The move is part of Google's effort to pump hundreds of millions of dollars into green energy sources, starting with solar thermal, high-altitude wind power and now, geothermal energy.
Heat from below the earth's surface could one day be a massive contributor to the nation's electricity supplies because it is available around the clock, Google said.
"It's 24-7, it's potentially developable all over the country, all over the world, and for all that we really do think it could be the 'killer app' of the energy world," Dan Reicher, Google's head of climate and energy initiatives, said in an interview. "Killer app" is a term used to describe revolutionary software.
That new "app," called enhanced geothermal systems, or EGS, improves upon the century-old technology of tapping geothermal energy from geysers, hot springs or volcanoes to generate electricity. With EGS, engineers drill their own geothermal outlets and pump in water to create steam to power a turbine.
The bulk of Google's first geothermal investment, $6.25 million, will help finance EGS company AltaRock Energy Inc of Sausalito, California. Other investors in the company include some of the top Silicon Valley venture capital firms.
About $4 million of Google's money will go to Potter Drilling Inc, a Redwood City, California company which has a hard rock drilling 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: Quote, Profile, Research) 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)