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01460 How to select a collector?
07 Alternative energy sources (solar energy) 00/01451 Comparison of three transient methods for testing solar flat-plate collectors Nayak, J. K. Energy Convers. Manuge, 2000, 41, (7). 677-700. This communication presents an extensive comparison of three transient methods (Perers, DSC and Wijeysundera) for testing solar flat-plate collectors. Results from different tests are compared with the steady state values obtained on the basis of the ASHRAE 93-86 standard. Based on the experimental results, it is seen that Perers’ method yields parameters closer to the steady state values. The sensitivity analysis shows that the results of Perers and DSC methods are greatly affected by measurement errors, whereas the Wijeysundera method is less sensitive. Comparison of the prediction of outlet temperature with measurements for the Perers and DSC methods show that the values based on the later method are closer to the measurements. 00/01452
Composite materials for photovoltaics: a realistic
aim? Kiesewetter,
T. et al. Solnr Energy Materids
& Solar Cells, 1999. 59, (4).
309-323.
Layer-type microcrystalline powders of WSz, MO&, WSez and MoSe2, which were tested for photoeffects with contact free microwave conductivity measurements, were incorporated into a nanostructured TiOz matrix in an attempt to obtain macroscopic photocurrents. Even though only 10% of the microcrystals were found to be active in contact with an iodide/iodine solution, photocurrents of the order of 100 pA/cm’ to 1 mA/cm’ were measured. The photoelectrochemical behaviour of microcrystals was studied with space resolved photocurrent and photovoltage measurement techniques and it was attempted to understand the mechanism of current generation via the TiOzimicrocrystallelectrolyte interaction. Critical and still unresolved problems are recognized to be the control and optimization of photoeffects in microcrystals and the adjustment of doping levels of the two material faces. Only small photopotentials could be observed up to now, probably due to an insufficient and inhomogeneous doping of microcrystals. More research will be needed to determine whether this strategy could lead to realistic photovoltaic systems.
Design and analysis of low-reflection grating microstructures for a solar energy absorber
00/01453
Hava, S. and Auslender, M. Sol. Dlergy. Mar. & Sol. Cc/Is, 2000. 61. (2), 143-151. The problem of calculating the photo-induced current in an n+p junction solar cell with a microstructure grating on the top is formulated. For the case where useful absorption regions lie below the grating a closed solution of the problem is obtained, in which the carrier photo-generation rate is calculated using a full-vector electromagnetic simulation technique. Two structures: filled lamellae grating and overlayer and filled V-groove grating and overlayer are considered. The first structure is optimized with respect to the integral photo-current and the second with respect to reflection loss. Both optimized structures are much less reflective and more efficient than an optimized flat-surface Si-SiOz layer cell.
Design and thermal analysis of a two storage solar concentrator for combined heat and thermoelectric power generation
00101454
Omer, S. A. and Infield, D. G. Energy Convers. Morwge, 2000. 41. (7), 737756. A design procedure and thermal performance analysis of a two-stage solar energy concentrator suited to combined heat and thermoelectric power generation are presented. The concentrator is comprised of a primary one axis parabolic trough concentrator and a second stage compound parabolic concentrator mounted at the focus of the primary. The thermoelectric device is attached to the absorber plate at the focus of the secondary. A cooling tube is fitted to the cold side of the thermoelectric device to extract the waste heat and maintain a high temperature gradient across the device to improve conversion efficiency. The key requirements of the concentrator design are to be tolerant of tracking misalignment, maintain temperature gradients to suit thermoelectric generation and minimize heat losses. A design methodology is presented which allows interception of rays within an angular region (+n). This results in a wider receiver for the parabolic trough concentrator than would usually be used for a similar concentration ratio. The role of the second stage concentrator in limiting heat losses from the absorber plate is evaluated. Results indicate that in addition to improving the concentration efficiency, the second stage compound parabolic concentrator of the proposed design also inhibits convective air movement and, consequently, improves the overall performance of the solar concentrator.
00101455 Earth day 200O-dawn
of the solar age
Hayes, D. Solrrr Today, 1999, 13. (6). 46 America’s gasoline consumption is reported here and the author calls upon readers to use Earth day as a means to draw attention to sustainable energy options such as solar power.
Effect of growth parameters on the MOVPE of GaAsl Ge for solar ceil applications AgarWal,S. K. Solar Energy Matericrls & Sohr Cells. 1999, 59, (I-2). 19-26.
