Showing papers on "Solar energy published in 1975"

Optical and thermal properties of compound parabolic concentrators

Abstract: Compound Parabolic Concentrators (CPC) are relevant for solar energy collection because they achieve the highest possible concentration for any acceptance angle (tracking requirement). The convective and radiative heat transfer through a CPC are calculated, and formulas for evaluating the performance of solar collectors based on the CPC principle are presented. A simple analytic technique for calculating the average number of reflections for radiation passing through a CPC is developed; this is useful for computing optical losses. In most practical applications, a CPC will be truncated because a large portion of the reflector area can be eliminated without seriously reducing the concentration. The effects of this truncation are described explicitly. The paper includes many numerical examples, displayed in tables and graphs, which should be helpful in designing CPC solar collectors.

Solar energy collector

Abstract: A solar energy collector for collecting, concentrating, and utilizing solar energy, including a target for transferring solar energy into another useable energy form and a reflector positioned to increase the amount of solar energy reaching the target and prevent solar energy from escaping around the target, the target including in its preferred form a transparent envelope and a heat pipe containing a heat transfer fluid, the heat pipe having an evaporator portion disposed within the transparent envelope and an emergent condenser portion with a flange forming a dry thermal interface with a manifold for conducting heat energy directly from the heat pipe to the manifold.

Efficient CuInSe2/CdS solar cells

Abstract: We report the preparation of a CuInSe2/CdS heterojunction solar cell having a solar power conversion efficiency of 12% measured on a clear day in New Jersey (∼92‐mW/cm2 solar intensity).

Radiant energy collection

Abstract: Disclosed are non-imaging systems and devices for collection and concentration of electromagnetic energy and particularly solar energy including one or more longitudinally-extending, generally trough-shaped bodies having curving inner reflective walls for concentration of energy from a relatively large entrance aperture toward a relatively small exit aperture. Solar energy concentrators of the invention include energy traps and collect and concentrate substantial amounts of direct solar energy, even at solstice, without substantial diurnal tracking.

Simple thermal decomposition reactions for storage of solar thermal energy

Abstract: Simple thermal decomposition reactions have been investigated for the purpose of solar thermal energy storage. Ten criteria regarding the thermodynamics and kinetics of the reaction and the physical properties of the components of the reaction have been established. One particular reaction, the decomposition of ammonium hydrogen sulfate, has been evaluated in a preliminary manner and appears to satisfy all of the established criteria. The efficiency of storage is high and the decomposition occurs in the vicinity of 500°C. Other compounds such as ammonium halides, alkali and alkaline earth metal hydroxides, carbonates, sulfates and oxides have also been examined.

Solar cells with concentrators

Abstract: The invention provides a unique arrangement for cooling solar cells that are associated with collectors for collecting solar radiation and concentrating the same on the solar cells.The solar energy concentrators are each characterized by having a chamber with a solar radiation transmissive entrance wall, sidewalls adapted to concentrate solar radiation, one or more solar cells disposed in each chamber, and means for passing a dielectric, transparent cooling fluid through each chamber. The cooling fluid has an index of refraction which promotes solar energy concentration onto the solar cells in addition to that provided by the sidewalls.

Thin film coatings in solar−thermal power systems

Abstract: The applications and requirements for thin film coatings in solar−thermal power systems are reviewed. The substantial impact of selective absorber coatings and antireflection coatings on both flat plate and concentrating type solar collectors is covered. The results of durability life tests on a high−temperature stable, vacuum−evaporated absorber coating consisting of layers of Al2O3−Mo−Al2O3 are reported. This coating was unaffected by 500 h at 930°C. Other tests included thermal cycling, thermal shock, ultraviolet irradiation, and solar wind simulation. An electroplated solar absorber coating for low−temperature applications (<200°C) has been developed which has a solar absorption of 0.96 and an infrared emittance of 0.07 at 100°C. A chemically etched antireflection coating for glass has been investigated. Solar transmission of 0.97 is possible with this low−cost technique.

