They follow the sun like giant sunflowers, shifting almost imperceptibly from dawn until dusk. Quietly and cleanly producing power, nearly 800 towering, computer-driven trackers stretch across the lonely Carrisa Plains, along State Highway 58 northeast of San Luis Obispo, California.

Spread across each tracker's Tapis blue face are thousands of photovoltaic cells, each one about the size of a playing card. The cells, made of chemically altered silicon, convert the area's abundant sunlight into thousands of kilowatts of electricity. At maximum output, each tracker can power roughly three houses. Run by Arco Solar, this is just one of several photovoltaic (PV) facilities in the West's sun-drenched locales, such as Phoenix and San Diego. And this month, an 86-acre research and development facility in Davis, California, will begin operation. Its purpose: to assess the cost-effectiveness and reliability of PV cells as major commercial sources of electricity.

Why this jolt of interest, when we seem to have changed our pre-oil embargo ways by cutting energy use significantly? (Consumption has inched up 2 to 3 percent a year since 1973; from the mid-'5Os until then, it rose about 7 percent annually.) Simple: PV cells are an environmentally sound source of energy. Once installed, the cells don't destroy land, deplete resources, or emit pollutants. They're also adaptable; the huge trackers are only one option smaller units can be installed on spare bits of land or on rooftops. And PV cells produce the most power where and when Westerners use it most: in hot, sunny locales, when air conditioners are cranked up high.

So why don't we all use PV power today? For the moment, it's too expensive. Most of us pay about 8 to 12 cents per kilowatt hour. PV power costs about three times that much right now. The goal of facilities such as those in Davis and San Luis Obispo is to find out how to cut the cost by at least 50 percent. Researchers predict that that will happen within 3 to 10 years. Though widespread use of large-scale sites is probably at least a decade away, PV power is already widely available. Right now you can buy PV cells to generate electricity in remote locations. Cells also power hand-held calculators, radios, outdoor lights, and marine, RV, and car batteries.