essays & effluvia: Geothermal Energy

Tuesday, January 23, 2007

Geothermal Energy

Cool idea:

"The United States could generate as much electricity by 2050 as that flowing today from all of the country’s nuclear power plants by developing technologies that tap heat locked in deep layers of granite, according to a new study commissioned by the Energy Department.

There are already dozens of power plants worldwide that have long exploited hot spots of geothermal energy to drive steam turbines, but they are restricted to a few areas.

The new report, published online yesterday, focuses on a process that it said could affordably harvest heat locked in deep layers of granite that exist almost everywhere on earth. The technique, called enhanced geothermal, involves drilling several holes — some two to three miles deep — into granite that has been held at chicken-roasting temperatures, around 400 degrees or more, by insulating layers of rock above.

In the right geological conditions, pressurized water can be used to widen natural mazelike arrays of cracks in the granite, creating a vast, porous subterranean reservoir.

In a typical setup, water pumped down into the reservoir through one hole absorbs heat from the rock and flows up another hole to a power plant, giving up its heat to generate steam and electricity before it is recirculated in the rock below.

There are successful plants harvesting heat from deep hot rock in Australia, Europe and Japan, the report noted, adding that studies of the technology largely stopped in the United States after a brief burst of research during the oil crises of the 1970s.

Source:
Study Says Tapping of Granite Could Unleash Energy Source
ANDREW C. REVKIN
NYT, January 23, 2007
http://www.nytimes.com/2007/01/23/business/23thermal.html

The Future of Geothermal Energy
The Impact of Enhanced Geothermal Systems (EGS)
on the United States in the 21st Century
http://geothermal.inel.gov/publications/future_of_geothermal_energy.pdf