When America's great economic machine begins to hum again, and to grow, where will the energy to run it come from?
One electric power expert says a significant amount, on the order of 2 to 3 percent, could be produced by solar installations and other ''renewable'' sources.
Despite reduced government support for development of such virtually inexhaustable energy sources, and some financial and technological problems, the US electric utility industry maintains its commitment to understanding these technologies and utilizing them as they become available, says Edgar DeMeo, manager of the solar power systems program of the Electric Power Research Institute (EPRI) in Palo Alto, Calif.
At the same time Mr. DeMeo cautions that fulfillment of the promise of solar and other alternative sources lies a decade or more in the future. He is concerned about a possible ''backlash,'' with people who were led to expect quick results deciding these energy sources are ''no good.''
But Mr. DeMeo's optimism about alternative energy sources is founded on fact. A report on solar energy activities in 1981, published in July 1982 under DeMeo's supervision, showed 236 utilities, public and private, across the US were involved in 943 projects involving development of solar heating and cooling , wind energy conversion, solar-thermal electric power, photovoltaics, biomass conversion, process heat, ocean thermal energy conversion, and general solar electric systems. The industry commitment to solar research and development increased by 12 percent between 1980 and 1981.
All figures for the EPRI's 1982 report on such projects are not yet in, but DeMeo says that overall figures - 235 utilities with 930 projects - indicate ''a level of activity comparable to 1981.'' He notes an increase in utilities' interest in photovoltaics. DeMeo adds, however, the process ''still requires significant research progress.''
Alternative energy projects are spread across the nation, but the areas with the most activity are the West, which had 398 projects in 1981, the Southeast, with 132, and the Northeast, with 104. Figures for 1982 will be about the same, DeMeo indicates.
California, rich in solar and geothermal resources, provides several significant examples of progress and problems in developing renewable energy sources.
Southern California Edison recently halted work on what would have been the first commercial-scale power plant in the US utilizing underground hot water when the California Public Utilities Commission ruled the company could not charge part of the facility's $147 million cost to its customers. The plant would produce enough electricity from briny hot water underlying much of the Imperial Valley to serve some 50,000 people. Although the project has been put on hold, the company is seeking other means of financing it.
Pacific Gas & Electric Company (PG&E), which serves most of central and northern California, has a geothermal complex at The Geysers in Sonoma County. It now produces more than 1 million kilwatts of electricity. That capacity was reached Dec. 17 when the 16th generating unit at The Geysers went ''on line.'' The power output of the thermal complex is 9 percent of PG&E's total capacity. The first Geysers generator began producing electricity in 1960; in 1973 the complex passed the Larderello project in Italy to become the world's largest geothermal plant.
PG&E marked another alternative-energy milestone Dec. 8 when it signed a contract with AeroTurbine Energy Corporation of Denver to build what it says will be the nation's largest windpower project on a 5,000-acre site in the rolling, windy hills of Solano County northeast of San Francisco. AeroTurbine will install 36 large wind turbines generating 3,500 kilowatts each. Modified versions of Boeing Aircraft Company's experimental MOD-2 wind turbines, each of the generators has a single 330-foot-long blade. The ''windfarm'' is expected to be turning out 411 million kilowatts of electricity annually by 1985. That is enough to serve 65,000 households, says PG&E. It would take 650,000 barrels of oil to generate that much power, according to the company.
The PUC ruling that affected Southern California Edison's hot-water power plant exemplifies regulatory situations that, from the industry point of view, impede progress in developing alternative energy systems. There is controversy nationwide over how much of the cost of new generating plants - conventional, nulcear, and other - can be passed on to customers in their monthly utility bills.
Also being debated, and litigated, is the matter of ''avoided cost'' - the amount utility companies must pay to producers of electricity from nonconventional sources, such as wind. Basically, that payment or credit to the owner of an alternative energy source is supposed to be the equivalent of what it would cost the electric company to generate the power at a convential power plant.
DeMeo cites a number of factors working against continued development of alternative energy sources - financing, ''moderation'' of the oil supply situation, the ''general poor state of the economy,'' and ''reduction of federal attention'' to the alternative energy field.
Despite such problems, which ''make it difficult to maintain momentum'' in the alternative energy field, he says ''corporate commitments to selected technologies are beginning to form.''
One of the most promising renewable sources is solar-thermal central receiver generation, he states. The bellwether of this effort is Southern California Edison's Solar One facility at Daggett, Calif., in the Mojave Desert. A cooperatove effort by Edison, the US Department of Energy, the Los Angeles Department of Water and Power, and the California Energy Commission, Solar One has an array of 1,818 computer-controlled heliostats that track the sun and reflect its rays onto a 300-foot ''power tower,'' where steam is produced to turn generator turbines.
Solar One generates 10 megawatts; DeMeo says that ''to advance the technology a big experiment is needed'' - one generating several times as much electricity. But the project would cost upwards of $200 million. ''Funding would be ''extremely difficult within the private sector,'' he declares, ''so a strong federal role is likely to be required.''