POWERSAT - A POWER PLANT IN SYNCHRONOUS ORBIT BEAMING ENERGY TO EARTH A solar power plant in a geosynchronous orbit could collect solar energy at maximum efficiency. It would be illuminated over 99 percent of the time by sunlight unattenuated by Earth's atmosphere or weather (even on a clear day sunlight at ground level is only about 65 percent of its intensity above the atmosphere). In space, the collector can be aimed directly at the Sun, maximizing its effectiveness. A heat engine converter is shown. Sunlight would be concentrated by the collector into a cavity, providing heat for a set of helium gas turbines. The satellite's alternators would be driven by Brayton cycle turbines typical of present-day jet aircraft. But, unlike a jet's turbine which vents off fuel-heated air after it turns the engine's fan, the Powersat turbine would use the Sun as its only fuel and operates on a closed loop. Helium would be heated in the cavity, pass through the turbines, then flow through a space radiator where the helium's heat would be rejected. The helium then would return to the cavity to begin the cycle. Electric power is routed to a phased array RF generator where it is converted to a narrow microwave beam at 2450 Mhz by high-efficiency crossed-field amplifiers (amplitrons). The beam can be directed to any desired load point visible from the satellite, which appears stationary relative to Earth's surface. At the load point, the power beam is reconverted to D.C. electric power by a fixed receiving antenna about five miles in diameter. A grid interface converter changes the D.C. power to 60 Hz high voltage A.C. Satellites generating 2500 to 10,000 megawatts of useful output on the ground appear feasible. A modular approach can provide this range of capability with a standard satellite design. In space there are no site-peculiar design requirements; a standard satellite design can serve all locations. The helium turbine conversion system is but one approach; solar cell (photovoltaic) and thermionic conversion systems also should be investigated.
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