Showing papers on "Solar energy published in 1977"

Applied solar energy. An introduction

Abstract: This book is an introduction into the theory that must be mastered in order to engineer and evaluate the performance of solar energy systems. An important goal in solar energy applications is the ability to calculate output from a proposed design application and thereby establish the value of the energy delivered and a fair price for the system. To this end the authors build the necessary background and information in successive chapters, culminating in a section on representative applications. (WDM)

Solar Energy-Assisted Electrochemical Splitting of Water. Some Energetical, Kinetical and Catalytical Considerations Verified on MoS2 Layer Crystal Surfaces

Abstract: Abstract Kinetical, energetical and solid state considerations were elaborated in a search for suitable electrodes for the oxidation of water with visible light. They led to layer type transition metal dichalcogenides and to the photo-electrochemical utilization of optical d-d-transition which do not break chemical bonds. MoS2 was selected as a promising compound and it was actually shown to react with water on illumination with light between 400 and 715 nm. At low electrode potentials the liberation of small quantities of molecular oxygen was traced with polarographic techniques. The main portion of the oxidation products of water was, however, found to be lost for the oxydation of crystal bound sulfur to sulfate. An improvement of this situation in favour of an increased rate of oxygen evolution has been accomplished by means of a redox-catalyst, tris (2,2'-bipyridine) -ruthenium (II), which is oxidized through photochemically generated holes from the MoS2 4 dz²- valence band and channels them into oxygen-evolution through nucleo-philic addition of hydroxide. A molecular mechanism was elaborated for the photoelectrochemical oxidation of water on MoS2 and its conclusions tested by investigating the oxidative behaviour of various additional layer-type transition metal compounds. It involves a hole mediated valence change of molybdenum with an intermediate formation of a 5-valent molybdenum hydroxide. A basic kinetical and energetical similarity is suggested with the function of manganese reaction centers in photosynthesis.

Theory of metal‐insulator‐semiconductor solar cells

Abstract: Recent reports in the literature indicate that the introduction of an interfacial oxide layer in a Schottky barrier can greatly increase the photovoltaic conversion efficiency of such devices. We propose an explanation for the operation of such solar cells based on the concept that they are minority‐carrier nonequilibrium MIS tunnel diodes. Calculations of efficiency as a function of insulator thickness, substrate carrier concentration, surfaces states, and oxide charge are presented. These indicate that a maximum theoretical efficiency of 21% is possible under AM2 illumination for high substrate doping and low interface defect density.

Spectral Response and Efficiency Relations in Semiconductor Liquid Junction Solar Cells

Abstract: States due to imperfections at or near surfaces of semiconductors in liquid junction solar cells can be identified by changes in the photoresponse spectra under short-circuit current conditions. These effects become dominant features in two-beam experiments with an intense pumping (laser) source and a weak modulated probing beam. The presence of these states can be correlated with drastic decreases in short-circuit currents, open-circuit voltages, fill factors, and maximum power conversion efficiencies of the cells. Elimination of the damaged surface regions by suitable etching allows AM2 solar conversion efficiencies of 1.3 and 7.2%, respectively, in the cells n-CdS/0.1F Na/sub 2/S--0.02F S-0.1F NaOH/C and n-CdSe/1F Na/sub 2/S--1F S-1F NaOH/C.

Tubular solar cell devices

Abstract: Tubular solar cells are provided which can be coupled together in series and parallel arrays to form an integrated structure. Solar energy concentrators are combined with the solar cells to maximize their power output. The solar cells may be cooled by circulating a heat exchange fluid through the interior of the solar cells and the heat captured by such fluid may be utilized, for example, to provide hot water for a heating system. The coolant circulating system of the solar cells also may be integrated with a solar thermal device so as to form a two-stage heating system, whereby the coolant is preheated as it cools the solar cells and then is heated further by the solar thermal device.

Radiative characteristics of Saharan dust at solar wavelengths

Abstract: Solar radiation measurements made on Sal in the Cape Verde Islands during the 1974 Gate project are analyzed in conjunction with aerosol size spectra data in order to describe the extinction and absorption of solar radiation by Saharan dust. From optical depth measurements, supported by Mie calculations, we were able to show that near-neutral extinction must exist across most of the solar spectrum as the result of a large effective scattering diameter of the dust. Absorption estimates were also made from our composite radiation data by inverting radiative transfer equations based on the delta-Eddington model. Imaginary indices of refraction obtained by this method at three wavelengths agree satisfactorily with laboratory measurements made with Saharan dust. Total depletion of solar energy as a function of path length and optical depth is presented along with an analysis of the extinction coefficient as a function of aerosol concentrations. From the latter we determined a near-linear relationship between optical depth as measured at the ground and total aerosol loading in an atmospheric column. A brief comparison is made between aerosol extinction properties at Sal and at Barbados.

