Showing papers on "Photovoltaic thermal hybrid solar collector published in 1995"

Solar concentrator for heat and electricity

Abstract: A solar concentrator for producing usable power as heat and/or electricity uses a self-steering heliostat 1502 to concentrate solar radiation 1509 onto an absorbing surface such as, or including, a solar cell array 1511 capable of absorbing power from the radiation, meanwhile removing heat (such as from long-wave infra-red radiation or resistive losses) from the surface with fluid heat transfer means 1503, 1504, then making effective use of that low-grade heat. Thus the solar cell array is kept relatively cool and a larger proportion of the solar energy incident on the reflector unit is used. The invention uses electricity 1506 from the solar cells to move a transporting fluid through a heat exchanger 1504. Excess electricity may be available for local storage or use 1510, or feeding 1512 to the power distribution grid. Applications include warming swimming pools 1501, heating hot-water supplies using excess electricity, or warming, lighting and ventilating open spaces.

Heat loss from an open cavity

Abstract: Cavity type receivers are used extensively in concentrating solar thermal energy collecting systems. The Solar Total Energy Project (STEP) in Shenandoah, Georgia is a large scale field test for the collection of solar thermal energy. The STEP experiment consists of a large field array of solar collectors used to supplement the process steam, cooling and other electrical power requirements of an adjacent knitwear manufacturing facility. The purpose of the tests, conducted for this study, was to isolate and quantify the radiative, conductive, and convective components of total heat loss, and to determine the effects of operating temperature, receiver angle, and aperture size on cavity heat loss. An analytical model for radiative heat loss was developed and compared with two other methods used to determine radiative heat loss. A proposed convective heat loss correlation, including effects of aperture size, receiver operating temperature, and receiver angle is presented. The resulting data is a source to evaluate the STEP measurements.

Optical Waveguide Solar Energy System for Lunar Materials Processing

Abstract: This paper discusses results of our work on development of the Optical Waveguide (OW) Solar Energy System for Lunar Materials Processing. In the OW system as shown, solar radiation is collected by the concentrator which transfers the concentrated solar radiation to the OW transmission line consisting of low-loss optical fibers. The OW line transmits the solar radiation to the thermal reactor of the lunar materials processing plant. The feature of the OW system are: (1) Highly concentrated solar radiation (up to 104 suns) can be transmitted via flexible OW lines directly into the thermal reactor for materials processing: (2) Solar radiation intensity or spectra can be tailored to specific materials processing steps; (3) Provide solar energy to locations or inside of enclosures that would not otherwise have an access to solar energy; and (4) The system can be modularized and can be easily transported to and deployed at the lunar base.

Roof module having an integral solar energy concentrator

Abstract: The present invention relates to a roof module having an integral solar energy concentrator. The present modules can be combined to form a weathertight roof with an integral solar concentrator. Radiant solar energy can be collected from this modular roof using reflected solar energy collectors, among other solar energy concentrating or energy transferring elements. The present invention results in a lower weight and easier to install system for placing solar energy concentrators atop a structure, and thus, lower the cost collecting radiant solar energy from atop a building or roofed structure.

Solar battery cell, a solar battery module, and a solar battery module group

Abstract: A solar battery cell, solar battery module, and solar battery module group achieving high product value by enabling the display of surface patterns without reducing the power generating efficiency of the solar battery cells are provided. The direction and/or reflectance of reflected light incident to the surface of the solar battery cell are varied by controlling the distribution of the rough surface structure imparted to the solar battery cell surface. The direction or reflectance of reflected light incident to the surface of the solar battery cell is changed in part depending upon the part of the semiconductor solar battery cell surface to which the light is incident. Semiconductor solar battery cells with high product value can therefore be achieved because patterns with strong visual impact can be displayed and easily recognized without reducing the power generation efficiency of the solar battery cell.

Low Cost and Efficient Photovoltaic Conversion by Nanocrystalline Solar Cells

Abstract: Solar cells are expected to provide environmentally friendly solutions to the worlds energy supply problem. Learning from the concepts used by green plants we have developed a molecular photovoltaic device whose overall efficiency for AM 1.5 solar light to electricity has already attained 10 %. The system is based on the sensitization of nanocrystalline oxide films by transition metal charge transfer sensitizers. In analogy to photosynthesis, the chemical solar cell achieves the separation of the light absorption and charge carrier transport processes. Extraordinary yields for the conversion of incident photons into electric current are obtained, exceeding 90% for transition metal complexes within the wave-length range of their absorption band. The use of molten salt electrolytes together with coordination complexes of ruthenium as sensitizers has endowed these cells with a remarkable stability making practical applications feasible. Quite aside from their intrinsic merits as photovoltaic device, the mesoscopic oxide semiconductor films developed in our laboratory offer attractive possibilities for a number Of Other applications. Thus, the first example of a briefly discussed.

