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00470 Solar energy gasification of solid carbonaceous material in liquid dispersion
07
Alternative energy sources (solar energy)
98/00464 Novel light-trapping schemes involving planar junctions and diffuse rear reflectors for thin-film silicon-based solar cells Winz, K. et al. Solar Energy Materials and Solar Cells, 1997, 49, (l-4), 195203. Improved conversion efficiency is offered by optical optimization of planar junction amorphous and microcrystalline silicon-based thin-film solar cells. Planar junction solar cells with diffuse and selective angle rear reflectors were examined in detail. The refractive index of the diffuser material needs to be as close to that of silicon as possible. Insulating diffuse rear reflectors must be used in conjunction with conductive rear-window layers of the appropriate hand gap, conductivity and refractive index. The refractive index of the rear window layer should be at least as large as that of the diffuser material. Rear windows comprised of ZnS, CdS and ZnSe used with a TiOz diffuse reflector could increase the current of optically thin silicon solar cells beyond that possible using rough TCO glass substrates. Selective angle reflectors must also be comprised of either the solar cell semiconductor itself (not possible in many cases) or comprised of a material having properties similar to those of the conducting rear windows used with the diffuse reflectors. 96100465 Optical modelling of a single-junction p-i-n type and tandem structure amorphous silicon solar cells with perfect current matching Stulik, P. and Singh, J. Solar Energy Materials and Solar Cells, 1997, 46, (3), 271-288. The optimal design of a single junction a-Si:H solar cell is suggested and its photovoltaic parameters are calculated using the admittance analysis method. The technique is then extended to design a tandem structure of two cells stacked one on the top of the other and connected in series. The top cell is considered of a-Si:H and bottom of a-SiGe:H and the condition of current matching is applied to determine the tandem’s optimal design. The efficiency of the single-junction cell with the optimal design is predicted to be 13.1% and that of the tandem cell with the perfect current matching is 20.8%. The results are discussed with reference to recent experimental results. Over 10% efficient CulnSa solar cell by sulfurization 96100466 Nakabayashi, T. et al. Solar Energy Materials and Solar Cells, 1997, 49, (l4), 375-381. Consisting of a CuIr& thin film prepared by sulfurization of a metallic precursor deposited either on a Pt sheet or a MO-coated soda lime glass substrate, the solar cell exhibited an efficiency of 10.5% at air mass 1.5 without anti-reflection coating. When the latter is used as a substrate, an initially more Cu-rich film was often torn off from the substrate. The film’s adhesion to it was significantly improved by introducing a very thin Ga layer between the Mu surface and a stacked Cu/In precursor layer. Using this adherent thin film, a heterojunction solar cell of the comparable efficiency was obtained. 98100467 Performance of liquid convective diodes Kolodziej, A. S. and Jaroszynski, M. Solar Energy, 1997, 61, (5), 321-326. The operation of convective heat diodes-passive solar heating devices have been the subject of a three-year study. The devices absorb and accumulate solar energy and then transport heat preferentially to the inside of a building. The study has been carried out in Gliwice, Poland, in a strongly industrialized region with a considerable level of air pollution. Four overlapping plastic thermal diodes comprised the constructed module. The diodes, which constitute only 6% of the test cell surface area, lead to energy savings as high as 37%?compared with the reference cells, which equals 700 MJ of energy per 1 rn- of the diode per year. The parameters have been estimated which appear in the energy balance equations for the diodes using the results of the experimentation. It is concluded that the thermal resistance of the insulation between the accumulator of one diode and the collector of another which has a crucial effect upon the efficiency of the diode. The paper suggests some modifications to present-day diode designs. 98100468 Photovoltaics and hydrogen: future energy options Lodhi, M. A. K. Energy Convers. Mgml, 1997, 38, (18), 1881-1893. For reasons concerning both the finite amount of fossil fuels and environmental damage consciousness, solar power is set to make a significant contribution to world energy supply. Global environmental damage caused thermodynamically is more alarming to life on Earth than the risk of exhausting the finite amount of fossil fuels being consumed at the present rate. Solar power plants can be designed and constructed to convert solar radiation into some concentrated form of useful energy first and then into electricity or directly into electricity. The latter kind is comprised of photovoltaic cells. Some of the solar energy options are discussed a historical overview is also presented. The rudimentary physical principles of the technology, the photovoltaic effect, the process to generate electricity in silicon solar cells, thin-film devices and high efficiency cells, and finally the state-of-the-art of the latest developments in solar cell technology are reported. Solar energy storage is recommended in the form of hydrogen as a future energy option.
