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Solar energy potential for heating and cooling systems in big cities of Turkey
07 Alternative energy sources (solar energy)
03100669 Mono- and tri-crystalline Si for PV application EndrOs, A. L. Solar Energy Materials and Solar Cells, 2002, 72, (1--4), 109-124. Crystalline silicon wafers are by far the dominant absorber materials for today's production of solar cells and modules due to their good price/performance relation and their proven environmental stability. These wafers are mainly produced either by a solar-optimized Czochralski (Cz)-growth method yielding crystalline silicon with low defect density (c-Si) or by a directional solidification or a ribbon growth method yielding large grained multi-crystalline (mc-Si) wafers with higher defect density. To further improve the price/performance relation of Cz solar ceils, tri-crystalline silicon (tri-Si) is being developed as a high-quality wafer material that combines both the high diffusion length of minority carriers of up to 1300 ~m of c-Si and the productivity of mc-Si. More than 1000 lam LID free diffusion length could be reached with specially doped tri-crystals. Due to an increased mechanical stability tri-Si allows both quasi-continuous pulling and thin slicing with higher mechanical yields. This paper reviews the structural, electronic, and mechanical properties of tri-crystalline silicon wafers with respect to c-Si wafers for solar applications. Actual non-textured solar cells processed with a simple cost effective fabrication process exhibit the same cell efficiencies up to 15.9% for both tri-silicon and mono-silicon wafers. With an improved process, up to 18% cell efficiency can be obtained with textured mono-Si.
03/00670 Parabolic trough collectors for industrial process heat in Cyprus Kalogirou, S. A. Energy, 2002, 27, (9), 813-830. The thermal utilization of solar energy is usually confined to domestic hot water systems and somewhat to space heating at temperatures up to 60°C. Industrial process heat has a considerable potential for solar energy utilization. Cyprus has a small isolated energy system, almost totally dependent on imported fuels to meet its energy demand. The abundance of solar radiation together with a good technological base, created favourable conditions for the exploitation of solar energy in the island. The number of units in operation today corresponds to one heater for every 3.7 people in the island, which is a world record. Despite this impressive record no solar industrial process heat system is in operation today. The main problem for this is the big expenditure required for such a system and the uncertainty of the benefits. The objective of this work was to investigate the viability of using parabolic trough collectors for industrial heat generation in Cyprus. The system is analysed both thermally and economically with TRNSYS and the TMY for Nieosia, Cyprus, in order to show the magnitude of the expected benefits. The load is hot water delivered at 85°C at a flow rate of 2000 kg/h for the first three-quarters of each hour from 8:00-16:00 h, 5 days a week. The system consists of an array of parabolic trough collectors, hot water storage tank, piping and controls. The optimum collector area for the present application is 300 m z, the optimum collector flow rate is 54 kg/m z h and the optimum storage tank size is 25 m3. The system covers 50% of the annual load of the system and gives life cycle savings of about C£6200 ([£]10800). This amount represent the money saved from the use of the system against paying for fuel. The savings however refer to a non-subsidized fuel price, which will be in effect from 2003. The optimum system can deliver a total of 896 GJ per year and avoids 208 tons of CO2 emissions to the atmosphere. The effect of various design changes on the system performance was investigated. The E-W tracking system (collector axis aligned in N-S direction) was found to be superior to the N-S one. The required load temperature affects the performance of the system as for higher temperatures the auxiliary energy required is bigger. Also a number of variations in the load use pattern have been investigated and presented in this paper. It was found that the bigger the load (double shift, full hour use pattern) the bigger the collector area required, the greater the first year fuel savings and the greater the life cycle savings of the installation. This means that it is more viable to apply solar industrial process heat to higher energy consumption industries.