Compact solar energy collector

Abstract: Compact solar energy collector that incorporates into the same housing the collector (6) itself and an accumulator (5) in the shape of a parallelepipedon and divided by walls to better withstand water pressure, being then complemented with the remaining conventional elements such as pump (1), differential thermostat, purges and valves, being the housing fitted with a transparent cover (3) and a heat exchanger inside (13) that is then connected to the pump (1) and to the collector (6) and at the other end to the valve (11) and to the lip (10) being the rest of the housing internally covered with insulating material (4,14).

Cost reducing potential of photovoltaic concentration

Abstract: Plausible costs of photovoltaic power plants of concentration are presented. Costs are based as much as possible on the recent experience of solar thermal plants. Efficiencies, on the existing world experience of PV power plants. The result is that the costs of concentrating photovoltaic plants should be of 0.08 ECUs/ kWh, about 1/3 of that of flat module plants, and of the same order of magnitude, even lower, than those attributed to solar thermal plants of present technology. For the future, high concentration systems based on Si or tandem cells seem to be the most promising, also in the range of costs of the advanced solar thermal plants.

Solar energy collecting system

Abstract: A solar energy collecting system includes a water tank and a solar collector and a pump for pumping water from the water tank to the solar collector. A sensor is arranged close to the solar collector. A CPU is connected to the pump and the temperature sensor in order to circulate the water according to the water temperature at the inlet of the solar collector. The water can be circulated in a fast speed when at noon. The water may be heated with a lengthened heating time and may be heated with a smaller temperature difference so as to effectively collect solar energy.

Summary of the final design for the 10 MWe Solar Two central receiver project

Abstract: The 10 MWe Solar One central receiver pilot plant used a water/steam receiver coupled directly to the turbine-generator, and an oil/rock thermal storage system from which the turbogenerator was operated at reduced steam conditions during cloudy weather and at night. The Solar Two project replaces the Solar One receiver and thermal storage systems with nitrate salt receiver, thermal storage, and steam generation systems. The existing collector system and electric power generation systems are retained, with some modifications, to hold project costs to a minimum. The paper presents a summary of the plant final design.

Thermoelectric solar collector for heating purposes or electricity generation

Abstract: The solar collector includes thermo-electric units, e.g. thermogenerators (4), between absorbtion surfaces (3) and built into a heatable medium (5). The collector surfaces convert sun rays (1) into heat for e.g. domestic heating using thermo-generator components installed between the absorption surface and the medium to be warmed. The thermoelectric generators may be used to convert a part of the warm energy flow into electrical energy using the Seebeck effect. To increase the internal working temperature an isolated housing with a transparent cover (2) is used. The housing is evacuated to minimise heat loss to the surroundings.

The self-sufficient Solar House Freiburg

Abstract: The Frauhofer Institute for Solar Energy Systems has built a completely Self-Sufficient Solar House (SSSH) in Freiburg Germany. The entire energy demand for heating, domestic hot water, electricity and cooking is supplied by the sun. The combination of highly efficient solar systems with conventional means to save energy is the key to the successful operation of the house. Seasonal energy storage is accomplished by electrolysis of water and pressurized storage of hydrogen and oxygen. The energy for electricity and hydrogen generation is supplied by solar cells. Hydrogen can be reconverted to electricity with a fuel cell or used for cooking. It also serves as a back-up for low temperature heat. There are provisions for short-term storage of electricity and optimal routing of energy. The SSSH is occupied by a family. An intensive measurement program is being carried out. The data are used for the validation of the dynamic simulation calculations, which formed the basis for planning the SSSH.

Development of a 75-kW heat-pipe receiver for solar heat-engines

Abstract: A program is now underway to develop commercial power conversion systems that use parabolic dish mirrors in conjunction with Stirling engines to convert solar energy to electric power. In early prototypes, the solar concentrator focused light directly on the heater tubes of the Stirling engine. Liquid-metal heat-pipes are now being developed to transfer energy from the focus of the solar concentrator to the heater tubes of the engine. The dome-shaped heat-pipe receivers are approximately one-half meters in diameter and up to 77-kW of concentrated solar energy is delivered to the absorber surface. Over the past several years, Sandia National Laboratories, through the sponsorship of the Department of Energy, has conducted a major program to explore receiver designs and identify suitable wick materials. A high-flux bench-scale system has been developed to test candidate wick designs, and full-scale systems have been tested on an 11-meter test-bed solar concentrator. Procedures have also been developed in this program to measure the properties of wick materials, and an extensive data-base on wick materials for high temperature heat pipes has been developed. This paper provides an overview of the receiver development program and results from some of the many heat-pipe tests.

