Showing papers on "Solar energy published in 1991"
TL;DR: In this article, the authors describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency.
Abstract: THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.
26,457 citations
TL;DR: In this paper, the use of phase change materials (PCM) for short-term heat storage in direct-gain passive solar applications is discussed, and approximate formulae are presented for optimum phase change temperature and the thickness of a PCM wall.
314 citations
Book•
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01 Jan 1991
TL;DR: In this paper, various papers on solar science are presented, including variability of solar irradiance, sunspot number, solar diameter, and solar wind properties; theory of luminosity and radius variations; standard solar models; the sun and the IMF; variations of cosmic-ray flux with time; accelerated particles in solar flares; solar cosmic ray fluxes during the last 10 million yrs; solar neutrinos and solar history.
Abstract: Various papers on solar science are presented. The optics considered include: variability of solar irradiance, sunspot number, solar diameter, and solar wind properties; theory of luminosity and radius variations; standard solar models; the sun and the IMF; variations of cosmic-ray flux with time; accelerated particles in solar flares; solar cosmic ray fluxes during the last 10 million yrs; solar neutrinos and solar history; time variations of Be-10 and solar activity; solar and terrestrial components of the atmospheric C-14 variation spectrum; solar flare heavy-ion tracks in extraterrestrial objects. Also addressed are: the faint young sun problem; atmospheric responses to solar irradiation; quaternary glaciations; solar-terrestrial relationships in recent sea sediments; magnetic history of the sun; pre- and main-sequence evolution of solar activity; magnetic activity in pre-main-sequence stars; classical T Tauri stars; relict magnetism of meteorites; luminosity variability of solar-type stars; evolution of angular momentum in solar-mass stars; time evolution of magnetic fields on solarlike stars.
282 citations
Book•
01 Jan 1991
TL;DR: In this paper, the authors investigate new material advances as well as applications, costs, reliability and industrial production of existing materials in the field of materials science and show that each contribution represents a landmark in materials science.
Abstract: Hardbound. Rapid advances in materials technology are creating many novel forms of coatings for energy efficient applications in solar energy. Insulating heat mirrors, selective absorbers, transparent insulation and fluorescent concentrators are already available commercially. Radiative cooling, electrochromic windows and polymeric light pipes hold promise for future development, while chemical and photochemical processes are being considered for energy storage. This book investigates new material advances as well as applications, costs, reliability and industrial production of existing materials. Each contribution represents a landmark in the field of materials science.
190 citations
Patent•
04 Nov 1991TL;DR: In this paper, a solar energy power source is provided comprising at least two flat photovoltaic panels disposed in co-planar side-by-side relation and an improved support structure for supporting the panels for pivotal movement on a pivot axis that extends transversely of the panels.
Abstract: A solar energy power source is provided comprising at least two flat photovoltaic panels disposed in co-planar side-by-side relation and an improved support structure for supporting the panels for pivotal movement on a pivot axis that extends transversely of the panels, the improved structure including a single selectively operable drive means for pivoting all of the panels simultaneously and by the same amount of angular displacement.
185 citations
TL;DR: In this article, the authors developed a semi-empirical model that describes the total solar spectral irradiance for clear and cloudy sky conditions based on readily available input data, which was applied to calculate spectral irradiances in short time.
Abstract: In a combined effort, the Centre for Solar Energy and Hydrogen Research in Germany and the Solar Energy Research Institute in the United States analyzed several thousand measurements of the solar spectral irradiance recorded at four sites. The goal was to develop a semiempirical model that describes the total solar spectral irradiance for clear and cloudy sky conditions based on readily available input data. To investigate how the spectral transmission of clouds deviates from an assumed neutral density filter, the measured spectra are compared with simulated clear-sky spectra. A correlation is established between the cloud thickness and the relatively higher transmission of clouds in the ultraviolet and blue region of the solar spectrum. Using this approach, a semiempirical model is proposed based solely on global and diffuse broadband irradiance measurements, precipitable water-vapor data, and the sun's position. The model, called SEDESI, is applied to calculate spectral irradiance in short time...
162 citations
TL;DR: In this article, the role of back reflectors in enhancing the absorption of weakly absorbing, long-wavelength light has been investigated as applied to amorphous silicon alloy solar cells.
Abstract: The role of back reflectors in enhancing the absorption of weakly absorbing, long‐wavelength light has been investigated as applied to amorphous silicon alloy solar cells. The reflectance and scattering properties of various types of back reflectors have been studied. The performance of p‐i‐n amorphous silicon alloy solar cells deposited on different back reflectors has been analyzed. The studies elucidate the role of back reflectors in improving the short‐circuit current density and thereby the efficiency of the cell.
161 citations
TL;DR: The results of studies on intramolecular interconversions in systems of norbornadiene quadricyclane and their derivatives are classified and discussed in this article, where the mechanisms of the forward photoreaction and reverse thermal process in relation to the nature of the substituents and carbocycles, type of sensitiser and catalyst, and properties of the medium are discussed in detail and classified.