40
Fuel and Energy Abstracts
January 1998
98lOO469 Solar cooling in Madrid: energetic efficiencies Izquierdo Millin, M. ef al. Solar Energy, 1997, 60, (6), 367-377. A clear day is defined in this paper as one generating a thermal load, and its daily level of solar energy, HglT is higher than the daily threshold energy imposed by the process, H,,,. In Madrid, for the air-conditioning of indoor spaces, H,-, varies from about 24 MJ rn-’ day-’ in June to about 18 MJ m-* day-1 in September. Applying the Rottel-Willier, Duffie, Beckman and Klein model, taking into account the heat capacity effects and the variable regime, a theoretical simulation of a lithium bromide absorption cooling system was performed to obtain a daily collector efficiency of about 22%, a daily COP of the cooling machine of about 55% and a daily efficiency of the solar energy-cooling conversion of about 12%. 98100470 Solar energy gasification of solid carbonaceous material in liquid dispersion Epstein, M. et al. U.S. US 5,647,877 (Cl. 48-210; ClOJ3146). 15 Jul 1997, US Appl. 270,676, 22, Jun 1994, 9 pp. Syngas can be produced from carbonaceous material using solar energy. An aqueous dispersion of carbonaceous material is injected into a reactor in the form of a shower or a jet of droplets, and the droplets are allowed to sink inside the reactor across a high-temperature focal zone projected into the reactor by a system for the concentration of solar radiation. Inside the reactor, the resident time is adjustable by a countercurrent gas flow or by the injection of two or more discrete droplet jets in an impinging jet arrangement. 98100471 Thermodynamic performance of solar-powered ideal absorption cycles Wijeysundera, N. E. Solar Energy, 1997, 61, (5), 313-319. Ideal absorption cycles with external heat transfer irreversibilities are considered in relation to obtaining the performance limits of solar-operated absorptions systems. The absorption machine is represented by the threeheat-reservoir ideal cycle and it is supplied with energy from a solar collector-storage system. The coefficient of performance, the cooling capacity, the entropy production and the second-law efficiency of the system are presented in analytical expressions. A comparison is made between the results obtained for cycles with external heat transfer irreversibilities and for fully reversible cycles and those obtained by detailed simulation of the absorption machine. Externally irreversible cycles are found to give realistic upper limits to the cooling capacity and the coefficient of performance of solar-powered absorption cooling systems. 98100472 Top heat-loss factor of double-glazed box-type solar cooker from indoor experiments Mullick, S. C. et al. Energy, 1997, 22, (6), 559-565. In a box-type solar cooker, the top heat-loss factor (U,) varies with plate temperature, wind heat-transfer coefficient and ambient temperature. A method for correlating II, with these variables is presented for a cooker with double glazing. A set of equations is developed for correlating data obtained in indoor experiments at different plate temperatures and wind speeds. 98100473 Transient analysis of a cylindrical solar water heater Saroja, S. et al. Energy Comers. Mgmt, 1997, 38, (18). 1833-1840. Details of an unsteady analysis of a cylindrical solar water heater are given. The physical parameters governing the physical system are identified. The governing equations have been solved using the fourth order Runge-Kutta method for different values of the parameters. The numerical and experimental results displayed good agreement. 98100474 Use of azine dye as a photosensitizer in solar cells: different reductants-safranine systems z5nOytri, K. M. and Regar, 0. P. ht. J. EnergyRes., 1997, 21, (14), 1345In photogalvanic cells containing safranine as photosensitizer, and EDTA, glucose and NTA as reductants in different systems, photogalvanic effect was studied. The photopotential and photocurrent generated were 760 mV and 50 PA in FDTA-safranine system, 373 mV and 35 /LA in glucosesafranine system and 415 mV and 35 /IA in NTA-safranine system, respectively. The effects of different parameters on electrical output of the cells were observed and a mechanism has been proposed for the generation of photocurrent in photogalvanic cells. 96100475 Utilization of Meteosat satellite-derived radiation data for integration of autonomous photovoltaic solar energy systems in remote areas Mueselli, M. et al. Energy Convers. Mgmt, 1998, 39, (l/2), l-19. Striking contrasts occur and turn a coastal Mediterranean climate on the littoral into an alpine one in the high mountains, due to the importance of the relief of Corsica. A spatial correlogram is used to demonstrate that for such countries it is not possible to deduce the solar irradiation received on any part of the island from the meteorological network. Consequently, satellites are a good alternative for determining these solar data. Good accordance was found between daily solar irradiation values estimated from Meteosat satellite data and measured data on the considered sites. From the previous data of daily horizontal total irradiations hourly total irradiations on tilted planes have been computed. These data have been used in an optimal sizing method of PV system easily applicable to any site.
