Hot rocks may be new power source

The MIT-led study of the potential for geothermal energy within the northeastern U.S. has found that mining the huge amounts of heat that reside as stored thermal energy in the Earth's hard rock crust could supply a substantial portion of Vermont's electricity-at competitive prices and with minimal environmental impact.

An 18-member panel led by MIT prepared the 400-plus page study, titled "The Future of Geothermal Energy." Sponsored by the U.S. Department of Energy, it is the first study in 30 years to take a new look at geothermal, a natural energy resource that has been largely ignored by planners and environmentalists.

"We've determined that heat mining can be economical in the short term, based on a global analysis of existing geothermal systems, an assessment of the total U.S. resource and continuing improvements in deep-drilling and reservoir stimulation technology," said Dr. Jefferson W. Tester of MIT.

The new assessment of geothermal energy by energy experts, geologists, drilling specialists and others is important for several key reasons, Tester said: Geothermal is an ideal zero greenhouse energy source and a compliment to a new generation of ultra-safe, peaceful nuclear power plants planned for the post-carbon future.

Unlike conventional fossil-fuel power plants that burn coal, natural gas or oil, no fuel is needed. And unlike wind and solar systems, a geothermal plant works night and day offering a non-interruptible source of electric power.

Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma (magma is lava before it reaches the surface). Almost everywhere, the shallow ground or upper ten feet of the Earth's surface maintains a nearly constant temperature between 50 and 60 F (10 and 16 C).

The MIT panel said drilling must reach depths in excess of three miles in places such as New England. Still, the possibility of drilling into Vermont's ultra deep subsurface rocks-fracturing them and pumping water in to produce steam-has already been shown to be feasible.

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