APPENDIX XI-A Terrestrial Solar Power Terrestrial solar plants generally fall into catagories of thermal, photovoltaic, wind-powered, or ocean thermal gradient. Numerous other designs have been considered fo*' the transformation of solar energy into electrical energy. Many devices have been built and proven workable, although often impractical. A few small systems have been developed to a level that comparisons with conventional systems can be reasonably estimated. Also, several large systems have been built into pilot plants for similar comparisons. These large solar plants such as the Soviet Union's Solar Technical Laboratory (Ref. 1) near the Turkish border, the University of Genoa's facility in Italy and the Solar Energy Laboratory at Odeillo, France have been operational for sufficient periods so that operational data is available. Another large pilot plant has been designed by The Martin-Marietta for location in central Arizona. A prototype to this is currently under construction at Sandia Labs, New Mexico. Those system designs which appear to have the greatest potential for large total capacity electrical power generation are being comparatively analyzed by the Jet Propulsion Laboratory (JPL) for the NASA Office of Energy Programs (Ref. 2). A more comprehensive analysis by JPL and others is summarized for each of the terrestrial solar power plant catagories. Basically solar thermal-electric power plants are classified as central receiver or distributed collector types. a. The central receiver plant uses large mirrors or arrays of many mirrors with tracking mechanisms (heliostats) so that the solar energy is reflected onto a centrally located receiver. This allows large concentrations of energy at the receiver for producing a high temperature carrier fluid. Obviously, mirror arrangement, size and type (flat or focusing) provide a variety of variables for optimizing the collector field. Similarily, the type of tracking mechanisms and the design of the receivers, heat exchangers, storage facility, turbine/generator sets and heat rejection systems suggest a detailed tradeoff analysis. b. The distributed collectors generally use parabolic dish collector surfaces which reflect and focus the solar energy with the assistance of tracking mechanisms onto individual receivers. The receivers can be coupled in parallel to produce large quantities of high temperature transport fluid (generally steam). However, a small heat engine such as a Brayton cycle engine can be located in the focal area for immediate mechanical to electrical energy conversion. Distributed collectors offer numerous variations as suggested by their intended function, including the generation of large quantities of electrical energy. James 0. Rippey Urban Systems Project Office
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