Alternative energy sources (solar energy)
98/00464 Novel light-trapping schemes involving planar junctions and diffuse rear reflectors for thin-film silicon-based solar cells Winz, K. et al. Solar Energy Materials and Solar Cells, 1997, 49, (l-4), 195203. Improved conversion efficiency is offered by optical optimization of planar junction amorphous and microcrystalline silicon-based thin-film solar cells. Planar junction solar cells with diffuse and selective angle rear reflectors were examined in detail. The refractive index of the diffuser material needs to be as close to that of silicon as possible. Insulating diffuse rear reflectors must be used in conjunction with conductive rear-window layers of the appropriate hand gap, conductivity and refractive index. The refractive index of the rear window layer should be at least as large as that of the diffuser material. Rear windows comprised of ZnS, CdS and ZnSe used with a TiOz diffuse reflector could increase the current of optically thin silicon solar cells beyond that possible using rough TCO glass substrates. Selective angle reflectors must also be comprised of either the solar cell semiconductor itself (not possible in many cases) or comprised of a material having properties similar to those of the conducting rear windows used with the diffuse reflectors. 96100465 Optical modelling of a single-junction p-i-n type and tandem structure amorphous silicon solar cells with perfect current matching Stulik, P. and Singh, J. Solar Energy Materials and Solar Cells, 1997, 46, (3), 271-288. The optimal design of a single junction a-Si:H solar cell is suggested and its photovoltaic parameters are calculated using the admittance analysis method. The technique is then extended to design a tandem structure of two cells stacked one on the top of the other and connected in series. The top cell is considered of a-Si:H and bottom of a-SiGe:H and the condition of current matching is applied to determine the tandem’s optimal design. The efficiency of the single-junction cell with the optimal design is predicted to be 13.1% and that of the tandem cell with the perfect current matching is 20.8%. The results are discussed with reference to recent experimental results. Over 10% efficient CulnSa solar cell by sulfurization 96100466 Nakabayashi, T. et al. Solar Energy Materials and Solar Cells, 1997, 49, (l4), 375-381. Consisting of a CuIr& thin film prepared by sulfurization of a metallic precursor deposited either on a Pt sheet or a MO-coated soda lime glass substrate, the solar cell exhibited an efficiency of 10.5% at air mass 1.5 without anti-reflection coating. When the latter is used as a substrate, an initially more Cu-rich film was often torn off from the substrate. The film’s adhesion to it was significantly improved by introducing a very thin Ga layer between the Mu surface and a stacked Cu/In precursor layer. Using this adherent thin film, a heterojunction solar cell of the comparable efficiency was obtained. 98100467 Performance of liquid convective diodes Kolodziej, A. S. and Jaroszynski, M. Solar Energy, 1997, 61, (5), 321-326. The operation of convective heat diodes-passive solar heating devices have been the subject of a three-year study. The devices absorb and accumulate solar energy and then transport heat preferentially to the inside of a building. The study has been carried out in Gliwice, Poland, in a strongly industrialized region with a considerable level of air pollution. Four overlapping plastic thermal diodes comprised the constructed module. The diodes, which constitute only 6% of the test cell surface area, lead to energy savings as high as 37%?compared with the reference cells, which equals 700 MJ of energy per 1 rn- of the diode per year. The parameters have been estimated which appear in the energy balance equations for the diodes using the results of the experimentation. It is concluded that the thermal resistance of the insulation between the accumulator of one diode and the collector of another which has a crucial effect upon the efficiency of the diode. The paper suggests some modifications to present-day diode designs. 98100468 Photovoltaics and hydrogen: future energy options Lodhi, M. A. K. Energy Convers. Mgml, 1997, 38, (18), 1881-1893. For reasons concerning both the finite amount of fossil fuels and environmental damage consciousness, solar power is set to make a significant contribution to world energy supply. Global environmental damage caused thermodynamically is more alarming to life on Earth than the risk of exhausting the finite amount of fossil fuels being consumed at the present rate. Solar power plants can be designed and constructed to convert solar radiation into some concentrated form of useful energy first and then into electricity or directly into electricity. The latter kind is comprised of photovoltaic cells. Some of the solar energy options are discussed a historical overview is also presented. The rudimentary physical principles of the technology, the photovoltaic effect, the process to generate electricity in silicon solar cells, thin-film devices and high efficiency cells, and finally the state-of-the-art of the latest developments in solar cell technology are reported. Solar energy storage is recommended in the form of hydrogen as a future energy option.
