Showing papers on "Solar energy published in 1990"
TL;DR: In this article, the advantages of using multi-quantum-well or superlattice systems as the absorbers in concentrator solar cells are discussed, and an effective band-gap variation that covers the high-efficiency region of the solar spectrum can be obtained.
Abstract: The advantages of using multi‐quantum‐well or superlattice systems as the absorbers in concentrator solar cells are discussed. By adjusting the quantum‐well width, an effective band‐gap variation that covers the high‐efficiency region of the solar spectrum can be obtained. Higher efficiencies should result from the ability to optimize separately current and voltage generating factors. Suitable structures to ensure good carrier separation and collection and to obtain higher open‐circuit voltages are presented using the (AlGa)As/GaAs/(InGa)As system. Efficiencies above existing single‐band‐gap limits should be achievable, with upper limits in excess of 40%.
491 citations
TL;DR: In this paper, an improved high-efficiency silicon solar cell structure was proposed, which overcomes deficiencies in an earlier structure by locally diffusing boron into contact areas at the rear of the cells.
Abstract: Significant improvements in silicon solar cell performance are reported using an improved high‐efficiency silicon solar cell structure. This structure overcomes deficiencies in an earlier structure by locally diffusing boron into contact areas at the rear of the cells. Terrestrial energy conversion efficiencies up to 24% are reported for silicon cells for the first time. Air Mass 0 efficiencies lie in the 20–21% range, the first silicon cells to exceed 20% efficiency under space illumination.
307 citations
Patent•
21 May 1990
TL;DR: The flexible circuit tape is formed by conductive strips sandwiched between layers of polymer dielectric tape and provided with tabs at predefined holes in the tape for bonding to current carrying surfaces of concentrated sunlight tandem solar cell units.
Abstract: Solar cells, particularly GaAs/GaSb tandem solar cells, are mechanically and electrically connected in the form of a string using a flexible circuit tape and mounted in optical alignment with solar energy concentrators in a module. A heat spreader body is attached to each cell unit as part of a heat sink and the cells are precisely positioned to provide optical alignment. The flexible circuit tape is formed by conductive strips sandwiched between layers of polymer dielectric tape and provided with tabs at predefined holes in the tape for bonding to current carrying surfaces of concentrated sunlight tandem solar cell units.
200 citations
TL;DR: In this paper, a new correlation for the estimation of monthly average daily global solar radiation was presented and compared with the correlations of Rietveld, Benson et al., Ogelman et al., and a recent formulation by Gopinathan.
172 citations
TL;DR: In this paper, a solar still was built based on the principle of a stacked tray array for tandem distillation and heat recovery, and a simple mathematical model was evolved and calibrated with field data to make it fit adequately experimental results gathered along some 14 months of continuous operation.
165 citations
TL;DR: The predicted steady-state performance of a single-effect solar still has been in the technical literature and solar energy textbooks for some time, but recent measurements of steady state solar still efficiencies and temperatures appear in conflict with earlier, apparently similar measurements which partially support the long-standing theory as discussed by the authors.
115 citations
Patent•
21 May 1990
TL;DR: In this paper, a honeycomb light weight panel is mounted on a front panel side with solar energy concentrators mounted on the rear panel side, and GaAs/GaSb tandem solar cells are mounted on metallized surfaces of the heat spreader.
Abstract: Solar cells, particularly GaAs/GaSb tandem solar cells, are mounted on a honeycomb light weight panel in optical alignment with solar energy concentrators mounted on a front panel side. The cells are mounted on metallized surfaces of the heat spreader that is attached to a panel wall rear panel side. A circuit carrier has conductors which are bonded to metallization islands that are on one side only of the heat spreader. The circuit carrier is adhered to the rear panel side.
105 citations
TL;DR: A critical overview on photoelectrochemical and photocatalytic methods for hydrogen production by water splitting is presented in this paper, where the solar spectral irradiance and energy distribution as well as the direct water photolysis are briefly mentioned.
76 citations
TL;DR: This is, to the authors' knowledge, the first directly solar-pumped laser operating at 77 K, pumping a 5-mm-diameter 62-mm exposed-length rod of Er,Tm,Ho:YAG to achieve a quasi-cw lasing of the Ho ion.
Abstract: Direct solar illumination was used to pump a 5-mm-diameter 62-mm exposed-length rod of Er,Tm,Ho:YAG to achieve a quasi-cw lasing of the Ho ion at an average power of 12 W. The solar radiation was chopped at a 20% duty cycle to avoid overloading of the cooling system. The peak power output was more than 65 W during the chopper's open times. The slope efficiency is 3.8%, and the threshold input energy is approximately 100 W. The laser was operated for long times (up to hours) while maintaining its performance. This is, to our knowledge, the first directly solar-pumped laser operating at 77 K.