00101456
GaAs has been grown on Ge substrate oriented 6” off towards (I 1 0) by atmospheric pressure MOVPE. Various growth rates and growth temperatures were tried to get device quality epitaxial layers suitable for solar cell
applications. It was observed that the growth temperatures and the growth rates affect the surface morphology, optical and interface properties and crystalline quality of the epitaxial layers. This was studied using optical microscope, photoluminescence, photovoltage measurements, ECV and double crystal X-ray diffractometry.
OOlO1457 Evaluation of sunshine and cloud cover based models for generating solar radiation data Muneer, T. and GUI, M. S. Energ], Corteers. & Mmuge., 2000, 41. (5). 461~ 482. Solar radiation models based on meteorological parameters serve as the substitute to measured irradiation and illuminance data. Models originating from sunshine or cloud cover information constitute the two main classes of meteorological radiation models. Further improvements in the accuracy of these models is under research. One such approach attempted by Page, has resulted in the formation of a model that utilizes a combination of the above mentioned variables. This article briefly discusses the new combined approach and evaluates it against other models developed by the authors: the Meteorological Radiation Model (MRM) based on sunshine fraction and the Cloud Cover Radiation Model (CRM) based on cloud cover. Results show that Page’s approach is quite successful under overcast conditions. The MRM, however appears to provide better.estimates under part clear and clear sky conditions.
00/01456 Experimental study of the basin type solar still under local climate conditions Akash, B. A. fG1erg.vConversion & Morrcrgcvownt, 2000. 41. (9). 883-890. This paper presents experimental results obtained using the basin type solar still. The experiments were conducted in Jordan using a solar still with various cover tilt angles of 15, 25, 35, 45 and 55”. An optimum tilt angle for water production was found to be 35” during the month of May. Salt was added to study the effect of the salinity of water on solar distillation. Distilled water production decreased with salinity. The effect of water depth was also studied. The results show that water production decreased in a somewhat linear relationship with increasing water depth in the still.
00/01459 Formation of porous silicon for large-area silicon solar ceils: a new method Saadoun,
M. et ul. Solor Etzergy Materitrh
& Solor Cell.~, 1999, 59. (4). 377-
385.
Luminescent porous silicon (PS) was prepared for the first time using a spraying set-up, which can diffuse in a homogeneous manner HF solutions, on textured or untextured (1 0 0) oriented monocrystalline silicon substrate. This new method allows us to apply PS onto the front-side surface of silicon solar cells, by supplying very fine HF drops. The front side of N+/P monocrystalline silicon solar cells may be treated for long periods without altering the front grid metallic contact. The monocrystalline silicon solar cells (N+/P, 78.5 cm2) which has undergone the HF-spraying were made with a very simple and low-cost method, allowing front-side Al contamination. A poor but expected 7.5% conversion efficiency was obtained under AMI illumination. It was shown that under optimized HF concentration, HF-spraying time and flow HF-spraying rate, Al contamination favours the formation of a thin and homogeneous hydrogen-rich PS layer. It was found that under optimized HF-spraying conditions, the hydrogen-rich PS layer decreases the surface reflectivity up to 3% (i.e., increase light absorption), improves the short circuit current (isc) and the fill factor (FF) (i.e., decreases the series resistance), allowing to reach a 12.5% conversion efficiency. The dramatic improvement of the latter is discussed throughout the influence of HF concentration and spraying time on the I-V characteristics and on solar cells parameters. Despite the fact that the thin surface PS layer acts as a good anti-reflection coating (ARC), it improves the spectral response of the cells, especially in the blue-side of the solar spectrum, where absorption becomes greater, owing to surface band gap widening and conversion of a part of UV and blue light into longer wavelengths (that are more suitable for conversion in a Si cell) throughout quantum confinement into the PS layer. 00/01460 How to select a collector? Abdel-Dayem, A. M. Applietl E~wrg,v. 1999, 64. (I-4). I59-~164. The collector is the main element that affects the so!,11 cv\tem’s performance. The collector’s efficiency is affected hy I(\ !,perating temperature. Different levels of heating were considered l~,r a milkprocessing factory. The optimal collector type (i.e. the one with the minimum payback period) that can be used for these levels was deduced.
