UPDATE 2-Google puts $10 mln into new geothermal technology

Enhanced geothermal systems that AltaRock is developing can work in a wider range of geographies than conventional geothermal ones, Google said.

"If you drill deep enough anywhere you can get to hot rock," Reicher said.

The key to keeping the cost of a project down, therefore, is to find hot rocks that lie close to the surface. Nevada has good geothermal resources, Reicher said, as do some Eastern states including West Virginia and Pennsylvania.

To help locate good geothermal resources, Google also announced a $489,521 grant for Southern Methodist University's Geothermal Lab to update geothermal mapping of North America.

Google is part of a $26.25 million round of funding AltaRock announced on Tuesday. Other investors include Microsoft Corp (MSFT.O) co-founder Paul Allen's investment firm, Vulcan Capital, and Silicon Valley venture capital firms Khosla Ventures, Kleiner Perkins Caufield & Byers and Advanced Technology Ventures.

Google's previous clean technology investments include $20 million for two solar thermal companies -- eSolar Inc and BrightSource Energy Inc, and $10 million to high-altitude wind company Makani Power Inec. (Editing by Gerald E. McCormick, Steve Orlofsky, Richard Chang)