GeoThermal Stirling

Instead of using steam it would be just as efficient and a lot cheaper
to use the well as a really long displacer cylinder in a beta Stirling.
MIT study touts geothermal energy: Heating water is key
By Jay Fitzgerald Technology Section
Boston Herald 1/23/07
America needs to get more steamed up to meet its future energy needs, a
new Massachusetts Institute of Technology study says.
An 18-member panel led by MIT yesterday reported that tapping into
natural heat under the Earth's rock crust could yield enough energy
generate a "substantial portion" of the nation's electric power
at a
relatively low economic cost.
The report, the first of its kind on geothermal energy in 30 years,
urged the federal government to invest more in promising technology,
which could meet about 10 percent of U.S. electricity needs by 2050.
The technology - in which water is pumped thousands of feet into the
rock crust and extracted as steam - should be tested first in western
states where underground hot rocks are closer to the surface, the
But so-called "heat mining" is also feasible in eastern states,
naturally heated rock exists deeper down toward the Earth's core, the
report said.
"We've determined that heat mining can be economical in the short
based on global analysis of existing geothermal systems," said panel
head Jefferson W. Tester, a professor of chemical engineering at MIT.
Ronald DiPippo, professor emeritus at the University of Massachusetts
Dartmouth, said rocks 15,000 feet to 20,000 feet deep in this area
should be sufficiently hot - at about 300 degrees Fahrenheit - to
produce steam energy.
Granite rock crusts at those levels have naturally radioactive
such as uranium and thorium, that heat them up.
One well could be drilled into the deliberately "fractured" rock
water could be pumped in, he said. A second well would extract the
to power electric plants, said DiPippo, a member of the panel that drew
up the nearly 400-page report.
So-called "hydrothermal" technology - in which heated water already
exists below the surface - is currentlybeing used in California, Nevada
and other western states to generate about 2,500 megawatts of power, he
Inserting water into other promising sites is merely modifying existing
technology, he said.
"It can be done anywhere in the United States," he said.
Funded by the U.S. Department of Energy, the report said geothermal
energy is cleaner and more plentiful than fossil fuels, which will
become more expensive in future years as they become more scarce.
Bret Cahill
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Bret Cahill
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