ENGINEERS seeking new ways to provide clean, renewable electric power quite literally take their inspiration from on high - the sun. And after decades of often-intermittent research, two of the main strategies for converting sunshine to electricity seem close to application by utilities. Wind-powered generation: Thomas Gray, executive director of the American Wind Energy Association, says the design of wind turbines has matured to the point where he thinks the technology ``is in position to make a significant contribution'' on a world scale.
Its development within the United States is currently on hold, because of withdrawal of federal tax credits that made its introduction commercially attractive. Nevertheless, Mr. Gray says, there are many areas around the world where wind power would be practical today. Its use is more a question of marketing than of technology. It is, he explains, ``a question of taking an industry from ground zero and building it into an international business.''
Photovoltaics (solar cells): For several years, optimists have claimed that this technology has developed to a point where its use by utilities could be commercially viable by the mid 1990s. Now, says John Cummings of the utility-sponsored Electric Power Research Institute, there's been enough progress for even a ``technological conservative like me'' to share that vision.
He cautions that there's still a lot to learn, including the basic physics of some of the photovoltaic (PV) devices. Nevertheless, he calls the successful operation of two pilot units in California ``good news.'' He forecasts that, if the technology continues to develop smoothly, and if the price of oil shoots back up to $30 a barrel, commercially competitive PV power ``could be available in the early 1990s in the sunny [US] Southwest.''
Utilities like PV generation because it is clean and reliable, and they can install it quickly in small increments as needed, unlike conventional units. They don't have to make a commitment to a billion-dollar, 1,000-megawatt unit that won't generate revenue for over a decade. PV generation can be added in units of 10s or a few hundred megawatts and begin returning revenue within about a year. As for being ``on'' only when the sun shines, utilities have other types of units and energy-storage capacity which can take up that slack. The PV generators add peak power when it's needed.
This fits neatly with the needs of California utilities. No new large nuclear or fossil-fuel plants are expected to be built in that state in the foreseeable future. Yet some new capacity is needed to meet peak demands during hot, sunny hours when air conditioners run and irrigation units pump.
It's no accident that the world's biggest PV pilot plants are in California.
Dr. Cummings referred specifically to units built and operated by Arco Solar. Lugo Station, on the high desert near Hesperia, Calif., is a 1-megawatt unit built in 1982. It feeds electricity to Southern California Edison's grid. The other generator, at 2,000 feet on the Carrisa Plain between San Luis Obispo and Bakersfield, Calif., has been providing something like 6.5 megawatts of peak power for the Pacific Gas & Electric grid for about three years.
Cummings says these plants show that PV generators can perform reliably. Now the challenge is to get the cost of the power down to a level comparable to electricity supplied conventionally. That means improving efficiency. He explains that, specifically, utilities need a PV cell with 25 percent or better efficiency that can be mass produced, and can be built into a power station with an overall conversion efficiency of sunshine to electricity of about 20 percent.
This is the goal that Cummings thinks could be reached within a decade. But he warns that a great deal of research, especially on the basic materials used to build the PV cells, is still needed. Fortunately, such research has wide application beyond developing cells for baseline power. Many electronic applications will benefit. Thus there is considerable support for the research from private companies as well as governments. ``Japan,'' Cummings observes, ``is pouring a fortune into it.'' Even the low-level support the Reagan administration gives to solar power favors PV research.
But withdrawal of that support has hurt other areas of solar-power development in the US. For example, progress of solar thermal power has slowed to a crawl. This is power production in which an array of mirrors focuses sunshine on a central collector to heat a working fluid that, in turn, raises steam to run a turbo-electric generator.
The most celebrated such federally sponsored project is Solar One - the ``power tower'' outside Barstow, Calif. The four-year-old facility uses 1,818 giant sun-tracking mirrors to heat a collector atop a 300-foot tower. This 10-megawatt unit, operated by Southern California Edison, has done its job of demonstrating the technical feasibility of a design that could be scaled up 10 or more times. Unfortunately, Cummings notes, federal support was withdrawn. The utility industry is unwilling unilaterally to put up the $500 million or so needed for the next scaled-up phase.
Cummings agrees with Gray that wind power, which has worked successfully in California, is ready for substantial use, in the sense that some good wind-turbine designs are available. American installations generated 1.2-billion kilowatt-hours of electricity in 1986, according to Gray. While that's small - equivalent only to about 2 million barrels of oil - it's twice what wind power provided in 1985. Thus the industry has begun to grow.
But both Gray and Cummings note that loss of tax credits has at least temporarily stymied wind-power development in the US. The hope, Cummings says, is that a few of the turbinemakers can survive until the next energy shortage.
Last in a three-part series. Part 1 (``Soviets still count on `the peaceful atom''') ran Monday and Part 2 (``Are new reactor designs the answer?'') on Tuesday.