00101461 issues in thin film PV manufacturing cost reduction Zweibel, K. Solar Energy Mnterinls & So/w Ce//.v,1999. 59, (l-2). I-1 8. Thin film PV technologies face a number of hurdles as they advance towards low-cost goals that are competitive with traditional sources of electricity. The US Department of Energy cost goal for thin films is about $0.33/Wp, which is based on a module efficiency goal of about 15% and module manufacturing costs of about $50/m”. This paper investigates the issues associated with achieving the $50/m’ goal based on opportunities for manufacturing cost reductions. Key areas such as capital costs, deposition rates, layer thickness, materials costs, yields substrates and front and hack end costs will be examined. Several prior studies support the potential of thin films to reach $50/m*. This paper will examine the necessary process research improvements needed in amorphous silicon, copper indium diselenide, cadmium telluride and experimental thin film silicon PV
Fuel and Energy Abstracts
May 2000
163
Composite materials for photovoltaics: a realistic
aim? Kiesewetter,
T. et al. Solnr Energy Materids
& Solar Cells, 1999. 59, (4).
309-323.
Layer-type microcrystalline powders of WSz, MO&, WSez and MoSe2, which were tested for photoeffects with contact free microwave conductivity measurements, were incorporated into a nanostructured TiOz matrix in an attempt to obtain macroscopic photocurrents. Even though only 10% of the microcrystals were found to be active in contact with an iodide/iodine solution, photocurrents of the order of 100 pA/cm’ to 1 mA/cm’ were measured. The photoelectrochemical behaviour of microcrystals was studied with space resolved photocurrent and photovoltage measurement techniques and it was attempted to understand the mechanism of current generation via the TiOzimicrocrystallelectrolyte interaction. Critical and still unresolved problems are recognized to be the control and optimization of photoeffects in microcrystals and the adjustment of doping levels of the two material faces. Only small photopotentials could be observed up to now, probably due to an insufficient and inhomogeneous doping of microcrystals. More research will be needed to determine whether this strategy could lead to realistic photovoltaic systems.
Design and analysis of low-reflection grating microstructures for a solar energy absorber
00/01453
Hava, S. and Auslender, M. Sol. Dlergy. Mar. & Sol. Cc/Is, 2000. 61. (2), 143-151. The problem of calculating the photo-induced current in an n+p junction solar cell with a microstructure grating on the top is formulated. For the case where useful absorption regions lie below the grating a closed solution of the problem is obtained, in which the carrier photo-generation rate is calculated using a full-vector electromagnetic simulation technique. Two structures: filled lamellae grating and overlayer and filled V-groove grating and overlayer are considered. The first structure is optimized with respect to the integral photo-current and the second with respect to reflection loss. Both optimized structures are much less reflective and more efficient than an optimized flat-surface Si-SiOz layer cell.
Design and thermal analysis of a two storage solar concentrator for combined heat and thermoelectric power generation
00101454
Omer, S. A. and Infield, D. G. Energy Convers. Morwge, 2000. 41. (7), 737756. A design procedure and thermal performance analysis of a two-stage solar energy concentrator suited to combined heat and thermoelectric power generation are presented. The concentrator is comprised of a primary one axis parabolic trough concentrator and a second stage compound parabolic concentrator mounted at the focus of the primary. The thermoelectric device is attached to the absorber plate at the focus of the secondary. A cooling tube is fitted to the cold side of the thermoelectric device to extract the waste heat and maintain a high temperature gradient across the device to improve conversion efficiency. The key requirements of the concentrator design are to be tolerant of tracking misalignment, maintain temperature gradients to suit thermoelectric generation and minimize heat losses. A design methodology is presented which allows interception of rays within an angular region (+n). This results in a wider receiver for the parabolic trough concentrator than would usually be used for a similar concentration ratio. The role of the second stage concentrator in limiting heat losses from the absorber plate is evaluated. Results indicate that in addition to improving the concentration efficiency, the second stage compound parabolic concentrator of the proposed design also inhibits convective air movement and, consequently, improves the overall performance of the solar concentrator.
00101455 Earth day 200O-dawn
of the solar age
Hayes, D. Solrrr Today, 1999, 13. (6). 46 America’s gasoline consumption is reported here and the author calls upon readers to use Earth day as a means to draw attention to sustainable energy options such as solar power.
Effect of growth parameters on the MOVPE of GaAsl Ge for solar ceil applications AgarWal,S. K. Solar Energy Matericrls & Sohr Cells. 1999, 59, (I-2). 19-26.
00101456
GaAs has been grown on Ge substrate oriented 6” off towards (I 1 0) by atmospheric pressure MOVPE. Various growth rates and growth temperatures were tried to get device quality epitaxial layers suitable for solar cell
applications. It was observed that the growth temperatures and the growth rates affect the surface morphology, optical and interface properties and crystalline quality of the epitaxial layers. This was studied using optical microscope, photoluminescence, photovoltage measurements, ECV and double crystal X-ray diffractometry.
