploit the solar energy for domestic hot water production. The primary energy consumption, the carbon dioxide emissions and the operating costs of the proposed plant configurations are evaluated based on simulation results and then compared with those associated to a conventional decentralized heating system in order to assess the main energy, environmental and economic benefits/drawbacks.
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Performance of Different Back-up Technologies for Micro-Scale Solar Hybrid District Heating Systems with Long-term Thermal Energy Storage
Energy Procedia, 2018Co-Authors: Antonio Rosato, Giovanni Ciampi, Antonio Ciervo, Sergio SibilioAbstract:Abstract In this paper the performance of a solar heating network devoted to satisfying the heating demand of a micro-scale district composed of 6 typical single-family houses and 3 typical schools under the climatic conditions of Naples (south of Italy) is investigated by means of the dynamic simulation software TRNSYS over a 5-year period. The proposed system is composed of a solar collectors array, a short-term thermal energy storage, a long-term double U-pipe vertical borehole thermal energy storage and a heat distribution network. Three different technologies are investigated as back-up devices to be included in the district heating system: (i) a natural gas-fired boiler, (ii) a vapor-compression electric heat pump and (iii) a natural gas-fuelled internal combustion engine-based micro-Cogeneration Unit. The simulation results are compared with those associated to a conventional heating system in terms of primary energy consumption, operating costs as well as simple pay-back period in order to identify the best option in terms of back-up system and assess the potential energy and economic benefits associated to each technology.
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experimental analysis of a micro trigeneration system composed of a micro cogenerator coupled with an electric chiller
Applied Thermal Engineering, 2014Co-Authors: Giovanni Ciampi, Michelangelo Scorpio, Antonio Rosato, Sergio SibilioAbstract:Abstract Micro-trigeneration is one of the most promising technologies allowing the simultaneous production of electricity, heat and cooling on a small-scale basis, with a potential contribution to significant primary energy saving and greenhouse gas emission reduction if compared with the conventional separate energy production. The on-site performance of a micro-trigeneration plant serving the Built Environment Control Laboratory of Second University of Naples (south of Italy) during summer were measured and analyzed; the system was composed of a 6.0 kW natural gas-fueled reciprocating internal combustion engine-based micro-Cogeneration Unit feeding a 7.5 kW electric air-cooled water chiller. The experimental data were compared with the performance of conventional systems based on separate energy production in order to assess the feasibility of the proposed system; the comparison was performed according to the Italian scenario by estimating the potential savings in terms of primary energy consumption, operating costs and carbon dioxide equivalent emissions.
Michelangelo Scorpio - One of the best experts on this subject based on the ideXlab platform.
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Impact of solar field design and back-up technology on dynamic performance of a solar hybrid heating network integrated with a seasonal borehole thermal energy storage serving a small-scale residential district including plug-in electric vehicles
Renewable Energy, 2020Co-Authors: Antonio Rosato, Michelangelo Scorpio, Giovanni Ciampi, Antonio Ciervo, Francesco Guarino, Sergio SibilioAbstract:Abstract A solar hybrid district heating network integrated with a seasonal borehole thermal energy storage is dynamically simulated and analyzed over a 5-year period. The system is devoted to satisfying the space heating and domestic hot water requirements of a small-scale district consisting of 6 typical Italian single-family houses, located in Naples, with home charging of 6 plug-in electric vehicles. Eight different plant schemes differing in terms of solar field configuration and/or back-up system used for compensating the intermittency of solar source are investigated. Two different configurations of solar field are analyzed: the first one with solar thermal collectors only and the second one integrating solar thermal collectors and photovoltaic panels coupled with a battery storage; three different alternative auxiliary Units are considered: natural gas-fired boiler, natural gas-fueled internal combustion engine-based micro-Cogeneration Unit and wood pellet boiler. An additional operating scheme is also proposed to better exploit the solar energy for domestic hot water production. The primary energy consumption, the carbon dioxide emissions and the operating costs of the proposed plant configurations are evaluated based on simulation results and then compared with those associated to a conventional decentralized heating system in order to assess the main energy, environmental and economic benefits/drawbacks.
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experimental analysis of a micro trigeneration system composed of a micro cogenerator coupled with an electric chiller
Applied Thermal Engineering, 2014Co-Authors: Giovanni Ciampi, Michelangelo Scorpio, Antonio Rosato, Sergio SibilioAbstract:Abstract Micro-trigeneration is one of the most promising technologies allowing the simultaneous production of electricity, heat and cooling on a small-scale basis, with a potential contribution to significant primary energy saving and greenhouse gas emission reduction if compared with the conventional separate energy production. The on-site performance of a micro-trigeneration plant serving the Built Environment Control Laboratory of Second University of Naples (south of Italy) during summer were measured and analyzed; the system was composed of a 6.0 kW natural gas-fueled reciprocating internal combustion engine-based micro-Cogeneration Unit feeding a 7.5 kW electric air-cooled water chiller. The experimental data were compared with the performance of conventional systems based on separate energy production in order to assess the feasibility of the proposed system; the comparison was performed according to the Italian scenario by estimating the potential savings in terms of primary energy consumption, operating costs and carbon dioxide equivalent emissions.
