Showing papers on "Solar energy published in 1976"

Amorphous silicon solar cell

Abstract: Thin film solar cells, ∼1 μm thick, have been fabricated from amorphous silicon deposited from a glow discharge in silane. The cells were made in a p‐i‐n structure by using doping gases in the discharge. The best power conversion efficiency to date is 2.4% in AM‐1 sunlight. The maximum efficiency of thin‐film amorphous silicon solar cells is estimated to be ∼14–15%.

Correlation equation for hourly diffuse radiation on a horizontal surface

Abstract: This paper presents an analysis of hourly diffuse radiation on a horizontal surface and recommends an equation to determine the hourly ratio of diffuse-to-total radiation received in a horizontal surface. The results of the new correlation equation are compared with earlier equations with recommendations made as to its use with solar energy computer simulation programs.

Tungsten trioxide as a photoanode for a photoelectrochemical cell (PEC)

Abstract: THE PEC1 has acquired popularity among researchers in the past years, mainly because of its possible use in solar energy conversion2,3. The major problem at present is to find a semiconductor electrode with an optical band gap (written as just band gap below) small enough to allow it to absorb a reasonably large portion of the solar spectrum, and at the same time being stable against photocorrosion. We here report that WO3 meets these criteria although it is not very efficient at solar wavelengths.

Thin‐film CuInSe2/CdS heterojunction solar cells

Abstract: The fabrication procedures and characteristics of several thin‐film p‐CuInSe2/n‐CdS heterojunction solar cells are presented. Two modes of operation (illumination through CuInSe2 or through CdS) are discussed. Efficiencies in the range of 4–5% are reported, under 100 mW/cm2 tungsten‐halogen illumination for 1.2‐cm2 devices. Included are the spectral response and J‐V characteristics for these photovoltaic junctions.

Transparent heat mirrors for solar-energy applications.

Abstract: Transparent heat-mirror films, which transmit solar radiation but reflect ir thermal radiation, have potentially important applications in solar/thermal/electric conversion, solar heating, solar photovoltaic conversion, and window insulation. We have used rf sputtering to prepare two types of films: TiO2/Ag/TiO2 and Sn-doped In2O3. To characterize the properties of heat-mirror films for solar-energy collection, we define the parameters αeff, the effective solar absorptivity, and ∊eff, the effective ir emissivity. For our Sn-doped In2O3 films, αeff/∊eff is comparable to the values of α/∊ reported for the leading selective absorbers. Even higher values of αeff/∊eff are obtained for the TiO2/Ag/TiO2 films.

Natural Convection in Enclosed Spaces—A Review of Application to Solar Energy Collection

Abstract: A useful solar-thermal converter requires effective control of heat losses from the hot absorber to the cooler surroundings. Based upon the theory and some experimental measurements it is shown that the spacing between the tilted hot solar absorber and successive glass covers should be in the range 4 to 8 cm to assure minimum gap conductance. Poor choice of spacing can significantly affect thermal conversion efficiency, particularly when the efficiency is low or when selective black absorbers are used. Recommended data for gap Nusselt number are presented as a function of the Rayleigh number for the high aspect ratios of interest in solar collector designs. It is also shown that a rectangular cell structure placed over a solar absorber is an effective device to suppress natural convection, if designed with the proper cell spacing d, height to spacing ratio L/d and width to spacing ratio W/d needed to give a cell Rayleigh number less than the critical value.

Solar energy collection system

Abstract: A solar energy collection system is provided in which a parabolic trough is oriented by a drive mechanism to reflect the rays of the sun onto an energy collector located at the parabolic focus. The system is constructed to track the sun to maintain focusing of reflected solar radiation during daylight hours. A counterweight is employed in association with the drive mechanism to effectuate tracking and to maintain gravitational equilibrium of the reflector trough despite changes in elevation of the center of the gravity of the trough. Shock absorbers are provided which inhibit disorientation of the trough by gusts of wind, yet which allow the trough to track the sun. Coaxial construction of the solar energy collector with an evacuated sleeve of parabolic configuration positioned thereabout allows a heat collection medium to circulate in the collector, yet minimizes radiant heat loss. The trough is selectively inclined at an angle relative to the earth's surface in accordance with the latitude of the location of the trough and the azimuth of the sun above the earth's horizon.

