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Hot rocks could help meet US energy needs

January 23, 2007 By Lucy Odling-Smee This article courtesy of Nature News.

Get more out of geothermal, experts advise.

A modest investment in geothermal technology could allow the United States to harness 10% of its electricity-generating capacity from the hot bowels of the Earth by 2050, a new study says.

The United States is the world's biggest producer of geothermal energy, but interest in it has remained low the resource makes up less than 1 percent of the country's electricity supply. That's partly because people have assumed that good geothermal spots are too few and far between for it to make a major impact at the national level.

"The federal government hasn't supported broad national assessments of Earth-based resources since the late 1970s," says Jefferson Tester, a chemical engineer at the Massachusetts Institute of Technology in Cambridge, and head of the 18-member panel that prepared the new report.

The basic idea behind geothermal energy is simple. Water forced through fractured rock deep underground picks up heat before coming up to the surface. The heat is then extracted the hot water or steam can be used to run electric generators before the water heads back down again to the depths to be re-heated.

The US Department of Energy commissioned the study to establish the potential costs and payoffs of pursuing advanced geothermal technologies on a much wider scale than currently used. That includes establishing new drilling sites, expanding existing reservoirs, and making use of depleted oil and gas wells.

"We want to emulate in a whole lot of systems what nature has done for us already in a few isolated spots around the world," says Tester. In the United States, the best sites are located in the tectonically active western states, where rock heated by volcanic activity lies close to the surface.

Long-term investment

Using data collected from existing geothermal projects in the United States, Australia, Japan and Europe, as well as from oil and gas projects, the team put a price tag on what it would take for geothermal to become a major player in the US electricity market. A combined private and public investment of about $800 million to $1 billion in the first 15 years, the group estimated, could make a significant difference by 2050.

That scales pretty well compared with the costs of other energy sources: "One clean-coal plant costs about a billion dollars," notes Tester.

Among the report's recommendations is long-term support from the federal government, including building on national and local policies that encourage geothermal development.

"There are considerable technical challenges to overcome," says engineer Chuck Kutscher of the National Renewable Energy Laboratory (NREL) in Golden, Colorado, who was not involved in the report. "But whether geothermal energy becomes more important will depend largely on how the nation addresses the climate-change crisis."

Stanley Bull, an energy expert also at NREL, notes that developers of other renewable energy sources, such as wind and solar power, get tax credits that are not attractive to investors in geothermal plants, which take much longer to set up. "You never know by the time you get the plant built whether the production tax credit will still be in place," he says.

But to some, geothermal energy is looking like an increasingly attractive option for the United States, given concerns about carbon dioxide emissions from fossil-fuel plants, the fluctuating price of oil and gas, and energy security concerns. "As part of an aggressive approach to resolve the climate-change issue," says Kutcher, "geothermal energy could be a major player."

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