Photon trapping and energy transfer in multiple-dye plastic matrices: an efficient solar-energy concentrator

Abstract: Experiments are described illustrating enhanced photon trapping and efficient energy transfer in mixed-dye planar solar concentrators containing, for example, Rhodamine 6G and Coumarin 6. These concentrators intercept more of the solar spectrum to give an enhanced photon-flux gain that exceeds the single-dye concentrator. It is also shown that the energy absorbed by the donor dye is transferred efficiently into the emitting acceptor by two competing processes.

Materials for luminescent greenhouse solar collectors.

Abstract: Luminescent greenhouse solar collectors are potentially useful for concentrating sunlight onto photovoltaic power cells. Measurements of the performance of small-scale collectors made of two commercially available materials (Owens-Illinois ED2 neodymium-doped laser glass and rhodamine 6G-doped plastic) are presented. The results are encouraging, but they indicate a need for further spectral sensitization and for reduced matrix loss coefficient. The measurements with monochromatic illumination agree with the predictions of a mathematical model developed to take account of reemission following the absorption of luminescence. Under solar illumination, the model predicts photon flux concentrations of about 15 for optimized full-scale collectors made of the materials studied and concentrations of 110 for reasonably improved glass.

Optimum efficiency of photogalvanic cells for solar energy conversion

Abstract: The performance of photogalvanic cells for the direct conversion of solar energy to electrical energy depends on the cell photochemistry, the homogeneous kinetics, the mass transport, the electrode kinetics and the load on the cell. The variation of the power output with the concentrations of the redox couples, their transport and kinetic parameters and the dimensions of the cell is found. The power conversion efficiency of the optimal cell could be as large as 18% but it is unlikely that all the necessary conditions can be met. A more realistic estimate of the maximum power conversion efficiency that could be achieved from a photogalvanic cell is between 5 and 9%.

Fluorescent solar energy concentrator

Abstract: Apparatus for concentrating radiant energy such as solar radiation, collected over a large area, to a smaller area for more efficient conversion of the radiant energy to a more useful form of energy. Fluorescent material in a thin film form is optically bonded by an adhesive or viscous, transparent medium to a massive slab of transparent material such as glass or plastic. Energy conversion devices, such as photovoltaic cells, are disposed around the edges of the slab.

Solar Lake (Sinai). 1. Physical and chemical limnology1

Abstract: In Solar Lake, a basin at the edge of the sea filled with brine and shielded from the wind, a pycnocline builds up in September due to seepage of seawater to the surface. Solar heating produces a mesothermic temperature curve with a maximum up to 60.5°C at 2.5–3-m depth and decreasing temperatures toward the bottom (40°C at 5 m). The temperature profile together with a supply of nutrients from seepage leads to the development of several bacterial plates and a benthic cyanobacterial bloom. A rapid development of anoxic conditions with up to 39 ppm H2S, a decrease in pH from top to bottom (8–6.9), redox potential gradients (+390 to −185 mV), and extremely pronounced light absorption are observed during the period of stratification which lasts from Sepember to July. With increasing solar energy, the seawater supply no longer compensates for the evaporation rate of 3.0 m yr−1 and the mesothermy becomes unstable. During a short period of holomixis, lasting from 4–13 weeks, the temperature is 27°C throughout the water column. The sediments of Solar Lake preserve a record of the last 4,600 years from the conditions of a marine lagoon to the development of the limnological cycle presented here.

Efficient sprayed In2O3 : Sn n‐type silicon heterojunction solar cell

Abstract: We present results concerning In2O3 (tin‐doped) n‐type silicon heterojunction solar cell. The transparent and conductive In2O3 : Sn layer was made using a very simple, cheap, and quick method. Conversion efficiency up to 10% is reported. Typical parameters under AM1 simulated sunlight are open‐circuit photovoltage Voc=500 mV, short‐circuit photocurrent Isc=32 mA cm−2, and fill factors around 0.6–0.65.

Limits on the yield of photochemical solar energy conversion

Abstract: Entropy and unavoidable irreversibility place a limit on the efficiency of photochemical solar energy conversion which is substantially lower than that placed by the first law of thermodynamics alone. Shockley and Queisser’s ’’detailed balance limit’’ on the efficiency of p‐n‐junction photovoltaic devices is a special case of this general thermodynamic limit on the efficiency of all quantum‐utilizing solar energy converters. For a single photochemical system operating at 20 °C in sunlight not attenuated by the atmosphere, this efficiency cannot exceed 29%. Under the same conditions, the efficiency of a solar converter composed of two photochemical systems can reach 41%.

