Sep 25 1974
From The Space Library
A helical rotary-screw expander that could be used to tap geothermal energy of hot aquifers under deserts for low-cost energy was described at a National Science Foundation conference at California Institute of Technology. The invention of Pasadena engineer Roger S. Sprankle was the first electrical power-generating system to use the entire amount of energy available in geothermally heated water and might reduce production costs 50%. Tested by Jet Propulsion Laboratory and Hydrothermal Power Co., the Sprankle system's rotary screws filtered impurities to make maximum use of the steady flow of pumped water. Once the geothermally heated water flowed through the screw expanders, the liquid dropped in pressure and temperature as water vaporized. The increasing mass flow of vapor turned rotors with an output shaft linked to an electric generator. (Caltech-JPL Release, 25 Sept 74)
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