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03258 The effect of substrate temperature on P-CVD deposited a-SiGe:H films
07
Alternativeenergy sources (solar energy)
99103256 Donor-acceptor interaction between non-aqueous solvents and I2 to generate lm3 and its implication in dye sensitized solar cells Kebede, Z. and Lindquist, S.-E. Solar Energy Materialsand Solar Cells, 1999, 57, (3), 259-275. A study was undertaken into the spectrophotometric properties of 1 , 12 and the 1 /I2 mixture in 1,2-dichloroethane (DCE), acetone (AC), acetonitrile (ACN), ethanol (EtOH), methanol (MeOH), tertiary-butanol (t-BuOH), dimethylformamide (DMF), propylenecarbonate (PC), 3-methoxypropionitrile (MePN), dimethylsulfoxide (DMSO), dioxane (DIO) and pyridine (PY) solutions. The results and their implications for dye sensitized solar cells are reported. The effect of emitter recombination on the effective 99103257 lifetime of silicon wafers Cuevas, A. Solar Energy Materials& Solar Ceils, 1999, 57, (3), 277-290. The paper reviews the application of photoconductance measurements of the effective lifetime of silicon wafers to determine the saturation current density of diffused emitter regions. To illustrate the technique, a sequence of experiments is presented with phosphorus diffusions of various types: oxide passivated and unpassivated, highly doped and heavily doped. Different material qualities (FZ, CZ and multi-crystalline silicon) are considered, as well as different substrate resistivities. The dependence of the effective minority carrier lifetime on injection level is discussed. The limitations imposed by emitter recombination on the measurable minority carrier lifetimes are clarified and demonstrated experimentally. This bound varies with the dopant density and thickness of the silicon wafer. The effect of substrate temperature on P-CVD 99103256 deposited a-SiGe:H films Rashada, A. et al. Solar EnergyMaterials& Solar Cells, 1999, 51, (3), 209-
216.
Using the RF plasma chemical vapour deposition method, undoped aFilms deposited at different substrate SiGe:H films were deposited. temperatures ranging between 100 and 300°C were studied for their optoelectronic and structural properties. Structural defects like vacancies and microvoids were studied by positron lifetime spectroscopy (PLTS) at room temperature. Opto-electronic properties of the films were correlated with the PLTS measurements. The observations show a decrease in the deposition rate with substrate temperature. A decrease in microvoid concentration has led to good opto-electronic properties and proper structural relaxation. Energy and mass balances in open-type multiple99103259 effect solar distillers with air flow through the last effect Yeh, H.-M. et al. Energy, 1999, 24, (2), 103-115. Improvements in the productivity of the title solar distillates may be obtained if water vapour is carried away directly by flowing air. Humidities at the condensing surfaces and in the outlet air were assumed to differ from the saturation values by empirically determined factors. The effects of operating conditions on these factors are discussed. Experimental studies on a solar air collector with 99103260 metal matrix absorber Kolb, A. et al. Solar Energy, 1999, 65, (2), 91-98. The present contribution describes the development and testing of an efficient single-glazed solar matrix air collector. This collector was designed in order to overcome the physical problems of conventional flat-plate air collectors as well as the technical problems of matrix air collectors, in particular. The absorber of the collector consists of two parallel sheets of black oxidized or black galvanized industrial woven, fine-meshed wire screens made of copper. The new collector can be readily produced industrially at acceptable costs. A test collector was developed and tested indoors by varying design features and operating conditions using a solar simulator as a radiation source. The new collector is very durable and flexible regarding mass flow rate and collector duct height and yields high thermal performances at very low pressure losses. High outlet temperatures are obtainable, thus improving the quality of the gained heat. This type of collector can be used for drying and heating applications and, due to its light-weight design and the possibility to serve as a sunshade (anti-glare device) which can be unrolled if there is dazzle by the sunlight inside of the building-it can be easily integrated vertically into double facades of buildings. Heat transfer enhancement in a latent heat storage 99103261 system Velraj, R. et al. Solar Energy, 1999, 65, (3), 171-180. Commercial acceptance and the economics of solar thermal technologies are tied to the design and development of efficient, cost-effective thermal storage systems. Thermal storage units that utilize latent heat storage materials have received greater attention in the recent years because of their large heat storage capacity and their isothermal behaviour during the charging and discharging processes. One major issue that needs to be addressed is that most phase-change materials (PCM) with high energy storage density have an unacceptably low thermal conductivity and hence heat transfer enhancement techniques are required for any latent heat thermal storage (LHTS) applications. In this paper the various heat
342
Fuel and Energy Abstracts
September
1999
transfer enhancement different experiments findings are reported.