40
Fuel and Energy Abstracts
January 1998
98lOO469 Solar cooling in Madrid: energetic efficiencies Izquierdo Millin, M. ef al. Solar Energy, 1997, 60, (6), 367-377. A clear day is defined in this paper as one generating a thermal load, and its daily level of solar energy, HglT is higher than the daily threshold energy imposed by the process, H,,,. In Madrid, for the air-conditioning of indoor spaces, H,-, varies from about 24 MJ rn-’ day-’ in June to about 18 MJ m-* day-1 in September. Applying the Rottel-Willier, Duffie, Beckman and Klein model, taking into account the heat capacity effects and the variable regime, a theoretical simulation of a lithium bromide absorption cooling system was performed to obtain a daily collector efficiency of about 22%, a daily COP of the cooling machine of about 55% and a daily efficiency of the solar energy-cooling conversion of about 12%. 98100470 Solar energy gasification of solid carbonaceous material in liquid dispersion Epstein, M. et al. U.S. US 5,647,877 (Cl. 48-210; ClOJ3146). 15 Jul 1997, US Appl. 270,676, 22, Jun 1994, 9 pp. Syngas can be produced from carbonaceous material using solar energy. An aqueous dispersion of carbonaceous material is injected into a reactor in the form of a shower or a jet of droplets, and the droplets are allowed to sink inside the reactor across a high-temperature focal zone projected into the reactor by a system for the concentration of solar radiation. Inside the reactor, the resident time is adjustable by a countercurrent gas flow or by the injection of two or more discrete droplet jets in an impinging jet arrangement. 98100471 Thermodynamic performance of solar-powered ideal absorption cycles Wijeysundera, N. E. Solar Energy, 1997, 61, (5), 313-319. Ideal absorption cycles with external heat transfer irreversibilities are considered in relation to obtaining the performance limits of solar-operated absorptions systems. The absorption machine is represented by the threeheat-reservoir ideal cycle and it is supplied with energy from a solar collector-storage system. The coefficient of performance, the cooling capacity, the entropy production and the second-law efficiency of the system are presented in analytical expressions. A comparison is made between the results obtained for cycles with external heat transfer irreversibilities and for fully reversible cycles and those obtained by detailed simulation of the absorption machine. Externally irreversible cycles are found to give realistic upper limits to the cooling capacity and the coefficient of performance of solar-powered absorption cooling systems. 98100472 Top heat-loss factor of double-glazed box-type solar cooker from indoor experiments Mullick, S. C. et al. Energy, 1997, 22, (6), 559-565. In a box-type solar cooker, the top heat-loss factor (U,) varies with plate temperature, wind heat-transfer coefficient and ambient temperature. A method for correlating II, with these variables is presented for a cooker with double glazing. A set of equations is developed for correlating data obtained in indoor experiments at different plate temperatures and wind speeds. 98100473 Transient analysis of a cylindrical solar water heater Saroja, S. et al. Energy Comers. Mgmt, 1997, 38, (18). 1833-1840. Details of an unsteady analysis of a cylindrical solar water heater are given. The physical parameters governing the physical system are identified. The governing equations have been solved using the fourth order Runge-Kutta method for different values of the parameters. The numerical and experimental results displayed good agreement. 98100474 Use of azine dye as a photosensitizer in solar cells: different reductants-safranine systems z5nOytri, K. M. and Regar, 0. P. ht. J. EnergyRes., 1997, 21, (14), 1345In photogalvanic cells containing safranine as photosensitizer, and EDTA, glucose and NTA as reductants in different systems, photogalvanic effect was studied. The photopotential and photocurrent generated were 760 mV and 50 PA in FDTA-safranine system, 373 mV and 35 /LA in glucosesafranine system and 415 mV and 35 /IA in NTA-safranine system, respectively. The effects of different parameters on electrical output of the cells were observed and a mechanism has been proposed for the generation of photocurrent in photogalvanic cells. 96100475 Utilization of Meteosat satellite-derived radiation data for integration of autonomous photovoltaic solar energy systems in remote areas Mueselli, M. et al. Energy Convers. Mgmt, 1998, 39, (l/2), l-19. Striking contrasts occur and turn a coastal Mediterranean climate on the littoral into an alpine one in the high mountains, due to the importance of the relief of Corsica. A spatial correlogram is used to demonstrate that for such countries it is not possible to deduce the solar irradiation received on any part of the island from the meteorological network. Consequently, satellites are a good alternative for determining these solar data. Good accordance was found between daily solar irradiation values estimated from Meteosat satellite data and measured data on the considered sites. From the previous data of daily horizontal total irradiations hourly total irradiations on tilted planes have been computed. These data have been used in an optimal sizing method of PV system easily applicable to any site.