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03107 Experimental studies on a solar still coupled with a flat-plate collector and a single basin still
07
Alternative
energy sources (solar energy)
9Iyo3108 Full-scale measurements of wind-induced convective heat transfer from a roof-mounted flat plate solar collector
Solar Energy The coal/Fe304 system for mlxing of solar and 98lo3102 fossil energies Tamaura, Y. et al. Energy, 1997, 22, (2/3), 337-342. Intended for mixing solar and fossil energy technology, the solar-driven endothermic reaction of coal and m’agnetite, is represented by the reaction CH, + Fes04 = CO + 3FeO + 1/2rHa, in which x depends on the stoichiometry of the coal utilized. Solar-driven experiments were conducted using a high-flux solar furnace. Pelleted samples were direct12 exposed for short time intervals to a solar flux irradiation of 300 W/cm The carbon content decreased rapidly after only 1 s exposure, suggesting efficient heat transfer and chemical conversion by direct absorption of concentrated solar energy at the reaction site. The process offers the simultaneous gasification of coal and iron oxide reduction, with production of a fuel of upgraded calorific value.
Sharples, S. and Charlesworth, P. S. Solar Energy, 1998, 62, (2), 69-77. To assess the magnitude and variability of wind-induced convective heat transfer from a raised heated surface mounted directly on to the pitched roof of a domestic size building, a series of full-scale measurements in the real environment were made. The heated plate had dimensions similar to those of a typical flat-plate solar collector, giving a Reynolds number range of approximately 1 x 10s to 5 x 105. The measured forced convective heat transfer coefficient hw was correlated against the wind speed V and the wind direction prevailing at the site of the building during the periods of measurement. For a range of wind directions it was found that both power and linear relationships between hw and V adequately represented the experimental results. When the heated plate was leeward to the prevailing wind direction, some sheltering effects were observed. Values of hw measured in this study agreed well with data derived from previous wind tunnel and field work.
Heat transfer calculation in a free convection air solar collector
98lo3109
An economic feasibility analysis of photovoltaics power during urban load shedding tlme
gal031 03
Koner, P. K. and Dutta, V. Solar Energy Materials and Solar Cells, 1998, 51, (314). 339-352. The authors report on a first-order cost analysis of photovoltaics power generation and DG power generation for urban emergency load. Field data collected over 6 years of operation of two DG sets installed at ITT, Delhi for emergency load have been thoroughly analysed to find out the requirements for such power generation model. Using different parameters the unit cost of emergency load energy is calculated. The unit cost of PV electricity is found to be cheaper or comparable with that from DG power at present market price. 98/03104
Effect of collector
orientation
on solar energy
availability Tiris, C. and Tiris, M. Energy Cowers. Mgmt, 1998, 39, (8) 843-852. Monthly-average meteorological data, total solar radiation in particular, are needed for the design of solar energy systems. Several simplified design procedures exist for estimating the monthly-average daily total radiation on tilted surfaces facing due south at various orientations. The monthlyaverage radiation on tilted surfaces with different orientations is estimated for Gebze, based on measured data on horizontal surfaces between 1988 and 1994 from the TUBITAK-M.R.C. station.
Effect of substrate heatin on the adhesion and 98103105 humidity resistance of evaporated MgF2%nS antireflectlon Coatin s and on the performance of high-efficiency silicon solar ceiTIs Zhang, G. et al. Solar Energy Materials and Solar Cells, 1998, 51, (3/4), 393-400. Experimental results of substrate heating during thermal evaporation of MgFa/ZnS DLAR (double-layer anti-reflection) coatings are presented. The higher substrate temperature significantly improves the adhesion and humidity resistance of such coatings, while the performance of highefficiency silicon PFRL (passivated emitter, rear locally diffused) cells are marginally reduced. The optimum substrate temperature for the evaporation of such DLAR coatings on the PFRL cells is approximately 150°C. At this temperature, the DLAR coatings have good durability, but give only slightly reduced PFRL cell performance compared to the unheated substrate case. It is believed that this reduction in the PFRL cell performance arises from the partial removal of the hydrogen passivation, which was introduced through a standard ‘alneal’ (aluminium anneal) process.
