The number of specialist hedge funds focused on clean technology is on the rise, according to a report from New Energy Finance.

The U.K.-based research firm reported Thursday that greentech-focused funds have at least $750 million under management today.

New Energy Finance expects at least 22 such funds will exist by the end of the summer, and said fund-of-fund managers predict the specialty hedge funds will number in the hundreds within a few years. The company did not say how many funds exist now.

Funds that invest in other funds focused on clean energy and the environment also are increasing, according to the firm. Six new funds of funds, which manage a total of about $300 million, have launched in 2007 and 2008, according to the report.

"Given climate change and energy security pressures, investment in clean energy is set to grow rapidly from the $148.4 billion figure reached worldwide in 2007," New Energy Finance CEO Michael Liebreich said in a written statement. "That gives big opportunities not just for long-only fund managers, but also for specialist long-short hedge funds looking to take advantage of valuation anomalies or aiming to reduce volatility for investors."