Amorphous silicon based solar cells and modules

Abstract: Hydrogenated amorphous silicon technology for solar module production is compared with the most advanced technologies for solar module production and the advantages of a-Si:H technology for low-cost production are described. The principle of a-Si:H solar cell operation is explained and the external characteristics which describe its performance are defined. The ways to improve open circuit voltage, short circuit current, fill factor, and stability are discussed. Multi-junction type of as solar cell, which can lead to higher efficiencies and stability compared with single junction solar cells, is described. The present status of a-Si:H solar cells performance is presented, paying attention to the difference betwen the initial stage of operation and a stabilized state. The results achieved at laboratory level are compared with the performance olcommercially available modules. The list of producers of a-Si:H based solar cells and modules is included.

Storing solar energy in salt

Abstract: This article describes the world`s largest power tower incorporating one of the newest commercial solar energy systems and being build in California`s Mojave Desert. The project -- sponsored by the Department of Energy (DOE) and a consortium of western utilities, municipalities, and associations -- is called Solar Two, and it will use molten salt to absorb solar energy and store that energy until it is needed to generate electricity. Construction will be completed on Solar Two in September. Solar thermal systems convert the sun`s rays into electricity by using a thousand or more dual-axis, sun-tracking mirrors, called heliostats, to focus optimum sunlight on the solar receiver of a power tower containing a working fluid. The fluid is heated to a desired temperature and sent to a storage facility. During periods of peak demand, the fluid is circulating through heat exchangers to generate steam used to drive a turbine.

Low intensity low temperature (LILT) measurements on new photovoltaic structures

Abstract: Past NASA missions to Mars, Jupiter and the outer planets were powered by radioisotope thermal generators (RTGs). Although these devices proved to be reliable, their high cost and highly toxic radioactive heat source has made them far less desirable for future planetary missions. This has resulted in a search for alternate energy sources, one of them being photovoltaics. In order to create a viable photovoltaic data base for planetary mission planners and cell designers, the authors have compiled low temperature low intensity (LILT) I-V data on single junction and multi-junction high efficiency solar cells. The cells tested here represent the latest photovoltaic technology. Using this LILT data to calculate dI{sub sc}/dT, dV{sub oc}/dT, dFF/dT, and also as a function of intensity, an accurate prediction of cell performance under the AM0 spectrum can be determined. When combined with Quantum efficiency at Low Temperature (QULT) data, one can further enhance the data by adding spectral variations to the measurements. This paper presents an overview of LILT measurements and is only intended to be used as a guideline for material selection and performance predictions. As single junction and multi-junction cell technologies emerge, new test data must be collected.

Low cost and efficient photovoltaic conversion by nanocrystalline solar cells

Abstract: The quality of human life depends to a large degree on the availability of energy sources. The present worldwide energy consumption already exceeds the level of 6000 gigawatt and is expected to further increase sharply. This implies enhanced depletion of fossil fuel reserves, leading to further aggravation of the environmental pollution. Adding to this the dangers arising from the accumulation of plutonium fission products from nuclear reactors, the quality of life on earth is threatened unless renewable energy resources can be quickly developed. Photovoltaic solar energy converters are expected to make important contributions to the identification of environmentally friendly solutions to the energy problem. One attractive strategy discussed in this paper is the development of systems that mimic natural photosynthesis in the conversion of solar energy for the fixation of carbon dioxide. We have developed a molecular photovoltaic device whose overall efficiency for solar energy conversion to electricity has already attained 10%. The system is based on the sensitization of nanocrystalline films by transition metal charge transfer sensitizers. In analogy to photosynthesis, the new chemical solar cell achieves the separation of the light absorption and charge carrier transport processes. Extraordinary yields exceeding 90% for the conversion of incident photons into electric current are obtained, in contrast to conventional photovoltaic cells which are not economical for base load utility electricity production. The low cost and ease of production of the new cell should benefit large-scale applications, in particular in underdeveloped or developing countries, which benefit from generous sunshine. Aside from its intrinsic merits as a photovoltaic device, nanocrystalline film development opens up a large number of additional avenues for energy storage ranging from intercalation batteries to the formation of chemical fuels. These systems will undoubtedly promote the acceptance of renewable energy technologies, not least by setting new standards of convenience and economy.