Experimental and theoretical performance of a demonstration solar chimney model-part I: mathematical model development
98103108
Pasumarthi, N. and Sherif, S. A. ht. J. Energy Res., 1998,22, (3), 277-288. In the solar chimney, solar radiation is used to provide upward momentum to the in-flowing air, thereby converting the thermal energy into kinetic energy. A study was undertaken to evaluate the performance characteristics of solar chimneys both theoretically and experimentally. In this paper, a mathematical model which was developed to study the effect of various parameters on the air temperature, air velocity, and power output of the solar chimney, is presented. Tests were conducted on a demonstration model which was designed and built for that purpose. The mathematical model presented here was verified against experimental test results and the overall results were encouraging.
Experimental studies on a solar still coupled with a flat-plate collector and a single basin still
98103107
Tiris, C. et al. Energy Cowers. Mgmt, 1998, 39, (8), 843-852. In this new solar still system, a storage tank and two flat-plate solar collectors are integrated with a basin type solar still. The collector and the still are coupled to form a naturally circulating closed loop. This system has been presented in terms of the design parameters of the solar still and the effectiveness of the heat exchanger. The average daily production of distilled water has been found to be 100% higher than for a simple basintype solar still.
Rodonb, G. and Volpes, R. Energy and Buildings, 1998, 27, (l), 21-27. The free convective air flow developing in a vertical channel with a rectangular cross-section heated on one side is discussed. An air solar collector suitable for building heating is simulated with the channel. A calculation method that can be applied to the transient combined heat transfer by conduction through the wall and by convection from the wall to the air stream is presented. The conduction across the wall is computed with a one-dimensional, time-dependent finite difference scheme, with convective boundary conditions at both wall surfaces. For the free convective flow along the channel, the air flow rate and the mean convective coefficient on the heated wall are evaluated by means of suitable correlations. Some cases have been calculated and the results are presented in an attempt to verify the applicability of the system in practice. The results show that the method lends itself to a relatively simple application in some realistic cases.
Infrared characterization of hot spots in solar cells 98lo3110 with high precision due to signal treatment processing Kaminski, A. et al. Solar Energy Materials and Solar Cells, 1998. 51, (3/4), 233-242. The resolution of IR thermography can be significantly improved with the use of two different signal treatment methods: a static treatment and a dynamic treatment. The study of 100 cm’ cells under low-forward or reverse-polarization conditions is facilitated by this method. The static method has the advantage of being fast, while the dynamic method does not need any reference image or cooling system. IR thermography is shown to be an interesting method for investigating shunts in solar cells. Thermal maps and I-Vcharacterization of the hot spots show that the origin and the behaviour of the shunts are varied and their influence on the efficiency is probably more important than is generally believed.
11 Measurement of concentrator solar cell efficiency at high concentration and narrow-band spectrum
gal031
Appelbaum, J. et al. Solar Energy Materials and Solar Cells, 1998, 51, (314). 317-325. It may be possible to obtain high efficiency of solar cells at high concentration and narrow-band spectrum system. Difficulties are encountered in determination of the cell efficiency using narrow-band-artificiallight sources at high concentration. The paper proposes a method for the determination of solar cell efficiency at high concentration and narrowband spectrum. It is based on measurement of the solar cell fill factor and the open-circuit voltage at moderate concentration and full spectrum and based on a calculation procedure. 12 Monte Carlo techniques to analyse the electrical mismatch losses In large-scale photovoltaic generators
gal031
Iannone, F. et al. Solar Energy, 1998, 62, (2), 85-92. The arrangement of modules with different electrical characteristics in large-scale photovoltaic generators could involve a considerable mismatch between the single components, resulting in a power loss. Therefore, the actual power is less than the sum of the maximum output powers of the individual PV modules, operating at same irradiance-temperature conditions. A statistical approach based on Monte Carlo simulation techniques, has been developed and validated to reduce the mismatch losses and for calculation under operating conditions. The simulation model shows that it is possible to meet the required mismatch level, with a random arrangement, starting from a modules population characterized in terms of short circuit current and open circuit voltage, by a probability density function with a imposed variance. Application of the method to a 100 kWp standard unit photovoltaic generator has been successful; the computational results have shown good agreement with the experimental data.
