Biofuel, solar and windpower companies, have seen venture funding climb 58 percent, reaching nearly $2 billion in one quarter, USA Today reported.

"Interest in clean tech continues to show robust growth, despite the impact of economic headwinds and credit market restraints," said John Balbach, a managing partner at Cleantech Group of San Francisco, which tracked the funding data.

"Investors and entrepreneurs are making two big bets," Brian Fan, Cleantech's senior director of research told the newspaper. "How do we replace coal as the primary fuel for electricity generation, and how do we replace oil as the primary fuel for transportation?"

While companies such as SkyFuel and BrightSource Energy are constructing large-scale, solar power plants to run turbines, Fan estimated it would still take up to 15 years before mainstream investors accept clean tech energy companies.