Abstract: The results of studies on intramolecular interconversions in systems of norbornadiene quadricyclane and their derivatives are classified and discussed. The mechanisms of the forward photoreaction and reverse thermal process in relation to the nature of the substituents and carbocycles, type of sensitiser and catalyst, and properties of the medium are discussed in detail and classified. An analysis is made of the influence of these factors on the spectroscopic, kinetic, and thermodynamic properties of this system as an accumulator and converter of light energy. Methods of improving its characteristics — light absorption, the quantum yield of the photoreaction, and stability of the photoproduct — have been established. The bibliography includes 188 references.
148 citations
Patent•
10 May 1991
TL;DR: In this paper, a photovoltaic cell array involving rows and columns of tandem or stacked solar cell units composed of GaSa/GaSb associated with a radiation collector has been demonstrated to achieve energy conversion efficiencies of 31% AMO.
Abstract: A photovoltaic cell array involving rows and columns of tandem or stacked solar cell units composed of GaSa/GaSb associated with a radiation collector have produced measured energy conversion efficiencies of 31% AMO. The booster GaSb cell is manufactured by a process which produces a p-type diffusion region within an n-type substrate, has improved energy conversion efficiencies and can be mounted as part of a four terminal stacked solar cell unit.
131 citations
Book•
01 Jan 1991
TL;DR: In this paper, the uses, advantages and costs of solar power plants, covering insolation - its variability, concentration and efficiency of use - and experimental and theoretical developments in the recently created field of solar-driven chemistry (thermal, quantum or electrical excitation).
Abstract: This work addresses the uses, advantages and costs of solar power plants, covering insolation - its variability, concentration and efficiency of use - and experimental and theoretical developments in the recently created field of solar-driven chemistry (thermal, quantum or electrical excitation). The authors of the papers in this book write from experience of the industry and describe design aspects of experimental and demonstration plants . The future potential of solar energy is considered, taking into account its non-detrimental impact on the environment.
TL;DR: In this article, the authors introduce materials for energy efficiency and solar energy utilization and discuss some current trends for basic research and development, which involve thin surface coatings, such as solar absorber surfaces, transparent infrared reflectors and transparent conductors, large area chromogenics for transmittance control in smart windows, and transparent convection-suppressing materials, whereas solar cell materials are not included.
Abstract: This paper introduces materials for energy efficiency and solar energy utilization and discusses some current trends for basic research and development. Most of the materials involve thin surface coatings. Overviews are given for solar absorber surfaces, transparent infrared reflectors and transparent conductors, large-area chromogenics for transmittance control in “smart windows”, and transparent convection-suppressing materials, whereas solar cell materials are not included. The paper also treats a few examples of specific coatings that are presently being investigated; data are given for angular-selective transmittance through porous Cr films with oblique columnar microstructure, transparent and conducting non-stoichiometric SnO2 films, and chromogenic effects in Li-intercalated VO2 films.
TL;DR: In this paper, a 170 kW reformer has been integrated into the GAST-circuit of the CESA-1 in Almeria, Spain to show experimentally the possibility of coupling the needs of a chemical process with the specific boundary conditions of the solar energy.
TL;DR: In this article, a two-stage optical design is proposed for parabolic trough solar collectors with tubular absorbers, which can boost the concentration ratio by a factor of 2.5 relative to the conventional design, while maintaining the large rim angles.
Book•
13 Dec 1991
TL;DR: The solar energy resource transmission through transparent materials absorption of solar energy at surfaces flat plate collectors line-axis concentrating collectors solar ponds solar dryers solar refrigeration greenhouses passive and active solar design of buildings as discussed by the authors.
Abstract: The solar energy resource transmission of solar energy through transparent materials absorption of solar energy at surfaces flat plate collectors line-axis concentrating collectors solar ponds solar dryers solar refrigeration greenhouses passive and active solar design of buildings.
TL;DR: In this article, suitable thermal tests have been identified for performance evaluation of a concentrating solar cooker, and the overall heat loss factor is obtained from the cooling curve and the optical efficiency factor is determined from the heating curve under full load conditions.
TL;DR: In this article, a theoretical model of the heat transfer process within the rock bed was developed for large storage materials, and the relationship between the model parameter and the air flow rate was derived from experimental measurements for some large materials as well as the pressure drop through the bed.
TL;DR: In this article, the authors present a new intermediate method of precise and easy application, and consists of a presentation and experimental proof of the method, named HORTICERN, which is based on a static study of the thermal energy balance.
TL;DR: In this paper, an experimental investigation of the enhancement of thermal performance of solar air heater having its duct packed with blackened wire-screen matrices was conducted to cover wide range of influencing parameters including geometry of wire screens, mass flow rates and input solar energy fluxes under actual outdoor conditions.
TL;DR: In this article, an advanced version of the box-type solar cooker is presented: a fixed cooking vessel in good thermal contact with a conductive absorber plate is set into the glazing; the results are improved thermal performance, easier access to the cooking vessel and less frequent maintenance due to protection of all absorbing and reflecting surfaces.