Non Ideal dark I-V curves behavior of silicon solar ::!? ’3 Kaminski, A. et al. Solar Energy Materials and Solar Cells, 1998, 51, (3/4), 221-231. Directional solidification (DS), Czochralsky (CZ) and cold crucible casting (CCC) silicon solar cells have been subjected to dark I-V experiments. Series and shunt resistances, ideality factors and saturation currents have
Fuel and Energy Abstracts
July 1998 287
Alternative
energy sources (solar energy)
9Iyo3108 Full-scale measurements of wind-induced convective heat transfer from a roof-mounted flat plate solar collector
Solar Energy The coal/Fe304 system for mlxing of solar and 98lo3102 fossil energies Tamaura, Y. et al. Energy, 1997, 22, (2/3), 337-342. Intended for mixing solar and fossil energy technology, the solar-driven endothermic reaction of coal and m’agnetite, is represented by the reaction CH, + Fes04 = CO + 3FeO + 1/2rHa, in which x depends on the stoichiometry of the coal utilized. Solar-driven experiments were conducted using a high-flux solar furnace. Pelleted samples were direct12 exposed for short time intervals to a solar flux irradiation of 300 W/cm The carbon content decreased rapidly after only 1 s exposure, suggesting efficient heat transfer and chemical conversion by direct absorption of concentrated solar energy at the reaction site. The process offers the simultaneous gasification of coal and iron oxide reduction, with production of a fuel of upgraded calorific value.
Sharples, S. and Charlesworth, P. S. Solar Energy, 1998, 62, (2), 69-77. To assess the magnitude and variability of wind-induced convective heat transfer from a raised heated surface mounted directly on to the pitched roof of a domestic size building, a series of full-scale measurements in the real environment were made. The heated plate had dimensions similar to those of a typical flat-plate solar collector, giving a Reynolds number range of approximately 1 x 10s to 5 x 105. The measured forced convective heat transfer coefficient hw was correlated against the wind speed V and the wind direction prevailing at the site of the building during the periods of measurement. For a range of wind directions it was found that both power and linear relationships between hw and V adequately represented the experimental results. When the heated plate was leeward to the prevailing wind direction, some sheltering effects were observed. Values of hw measured in this study agreed well with data derived from previous wind tunnel and field work.
Heat transfer calculation in a free convection air solar collector
98lo3109
An economic feasibility analysis of photovoltaics power during urban load shedding tlme
gal031 03
Koner, P. K. and Dutta, V. Solar Energy Materials and Solar Cells, 1998, 51, (314). 339-352. The authors report on a first-order cost analysis of photovoltaics power generation and DG power generation for urban emergency load. Field data collected over 6 years of operation of two DG sets installed at ITT, Delhi for emergency load have been thoroughly analysed to find out the requirements for such power generation model. Using different parameters the unit cost of emergency load energy is calculated. The unit cost of PV electricity is found to be cheaper or comparable with that from DG power at present market price. 98/03104
Effect of collector
orientation
on solar energy
availability Tiris, C. and Tiris, M. Energy Cowers. Mgmt, 1998, 39, (8) 843-852. Monthly-average meteorological data, total solar radiation in particular, are needed for the design of solar energy systems. Several simplified design procedures exist for estimating the monthly-average daily total radiation on tilted surfaces facing due south at various orientations. The monthlyaverage radiation on tilted surfaces with different orientations is estimated for Gebze, based on measured data on horizontal surfaces between 1988 and 1994 from the TUBITAK-M.R.C. station.
Effect of substrate heatin on the adhesion and 98103105 humidity resistance of evaporated MgF2%nS antireflectlon Coatin s and on the performance of high-efficiency silicon solar ceiTIs Zhang, G. et al. Solar Energy Materials and Solar Cells, 1998, 51, (3/4), 393-400. Experimental results of substrate heating during thermal evaporation of MgFa/ZnS DLAR (double-layer anti-reflection) coatings are presented. The higher substrate temperature significantly improves the adhesion and humidity resistance of such coatings, while the performance of highefficiency silicon PFRL (passivated emitter, rear locally diffused) cells are marginally reduced. The optimum substrate temperature for the evaporation of such DLAR coatings on the PFRL cells is approximately 150°C. At this temperature, the DLAR coatings have good durability, but give only slightly reduced PFRL cell performance compared to the unheated substrate case. It is believed that this reduction in the PFRL cell performance arises from the partial removal of the hydrogen passivation, which was introduced through a standard ‘alneal’ (aluminium anneal) process.