75 citations
TL;DR: The early 1970s stimulated numerous investigations of semiconductor/liquid junctions for the conversion and storage of solar energy as discussed by the authors, with the potential for inexpensive, chemically based energy conversion devices, with the accompanying potential to effect the direct conversion of light into chemical fuels.
Abstract: The energy crisis of the early 1970s stimulated numerous
investigations of semiconductor/liquid junctions for the conversion and storage of solar energy Although similar in concept to solid-state photovoltaic devices, semiconductor /liquid junctions offered the potential for inexpensive, chemically based energy-conversion devices, with the accompanying potential to effect the direct conversion of light into chemical fuels
74 citations
TL;DR: In this article, the design, construction, and operation experience of a 5 MW solar pond power plant is presented, which features include extraction of pond surface water to an auxiliary pond for condenser cooling, a low-cost liner consisting of polyethylene and clay, and a series of high-velocity, low-fluid-volume jets for gradient formation and repair.
TL;DR: In this article, the authors present a procedure and solar radiation related data from which the diurnally, hourly and daily variation of the global, direct beam and diffuse insolation on Mars are calculated.
01 Aug 1990
TL;DR: In this paper, the spectral properties of a multilayer of thin films, produced by sputtering, were investigated for service as efficient solar photothermal energy converters, and a full scale production machine was constructed.
Abstract: Spectrally selective absorber coatings, deposited on engineering material substrates such as
stainless steel, have been developed for service as efficient solar photothermal energy converters.
The selective solar absorber is based on a multilayer of thin films, produced by sputtering. The
main solar absorber is a metal/ceramic (cermet) composite, such as, Mo/Al2th or Mo/Si02, with a
graded metal concentration. Such a cermet layer, strongly absorbs radiation over most of the range
of the solar spectrum but is transparent to longer wavelength radiation. The cermet layer is
deposited on a highly reflecting infrared metal layer. Two more layers were added: An AhO
diffusion barrier layer which is deposited first on the substrate and an AI2O or a Si02 antireflection
layer which is deposited on the top of the cermet film. In order to better understand the spectral
reflectivity of the multilayered selective coating, a procedure for the calculation of the optical
properties was developed.
After the R&D development phase was successfully completed, a full scale production
coating machine was constructed. The production machine is a linear in line coater. The selective
coating is deposited on stainless steel tubes, translating in the coating machine while rotating about
their axes, along their axial direction. Measurements of reflectance, solar absorptivity, a, thermal
emissivity, C, and high temperature durability, are all parts of the quality control routine. The
results show values of a in the range 0.96 - 0.98. The thermal emissivity at 350CC is in the range
0.16 - 0.18. Thermal durability tests, show no degradation of the coating when subjected to up to
65O in vacuum for one month and when passed through a temperature cycling test which
includes 1200 cycles between temperatures of 150CC and 450CCfor a period of two months.
TL;DR: In this article, a novel solar cooker has been described and compared with a solar oven and a hot box solar cooker, which has a tilted absorbing surface so that more radiation can be obtained even during winter.
01 Jan 1990
TL;DR: In this article, an extended, annotated bibliography in the solar thermal energy collection field, documenting the state-of-the-art in the late 1980s, is presented, including salt gradient solar ponds, flat plate collectors, compound parabolic concentrators.
Abstract: This volume was prepared as an extended, annotated bibliography in the solar thermal energy collection field, documenting the state-of-the-art in the late 1980s. It covers collectors of solar thermal energy, including salt gradient solar ponds, flat plate collectors, compound parabolic concentrators, and other stationary and tracking collection systems. Collectors that are used for building applications are emphasized since power and industrial applications are considered in other volumes.
TL;DR: In this article, a new discrete numerical model is proposed to calculate the flow and temperature distribution in solar collector arrays, where flow nonuniformity, the longitudinal heat conduction, and the buoyancy effect are all taken into account in the analysis.
TL;DR: In this paper, a simple transient analysis of a conventional solar still has been presented by incorporating the effects of water flow over the glass cover and heat capacity of the water mass in the basin.
TL;DR: In this article, the monthly average daily global and global ultraviolet solar radiation over a period of three years (1985, 1986, 1987) in Kuwait are reported and the effect of atmospheric dust on the measured solar radiation components is investigated.
TL;DR: The location of active geyser-like eruptions and related features close to the current subsolar latitude on Triton suggests a solar energy source for these phenomena and a variety of models for the storage of solar energy in a sub-greenhouse layer and for the supply of gas and energy to a geysers are examined.