methods for LHTS systems are discussed. Three to augment heat transfer were conducted and the
99103262 High efficiency evacuated flat-plate solar collector for process steam productlon Benz, N. and Beikircher, T. Solar Energy, 1999, 65, (2), 111-118. A flat-plate solar collector for process steam production was developed. The operating temperatures are in the range between 100 and 150°C. The boiling collector can be used for process heat supply in the industry and for solar cooling applications as well. It operates as a system with controlled influx of liquid. Instabilities of the two-phase flow in the internal evaporator have been successfully suppressed and the design of the system has been investigated. A prototype collector based on a commercially available evacuated flat-plate collector was constructed. To realize high thermal efficiencies at temperatures up to 15o”C, the thermal losses of the absorber have been drastically reduced using an ultra low emissive selective absorber, a low pressure krypton filling (50 hPa) in the collector casing and a highly reflecting aluminium foil between absorber and rear side. The prototype collector was dynamically tested at an outdoor test facility and showed very high efficiencies of more than 60% at 100°C steam temperature and of 45% at 150 0C steam temperature (Tamb = 15°C). The operation behaviour of the prototype was always stable and the steam mass quality showed excellent values of nearly 100%. High-flux solar concentration with imaging designs 99103263 Feuermann, D. et al. Solar Energy, 1999, 65, (2), 83-89. Most large solar concentrators designed for high flux concentration at high collection efficiency are based on imaging primary mirrors and non-imaging secondary concentrators. In this paper, an alternative is offered, purely imaging two-stage solar concentrator that can attain high flux concentration at high collection efficiency. Possible practical virtues include: (1) an inherent large gap between absorber and secondary mirror; (2) a restricted angular range on the absorber; and (3) an upward-facing receiver where collected energy can be extracted via the (shaded) apex of the parabola. Efficiency-concentration plots are used to characterize the solar concentrators considered and to evaluate the potential improvements with secondary concentrators. Influence of carrier recombination in the space 99103264 charge region on minority carrier lifetime in the base region of solar cells Garrido, C. L. et al. Solar Energy Materials& Solar Cells, 1999, 57, (3), 239-247. Calculated here is the minority carrier lifetime (7) in the base region of an n+/p silicon solar cell, employing the open circuit voltage decay method. The influence of carrier recombination in the space charge region is considered through an interface recombination velocity, Si. An analytical expression for 7 is obtained and its value for one particular case is reported. 99103265 Influence of the global radiation variability on the hourly diffuse fraction correlations Gonz?ilez, J.-A. and Calb6, J. Solar Energy, 1999, 65, (2), 119-131. In this paper, the influence of global radiation temporal variability on diffuse fraction correlations has been analysed. The variability of a zenith angle independent clearness index within an hour is defined by means of three parameters, from a five-minute basis data set and assigned to the corresponding hour. Although description of sky condition is usually based only on the clearness index k, leading to Liu-Jordan type correlations, various authors use k, along with solar altitude, which is considered as the second most important variable in the diffuse fraction predictions. The use of a variability parameter also improves the correlations. More specifically, the analysis reveals that the variability parameters play a role as important as the solar altitude. The influence of the variability parameters is more effective under clear sky conditions and high k, values. The linear correlations obtained by using the clearness index, the solar altitude and a variability parameter reduce the RMSE of the diffuse fraction estimation by about 15%, relative to the k,-only correlation. The analysis used two series of data recorded in Catalonia (NE of lberian Peninsula), which are three years and one year long, respectively. Investigation of manganese-molybdenum99103266 diethyldithiocarbamate complex as a potential system for solar energy conversion Suresh, E. et al. ht. J. EnergyRes., 1999, 23, (3), 229-233. When studied in a Honda cell, manganese-molybdenumdiethyldithiocarbamate [MnMoOz(Et2dtc)4(H20)] {Et,dtc = diethyldithiocarbamate) complex has exhibited reversible photogalvanic behaviour in aqueous dimethylformamide medium. The photogalvanic behaviour has been further investigated by varying the pH, temperature and photosensitizers. UV, visible and sunlight were used as the radiation sources. A maximum potential of 345 mV was obtained at 80°C in visible light and the system was found to be reversible for several cycles. A photoelectrochemical cell was constructed by coupling a charged nickel electrode with the complex electrode which incorporates the experimental compound in acetylene black on a nickel substrate.
