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Power Tower. New York Telephone's central exchange in Cutchogue, N.Y., gets up to 70% of its heat from the 170 solar collectors that cover its roof. Sunlight is expected to provide up to one-third of the energy requirements of the new Norris Cotton Federal Building in Manchester, N.H. The sun also warms most of the hot water for a 16-story high-rise apartment for the elderly in Brookline, Mass.
The practicality of photovoltaic cells —thin sandwiches of silicon or metals that generate current when struck by light—has been amply demonstrated by the space program. Solar cells power satellites that orbit the earth and drive the instruments on the Viking orbiters currently circling Mars. They are used on earth to power digital watches, remote weather stations and navigation buoys at sea—and may some day save gasoline. Researchers at the University of Florida have outfitted an experimental Volkswagen bus with an electric motor that runs on batteries charged by current generated by solar cells.
At Odeillo, in the Pyrenees, French officials have constructed a parabolic mirror half the size of a football field (TIME, May 18, 1970) that focuses the sun's rays on a single point. The solar furnace has already been used to melt tungsten, which must be heated to nearly 6,000° F. before it liquefies, and has also been used to test boilers for a power-generating plant. The Energy Research and Development Administration (ERDA) is planning to fund an experimental program in which 100 acres of mirrors would direct sunlight at a "tower of power," where the sun's rays would be concentrated and used to heat water in a boiler, thus generating steam for a turbine. ERDA believes such an arrangement could generate up to 10,000 kw., or enough to supply a town of 5,000 to 10,000 people with electricity.
Engineers at NASA have gone even further, embracing an idea originally proposed by Peter Glaser of the Cambridge, Mass., consulting firm Arthur D. Little, Inc. He suggested mounting huge arrays of solar cells on a space satellite that would be exposed to sunlight for almost 24 hours a day. The cells would generate electricity that could be beamed to a ground receiver in the form of microwaves, then transformed back into electrical current for transmission to power customers.
Sun Rights. The major obstacles to any of these far-out schemes are more economic than technological. Harnessing solar energy is currently far more costly than burning fossil fuels. ERDA estimates that tower-supplied electricity would cost from six to ten times more than electric power generated from fossil fuels. Electricity from solar cells, which costs from 50 to 100 times as much as that produced by more conventional means, is still far too costly for anything except specialized applications. Even home heat tends to be uneconomical for widespread use. A solar heating system adds from $5,000 to $10,000 to the cost of a new house, an investment that could take from ten to 20 years to amortize at current fuel prices. Says an ERDA official simply: "The economics are not good."