Abstract: The location of active geyser-like eruptions and related features close to the current subsolar latitude on Triton suggests a solar energy source for these phenomena. Solid-state greenhouse calculations have shown that sunlight can generate substantially elevated subsurface temperatures. A variety of models for the storage of solar energy in a subgreenhouse layer and for the supply of gas and energy to a geyser are examined. 'Leaky greenhouse' models with only vertical gas transport are inconsistent with the observed upper limit on geyser radius of about 1.5 km. However, lateral transport of energy by gas flow in a porous N2 layer with a block size on the order of a meter can supply the required amount of gas to a source region about 1 km in radius. The decline of gas output to steady state may occur over a period comparable with the inferred active geyser lifetime of 5 earth years. The required subsurface permeability may be maintained by thermal fracturing of the residual N2 polar cap. A lower limit on geyser source radius of about 50 to 100 m predicted by a theory of negatively buoyant jets is not readily attained.
TL;DR: In this paper, the authors describe the development of an inflatable concentrator for solar propulsion, providing the source of heat to a hydrogen engine aboard the Solar Rocket, a device designed to carry payloads from a low earth orbit (LEO) to a geosynchronous orbit (GEO) at significant mass savings in comparison to chemical propulsion; it involves two light-weight parabolic reflectors in an off-axis configuration focusing solar radiation into the absorbers of the engine, which causes the emission of a hot hydrogen jet.
Abstract: This paper describes the development of an inflatable concentrator for solar propulsion, providing the source of heat to a hydrogen engine aboard the Solar Rocket. The latter is a device designed to carry payloads from a low earth orbit (LEO) to a geosynchronous orbit (GEO) at significant mass savings in comparison to chemical propulsion; it involves two light-weight parabolic reflectors in an off-axis configuration focusing solar radiation into the absorbers of the engine, which causes the emission of a hot hydrogen jet. Each of the reflectors has an elliptical rim with a 40 m major axis, providing heat to the propellant sufficient to produce about 40 lbs. of thrust. The same concentrator concept is contemplated for space power application to focus solar radiation on a conversion device, e.g., a photovoltaic array or the high temperature end of a dynamic engine. Under the present project, a one-fourth scale, 9X7 m off-axis inflatable concentrator has been under development as a pilot for the full-scale flight unit. The reflector component consists of a reflective membrane made of specially designed gores and a geometrically identical transparent canopy. The two form together an inflatable lenslike structure which, upon inflation, assumes the accurate paraboloidal shape. Thismore » inflatable structure is supported along its rim by a strong, bending-resistant torus. The paper describes the development of this system including the analysis leading to determination of the gore shapes, the reflector membrane design and testing, the analysis of the supporting torus, and a discussion of the effects of the space environment.« less
Patent•
07 Mar 1990
TL;DR: A solar greenhouse as discussed by the authors is a closed chamber with walls and a roof which together with a floor form a closed closed chamber, and windows are provided to permit the entry of light into a major part of the chamber where growth will occur while restricting light to a minor portion thereof where germination of seeds occurs.
Abstract: A solar greenhouse includes walls and a roof which together with a floor form a closed chamber. Windows are provided to permit the entry of light into a major part of the chamber where growth will occur while restricting light to a minor portion thereof where germination of seeds occurs. Racks for stacked growing trays are provided; preferably the upper part of the chamber is used for germination. The greenhouse further includes apparatus for accumulating solar energy in the form of electrical energy so as to drive irrigation pumps and fans and also in the form of thermal energy to assist in maintaining desired temperatures in the chamber.
27 Nov 1990
TL;DR: In this article, a highly efficient power electronic converter for converting the output voltage of a solar panel or wind generator to the required DC battery bus voltage has been realized, where the converter is controlled to track the maximum power point of the nput source under varying input and output parameters.
Abstract: It is argued that a well-engineered renewable remote energy system utilizing the principal of maximum power point tracking (MPPT) can be cost effective, has a high reliability, and can improve the quality of life in remote areas. A highly efficient power electronic converter for converting the output voltage of a solar panel or wind generator to the required DC battery bus voltage has been realized. The converter is controlled to track the maximum power point of the nput source under varying input and output parameters. MPPT for relatively small systems is achieved by maximization of the output current in a battery charging regulator, using an optimized hill-climbing, inexpensive microprocessor-based algorithm. Through field measurements it is shown that a minimum input source saving of 15% on 3-5 kWh/day systems can easily be achieved. >
Patent•
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03 Aug 1990
TL;DR: In this article, a building roof over an air space requiring forced ventilation of solar energy heated air from the space through a vent hole in the roof, an electrically operated exhaust fan mounted in air exhausting relation on the roof and over the vent hole, and a solar panel for supplying electrical power to a fan driving motor when exposed to solar rays.
Abstract: There is provided in combination with a building roof over an air space requiring forced ventilation of solar energy heated air from the space through a vent hole in the roof, an electrically operated exhaust fan mounted in air exhausting relation on the roof and over the vent hole, and a solar panel for supplying electrical power to a fan driving motor when exposed to solar rays. Air exhaust passage through the device includes a backwash turbulence preventing ring-shape plate extending between a supporting ring body which is of smaller diameter than an exhaust air directing hood on which the solar panel is mounted, and a ring channel member supporting the exhaust fan in a manner to draw the exhaust air through the ring channel into the hood.