03•00671 Possibilities for biomass-based power plant and wind system integration Jurado, F. and Saenz, J. R. Energy, 2002, 27, (10), 955-966. In this paper, the integration of a biomass-based diesel-wind system is investigated. The system consists of a pitch controlled wind turbine, which is equipped with an induction generator. The induction generator is connected to an ac bus-bar in parallel with a dieselgenerator set consisting of a diesel engine driving a synchronous generator. A power plant can generate electric power using biomass from the olive tree in Spain, A gasifier is capable of converting tons of wood chips per day into a gaseous fuel that is fed into a diesel engine. While there are significant systems whose models may be exactly obtained from physical laws and whose states are measured, it is much less realistic to assume that all the parameters, such as the higher heating value of the biogas or wind speed, are exactly known. It is then natural to investigate what happens to control systems involving
unknown, or not precisely known, parameters. In this paper, the derived model of biomass-based wind-diesel systems is quite valid for robust control studies.
03•00672 Practical scenario by solar hybrid fuel for opening hydrogen energy era Tamaura, H. Petrotech (Tokyo, Japan), 2002, 25, (1), 34-39. (In Japanese) A review of production of solar hybrid fuels, such as methanol, di-Me ether, and hydrogen from coal and natural gas and solar energy.
03/00673
Silicon ribbons and foils-state of the art
Kalejs, J. P. et al. Solar Energy Materials and Solar Cells, 2002, 72, (14), 139-153. Research and development on crystal growth technologies for production of crystalline silicon ribbon have been under way now for three decades. Their progress toward establishment of manufacturing capabilities for silicon wafers for photovoltaic applications is reviewed. Technology improvements that are currently being explored for a future generation of low-cost solar products based on ribbon wafers are considered, and potential limits of the technology are discussed.
03100674 Solar cooling by thermal compression: the dependence of the jet thermal compressor efficiency on the compression ratio Korres, C. J. et al. Energy, 2002, 27, (8), 795-805. This paper presents an experimental work relating the thermodynamic efficiency of jet compressors to the compression ratio of the corresponding cooling cycle. The working fluid used in the experimental work was R-114 for both motive and suction sides. Two jet compressors, designed to operate at conditions relevant to solar cooling, were used. Each exhibited a characteristic efficiency vs compression ratio curve, with a peak at the point of its nominal design conditions. The peak is either sharp or flat, depending on the intrinsic parameters (geometry) of each specific jet compressor.
03/00675 Solar energy potential for heating and cooling systems in big cities of Turkey ~aylan, L. et al. Energy Conversion and Management, 2002, 43, (14), 1829-1837. In this study, the solar energy gain on vertical surfaces for heating and cooling systems in big cities, such as Istanbul, Ankara and Izmir of Turkey, has been estimated for different orientations using hourly solar radiation measurements. During summer, the monthly mean solar energy potential on vertical surfaces comes from the east and west directions more than other orientations in all the cities. However, during winter, it comes from the south, and the highest solar energy is received in Izmir, where the average annual global radiation attains its maximum. Additionally, north oriented surfaces produce between 65% and 75% lower total solar energy than other orientations in all the cities.
03100676 Technical feasibility and economic viability of a small-scale grid connected solar thermal installation for electrical-energy saving Bakos, G. C. and Tsagas, N. F. Applied Energy, 2002, 72, (3-4), 621630. This paper reports on the techno-economic assessment of a gridconnected solar thermal system used for electrical-energy saving in the residential sector. The technical characteristics of the solar thermal system, based on a line-focus parabolic-trough concentrator, are given and its useful electrical and thermal-energy production is estimated using a simulation program based on a Monte Carlo method for reading solar radiation data. The economic assessment is performed using the Life-Cycle Savings (LCS) method and the payback period (PBP) of the investment's initial capital cost is determined.
