Solar thermal was a leading investment play in 2Q 2008.

The global economy may be hurting, thanks to a popped real estate bubble in the United States and rising energy costs around the world, but investors aren’t shying away from cleantech. According to The Cleantech Group, venture capital investments during the second quarter of 2008 were higher than ever before. A full 75 percent of the investments made last quarter went to North American companies.

Cleantech investments in North America, Europe, China and India spiked to $2 billion for the first time last quarter. The previous record for venture capital investments in cleantech companies came during the third quarter of 2007, when investors pumped $1.8 billion into the space. The amount invested last quarter represents a 58 percent increase over the same period a year ago, and 48 percent over the first quarter of the year.

Companies working on second-generation biofuels raised money hand-over-fist last quarter, as first-generation biofuels continued to disappoint. Companies working on cellulosic ethanol and biofuels from algae raised $280 million. Cellulosic ethanol was the investment darling of the sector, accounting for $136 million of investments while $84 million went toward companies working with algae as a feedstock. The number was boosted thanks to industry darling Sapphire Energy, which brought in more than any other algae startup ever: $50 million last quarter alone, according to The Cleantech Group.

Solar thermal technology companies claimed their share of investments as well. They raised $278 million in capital. The Cleantech Group notes that year to date, solar thermal companies have raised more than half a billion dollars.

Nearly $1.5 billion was invested in U.S. companies during the second quarter, with California companies alone accounting for $794 million—about 37 percent of the global total.