Transparent heat-mirror

Abstract: Transparent heat-mirrors are disclosed which are comprised of composite films. These films include a discrete and continuous layer of metallic silver sandwiched between a transparent, outer, protective, anti-reflection layer and a transparent, phase-matching layer. This combination of layers is chosen to provide high solar transmission with minimum loss of thermal radiation. Transparent heat-mirrors are useful in the collection and trapping of solar energy, and in other applications where it is desired or necessary to have high infrared reflectivity with high solar transmission.

Solar energy collection

Abstract: Apparatus and methods for concentrating and collecting solar energy are disclosed. In accordance with the invention, solar energy is concentrated by economical refringent lenses or lens systems including fluid lenses and/or Fresnel-type lenses. The lenses concentrate the solar energy preferably along lines in continuous linear foci or in discrete foci at an elongated collector comprising one or more fluid-carrying conduits and one or more fluids therein. In one embodiment, a plurality of photoelectric cells are located in or on the collector along the linear foci or at the discrete foci and operate at increased efficiency with heat being removed by the collector. A first fluid in the collector is heated by the concentrated solar energy and in a preferred embodiment is used to heat a second fluid contiguous to the first fluid, the first fluid having a boiling point exceeding that of the second fluid. In a preferred embodiment, the first fluid is carried in an inner conduit while the second fluid is carried by an outer conduit which encloses the inner conduit and first fluid. Thus, the two fluids can be heated to different temperatures by a single concentrating system and used for different purposes. Additionally, the invention provides for the storage of energy using two fluids of different boiling points. Also disclosed are methods and fixed and portable apparatus for distilling water containing salt or other substances by evaporation of the water and condensation of the water vapor wherein preferably the heat of condensation is recovered. The invention also provides for assemblies of individual systems to form larger systems. The present invention provides heat from solar energy at a cost competitive with heat produced from fuels.

Solar absorptance and emittance properties of several solar coatings

Abstract: Solar absorptance αs and total hemispherical emittance et,H properties of two potential solar selective coating systems are reported. The first coating system studied is a semiconductor‐pigmented paint which consists of a high‐temperature silicone binder mixed with small particles of Ge, Si, or PbS. Although most of the paints have αs values above 0.90, all the paints suffer from high et,H values (∠0.70 to 0.90), which are shown to be due to the high emittance of the silicone binder itself. The second system studied is electroplated films of ’’black nickel’’ and a proprietary ’’black chrome.’’ Both αs and et,H values have been obtained as a function of the electroplating time and the substrate surface roughness. Increasing the plating time initially increases both αs and et,H; however, for long plating times, there is no improvement in αs, while et,H continues to increase. By increasing the surface roughness of nickel‐plated substrates, the solar absorptance can be increased while maintaining approximatel...

Solar Heating and Cooling.

Abstract: We have adequate theory and engineering capability to design, install, and use equipment for solar space and water heating. Energy can be delivered at costs that are competitive now with such high-cost energy sources as much fuel-generated, electrical resistance heating. The technology of heating is being improved through collector developments, improved materials, and studies of new ways to carry out the heating processes. Solar cooling is still in the experimental stage. Relatively few experiments have yielded information on solar operation of absorption coolers, on use of night sky radiation in locations with clear skies, on the combination of a solar-operated Rankine engine and a compression cooler, and on open cycle, humidification-dehumidification systems. Many more possibilities for exploration exist. Solar cooling may benefit from collector developments that permit energy delivery at higher temperatures and thus solar operation of additional kinds of cycles. Improved solar cooling capability can open up new applications of solar energy, particularly for larger buildings, and can result in markets for retrofitting existing buildings. Solar energy for buildings can, in the next decade, make a significant contribution to the national energy economy and to the pocketbooks of many individual users. very large-aggregate enterprises in manufacture, sale, and installation of solar energy equipment can result, which can involve a spectrum of large and small businesses. In our view, the technology is here or will soon be at hand; thus the basic decisions as to whether the United States uses this resource will be political in nature.

