More and more worldwide venture funding pores into clean technologies with U.S. companies in California leading the way, according to the report released on Tuesday by the Clean tech Group, a San Francisco research and strategy firm.

As oil prices continue rocketing and global warming is on the rise, more companies look to solar energy, biofuels, advanced lighting and such for alternatives.

From April to June, venture investments around the globe in clean-tech reached 2 billion U.S. dollars, an all-time record, said the report.

That's up 58 percent from the same period in 2007 and 48 percent from the first three months of 2008, said Brian Fan, the group's senior director of research.

"We continue to see clean-tech attracting strong and growing amounts of venture capital despite economic head winds, despite other aspects of the economy hitting rough patches," he said.

The report tracked 96 investments made in North America, Europe, Israel, China and India. Of that 2 billion dollars, 74 percent went to U.S. companies, and 794 million dollars of it went to California companies. Information about specific investments in Bay Area companies was not available.

The firm added Chinese and Indian clean-tech investments for the first time this quarter, Fan said, but also included previous investments over the last eight years in those nations to its statistical analyses.

Big gainers in the most recent quarter were companies building utility-scale solar power plants and those working on second-generation biofuels, which produce fuels not from advertisement corn but from waste wood, grass clippings, garbage or even algae.

"This was a breakout quarter for algae," Fan said. Two companies, Sapphire Energy of San Diego and Green fuel Technologies of Cambridge, Mass., raised more than 80 million dollars for their efforts to turn algae into fuel.

The Cleantech Group also reported 4.2 billion dollars worth of merger and acquisition activity among clean-tech companies, and 4.4 billion dollars worth of clean-tech initial public offerings in the second quarter.

The Cleantech Group said Silicon Valley continues to be the leading source of investment into the various technologies in the segment. It identified four local venture firms -- Kleiner Perkins Caufield & Byers, Foundation Capital, Khosla Ventures and Draper Fisher Jurvetson -- among the top five investors.

Woeful news on the U.S. economy -- falling homes prices and car sales, the credit crunch, stock-market losses and rising unemployment -- hasn't hindered clean-tech investments.

"That's the nature of venture investing," Fan said.

The problems clean-tech companies are trying to solve, including replacing oil as the primary transportation fuel, replacing coal as the primary heating fuel and getting clean water and food to the world's 7 billion people are massive, Fan said. And they require large investments to solve, he said.