Google said Tuesday it has invested $10.25 million to develop geothermal-energy technology aimed at extracting steam deep inside the earth to generate more electricity.

The search giant's investment arm, Google.org, has committed $6.25 million to AltaRock Energy, $4 million to Potter Drilling and $489,521 to the Southern Methodist University Geothermal Lab.

Google.org is spending the money to advance enhanced geothermal systems – also known as EGS – which refers to the process of drilling deep wells and cracking hot rocks miles underneath the earth and by injecting water into the wells. Production wells are drilled nearby to reclaim the hot water and extract the heat to drive electricity-generating turbines.

The process has the potential to greatly expand geothermal-energy development in areas without an abundant supply of naturally occurring steam and hot water underneath the Earth's surface.

In a comprehensive review of the U.S. geothermal-energy potential, a team led by the Massachusetts Institute of Technology and funded by the U.S. Department of Energy found that EGS technology could enable the country to produce 2,000 times the energy the United States used in 2005.

With improvements to the EGS technology, the country could produce more than 100 gigawatts of new capacity from geothermal sources by 2050, if the government and industry are willing to spend $1 billion in research and development over 15 years, according to the review.

EGS is a concept that scientists have been exploring since the 1970s. Companies such as Calpine Corp. (NYSE: CPN) have explored process in their natural geothermal fields, and the U.S. Department of Energy also has funded research in this area.

The United States already is the world's leading producer of geothermal energy, reaching 2,960 megawatts in capacity in seven states including California, Alaska, Hawaii and Idaho, according to an Earth Policy Institute report released Tuesday. California alone has 2,555 megawatts of geothermal capacity and generates 5 percent of the state's electricity from the steam fields.

Other countries with active geothermal development activities include Italy and Iceland. Iceland gets 27 percent of its electricity from turning heat into energy.

One of the companies funded by Google.org, AltaRock, has attracted a lot of attention from other investors as well (see AltaRock Breaks New Ground with Geothermal Power).

The Google.org investment is part of a $26.25 million round that AltaRock announced Tuesday. Other investors include Khosla Ventures, Kleiner Perkins Caufield & Byers, Advanced Technology Ventures and Vulcan Capital.

AltaRock, based in Sausalito, Calif., plans to use the money to develop and demonstrate its EGS technology. The funding came from existing investors as well as new additions, including Advanced Technology Ventures and Vulcan Capital.

Redwood City, Calif.-based Potter Drilling, which was founded in 2004, is developing new ways to drill deep wells to mine the heat. In addition to Google.org, the company has also received funding from MIT.

The Southern Methodist University Geothermal Lab plans to use the new fund from Google.org to study the distribution and mapping of geothermal energy sources in North America. 

Google.org has been funding renewable energy and electric car companies as part of its effort to promote alternative energy developments aiming to produce renewable electricity for less than coal-fired power plants (see Googling GreentechGoogle Leaves Out Clean Diesel, Hydrogen, Google.org Director: 'Technology Can Solve Climate Change' and Google Heats Up eSolar with $10M). 

It recently announced investments in electric-carmaker Aptera Motors and car-battery maker ActaCell (see Aptera Scores $24M to Produce Electric Ride and Move to Greener Cars Accelerates).