Large reserves of heat reside as stored thermal energy deep within the Earth's crust. Mining this energy could meet a significant portion of the United States' future energy needs, at competitive prices and with minimal environmental impact, according to an MIT-led 18-member panel, which just released the first study in 30 years to explore the largely ignored concept of harnessing geothermal heat as an energy resource.
You might want to cancel all your appointments for the day before settling in to read their findings—at 400 pages, it's a real doozy.Although the United States is the world's largest commercial producer of geothermal energy, existing U.S. plants are mostly located in remote regions of the west, where the hot rocks are closer to the surface and less drilling is required. Our intrepid scientists wanted to know how feasible and economically viable it was to use enhanced geothermal system (EGS) technology to recover geothermal energy at a much larger scale.
"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 panel head Jefferson W. Tester (pictured above), the H. P. Meissner Professor of Chemical Engineering at MIT.
"EGS technology has already been proven to work in the few areas where underground heat has been successfully extracted. And further technological improvements can be expected," he said.
Here's the CliffsNotes version of how geothermal energy works: You drill several wells to reach the hot rock of the Earth's crust (where, handily, the temperature never fluctuates with the seasons). These wells are then connected to a fractured rock region through which water can flow. This creates a heat-exchanger that can produce more hot water or steam than you can shake a stick at, which then power up electric generators at the surface. Unlike conventional fossil-fuel power plants that burn coal, natural gas, or oil, these generators don't need any fuel. Plus, they're not tethered to the same constraints as wind- and solar-based systems are, resulting in a potentially non-interruptible source of electric power.
Our eggheads also concluded that the environmental impacts of geothermal development are "markedly lower than conventional fossil-fuel and nuclear power plants."
"This environmental advantage is due to low emissions and the small overall footprint of the entire geothermal system, which results because energy capture and extraction is contained entirely underground, and the surface equipment needed for conversion to electricity is relatively compact," Tester said.
Just a couple of issues mar our grand scheme: the availability of water (especially in arid regions) and potential seismic risk. The panel recommends more detailed assessments of various sites, as well as field trials running from three to five years.
Somewhere, Malcolm Gladwell is weeping silent tears of joy into his Wheaties.