TL;DR: In this article, the authors examined the impact of operating PV systems on the electric utility production cost (fuel and variable operation and maintenance), the load profile of a southeastern utility and the PV output data from solar test facilities in Virginia and North Carolina are used.
Abstract: The parameters which impact the value of photovoltaics (PV) to the electric utility is examined. High, medium, and low-load days in winter (January) and summer (July) are studied. The daily peak load is varied from 5838 MW to 9712 MW. These six days are studied for reference (no PV), high, medium, low, and intermittent-PV output cases. Results from these 30 case studies are summarized. In order to study the impact of operating PV systems on the electric utility production cost (fuel and variable operation and maintenance), the load profile of a southeastern utility and the PV output data from solar test facilities in Virginia and North Carolina are used. The performance analysis shows that, while the total production (fuel and variable O&M) cost savings are higher for higher solar days, the increase is not proportional to the amount of PV energy output. It is shown that the high solar day never produced the highest per-unit PV energy value. The highest per-unit PV energy values for both winter and summer days are found to be for the low solar days. >
TL;DR: In this article, a simple computer simulation method is adopted to study the ground heat loss and the heat recovery rate under varied combinations of the depth of the underground water table, the thickness of the lower convective zone, the heat withdrawal pattern, and the thermal properties of the soil.
Patent•
20 Mar 1990
TL;DR: In this article, a thin, lightweight solar cell utilizes front contact metallization, where both the front light receiving surface and the facing surface of the cover glass are recessed.
Abstract: A thin, lightweight solar cell utilizes front contact metallization. Both the front light receiving surface of the solar cell and the facing surface of the cover glass are recessed to accommodate this metallization. This enables the two surfaces to meet flush for an optimum seal.
Patent•
06 Dec 1990
TL;DR: In this paper, a swimming pool skimmer includes a paddle wheel that directs fluid and debris into a debris catcher, which is powered by a motor that is powered from an array of solar cells.
Abstract: A swimming pool skimmer includes a paddle wheel that directs fluid and debris into a debris catcher. The paddle wheel is turned by a motor that is powered from an array of solar cells. A solar concentrator focuses solar energy onto the solar cells, and an alarm circuit includes a strain gauge on the debris catcher. The strain gauge forms one leg of a bridge circuit that is connected to a comparator having a feedback loop. The output of the comparator is connected to an alarm element either directly or remotely.
TL;DR: The U.I. salt gradient solar pond facility at the University of Illinois (U.I.) as mentioned in this paper has demonstrated that solar ponds for low grade heating applications, such as space heating and grain drying, can be designed in a simple manner that requires minimal maintenance duties.
TL;DR: The most recent developments in the utilization of materials in photovoltaic devices can be found in this paper, which is limited primarily to publications from 1987 through 1989, focusing on the most recent development in the development of materials for photovolastic energy conversion.
Abstract: Despite the fact that the 1980s have been a period in which public and government support for photovoltaics has been greatly underemphasized, it is heartening to realize that considerable activity in research and development of solar cells continues, as does a steady, positive experience in the field. In order to focus on the most recent developments in the utilization of materials in photovoltaic devices, this paper is limited primarily to publications from 1987 through 1989. The development of materials for photovoltaic energy conversion is a significant contribution to the development of alternative energy sources. Students of the energy question have realized for some time that traditional sources of energy (coal, oil, natural gas) supply only a limited reservoir when future energy needs of the earth are considered in terms of hundreds rather than tens of years. Recently, we have become increasingly aware of other problems associated with energy production by the combustion of fossil fuels as well: air pollution, acid rain, and the greenhouse effect, to mention only a few. In particular, the greenhouse effect is raising an increasing concern. This paper discusses the materials used for photovoltaics.
TL;DR: In this article, a numerical model of axisymmetric solar cavity receivers is compared with experimental data for tests of a novel test bed receiver in the Saudi National Laboratories solar furnace.
Abstract: Results from a numerical model of axisymmetric solar cavity receivers are compared with experimental data for tests of a novel test bed receiver in the Saudi National Laboratories solar furnace. The computed energy transfer rates and temperatures are compared with the experimental data for different receiver geometries, aperture sizes, and operating conditions. In general, the agreement between the numerical model and the experimental data is better for the small-to-midsized apertures than for the large apertures. The analysis indicates that for the larger apertures, the convective heat losses are overpredicted. It also suggests that these losses could be better characterized. Sensitivity analyses show that both the total solar energy input rate and the convective heat-loss coefficient significantly affect the receiver thermal performance and that the distribution of the input solar flux significantly affects the temperature distribution in the receiver.