Alternativeenergy sources (solar energy)
99103256 Donor-acceptor interaction between non-aqueous solvents and I2 to generate lm3 and its implication in dye sensitized solar cells Kebede, Z. and Lindquist, S.-E. Solar Energy Materialsand Solar Cells, 1999, 57, (3), 259-275. A study was undertaken into the spectrophotometric properties of 1 , 12 and the 1 /I2 mixture in 1,2-dichloroethane (DCE), acetone (AC), acetonitrile (ACN), ethanol (EtOH), methanol (MeOH), tertiary-butanol (t-BuOH), dimethylformamide (DMF), propylenecarbonate (PC), 3-methoxypropionitrile (MePN), dimethylsulfoxide (DMSO), dioxane (DIO) and pyridine (PY) solutions. The results and their implications for dye sensitized solar cells are reported. The effect of emitter recombination on the effective 99103257 lifetime of silicon wafers Cuevas, A. Solar Energy Materials& Solar Ceils, 1999, 57, (3), 277-290. The paper reviews the application of photoconductance measurements of the effective lifetime of silicon wafers to determine the saturation current density of diffused emitter regions. To illustrate the technique, a sequence of experiments is presented with phosphorus diffusions of various types: oxide passivated and unpassivated, highly doped and heavily doped. Different material qualities (FZ, CZ and multi-crystalline silicon) are considered, as well as different substrate resistivities. The dependence of the effective minority carrier lifetime on injection level is discussed. The limitations imposed by emitter recombination on the measurable minority carrier lifetimes are clarified and demonstrated experimentally. This bound varies with the dopant density and thickness of the silicon wafer. The effect of substrate temperature on P-CVD 99103256 deposited a-SiGe:H films Rashada, A. et al. Solar EnergyMaterials& Solar Cells, 1999, 51, (3), 209-
216.
Using the RF plasma chemical vapour deposition method, undoped aFilms deposited at different substrate SiGe:H films were deposited. temperatures ranging between 100 and 300°C were studied for their optoelectronic and structural properties. Structural defects like vacancies and microvoids were studied by positron lifetime spectroscopy (PLTS) at room temperature. Opto-electronic properties of the films were correlated with the PLTS measurements. The observations show a decrease in the deposition rate with substrate temperature. A decrease in microvoid concentration has led to good opto-electronic properties and proper structural relaxation. Energy and mass balances in open-type multiple99103259 effect solar distillers with air flow through the last effect Yeh, H.-M. et al. Energy, 1999, 24, (2), 103-115. Improvements in the productivity of the title solar distillates may be obtained if water vapour is carried away directly by flowing air. Humidities at the condensing surfaces and in the outlet air were assumed to differ from the saturation values by empirically determined factors. The effects of operating conditions on these factors are discussed. Experimental studies on a solar air collector with 99103260 metal matrix absorber Kolb, A. et al. Solar Energy, 1999, 65, (2), 91-98. The present contribution describes the development and testing of an efficient single-glazed solar matrix air collector. This collector was designed in order to overcome the physical problems of conventional flat-plate air collectors as well as the technical problems of matrix air collectors, in particular. The absorber of the collector consists of two parallel sheets of black oxidized or black galvanized industrial woven, fine-meshed wire screens made of copper. The new collector can be readily produced industrially at acceptable costs. A test collector was developed and tested indoors by varying design features and operating conditions using a solar simulator as a radiation source. The new collector is very durable and flexible regarding mass flow rate and collector duct height and yields high thermal performances at very low pressure losses. High outlet temperatures are obtainable, thus improving the quality of the gained heat. This type of collector can be used for drying and heating applications and, due to its light-weight design and the possibility to serve as a sunshade (anti-glare device) which can be unrolled if there is dazzle by the sunlight inside of the building-it can be easily integrated vertically into double facades of buildings. Heat transfer enhancement in a latent heat storage 99103261 system Velraj, R. et al. Solar Energy, 1999, 65, (3), 171-180. Commercial acceptance and the economics of solar thermal technologies are tied to the design and development of efficient, cost-effective thermal storage systems. Thermal storage units that utilize latent heat storage materials have received greater attention in the recent years because of their large heat storage capacity and their isothermal behaviour during the charging and discharging processes. One major issue that needs to be addressed is that most phase-change materials (PCM) with high energy storage density have an unacceptably low thermal conductivity and hence heat transfer enhancement techniques are required for any latent heat thermal storage (LHTS) applications. In this paper the various heat
342
Fuel and Energy Abstracts
September
1999
transfer enhancement different experiments findings are reported.