Method for producing solar energy panels by automation

Abstract: A solar cell panel is fabricated by photoetching a pattern of collector grid systems with appropriate interconnections and bus bar tabs into a glass or plastic sheet. These regions are then filled with a first, thin conductive metal film followed by a layer of a mixed metal oxide, such as InAsO x or InSnO x . The multiplicity of solar cells are bonded between the protective sheet at the sites of the collector grid systems and a back electrode substrate by conductive metal filled epoxy to complete the fabrication of an integrated solar panel.

Directionally controlled array of solar power units

Abstract: A directionally controlled array of solar power units includes a supporting frame having conduits for flow of hot and cold water to each of the units supported on the frame, and each unit includes a solar cell which directly converts solar energy into electrical energy, the solar energy being concentrated on the cells by lenses. The solar cells are electrically connected for desired use of the electrical energy produced thereby, and the hot and cold water conduits are connected with the cells for flow of cold water in heat exchange relationship with the cells to cool the cells and heat the water and the hot water is available for work. Thermocouples and controls are connected with the units for moving the units to keep them pointed at the sun to thus utilize maximum energy therefrom throughout daylight hours.

Conversion of solar to electrical energy

Abstract: Solar energy is collected by a concave mirror and directed onto a body located within a container which is lined with solar cells. The heated body radiates energy to the solar cells. The solar cells convert a portion of such radiated energy to electricity. Another portion is converted to heat which is removed by a heat exchanger. A third portion of the radiated energy which is not absorbed by the solar cells or their support structure is reflected back to the radiating body to help maintain its temperature.

Solar energy window

Abstract: An energy absorbing venetian blind type device for generating electricity,roviding heat, and serving as a sun shade. A plurality of slats covered with an array of photovoltaic cells are enclosed between two panes of glass of a window housing. A heat removal system using forced air cools the photovoltaic cells and collects heat for heating purposes elsewhere. The electricity generated by the photovoltaic cells is collected for immediate use or stored in storage batteries for later use.

Stable Semiconductor Liquid Junction Cell with 9 Percent Solar-to-Electrical Conversion Efficiency.

Abstract: The semiconductor liquid junction cell n- GaAs/0.8 M K 2 Se-0.1 M K 2 Se 2 - 1 M KOH/C has been shown to attain 9 percent photovoltaic power conversion efficiency in sunlight. Accelerated tests under 3100°K light sources of several solar intensities indicate very low photocorrosion currents and high output stability.

Solar collector system

Abstract: An improved solar collector system includes a moveable surface to receive solar radiation. The moveable collector surface is supported by at least one load bearing universal joint. The movement of the collector surface is accomplished by a hydraulic actuated tracking system to enable the collector surface to be oriented toward the sun to achieve maximum solar energy recovery. The hydraulic actuated tracking system includes at least two hydraulic cylinders and pistons whereby the primary piston and cylinder control the position of the secondary piston and cylinder which, in turn, control the orientation of the collector surface.

Design considerations for high‐intensity solar cells

Abstract: The factors affecting the efficiency of a solar cell change when the solar cell is subjected to concentrated sunlight. In this paper, we examine the effects of high solar intensities on Si and GaAs solar cells. It is shown that the current‐collection efficiency in Si solar cells increases at intermediate levels but may be reduced at very high solar intensities due to plasma recombination. Methods to avoid the degradation of efficiency are suggested. The open‐circuit voltage increases with concentration, and the rate of increase is faster in Si than in GaAs. The fill factor also increases with concentration, again at a faster rate in Si than in GaAs. Consequently, the efficiency in a Si solar cell under concentration may increase faster than in a GaAs solar cell. The effect of increased temperature is also examined. It is shown that the increase in temperature degrades the efficiency of Si faster than in GaAs. Thermal analysis shows that it is possible to limit the temperature rise to a low value (25 °C) even under 1000 sun concentration by using simple designs of heat sinks. Consequently, there is no significant advantage of GaAs solar cells over Si solar cells for high‐intensity operation, except when high temperatures are desired for a complementary thermal system.

Water-borne rotating solar collecting and storage systems

Abstract: A water-borne solar energy collecting and converting system employing an azimuth-tracking, floating platform equipped with reflectors and associated thermal collector tubes.

Apparatus for converting light energy into electrical energy

Abstract: An apparatus for the conversion of light energy into electrical energy, byhich solar energy may be converted into electrical energy effectively and cheaply. The invention further relates to fluorescent centers (light concentrators) which consist of thin layers of transparent solid or liquid materials with embedded fluorescent centers and which in conjunction with solar cells serve to convert solar energy into electrical energy.