A new concept for solar energy thermal conversion

Abstract: A material has been developed which allows a new approach to be made to the conversion of solar energy to heat. It consists of a dense array of metal whiskers grown with spacings of a few wavelengths of visible light. The material selected has low emissivity, and achieves significant optical absorption by trapping the light by a geometric maze effect. We have deomonstrated that absorption of normal incidence light is greater than 98% from 0.5 to 40‐μm wavelengths, and hemispherical emissivity at 550 °C can be made less than 0.26. Since surfaces can be made of a single refractory element, such as W, high‐temperature solar conversion (550 °C) should be maintained with good surface stability.

Electrochemical aspects of solar energy conversion

Abstract: Current research and development work in solar energy utilization is very briefly reviewed. Attention is drawn to the possible use of photoelectrochemical effects to convert solar energy directly to electric power or synthetic fuel. Photoelectrochemical cells that have been proposed for this purpose are classified into three types, and a detailed description of their mode of action is given. The solar spectrum at the earth's surface and terrestrial receipts of solar energy are discussed. The factors that limit the power conversion efficiency of photoelectrochemical cells are described, and a brief reference is made to the thermodynamics of photoelectric transducers. Some work that, although not directly related to solar energy conversion, is of possible relevance, is summarized: the topics covered are the photosensitization of processes at semiconductor electrodes, pigment films on metal electrodes, and the primary processes of energy and charge transfer in natural and artificial photosynthetic membranes.

Solar energy conversion

Abstract: Solar energy conversion is provided by a structure formed of a plurality of photovoltaic sources. An electrolyte wets the sources. Upon exposure to light the photovoltaic sources cause a current to flow in the electrolyte producing an electrochemical reaction. The products of this reaction may then be collected and stored. In a preferred embodiment the electrolyte is an aqueous solution of hydrogen iodide, and the hydrogen produced by the electrochemical reaction may be stored, burned as a fuel or used in a fuel cell to produce electrical energy.

Apparatus for enhancing the output of photovoltaic solar cells

Abstract: An array of photovoltaic cells and a parabolic concentrator for concentrating solar energy onto the cells. A watertight chamber including a solar energy pervious window adjacent the focus of the parabolic concentrator. The solar cell array is disposed within the chamber in alignment with the window. A quantity of water disposed in the chamber, the quantity being sufficient to absorb heat energy so as to limit the temperature rise of the solar cell array during periods of solar energy impingement thereon. The watertight chamber has sufficient external surface area that the heat energy stored therein is transferred away during non-solar energy producing periods of the diurnal cycle.

High efficiency converter of solar energy to electricity

Abstract: Apparatus is disclosed which permits the use of a large proportion of the solar spectrum in the coversion of solar energy to electricity by means of photovoltaic cells. The apparatus comprises a collecting element which concentrates the incident radiation, a collimating element which forms the concentrated incident radiation into a beam of parallel photons, a spectral separation element, such as a prism, prism plate or diffraction grating which spectrally separates the solar radiation in the collimated beam and a plurality of photovoltaic cells disposed in the separated spectrum, the energy gap of the cells being matched to the energy of the photons in that portion of the spectrum in which the cells are located.

p−InP/n−CdS solar cells and photovoltaic detectors

Abstract: We have prepared p−InP/n−CdS heterodiode photovoltaic detectors with a uniform quantum efficiency of ∼70% for wavelengths between 550 and 910 nm. On a cloudy day in New Jersey, (53 mW/cm2) solar power conversion efficiencies of 12.5% have been measured on cells provided with antireflection coatings.

Solar energy converter with waste heat engine

Abstract: A solar energy converter uses gallium arsenide photovoltaic cells to convert light to direct current. Optical concentrators reduce the needed area of cells. Gallium arsenide retains high conversion efficiency up to several hundred degrees, so the waste heat may be used to produce mechanical power in a Rankine cycle engine.

