FIRST came electronic calculators and wristwatches with photovoltaic cells, which convert sunlight to electricity. Now lights for walkways and radios and tape players are solar powered, as are gadgets that keep boats and car batteries charged. For the rich - and the brave - there are solar systems that power a house. Producing electricity from sunlight, once the domain of the National Aeronautics and Space Administration and other space pioneers, is now finding earthly applications.
``The average American can expect solar electricity to become an integral part of his day-to-day life over the next decade,'' predicts Christopher Pope, a spokesman for Solarex Corporation.
For more than 15 years, photovoltaics has been an article of faith at Solarex, a subsidiary of oil giant Amoco Corporation. Back in the 1970s, after the Arab oil embargo, it helped plant the seeds of this technology, nurtured it along, and now seems poised to lead the industry ahead.
John Corsi, president and chief executive of the company, based in Rockville, Md., is among the true believers who predict that, if costs continue to tumble, photovoltaics could become a multibillion-dollar industry over the next decade.
``There is every reason to believe in the growth of the photovoltaic market,'' he says. ``Over the next 15 years, fossil fuels will become more scarce and expensive. Environmental concerns will continue to drive the use of solar electricity as well as other renewables.''
Right now, solar's share of the overall energy market is rising in specialty applications. The photovoltaics industry, however, stands at a crossroads. Sales are going up somewhat, but the industry as whole is not yet profitable. And over the last few years several oil companies have threatened to abandon the market.
Industry sources say that the companies have just lost patience with the technology.
``What has to happen over the next few years is that new markets have to materialize, and new products developed for the industry to maintain its momentum,'' observes Edgar DeMeo, manager of the solar power program at the Electric Power Research Institute in Palo Alto, Calif., a nonprofit organization funded by the utility industry.
Concern is also mounting over proposed cutbacks in federal funding, and there is concern that Japan and West Germany could eventually dominate the market.
Today, Solarex systems are common throughout the third world, where the cells power irrigation pumps and charge the batteries that run television sets and radios where there is no electricity, and run refrigerators for remote health clinics. The company has enlisted and won the support of such agencies as the World Bank, United States Agency for International Development, and the Organization of American States.
While the third world has been fertile ground for this technology, the US market has been clouded over by the concern over expense. The major hurdle firms in the industry still have to overcome is public perception that solar power is more expensive than conventional energy forms - and a risky, unsure method at that.
As solar power producers bring down prices and apply their products to new markets, that perception will change, Mr. Corsi says. It costs about $8 a watt to power many photovoltaic products. But to serve the ultimate user - the bulk utility power market - total system costs need to come down about $2 a watt, says Mr. DeMeo.
``This is likely to happen over the next 10 years,'' he says, ``as the markets for near-term higher-value applications expand, and as production costs come down.''
Meanwhile, Solarex is branching much further afield, into other solar-powered consumer products. ``The industry itself is finding dozens of new applications every year,'' says Mr. Pope.
The next generation of solar technology - what industry officials call the ``mainstream'' - could find some mass generation of electricity, according to Pope. ``It's still three to five years off,'' he says, ``but we have utilities and large manufacturing firms that are interested.''
In fact, a 50 megawatt power plant is being constructed near Los Angeles to generate energy for 25,000 homes.
The real potential of solar power lies with direct competition with traditional means of electrical generation - perhaps as an off-grid supplement, or replacement, to electrical power on existing grids. This is the future for photovoltaics, as Corsi sees it. It could prevent, for example, brownouts and shortages in areas like Long Island, he says.