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GEOTHERMAL POWER. Though underground reservoirs of steam and water have long been tapped in Iceland, New Zealand, Italy and Japan, the only large geothermal enterprise in the U.S. is a steam field known as the Geysers in California's Sonoma County. There, steam from deep in the earth drives turbogenerators that produce some 302,000 kw. of electricity, roughly 40% of San Francisco's total requirements.
A greater challenge to scientists lies in finding ways of utilizing the earth's internal heat in the vast areas that are relatively barren of subterranean water. One proposal, under test by the AEC's Los Alamos Scientific Laboratory, involves sinking two side-by-side holes deep into the earth until they reach hot basement rock (approximately 1,000° F.). Then by pumping cold water into one hole, the scientists hope to extract steam from the other. Project Director Morton Smith reports that test borings to a depth of only 2,500 ft. (v. the final goal of 7,500 ft.) already have produced significant heating. Battelle Memorial Institute is proposing a similar experiment in Montana.
Indeed, the U.S.'s potential geothermal resources are so rich that a National Science Foundation report recently estimated they could generate the equivalent of today's total U.S. electrical output by the year 2000.
SOLAR ENERGY. Rooftop solar stoves, used to heat water, are found in Australia, Israel and Japan as well as in some areas of the U.S. Scientists now want to convert sunlight into electricity —a much more difficult task. One technique, proposed by Aden and Marjorie Meinel, a man-and-wife team of scientists at the University of Arizona, involves spreading a "solar farm," consisting of piping containing a mixture of chemicals, over 25 sq. mi. of desert. Heated by the sun, the mix would be used to make steam, which would power turbines capable of producing some 1,000 megawatts of electricity.
WINDS AND TIDES. Though the earth's winds are too irregular to serve as a major power source, Marine Engineer William E. Heronemus figures that they could still be helpful. He suggests building high windmills out in the ocean on floating platforms, where they could generate the electrical power necessary to distill and break down sea water to obtain hydrogen for fuel cells. The old idea of tidal power is also getting new attention. By harnessing the daily rise and fall of the tides (average: 27 ft.) in the Rance River estuary in Brittany, the French are producing some 240 million watts of electricity. In North America, most of the promising tidal sites, like the Bay of Fundy between Maine and Canada, are located so far from potential users in large population centers that much of the cheap electricity would be dissipated in transmission lines before it reached them.