Tech: From the Ground Up

By Mark Anderson

Illustration by Thomas Fuchs

Humans have used heat from the earth for thousands of years. While early on we relied on hot springs for warmth and bathing, these days geothermal energy heats and cools homes and generates electricity. And with an influx of federal dollars, a new take on this renewable resource could eventually provide more power than nuclear energy supplies today.

In January, MIT released the first nationwide survey of the potential for enhanced geothermal systems (EGS)—manmade reservoirs that tap into energy stored in the earth’s crust. The report concludes that EGS is a vast, clean energy source. “In 50 years, we’ll be able to get 100,000 megawatts, economically. That’s enough for 100 million people,” says report co-author Ronald DiPippo, emeritus professor of mechanical engineering at the University of Massachusetts Dartmouth.

Conventional commercial-scale geothermal systems depend on a series of geological flukes. Cold water pumped into one hole in the ground travels a circuitous route through naturally occurring cracks in bedrock two miles deep or less. It returns to the surface through a second hole as boiling, pressurized water that pushes turbines to generate electricity. The conditions have to be just right, which explains in part why geothermal systems produce less than 1 percent of all electricity consumed in the U.S. annually. According to the Geothermal Energy Association, a trade group, only Alaska, California, Hawaii, Nevada, and Utah have commercial-scale geothermal power plants.

No EGS power plants currently exist in the U.S., but recent advances make them technoologically feasible nationwide (though not economically viable everywhere), say the report authors. Improved drilling technologies allow access to geothermal sources six miles deep, and engineers now pump water to create small cracks in bedrock instead of relying on Mother Nature. From there, engineers employ the same electricity-generating methods used in conventional systems.

“We’ve known for many years that [geothermal] is a huge, untapped resource,” says Richard Campbell, an engineer at the Colorado-based Industrial Company. According to a 2006 National Renewable Energy Laboratory report, geothermal energy is “equivalent to a 30,000-year energy supply at our current rate for the United States!” Geothermal facilities have minimal environmental impacts, and, unlike wind and solar systems, they can run continuously.

Despite these advantages, federal support for all geothermal energy has plummeted in recent years. The Department of Energy budget earmarked $23 million for geothermal research in 2006, but only $5 million this year. Last year the Bush administration proposed cutting funding altogether for 2008, sparking an ongoing debate on Capitol Hill about the merits of the research.

Such cuts don’t bode well for EGS plants, which require at least a $300 million investment over the next 15 years to be competitive, according to the report. But funding may increase in the near future. On May 14, California Representative Jerry McNerney, a Democrat, introduced HR 2304, which proposes to boost the agency’s geothermal energy research funding to $80 million annually through 2012. The bill will likely be sent to the White House this fall as part of the congressional energy package. Karl Gawell of the Geothermal Energy Association estimates that it has a “better than 50/50” chance of surviving the legislative process.  

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Issue 25

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