methods for LHTS systems are discussed. Three to augment heat transfer were conducted and the
99103262 High efficiency evacuated flat-plate solar collector for process steam productlon Benz, N. and Beikircher, T. Solar Energy, 1999, 65, (2), 111-118. A flat-plate solar collector for process steam production was developed. The operating temperatures are in the range between 100 and 150°C. The boiling collector can be used for process heat supply in the industry and for solar cooling applications as well. It operates as a system with controlled influx of liquid. Instabilities of the two-phase flow in the internal evaporator have been successfully suppressed and the design of the system has been investigated. A prototype collector based on a commercially available evacuated flat-plate collector was constructed. To realize high thermal efficiencies at temperatures up to 15o”C, the thermal losses of the absorber have been drastically reduced using an ultra low emissive selective absorber, a low pressure krypton filling (50 hPa) in the collector casing and a highly reflecting aluminium foil between absorber and rear side. The prototype collector was dynamically tested at an outdoor test facility and showed very high efficiencies of more than 60% at 100°C steam temperature and of 45% at 150 0C steam temperature (Tamb = 15°C). The operation behaviour of the prototype was always stable and the steam mass quality showed excellent values of nearly 100%. High-flux solar concentration with imaging designs 99103263 Feuermann, D. et al. Solar Energy, 1999, 65, (2), 83-89. Most large solar concentrators designed for high flux concentration at high collection efficiency are based on imaging primary mirrors and non-imaging secondary concentrators. In this paper, an alternative is offered, purely imaging two-stage solar concentrator that can attain high flux concentration at high collection efficiency. Possible practical virtues include: (1) an inherent large gap between absorber and secondary mirror; (2) a restricted angular range on the absorber; and (3) an upward-facing receiver where collected energy can be extracted via the (shaded) apex of the parabola. Efficiency-concentration plots are used to characterize the solar concentrators considered and to evaluate the potential improvements with secondary concentrators. Influence of carrier recombination in the space 99103264 charge region on minority carrier lifetime in the base region of solar cells Garrido, C. L. et al. Solar Energy Materials& Solar Cells, 1999, 57, (3), 239-247. Calculated here is the minority carrier lifetime (7) in the base region of an n+/p silicon solar cell, employing the open circuit voltage decay method. The influence of carrier recombination in the space charge region is considered through an interface recombination velocity, Si. An analytical expression for 7 is obtained and its value for one particular case is reported. 99103265 Influence of the global radiation variability on the hourly diffuse fraction correlations Gonz?ilez, J.-A. and Calb6, J. Solar Energy, 1999, 65, (2), 119-131. In this paper, the influence of global radiation temporal variability on diffuse fraction correlations has been analysed. The variability of a zenith angle independent clearness index within an hour is defined by means of three parameters, from a five-minute basis data set and assigned to the corresponding hour. Although description of sky condition is usually based only on the clearness index k, leading to Liu-Jordan type correlations, various authors use k, along with solar altitude, which is considered as the second most important variable in the diffuse fraction predictions. The use of a variability parameter also improves the correlations. More specifically, the analysis reveals that the variability parameters play a role as important as the solar altitude. The influence of the variability parameters is more effective under clear sky conditions and high k, values. The linear correlations obtained by using the clearness index, the solar altitude and a variability parameter reduce the RMSE of the diffuse fraction estimation by about 15%, relative to the k,-only correlation. The analysis used two series of data recorded in Catalonia (NE of lberian Peninsula), which are three years and one year long, respectively. Investigation of manganese-molybdenum99103266 diethyldithiocarbamate complex as a potential system for solar energy conversion Suresh, E. et al. ht. J. EnergyRes., 1999, 23, (3), 229-233. When studied in a Honda cell, manganese-molybdenumdiethyldithiocarbamate [MnMoOz(Et2dtc)4(H20)] {Et,dtc = diethyldithiocarbamate) complex has exhibited reversible photogalvanic behaviour in aqueous dimethylformamide medium. The photogalvanic behaviour has been further investigated by varying the pH, temperature and photosensitizers. UV, visible and sunlight were used as the radiation sources. A maximum potential of 345 mV was obtained at 80°C in visible light and the system was found to be reversible for several cycles. A photoelectrochemical cell was constructed by coupling a charged nickel electrode with the complex electrode which incorporates the experimental compound in acetylene black on a nickel substrate.