When most people think about solar energy, they picture photovoltaic panels on top of someones cabin in the woods. Thousands of homes are powered this way, and not just cabins (George W. Bushs Crawford ranch house, for one). But while were waiting for photovoltaics (PV) to become commercially viable, other solar technologies may be much closer.
"The problem with solar is how to get significant quantities of energy out of it," says Rich Ferguson, energy chair of Sierra Club California. Despite substantial improvements in PV cells, they remain extremely expensive, delivering electricity at about 30 cents a kilowatt. (Wind power, by comparison, is down to 4 cents a kilowatt, about the same as modern natural-gas plant.)
But theres more to solar power than PV. One of the most promising approaches to large-scale solar-energy production is called "solar thermal," in which huge arrays of mirrored, parabolic troughs focus sunbeams on central tubes, heating oil to 750 degrees to drive steam turbines. "If this country is going to get serious about solar power," says Ferguson, "its going to look more like this than PV."
Since 1985, solar thermal plants in Californias Mojave Desert have been generating 354 megawatts at a cost of about 15 cents a kilowatt-hour. The price could go much lower, supporters say, as more plants are built. "This is the most cost-effective form of solar energy today," says Gary Bailey, West Coast head of Duke Solar, which is seeking to build a 300- to 500-megawatt solar facility in the Mojave, and another in Nevada. The holdup, he says, is lack of demand. "We need long-term contracts."
While the solar trough is the most developed of alternative solar systems, two others are jockeying for position. One is the "power tower," in which thousands of heliostats, or movable mirrors, beam sunlight up to a central tower, powering steam turbines. Other innovators are working on a similar design powering the elusive "Stirling engine," a piston engine driven not by internal combustion but by heat from an outside sourcefor instance, by the sun.
Third on the solar smorgasbord is the dish system, in which parabolic mirrors focus sunlight onto a receiver (they look like satellite dishes) to run a Stirling engine. The technical challenge with this method is finding materials that can withstand temperatures well above 1,000 degrees.
Even so, enthusiasts insist that the main impediment to major advancements in solar energy is lack of political will. "Why do people always think in the short term?" grouses Dukes Bailey. "When you sign up a new natural-gas plant, you dont know how much gas is going to cost in ten years, or even if youll have a supply. But we have the only stable energy source there is; theres no fuel-cost escalation in the sun." Paul Rauber