TL;DR: In this paper, the authors describe a unique new solar furnace at the Solar Energy Research Institute (SERI) that can generate a wide range of flux concentrations to support research in areas including materials processing, high-temperature detoxification and high-flux optics.
TL;DR: In this paper, a sintered ZrO2 + 8 mol% Y2O3 ceramic is used as an electrolyte for high-temperature steam electrolysis using solar energy as a heat source.
Patent•
10 Jun 1991
TL;DR: In this paper, the authors proposed a method for concentrating moderate solar flux uniformly on a target plane on a solar cell array, the dish having a stepped reflective surface characterized by a plurality of ring-like segments arranged about a common axis, and each segment having a concave spherical configuration.
Abstract: A dish reflector and method for concentrating moderate solar flux uniformly on a target plane on a solar cell array, the dish having a stepped reflective surface that is characterized by a plurality of ring-like segments arranged about a common axis, and each segment having a concave spherical configuration.
Book•
01 Jan 1991
TL;DR: The list of SI Units and Conversion Factors to SI, compiled by V.H.Burton and A.A.Oosterbaan as discussed by the authors, is a collection of SI units and conversion factors to SI.
Abstract: General Preface (B.A. Stout). Preface to Volume 4 (B.F. Parker). 1. Techniques of Estimating Incident Solar Radiation (D.G. Colliver). 2. Photovoltaic System Design (L. Rosenblum). 3. Agricultural Applications of Photovoltaic Systems (A. Ratajczak and W.J. Kaszeta). 4. Solar-Thermal Design (B.F. Parker). 5. Solar Water Heating (D. Faiman). 6. Production Solar Greenhouses (L.D. Albright). 7. Animal Housing: Solar Application (J.A. DeShazer and G.R. Bodman). 8. Water Desalination (A.I. Kudish). 9. Solar Grain Drying (H.M. Keener). 10. Design of Solar-Heated Forage Dryers (B.F. Parker). 11. Solar Fruit Drying (E.J. Carnegie). 12. Solar-Heated Lumber Kilns (R.A. Plumptre). 13. Solar Curing of Specialty Crops (J.M. Bunn). 14. Free Convection Dryers (R. Corvalan and W. Zambrano). 15. Solar Thermal Water Pumping (R. Burton). List of Contributors. List of SI Units and Conversion Factors to SI, compiled by V.H.A.M. Oosterbaan. Subject Index
TL;DR: In this article, the reduction of Fe2O3 with graphite in a solar furnace was investigated and an idealization of a blast furnace for achieving it was presented. But the results of the experiments were limited to the nominal temperature range of 1300-2390 K.
TL;DR: In this paper, the authors discuss the hydrodynamical issues that affect the performance of the solar pond as an energy collector and storage system, e.g., mass and energy balance; formation, stability, and maintenance of the gradient layer; energy extraction from the bottom mixed layer; stability of stratified fluids to shearing flows; interface dynamics; and wall effects.
01 Sep 1991
TL;DR: In this article, a procedure and solar radiation related data are presented from which the daily variation of the global, direct beam and diffuse insolation on Mars are calculated, given the optical depth of the Mars atmosphere, the global radiation is calculated from the normalized net flux function based on multiple wavelength and multiple scattering of the solar radiation.
Abstract: Detailed information on solar radiation characteristics on Mars are necessary for effective design of future planned solar energy systems operating on the surface of Mars. A procedure and solar radiation related data are presented from which the daily variation of the global, direct beam and diffuse insolation on Mars are calculated. Given the optical depth of the Mars atmosphere, the global radiation is calculated from the normalized net flux function based on multiple wavelength and multiple scattering of the solar radiation. The direct beam was derived from the optical depth using Beer's law, and the diffuse component was obtained from the difference of the global and the direct beam radiation. The optical depths of the Mars atmosphere were derived from images taken of the Sun with a special diode on the cameras used on the two Viking Landers.
01 Jul 1991
TL;DR: A microprocessor-based automatic position control scheme has been designed for controlling the azimuth angle of an optimally tilted photovoltaic flat type solar panel or a cylindrical parabolic reflector to get the illuminating surface appropriately positioned for the collection of maximum solar irradiance as discussed by the authors.
Abstract: A microprocessor-based automatic position control scheme has been designed for controlling the azimuth angle of an optimally tilted photovoltaic flat type solar panel or a cylindrical parabolic reflector to get the illuminating surface appropriately positioned for the collection of maximum solar irradiance. The scheme presented results in considerable saving in power and is independent of the geographical location of the site of erection or temporal variations in environmental parameters.
01 Jan 1991
TL;DR: Several pathways for renewable energy conversion are introduced in this article, where materials for specific solar energy applications have optical properties tailored to the requirements set by the radiation in our surroundings, and the goals of materials science for several solar energy conversion systems are discussed.
Abstract: Several pathways for renewable energy conversion are introduced. Materials for specific solar energy applications have optical properties tailored to the requirements set by the radiation in our surroundings. This “natural” radiation is outlined, and the goals of materials science for several solar energy conversion systems are discussed.