While still on the fringes of the energy mix, United States venture capital flowing into clean energy leapfrogged to more than $2.4 billion in 2006, well more than double that invested in 2005, and more than triple from 2004, according to Clean Edge, a research and consulting firm. The numbers are still small compared with the research budgets of the big oil companies, but the ascent of venture capital in renewable energy has reminded some Silicon Valley venture capitalists of the early flow of money into the Internet in the mid-1990s.

“Venture capital in energy has reached a critical mass,” said Daniel Yergin, the energy historian and consultant. “Enough is happening so that significant things will come out of this. With the same intent to do in energy what they did in biotech, they bring not only money and discipline, but they are results-oriented."

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“If the U.S. put 15 million acres of desert into algae production, we could produce enough volume of liquid fuels to get us off the Middle East oil addiction and give Iowa back to the songbirds,” said B. Gregory Mitchell, an algae research biologist at the University of California, San Diego. . .