Solar Sell

The sun rises in the West

It is not called the Golden State for nothing. California is becoming the nation's leading proving ground for solar energy, accounting for nearly half of all U.S. solar sales of $190 million last year. The state has plenty of sun and plenty of activists who see nonpolluting solar energy as the benign antidote to nuclear power. It also has a generous law-put through by Governor Jerry Brown--that allows 55% of solar costs, up to a maximum of $3,000, to be written off as a credit against state income taxes. The resulting demand has persuaded more than half of America's solar manufacturers, including Arco Solar, the well-bankrolled subsidiary of Atlantic Richfield, to locate their headquarters in the state.

Nearly 90% of all sales are for conventional thermal devices that use the sun's rays to heat rooftop water panels, which in turn heat swimming pools and home water systems. But the exciting side of the industry that is attracting the larger companies is photovoltaics--the direct conversion of sunlight into electricity. The theory is simple. A wafer-thin, 3-in. to 4-in. plate or "cell' that is sliced from a chemically treated silicon crystal will give off direct-current electricity when exposed to light. The amount that comes from each cell is minute, but many cells can be wired together in rooftop units to provide a maintenance-free, long-lasting, nonpolluting power source. During the day the cells simultaneously produce electricity and charge up batteries for nighttime use.

But even in California the science of photovoltaics is in its infancy, and the cells remain expensive and not very efficient; the 1,500 sq. ft. of units required to power a typical one-family home would cost at least $40,000. Electrical power is measured in the number of watts that can be generated from a single power source. The cost of building and maintaining a plant to generate a single watt is about $1 from a coal-powered utility and about $1.25 from a nuclear power plant. The cost of a watt from photovoltaic cells has come down from $22 in 1975 to between $8 and $10 today. The Department of Energy has set a goal of reducing the cost to $2 by 1982, to 50-c- by 1986 and to no more than 30-c- by 1990.

The Los Angeles department of water and power plans to build a 200-kw photovoltaic system that may provide the energy to run a power plant's cooling tower in suburban Sun Valley, Calif. If this project gets federal funding and goes through, it would be eight times larger than the biggest existing photovoltaic system. Up to now, such systems have generally been confined to remote and inaccessible locations where the costs of providing conventional power are prohibitive. For example, in California solar cells generate energy for Coast Guard buoys, rural water pumps, VHF telecommunications relay towers, automatic weather stations and even an Air Force radar station. In addition, Kansas oil wells use solar electricity to inhibit the rusting of metal; a remote Arizona Indian reservation gets its power from cells, and even the Saudi Arabian government plans to line its Jidda-Riyadh highway with 400 solar-powered emergency call boxes.

The efficiency of cells is also rising. Ten years ago, they could convert to electricity only 2% of the theoretical average 100 watts of the sun's energy that falls on a square foot of earth; now they can convert 16%. To intensify the sun's rays, the Los Angeles project would use parabolic and elliptical cells instead of flat ones. Arco Solar and other companies including Exxon, Mobil and Shell are working in intense rivalry and secrecy on such matters as improving storage batteries, finding better materials to substitute for silicon and even mass-producing flat "ribbons" of silicon to replace the present chunky and uneconomical crystals.

Even if breakthroughs are made, solar power probably will be able to provide no more than 5% of the nation's energy needs by the end of the century. But there is potential for more over the longer term, now that an increasing number of large companies are putting more effort and more money into research and development. Unlike conventional centralized power stations with their huge distribution networks, photovoltaic cells can be located where the demand is and, in time, can probably be mass-produced.

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