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"Hot Rocks" for Home Energy
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Geothermal power, a renewable energy source that has been largely ignored in the United States, can supply a significant share of the country’s future energy needs, according to a new Massachusetts Institute of Technology (MIT) study. The study notes that by investing some $1 billion over 15 years—less than the cost of building a single clean-coal power plant—geothermal energy could power about 25 million U.S. homes by 2050.

“We’ve determined that heat mining can be economical in the short term,? said Jefferson Tester, a professor of chemical engineering at MIT and the head of the 18-member panel that prepared the report. The 400-page assessment, sponsored by the U.S. Department of Energy, is considered the broadest review of geothermal energy in 30 years. It is based on a global analysis of existing geothermal systems, an assessment of U.S. geothermal resources, and continuing improvements in the technologies of deep drilling and reservoir stimulation.

Most commercial production of geothermal energy in the United States today occurs in isolated reaches of the West, where higher-grade heat sources lie closest to the surface. But the report notes that subsurface “hot rocks? (areas of the Earth’s hard rock crust that store thermal energy) are present across the nation, offering the potential for more widespread use of the renewable resource. By drilling wells into hot rock regions and connecting them to water, geothermal developers could generate large amounts of steam that could be used to power electric generators on the surface.

Because geothermal power is derived from the Earth’s heat and from steam, the environmental impacts of geothermal development are considerably lower than those from conventional coal-fired and nuclear power plants, the report notes. Geothermal also offers an uninterrupted power supply, unlike renewable energy sources like solar and wind that are affected by weather and time of day. The downsides of geothermal, according to the study, include large water requirements, particularly in arid regions, and higher seismic risk because the easiest places to access the hot rocks are near fault lines.

Overall, however, the report’s authors believe that large geothermal stores could contribute significantly to U.S. energy needs, providing a viable alternative to fossil fuel use. “Geothermal energy could play an important role in our national energy picture as a non-carbon-based energy source,? said panel member M. Nafi Toksöz, a professor of geophysics at MIT. Among the recommendations outlined in the study are conducting more detailed and site-specific assessments of the U.S. geothermal resource and making a multiyear federal commitment to demonstrate the concept in the field at commercial scale.

Alana Herro writes for Eye on Earth (e²), a service of World Watch Magazine in partnership with the blue moon fund. e² provides a unique perspective on current events, newly released studies, and important global trends.

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Jeff Tester has been on this case for many years now. Unfortunately, the Bureau of Land Management has a twenty-five year backlog in dealing with existing proposals for geothermal installations, according to Edwin Black in _Internal Combustion_. Also according to Black, the Feds have pretty much zeroed out the research budget on geothermal, too.

Don't mean to be a buzzkill just mean to point out that if you want geothermal to happen you're gonna havta fight like hell against entrenched power long and hard.

Posted by: gmoke on 31 Jan 07

It is not very clear to me if the "hot rocks" you are talking about have stored solar energy (renewable resource with mean around 180 watt / square meter) or have stored geothermic energy (from the depths of the earth) ... in the second case, the "renewable" part of the resource is only about 0,08 watt / square meter and most energy is not renewable at all (in the same sense as for oil).

Or is there something I missed ?

Posted by: ccalmet on 1 Feb 07

This is being trialled in Switzerland. Unfortunately the trials were suspended after they started causing Earthquakes.

Another problem is that apparently it's not really sustainable. After you have been mining the heat for so many years, there is none left and the rocks are cool.

Posted by: Mike Hearn on 2 Feb 07



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