OOlO1457 Evaluation of sunshine and cloud cover based models for generating solar radiation data Muneer, T. and GUI, M. S. Energ], Corteers. & Mmuge., 2000, 41. (5). 461~ 482. Solar radiation models based on meteorological parameters serve as the substitute to measured irradiation and illuminance data. Models originating from sunshine or cloud cover information constitute the two main classes of meteorological radiation models. Further improvements in the accuracy of these models is under research. One such approach attempted by Page, has resulted in the formation of a model that utilizes a combination of the above mentioned variables. This article briefly discusses the new combined approach and evaluates it against other models developed by the authors: the Meteorological Radiation Model (MRM) based on sunshine fraction and the Cloud Cover Radiation Model (CRM) based on cloud cover. Results show that Page’s approach is quite successful under overcast conditions. The MRM, however appears to provide better.estimates under part clear and clear sky conditions.
00/01456 Experimental study of the basin type solar still under local climate conditions Akash, B. A. fG1erg.vConversion & Morrcrgcvownt, 2000. 41. (9). 883-890. This paper presents experimental results obtained using the basin type solar still. The experiments were conducted in Jordan using a solar still with various cover tilt angles of 15, 25, 35, 45 and 55”. An optimum tilt angle for water production was found to be 35” during the month of May. Salt was added to study the effect of the salinity of water on solar distillation. Distilled water production decreased with salinity. The effect of water depth was also studied. The results show that water production decreased in a somewhat linear relationship with increasing water depth in the still.
00/01459 Formation of porous silicon for large-area silicon solar ceils: a new method Saadoun,
M. et ul. Solor Etzergy Materitrh
& Solor Cell.~, 1999, 59. (4). 377-
385.
Luminescent porous silicon (PS) was prepared for the first time using a spraying set-up, which can diffuse in a homogeneous manner HF solutions, on textured or untextured (1 0 0) oriented monocrystalline silicon substrate. This new method allows us to apply PS onto the front-side surface of silicon solar cells, by supplying very fine HF drops. The front side of N+/P monocrystalline silicon solar cells may be treated for long periods without altering the front grid metallic contact. The monocrystalline silicon solar cells (N+/P, 78.5 cm2) which has undergone the HF-spraying were made with a very simple and low-cost method, allowing front-side Al contamination. A poor but expected 7.5% conversion efficiency was obtained under AMI illumination. It was shown that under optimized HF concentration, HF-spraying time and flow HF-spraying rate, Al contamination favours the formation of a thin and homogeneous hydrogen-rich PS layer. It was found that under optimized HF-spraying conditions, the hydrogen-rich PS layer decreases the surface reflectivity up to 3% (i.e., increase light absorption), improves the short circuit current (isc) and the fill factor (FF) (i.e., decreases the series resistance), allowing to reach a 12.5% conversion efficiency. The dramatic improvement of the latter is discussed throughout the influence of HF concentration and spraying time on the I-V characteristics and on solar cells parameters. Despite the fact that the thin surface PS layer acts as a good anti-reflection coating (ARC), it improves the spectral response of the cells, especially in the blue-side of the solar spectrum, where absorption becomes greater, owing to surface band gap widening and conversion of a part of UV and blue light into longer wavelengths (that are more suitable for conversion in a Si cell) throughout quantum confinement into the PS layer. 00/01460 How to select a collector? Abdel-Dayem, A. M. Applietl E~wrg,v. 1999, 64. (I-4). I59-~164. The collector is the main element that affects the so!,11 cv\tem’s performance. The collector’s efficiency is affected hy I(\ !,perating temperature. Different levels of heating were considered l~,r a milkprocessing factory. The optimal collector type (i.e. the one with the minimum payback period) that can be used for these levels was deduced.
00101461 issues in thin film PV manufacturing cost reduction Zweibel, K. Solar Energy Mnterinls & So/w Ce//.v,1999. 59, (l-2). I-1 8. Thin film PV technologies face a number of hurdles as they advance towards low-cost goals that are competitive with traditional sources of electricity. The US Department of Energy cost goal for thin films is about $0.33/Wp, which is based on a module efficiency goal of about 15% and module manufacturing costs of about $50/m”. This paper investigates the issues associated with achieving the $50/m’ goal based on opportunities for manufacturing cost reductions. Key areas such as capital costs, deposition rates, layer thickness, materials costs, yields substrates and front and hack end costs will be examined. Several prior studies support the potential of thin films to reach $50/m*. This paper will examine the necessary process research improvements needed in amorphous silicon, copper indium diselenide, cadmium telluride and experimental thin film silicon PV
Fuel and Energy Abstracts
May 2000
163