03/00677 Thermochemical energy storage based on magnesium hydride for a small solar power station Wierse, M. Fortschritt Berichte VDI, Reihe 6: Energietechnik, 2001, 463, (i-xiii), 1-148. (In German) A review is presented of the principles of thermal energy storage an especially thermochemical energy storage based on reversible reactions between metals and hydrogen. The state of the art is reported. The body of the work involves the investigation of the operating behaviour of a thermochemical energy storage system based on magnesium hydride in a small-scale solar-thermal power station. For this purpose, two lab models have been developed and built. Their design as well as the result of the experimental investigation are described. 'Mathematical models of the different components are explained; they were developed within the frame of the theoretical investigation of the two lab models. A computer program is presented which allows the
Fuel and Energy Abstracts
March 2003 91
03100669 Mono- and tri-crystalline Si for PV application EndrOs, A. L. Solar Energy Materials and Solar Cells, 2002, 72, (1--4), 109-124. Crystalline silicon wafers are by far the dominant absorber materials for today's production of solar cells and modules due to their good price/performance relation and their proven environmental stability. These wafers are mainly produced either by a solar-optimized Czochralski (Cz)-growth method yielding crystalline silicon with low defect density (c-Si) or by a directional solidification or a ribbon growth method yielding large grained multi-crystalline (mc-Si) wafers with higher defect density. To further improve the price/performance relation of Cz solar ceils, tri-crystalline silicon (tri-Si) is being developed as a high-quality wafer material that combines both the high diffusion length of minority carriers of up to 1300 ~m of c-Si and the productivity of mc-Si. More than 1000 lam LID free diffusion length could be reached with specially doped tri-crystals. Due to an increased mechanical stability tri-Si allows both quasi-continuous pulling and thin slicing with higher mechanical yields. This paper reviews the structural, electronic, and mechanical properties of tri-crystalline silicon wafers with respect to c-Si wafers for solar applications. Actual non-textured solar cells processed with a simple cost effective fabrication process exhibit the same cell efficiencies up to 15.9% for both tri-silicon and mono-silicon wafers. With an improved process, up to 18% cell efficiency can be obtained with textured mono-Si.
03/00670 Parabolic trough collectors for industrial process heat in Cyprus Kalogirou, S. A. Energy, 2002, 27, (9), 813-830. The thermal utilization of solar energy is usually confined to domestic hot water systems and somewhat to space heating at temperatures up to 60°C. Industrial process heat has a considerable potential for solar energy utilization. Cyprus has a small isolated energy system, almost totally dependent on imported fuels to meet its energy demand. The abundance of solar radiation together with a good technological base, created favourable conditions for the exploitation of solar energy in the island. The number of units in operation today corresponds to one heater for every 3.7 people in the island, which is a world record. Despite this impressive record no solar industrial process heat system is in operation today. The main problem for this is the big expenditure required for such a system and the uncertainty of the benefits. The objective of this work was to investigate the viability of using parabolic trough collectors for industrial heat generation in Cyprus. The system is analysed both thermally and economically with TRNSYS and the TMY for Nieosia, Cyprus, in order to show the magnitude of the expected benefits. The load is hot water delivered at 85°C at a flow rate of 2000 kg/h for the first three-quarters of each hour from 8:00-16:00 h, 5 days a week. The system consists of an array of parabolic trough collectors, hot water storage tank, piping and controls. The optimum collector area for the present application is 300 m z, the optimum collector flow rate is 54 kg/m z h and the optimum storage tank size is 25 m3. The system covers 50% of the annual load of the system and gives life cycle savings of about C£6200 ([£]10800). This amount represent the money saved from the use of the system against paying for fuel. The savings however refer to a non-subsidized fuel price, which will be in effect from 2003. The optimum system can deliver a total of 896 GJ per year and avoids 208 tons of CO2 emissions to the atmosphere. The effect of various design changes on the system performance was investigated. The E-W tracking system (collector axis aligned in N-S direction) was found to be superior to the N-S one. The required load temperature affects the performance of the system as for higher temperatures the auxiliary energy required is bigger. Also a number of variations in the load use pattern have been investigated and presented in this paper. It was found that the bigger the load (double shift, full hour use pattern) the bigger the collector area required, the greater the first year fuel savings and the greater the life cycle savings of the installation. This means that it is more viable to apply solar industrial process heat to higher energy consumption industries.
