The renewable energy industries, such as windmills and solar electric cells, are still emerging from a gawky adolescence - growing fast, beginning to be taken seriously, but still uncertain of their own futures.
The crowning uncertainty remains the future of federal tax credits for investors in renewable-energy projects.
Although the industries are maturing quickly, and finding increasing acceptance by banks, venture capitalists, the stock market, and the business mainstream, ''it has been a roller-coaster ride,'' says solar stock analyst Martin Enowitz of Energy Investment Research.
As the field gathers here this week at the annual Renewable Energy Technologies Symposium and International Exposition, there is an undeniable boom going on, as well as a shakeout.
The solar industries in particular, Mr. Enowitz says, ''got bad press and deservedly so'' in past years. Rebate schemes, unstable companies, and management hype were bad for the industry's image. Now, some of the foremost solar-cell companies have become glamour stocks, though many have taken a beating in the last six months.
The future is ambiguous. Few doubt that the renewable-energy industries, taken together, will grow much faster than the American economy at large. Yet if the solar tax credits are discontinued, as the White House has proposed (the bill now sits in joint committee), most of these industries will be hard pressed to survive.
''If you could sit in board rooms with the chairmen of these companies, you would understand why they're diversifying and getting into other industries,'' says Enowitz.
The general view here is that most of these young businesses need several more years of tax shelter before they can compete for investment dollars with more established, mature industries.
But the strong outfits among the renewables are emerging from the pack and appear to be heading toward financial independence.
The most robust - even frenetic - of the renewable-energy fields has been wind farming, as the erection of gigantic propellers with Volkswagen-size turbines has come to be called. During 1983, the power capacity of installed wind machines tripled, almost all the increase taking place in California. This pace is not likely to abate through 1985.
Photovoltaics (solar electricity) is a more worldwide market. The number of solar cells made and shipped doubled in the past year, although the pace may slow this year. The industry is at a point of decision between several major variations in the cell technology.
In both wind and photovoltaics, the market share of American products is declining. Americans build about three-quarters of the world's windmills, but the sleek, high-performance American machines are still generally less reliable than windmills from Denmark and some other Northern European countries.
In 1978, 85 percent of the world's solar cells were American. In 1983, the US share had fallen to 63 percent. These figures, supplied by the United States Export Council for Renewable Energy, are rough, but indicate the growing competition Americans face from Western Europeans and, especially, the Japanese.
Foreign markets in Southern Europe and the third world hold great potential for renewable technologies, but for a young industry these are tough markets to tap. ''The United States has the best technology around, but we really don't know what to do with it when we leave the country,'' says Thomas Mayfield, chairman of the Export Council. ''We're competing with experts who have their government's support.''
Without tax credits, he adds, ''the only business we're going to have is international.'' Yet no industry can survive internationally without a strong domestic base, he says.