Solar heating/cooling system

Abstract: A heliothermal heating and cooling system of the type using a heat transport fluid such as water is disclosed The energy collector comprises an assembly of individual solar collector panel modules in a series/parallel configuration and function to heat water flowing therethrough Each solar collector panel includes a pair of stepped headers respectively disposed at its input and output portions and which function to reduce water flow resistance therethrough The input and output headers communicate with an insulated water storage tank by way of return and supply lines, respectively A pump is provided in the return line to circulate the water through the system upon receipt of a command signal The storage tank communicates with a thermal energy utilization device and includes an integral, internal expansion chamber to accomodate expansion of the water The storage tank is stratified by means of baffles, and the strata are interconnected by a selector valve under the control of a differential temperature detector thereby to assure that the hottest available water is presented to the utilization deviceThe danger of freezing is avoided and the need for anti-freeze additives or solutions is eliminated by means of a vent line which connects the expansion chamber at the top of the storage tank to the top of the energy collector assembly and functions to drain the energy collector assembly of its water charge when the pump is de-energized

GaAs concentrator solar cell

Abstract: For terrestrial applications, the figure of merit for photovoltaic solar energy conversion devices is watts output per dollar of cost. AlGaAs/GaAs heterojunction cells have a very favorable watts per dollar figure of merit when used at high values of sunlight concentration. An experimental 1/2−in.−diam cell was operated in air mass 1.4 sunlight with an output power density of 4.52 W/cm2 at an effective concentration of 312 suns with a power conversion efficiency of 17.5%. The same cell was operated at 200 °C with an output power density of 3.45 W/cm2 at a 14% efficiency. The efficiency of the cell was 23% with a fill factor of 0.85 at a lower concentration ratio which is obtainable using simple concentrator schemes.

Energy and Resources: A plan is outlined according to which solar and wind energy would supply Denmark's needs by the year 2050.

Abstract: Two possible futures for the industrial world may be distinguished: (i) Large amounts of low-cost energy become available and the more energy-intensive methods for extracting resources from lowergrade deposits continue to sustain industrial expansion until either the environmental impact becomes unacceptable or ultimate limits, such as climate disruptions, put an end to such growth. (ii) The cost of nonrenewable energy resources continue to rise, but a fixed amount of energy from continuous sources may be utilized at constant cost. In this case a lower production level may be set by the amount of energy that is available from renewable sources, and society may thus have to be reshaped with energy economization in focus. If it is possible to choose between these two alternatives, the choice should be based on a discussion of the pros and cons of each one, and in particular on the desirability of having to process an increasing fraction of the earth9s crust in search of raw materials in order to maintain growth as long as possible. However, the availability, of the first option is far from certain and it thus seems reasonable to plan for the second alternative. I have tried to propose such a plan for a small, homogeneous geographical region, namely Denmark. The ceiling on the consumption of energy from continuous sources is chosen in accordance with the criterion of not having to convert a major part of the land area to energy-collecting systems. The proposed annual average energy consumption of 19 gigawatts by the year 2050 corresponds to solar energy collecting panels (in use only 50 percent of the time) with an area of roughly 180 square kilometers and a windmill swept area of about 150 square kilometers. These (vertical) areas constitute less than 1 percent of the total land area. The selection of solar or wind energy for different applications has been based on known technology and may be subject to adjustments. The project has been shown to be economically feasible according to estimates of the cost of various alternatives during the 25-year depreciation period adopted. However, the initial cost per energy unit produced is higher than that for most of the alternatives, so that action is not expected to be taken immediately as a result of purely private initiative. In a public economic evaluation, other factors must be considered in addition to the cost of energy per kilowatt-hour. At present, Denmark has over 10 percent of its labor force out of employment and a substantial deficit on its balance of payments, so that an early start on the solar and wind energy project, based on national industry, would have additional payoffs compared with energy systems based on imported technology or imported fuels. Several factories that are now being closed down as a result of the economic crisis could be adapted to the production of parts for solar or wind power systems, and the building industry, badly hit by unemployment, would receive legitimate work.

