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Renewable energy advocates are looking to geothermal sources like this plant in Calipatria, Calif., to provide electricity to help California meet its goal of generating 33 percent of its power from renewable sources by 2020. But some conventional geothermal sites are, quite literally, running out of steam.
Renewable energy advocates are looking to geothermal sources like this plant in Calipatria, Calif., to provide electricity to help California meet its goal of generating 33 percent of its power from renewable sources by 2020. But some conventional geothermal sites are, quite literally, running out of steam. David McNew/Getty Images
Fourth of five stories on renewable energy in California
Geothermal plants rely on steam from deep below the surface to turn turbines to generate electricity. Plants at The Geysers geothermal field in California are "always on," unlike wind and solar, and they have a low carbon footprint.
Geothermal plants rely on steam from deep below the surface to turn turbines to generate electricity. Plants at The Geysers geothermal field in California are "always on," unlike wind and solar, and they have a low carbon footprint. Craig Miller/KQED
Right below your feet is enough potential clean energy to keep the whole country humming with electricity for 30,000 years, according to Department of Energy calculations. And this geothermal energy could play a big role in California as the state strives to reach an ambitious clean energy target by 2020.
But there is a catch: We have to get to it.
Running Out Of Steam
About two hours north of San Francisco, atop a ridge crisscrossed with pipes, is the world's biggest field for producing geothermal energy: The Geysers. Wandering around at The Geysers is sort of like hiking across the top of a tea kettle — pipelines hiss with steam pressure tapped from far below the surface, and the steam drives turbines to generate electricity.
In California, geothermal energy plants like this one provide more than twice as much renewable energy as wind and solar combined.
"The pot of gold, if you will, is that we have a huge renewable energy resource that produces base-load electrical power, which is what geothermal does," says Jim Turner, of AltaRock Energy, a geothermal company. "Unlike solar, where you have to have the sun shining, or wind where you have to have the wind blowing, geothermal is basically running all the time."
The trouble is that after several decades, some conventional geothermal sites are literally running out of steam.
AltaRock Energy used a 175-foot drilling rig for its now-defunct demonstration well in California. The well was abandoned due to unstable geology beneath the surface.
AltaRock Energy used a 175-foot drilling rig for its now-defunct demonstration well in California. The well was abandoned due to unstable geology beneath the surface. Craig Miller/KQED
A New Approach
So AltaRock was trying out a new technology to boost the output by drilling a hole 10,000 feet down to where the Earth's natural radiation heats the rock to about 500 degrees. This "enhanced" geothermal process forces water from the surface into those spaces, releasing more steam than would naturally work its way up.
"At its root, it's hot rocks," says John Geesman, who co-chairs the American Council on Renewable Energy. "The challenge is a technological one, and that is harvesting that resource in an economic and environmentally acceptable fashion," he says.
But there is a minor public relations issue: Building geothermal facilities has been known to cause earthquakes — small ones, at least. A series of them shook a small town when a similar kind of work was tried in Switzerland.
"Think of it as a sponge — a big wet sponge," says David Oppenheimer, a geologist with the U.S. Geological Survey, who was part of a federal review of the seismic risk. "That's the Earth's crust." And when sponges dry, they shrink.
Oppenheimer explains: "[The Earth has] all these little tiny fractures, and then [geothermal companies] come in with their wells — their steam wells or their injection wells — and start taking out heat, and they start taking out water. The area is contracting, and these fractures are moving. So, you have the conditions for small earthquakes, but big earthquakes are rather unlikely."
NPR and member station KQED are exploring California's ambitious plans to generate one-third of its electricity from renewable sources by 2020.
The Department of Energy agreed with Oppenheimer that AltaRock's plans didn't pose a significant earthquake risk.
"You know, there's no source of energy that I'm aware of that is completely benign and, in this case, this is actually a pretty attractive renewable energy resource," Oppenheimer says.
Full Steam Ahead?
But you still have to get at it. AltaRock eventually gave up on its California well when the bore hole kept collapsing. So it moved on to a new site in Oregon. Still, geothermal technology is attracting money from top venture capital firms and even Google, which has invested in AltaRock.
"Enhanced geothermal — where you can access heat virtually anywhere on the planet by drilling deeply — is scalable," says Bill Weihl, Google's green energy czar. "So, it could satisfy potentially a very large fraction of our energy needs."
That won't happen right away, though — 80 percent of the nation's geothermal energy is still generated in California, but federal stimulus money is driving more than 100 projects across the U.S.