Apr 29 2009

Enhanced Geothermal: A Promising Work in Progress

Posted by: Jonathan Marshall

A little-reported "well incident" this week in a remote part of Australia is a sobering reminder of the challenges facing the geothermal industry's next generation of technology.

Geodynamics Ltd., the largest publicly traded company in Australia focused on recovering goethermal energy by injecting water into hot granite rocks deep underground to create steam, acknowledged a breach of its first commercial-scale production well in the Cooper Basin in the southern part of the country.

The company says the crew responsible for commissioning the 1 MW plant is being "progressively demobilised" while experts (reportedly flown in from the United States) assess damage to the Habanero 3 well, which is 13,800 feet deep. Geodynamics offered no estimate of when operations would resume. 

Geodynamics is a leader in the field of enhanced geothermal technology, which holds tremendous promise as a source of renewable energy. A massive report issued by the Massachusetts Institute of Technology in 2007 estimated that it could affordably supply 10 percent of U.S. power needs within 50 years, at about the same low price as today's coal-fired plants.

Today's conventional plants, such as those located at The Geysers in Sonoma County (the world's largest geothermal field, with 850 MW of power capacity), use existing reservoirs of underground hot water or steam to drive turbines. Promising locations for new production including California's Imperial Valley, northern Nevada and the Oregon and Washington Cascades.

But if water can be injected from the surface, the main resource a developer needs is hot rocks, which exist almost everywhere on earth if you dig deep enough. Plants in The Geysers pioneered this concept by injecting treated effluent from nearby cities to supplement natural steam. The trick is finding rocks with the right characteristics to allow water to filter through them and heat up reliably.

Experts say that once the geologic and engineering challenges are worked out, so-called "enhanced geothermal" energy could become one of the 21st century's most promising resources.

"It brings an absolutely gigantic amount of power into the realm of economic feasibility," said Susan Petty, a former MIT scientist and chief technology officer of Sausalito-based AltaRock Energy, an enhanced geothermal energy firm. AltaRock Energy, which is funded in part by Google.org and the Department of Energy, has a major demonstration project in The Geysers area.

Paul Brophy, past president of the Geothermal Resources Council and a consulting geologist to one of the industry's leading drilling companies, agreed. "It would not be unreasonable to say the broad potential for geothermal is almost limitless," he told NEXT100. "Oil and gas wells go down 30,000 feet or more. You could drill down that far almost anywhere in the earth's crust and attain the sort of heat" necessary for geothermal power.

As it happens, however, most of the test wells in this country are being drilled in the West, where hot rocks lie closer to the surface, minimizing drilling costs.

Geothermal isn't the sexiest of renewable energy sources--it certainly can't compete with space solar power in that respect--but it's a proven workhorse. Unlike wind and solar power, it provides power around the clock, every day. It also has a much smaller footprint, Brophy noted, thus creating fewer environmental obstacles.

Around the world, geothermal supplies more than 10,000 MW of power. The United States is the leading producer, and California the leading state. Across the country, 126 new projects are under development--27 of them in California--with the potential to produce as much as 5,500 MW of new power, according to the Geothermal Energy Association.

PG&E played a major part in developing the industry, opening the first commercial geothermal power plant at The Geysers in 1960. The utility was required to divest its plants there in the late 1990s, but PG&E still purchases about 5 percent of its power from them, making geothermal the single largest source of renewable power in its portfolio.

Thanks to significant injections of new R&D money from the Department of Energy in just the past couple of years, the geothermal industry is enjoying a rebirth, with a focus on enhanced recovery techniques. In addition, the Obama administration's new stimulus program set aside $400 million for new geothermal development, a landmark commitment of government resources. "Research is progressing very rapidly," Brophy said.

But Geodynamics' setback is a reminder that enhanced geothermal is still more promise than reality. Some estimates put the cost of their wells at $12 million each, so the company can't afford too many mistakes.

But Brophy takes the news in stride. "When you are trying to do things for the first time, things will go wrong," he said. "We are still in the early stages of research and demonstration."

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