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dynamic performance assessment of a residential building integrated Cogeneration system under different boundary conditions part i energy analysis
Energy Conversion and Management, 2014Co-Authors: Antonio Rosato, Sergio Sibilio, Michelangelo ScorpioAbstract:Abstract This work examines the energy performance of a residential building-integrated micro-Cogeneration system during the winter season by means of a whole building simulation software; a 6.0 kWel natural gas-fuelled internal combustion engine-based Cogeneration Unit was coupled with a multi-family house composed of three floors, compliant with the thermal transmittances of both walls and windows equated to the threshold values suggested by the Italian Law. The main purpose of the paper is to compare the proposed system with a conventional system composed of a natural gas-fired boiler (for thermal energy production) and a power plant mix connected to the Italian central grid (for electric energy production) in order to assess the potential energy saving under various operating scenarios. The simulations were performed by considering the multi-family house located into four different Italian cities (Palermo, Napoli, Roma and Milano) representative of different climatic regions of Italy in order to estimate the influence of climatic conditions; a parametric analysis was also performed with the aim to evaluate the sensitivity of the energy flows when varying the volume of the combined storage tank; taking into consideration that the economic viability of the Cogeneration Unit strongly depends also on the value of the co-produced electricity, the system performance was also evaluated by considering two different electric demand profiles (with and without the electric consumption associated to the overnight charging of an electric vehicle); the operation of the micro-Cogeneration device was estimated under both electric and thermal load-following control strategies. The analyses showed that, in comparison to the conventional system, the proposed system allows for a relevant reduction of primary energy consumption under thermal load-following logic; significant effects of climatic conditions, tank volume, as well as electric demand profile on the simulation results were highlighted. In the companion paper (Part II: Environmental and economic analyses) the performance of the proposed system was analyzed and compared with those of the reference system from both environmental and economic point of views.
William Dhaeseleer - One of the best experts on this subject based on the ideXlab platform.
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the impact of thermal storage on the operational behaviour of residential chp facilities and the overall co2 emissions
Renewable & Sustainable Energy Reviews, 2007Co-Authors: Dries Haeseldonckx, Leen Peeters, Lieve Helsen, William DhaeseleerAbstract:When evaluating the environmental impact of small-scale Cogeneration facilities, two important boundary conditions are often overlooked. Firstly, Cogeneration Units are mostly considered as stand-alone facilities, although, in reality, they will be part of a system that may also contain a thermal-storage tank and back-up boiler. Secondly, usually mainly static and simplified methods are used to calculate the possible reduction of CO2 emissions. In this paper, these issues are discussed in two parts. The dimensioning of Cogeneration facilities to fulfil a certain heat demand and the impact of thermal-storage tanks on the operational behaviour of these Units are dealt with. It is shown that the use of thermal-storage tanks prolongs the yearly operation time of a CHP facility and allows the Cogeneration Unit to operate more continuously. Also, it is clarified how to interpret thermal load-duration diagrams in a correct way. Furthermore, the impact of thermal storage on the overall CO2 emissions is investigated. Hereby, the interaction with the expansion of the central power system and the annual use of the Cogeneration Units are two important parameters. Using a small thermal-storage device causes the net reduction of CO2 emissions, in comparison with a reference scenario without additionally installed Cogeneration, to be almost three times higher compared to the case without heat buffer. Finally, it is shown that the operational behaviour of multiple small-scale Cogeneration Units can be approximated by the behaviour of one large fictitious Unit for the determination of the net reduction of CO2 emissions.
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the evaluation of small Cogeneration for residential heating
International Journal of Energy Research, 2002Co-Authors: Kris Voorspools, William DhaeseleerAbstract:The decision whether or not to install small Cogeneration for residential purposes mainly depends on individual economic considerations, combined with ecological awareness. Since in most cases, the economic balance is still unfavourable, government grants are considered in order to bridge this economic barrier. It is however still unclear how these grants are best spent to obtain an optimal environmental benefit. In the case of Cogeneration, mainly static and simplified methods are used, completely neglecting the dynamic interaction between the Cogeneration systems and the central power system and the dynamic response of the Cogeneration Units themselves. In this paper, these issues are discussed in two parts. The first part clarifies how an actual Cogeneration Unit, if necessary in combination with a back-up boiler and heat storage, will respond to a certain demand. For this purpose, experiments were performed to establish the transient and stationary behaviour of the system. It is shown that the transient heating of the Cogeneration engine is rather slow (e.g. half an hour after cold start, the engine only produced 65% of the heat it would have in stationary regime) where the electric transient behaviour is negligible. In the second part of the paper, dynamic simulations are performed to quantify the impact (primary energy saving and reduction in greenhouse-gas emissions) of the massive installation of Cogeneration for residential heating. Two important parameters are isolated. First, the interaction with the expansion of the central power system is very important. If the installation of Cogeneration prevents the commissioning of new power plants, the potential energy saving and (especially) emission reduction are reduced. The second parameter is the annual use of the Cogeneration Units. Here, the potential energy saving and emission reduction increase with increasing annual use. Copyright © 2002 John Wiley & Sons, Ltd.