03•00671 Possibilities for biomass-based power plant and wind system integration Jurado, F. and Saenz, J. R. Energy, 2002, 27, (10), 955-966. In this paper, the integration of a biomass-based diesel-wind system is investigated. The system consists of a pitch controlled wind turbine, which is equipped with an induction generator. The induction generator is connected to an ac bus-bar in parallel with a dieselgenerator set consisting of a diesel engine driving a synchronous generator. A power plant can generate electric power using biomass from the olive tree in Spain, A gasifier is capable of converting tons of wood chips per day into a gaseous fuel that is fed into a diesel engine. While there are significant systems whose models may be exactly obtained from physical laws and whose states are measured, it is much less realistic to assume that all the parameters, such as the higher heating value of the biogas or wind speed, are exactly known. It is then natural to investigate what happens to control systems involving
unknown, or not precisely known, parameters. In this paper, the derived model of biomass-based wind-diesel systems is quite valid for robust control studies.
03•00672 Practical scenario by solar hybrid fuel for opening hydrogen energy era Tamaura, H. Petrotech (Tokyo, Japan), 2002, 25, (1), 34-39. (In Japanese) A review of production of solar hybrid fuels, such as methanol, di-Me ether, and hydrogen from coal and natural gas and solar energy.
03/00673
Silicon ribbons and foils-state of the art
Kalejs, J. P. et al. Solar Energy Materials and Solar Cells, 2002, 72, (14), 139-153. Research and development on crystal growth technologies for production of crystalline silicon ribbon have been under way now for three decades. Their progress toward establishment of manufacturing capabilities for silicon wafers for photovoltaic applications is reviewed. Technology improvements that are currently being explored for a future generation of low-cost solar products based on ribbon wafers are considered, and potential limits of the technology are discussed.
03100674 Solar cooling by thermal compression: the dependence of the jet thermal compressor efficiency on the compression ratio Korres, C. J. et al. Energy, 2002, 27, (8), 795-805. This paper presents an experimental work relating the thermodynamic efficiency of jet compressors to the compression ratio of the corresponding cooling cycle. The working fluid used in the experimental work was R-114 for both motive and suction sides. Two jet compressors, designed to operate at conditions relevant to solar cooling, were used. Each exhibited a characteristic efficiency vs compression ratio curve, with a peak at the point of its nominal design conditions. The peak is either sharp or flat, depending on the intrinsic parameters (geometry) of each specific jet compressor.
03/00675 Solar energy potential for heating and cooling systems in big cities of Turkey ~aylan, L. et al. Energy Conversion and Management, 2002, 43, (14), 1829-1837. In this study, the solar energy gain on vertical surfaces for heating and cooling systems in big cities, such as Istanbul, Ankara and Izmir of Turkey, has been estimated for different orientations using hourly solar radiation measurements. During summer, the monthly mean solar energy potential on vertical surfaces comes from the east and west directions more than other orientations in all the cities. However, during winter, it comes from the south, and the highest solar energy is received in Izmir, where the average annual global radiation attains its maximum. Additionally, north oriented surfaces produce between 65% and 75% lower total solar energy than other orientations in all the cities.
03100676 Technical feasibility and economic viability of a small-scale grid connected solar thermal installation for electrical-energy saving Bakos, G. C. and Tsagas, N. F. Applied Energy, 2002, 72, (3-4), 621630. This paper reports on the techno-economic assessment of a gridconnected solar thermal system used for electrical-energy saving in the residential sector. The technical characteristics of the solar thermal system, based on a line-focus parabolic-trough concentrator, are given and its useful electrical and thermal-energy production is estimated using a simulation program based on a Monte Carlo method for reading solar radiation data. The economic assessment is performed using the Life-Cycle Savings (LCS) method and the payback period (PBP) of the investment's initial capital cost is determined.
03/00677 Thermochemical energy storage based on magnesium hydride for a small solar power station Wierse, M. Fortschritt Berichte VDI, Reihe 6: Energietechnik, 2001, 463, (i-xiii), 1-148. (In German) A review is presented of the principles of thermal energy storage an especially thermochemical energy storage based on reversible reactions between metals and hydrogen. The state of the art is reported. The body of the work involves the investigation of the operating behaviour of a thermochemical energy storage system based on magnesium hydride in a small-scale solar-thermal power station. For this purpose, two lab models have been developed and built. Their design as well as the result of the experimental investigation are described. 'Mathematical models of the different components are explained; they were developed within the frame of the theoretical investigation of the two lab models. A computer program is presented which allows the
Fuel and Energy Abstracts
March 2003 91