Packed Bed Thermal Storage Models for Solar Air Heating and Cooling Systems

Abstract: In order to simulate solar heating systems where air is the transfer fluid, an adequate model of the packed gravel bed energy store is required. One model of a packed bed thermal store can be obtained by solving the partial differential equations of the Schumann Model as described by Jakob (1957). However, when these equations are solved as part of a long term simulation, the computing costs become unacceptably high. This paper describes the development of a simple model, whose validity is demonstrated by comparing the long term behavior of a system incorporating both the complex and simplified packed bed models. (WDM)

Solar power plant

Abstract: The specification discloses a Solar Power Plant which utilizes a sun-tracking parabolic collector and a plurality of energy storage and conversion devices, all of which are operated under the control of a novel energy management system Allocation of energy to a particular storage component or to useful output is dependent upon the state of the system as well as the nature of the demand Outputted energy may also be recaptured and reallocated to minimize losses Efficiency at the component level is enhanced by the utilization of novel heat exchangers which effectuate complete conversion of the operating liquid to superheated gas

Photoelectrolysis of water with TiO2‐covered solar‐cell electrodes

Abstract: A TiO2–solar‐cell hybrid structure has been used successfully as the anode electrode in the photoelectrolysis of water. The TiO2 films have been fabricated by chemical vapor deposition. Conversion efficiency of solar energy of about 0.1% has been attained in the preliminary experiment.

Open‐circuit voltage of MIS silicon solar cells

Abstract: The open‐circuit voltage of MIS solar cells realized on n‐type silicon has been investigated. Chemically formed and evaporated SiOx layers have been used for the insulating film. The latter has given the best results on polished samples, since Voc reached 0.55V. The influence of different parameters like n or ΦBn are discussed.

High-intensity, solid-state-solar cell device

Abstract: A semiconductor solar cell capable of converting incident radiation to electrical energy at high efficiency includes a plurality of series-connected unit solar cells formed on a common wafer of semiconductor material. The unit solar cells each include a semiconductor substrate of one conductivity type and a p-n junction formed in the substrate. The light-receiving surface of the cell may have an opaque member thereon, and incident light is directed onto the portion of that surface not covered by the opaque member. A variety of embodiments illustrates the invention.

MIS solar cell—General theory and new experimental results for silicon

Abstract: The metal–thin‐insulator–semiconductor structure recently has been shown to have potential as a simple efficient solar cell. A general theory of these solar cells as well as experimental results for silicon devices optimized on the basis of this theory are described. The experimental devices have exceptionally good open‐circuit voltages. Under illumination resulting in a short‐circuit current density of 32 mA/cm2, an open‐circuit voltage of 618 mV and a fill factor of 0.6 were obtained.

Solar cell electric and heating system

Abstract: A system for converting solar energy into electric energy at reduced cost makes use of an array of light sensitive, voltage producing solar cells of the flat disc silicon type. To increase power, while using fewer costly cells, each cell of the array has a truncated conical shell mounted on legs at a spaced distance thereover, the shell having a mirror-like reflective inner surface. Thus, sunlight is received in the large end and reflected through the small end to the cell. A sealed, weather-tight enclosure for the array, has fluid inlets and outlets for producing heat, the heat conductive shells absorbing and radiating heat.

High intensity solar energy converter

Abstract: A photovoltaic energy converter for converting incident radiant energy, such as solar energy, to electrical energy. The converter comprises a cell formed from a plurality of integrally interconnected p-n junction-containing semiconductor wafers. The wafers are stacked end-to-end in the cell so that the respective junctions in each wafer are parallel to each other. The efficiency and performance of the cell is improved, particularly upon exposure to concentrated sunlight, by imposing various conditions on the cell fabrication and design. Improvements result, for example, by selecting a high resistivity semiconductor as the starting material in the fabrication of the cell, controlling the diffusion process to optimize the junction gradient and minimize the thickness of the base region in each wafer, orienting the wafers in the cell so that they are illuminated at a small angle relative to the plane of the respective junctions therein, and treating the exposed surfaces of the wafer to reduce reflectivity and surface recombination velocities.