How underground 'hot rocks' could power America’s future

Could hot rocks miles below the earth’s surface be the “killer app” of the energy industry?

Google thinks so. It’s investing more than $10 million to develop new technology that would make this subterranean resource a widespread, economically viable competitor to fossil fuels.

Geothermal heat could meet 10 percent of America’s energy needs by mid-century, according to the US Department of Energy. What’s more, it would not generate the climate-warming carbon emissions associated with fossil fuels.

Once tapped, a geothermal system would stay online for centuries. Unlike wind and solar, it would be a “base load” energy source, available 24 hours a day, 365 days a year.

That all sounds great – but of course there’s a catch. A geothermal well costs millions of dollars to drill and drilling is the only way to determine if a location has the right kind of hot rock. The result: With only a trickle of federal aid allotted to developing the resource, geothermal is growing slowly.

That may change under the Obama administration, which has pledged strong support for renewable energy.

“If sufficient [research and development] funding were invested in the next 20 years or so, as much as 10 or 20 percent of the electricity in the United States could come from geothermal,” says Robert Neilson, who manages the Renewable Energy and Power Technologies Department at the US Department of Energy’s Idaho National Laboratory.

The US already produces more geothermal electricity than any country in the world. In California, it accounts for nearly 5 percent of total electrical capacity. But these traditional geothermal plants require three things: hot rock formations near the surface, water to take the heat out of the rock and bring it to the surface, and fractures in the rock to allow the hot water to circulate.

Most known locations with all these qualities are found in the western US and are already being tapped.
The possibility of enhanced geothermal systems (EGS), however, have reenergized the movement. These systems would use technology to either fracture the rock or inject needed water. If EGS can surmount the technical and cost hurdles, many more places, including the eastern and central US, suddenly would be candidates for geothermal plants.

“EGS could be the ‘killer app’ of the energy world,” said Dan Reicher, director of climate and energy initiatives for Google.org, announcing Google funding for EGS research last August. “It has the potential to deliver vast quantities of power 24/7 and be captured nearly anywhere on the planet. And it would be a perfect complement to intermittent sources like solar and wind.”

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