Experimental and theoretical performance of a demonstration solar chimney model-part I: mathematical model development
98103108
Pasumarthi, N. and Sherif, S. A. ht. J. Energy Res., 1998,22, (3), 277-288. In the solar chimney, solar radiation is used to provide upward momentum to the in-flowing air, thereby converting the thermal energy into kinetic energy. A study was undertaken to evaluate the performance characteristics of solar chimneys both theoretically and experimentally. In this paper, a mathematical model which was developed to study the effect of various parameters on the air temperature, air velocity, and power output of the solar chimney, is presented. Tests were conducted on a demonstration model which was designed and built for that purpose. The mathematical model presented here was verified against experimental test results and the overall results were encouraging.
Experimental studies on a solar still coupled with a flat-plate collector and a single basin still
98103107
Tiris, C. et al. Energy Cowers. Mgmt, 1998, 39, (8), 843-852. In this new solar still system, a storage tank and two flat-plate solar collectors are integrated with a basin type solar still. The collector and the still are coupled to form a naturally circulating closed loop. This system has been presented in terms of the design parameters of the solar still and the effectiveness of the heat exchanger. The average daily production of distilled water has been found to be 100% higher than for a simple basintype solar still.
Rodonb, G. and Volpes, R. Energy and Buildings, 1998, 27, (l), 21-27. The free convective air flow developing in a vertical channel with a rectangular cross-section heated on one side is discussed. An air solar collector suitable for building heating is simulated with the channel. A calculation method that can be applied to the transient combined heat transfer by conduction through the wall and by convection from the wall to the air stream is presented. The conduction across the wall is computed with a one-dimensional, time-dependent finite difference scheme, with convective boundary conditions at both wall surfaces. For the free convective flow along the channel, the air flow rate and the mean convective coefficient on the heated wall are evaluated by means of suitable correlations. Some cases have been calculated and the results are presented in an attempt to verify the applicability of the system in practice. The results show that the method lends itself to a relatively simple application in some realistic cases.
Infrared characterization of hot spots in solar cells 98lo3110 with high precision due to signal treatment processing Kaminski, A. et al. Solar Energy Materials and Solar Cells, 1998. 51, (3/4), 233-242. The resolution of IR thermography can be significantly improved with the use of two different signal treatment methods: a static treatment and a dynamic treatment. The study of 100 cm’ cells under low-forward or reverse-polarization conditions is facilitated by this method. The static method has the advantage of being fast, while the dynamic method does not need any reference image or cooling system. IR thermography is shown to be an interesting method for investigating shunts in solar cells. Thermal maps and I-Vcharacterization of the hot spots show that the origin and the behaviour of the shunts are varied and their influence on the efficiency is probably more important than is generally believed.
11 Measurement of concentrator solar cell efficiency at high concentration and narrow-band spectrum
gal031
Appelbaum, J. et al. Solar Energy Materials and Solar Cells, 1998, 51, (314). 317-325. It may be possible to obtain high efficiency of solar cells at high concentration and narrow-band spectrum system. Difficulties are encountered in determination of the cell efficiency using narrow-band-artificiallight sources at high concentration. The paper proposes a method for the determination of solar cell efficiency at high concentration and narrowband spectrum. It is based on measurement of the solar cell fill factor and the open-circuit voltage at moderate concentration and full spectrum and based on a calculation procedure. 12 Monte Carlo techniques to analyse the electrical mismatch losses In large-scale photovoltaic generators
gal031
Iannone, F. et al. Solar Energy, 1998, 62, (2), 85-92. The arrangement of modules with different electrical characteristics in large-scale photovoltaic generators could involve a considerable mismatch between the single components, resulting in a power loss. Therefore, the actual power is less than the sum of the maximum output powers of the individual PV modules, operating at same irradiance-temperature conditions. A statistical approach based on Monte Carlo simulation techniques, has been developed and validated to reduce the mismatch losses and for calculation under operating conditions. The simulation model shows that it is possible to meet the required mismatch level, with a random arrangement, starting from a modules population characterized in terms of short circuit current and open circuit voltage, by a probability density function with a imposed variance. Application of the method to a 100 kWp standard unit photovoltaic generator has been successful; the computational results have shown good agreement with the experimental data.
Non Ideal dark I-V curves behavior of silicon solar ::!? ’3 Kaminski, A. et al. Solar Energy Materials and Solar Cells, 1998, 51, (3/4), 221-231. Directional solidification (DS), Czochralsky (CZ) and cold crucible casting (CCC) silicon solar cells have been subjected to dark I-V experiments. Series and shunt resistances, ideality factors and saturation currents have
Fuel and Energy Abstracts
July 1998 287