Solar energy heat transfer system

Abstract: A heat transfer system for the heating of water by solar energy. The apparatus is especially suitable for heating large quantities of water by small temperature increments by circulating the water in repeated cycles in a thin layer between two thin flexible sheets of a dark colored panel. The apparatus includes one or more large panels disposed on a sloping surface exposed to the sun. A pumping means supplies a continuous supply of water to be warmed to the upper edge of the panel. A distributor pipe, evenly distributes the water along the top edge of the panel where it flows over a member for spreading the water evenly over the entire surface area of the inside of the panel. A collector pipe collects the water at the bottom edge of the panel and a return piping system returns the warmed water to the pool of water.

Combined high density solar panels and vertical wind turbines

Abstract: The combined high density solar panels and vertical wind turbines consist of multiple solar panels with closely spaced solar cells on both sides which are supported by an open framework and vertical posts. The adoption of an elevated, rooftop solar panel array, supported by vertical posts makes the basic structure attractive for the inclusion of multiple vertical wind turbines, as a supplementary power source. This combined natural power conversion arrangement is intended for mounting on the flat roofs of city buildings and other similar flat, limited area sites. Each solar panel is pivoted within the open framework to follow the sun's excursion relative to the earth, and the solar cells on the panel underside receive the solar energy by way of thin edge reflectors secured to both sides of the solar panels, for a high density exposure configuration. A washing spray provision is included for the panel array, to keep the panels clean and operation at optimum efficiencies.

Solar power system

Abstract: A method and apparatus for use of solar energy. The method and apparatus has the advantage and benefit of providing for use of all collected solar energy, whether or not there is an immediate need in the home for heating. Solar energy is also used for cooling a home or existing building structure via utilization of a heat pump system. The apparatus comprises in combination a direct boil solar collector which boils a refrigerant therein, a Rankine cycle engine for converting heat energy transferred to said refrigerant to kinetic energy, a generator, a heat pump system, and means connected to the Rankine cycle to selectively transfer said kinetic energy from the Rankine engine to the generator or the heat pump. Excess energy not utilized for heating or cooling the home system is returned to a utility power grid for a credit for the home owner and immediate redistribution by the utility to other users.

Silicon solar cells for high concentration applications

Abstract: The use of solar concentrators can significantly reduce the cost of solar energy conversion, provided that the photovoltaic cells can be operated at high efficiencies under high illumination conditions. This paper describes the design, fabrication, and results of testing a cell with interdigitated p+and n+fingers on the unilluminated side of the solar cell. This design significantly reduces the problems of series resistance, contact grid shadowing, and voltage saturation which limit the performance of conventionally designed solar cells at high illumination intensities. The performance of such a cell at illumination intensities up to 22 watts/cm2is also presented.

Solar energy collector

Abstract: An infrared solar energy collector is disclosed. The collector comprises a heat absorber which in a first embodiment is a tube through which a heat transfer fluid is circulated. The heat absorber is disposed within a larger glass tube. In a modified embodiment, the heat absorber is in the form of a heat pipe which conducts heat to a heat transfer fluid circulated through a manifold. A wick carrying a volatile fluid may also surround the heat pipe. Absorbed heat evaporates the fluid which is in turn condensed on the cooler manifold. Either the entire interior of the glass tube surrounding the heat absorber is under reduced pressure, or an annular region between the surrounding glass tube and a second, larger diameter surrounding glass tube is under reduced pressure. An energy director such as a reflector within the enclosing glass tube directs solar energy on the heat absorber. The relative positions between the energy director and the heat absorber are changed progressively during the course of each day to enable the maximum utilization of solar energy.