Can Geothermal Energy Offset Global Warming?
by Karl Gawell
Q: If we extract enough heat from the earth using geothermal energy, could
we offset global warming? -- Linda P., Portland Oregon
A:
Great question. You apparently know the basics of geothermal electricity
production, but let me recap for those not as familiar. To oversimplify,
geothermal electricity consists of:
1. Locating a suitable geothermal reservoir (underground collection of
hot water or steam).
2. Drilling a well to penetrate the hot underground water or vapor
(geothermal fluid).
3. Extracting the hot fluid.
4. Using a power plant and related infrastructure to produce
electricity, cool the geothermal fluid, and inject some of it back into the
system for reuse.
Since we are using the heat of the earth to run the power plant, some of
this energy is transformed into electricity. This means there will be a net
heat loss from the reservoir, and the earth temperature must decrease (blame
the laws of thermodynamics). Your question is, could we do enough of this to
actually measurably cool the earth. The simple answer is no-geothermal does
result in cooling, but the impact is insignificant.
Some 42 million megawatts of energy reach the surface continually and are
radiated into space as the earth cools from its initial molten state more
than 4 billion years ago. No feasible amount of geothermal development could
make even a small dent in this process. Furthermore, the earth's heat budget
is continually replenished by the radioactive decay of naturally occurring
elements, and almost all of the energy associated with each decay event is
converted to heat. Plus, the heat content of the geothermal reservoir rocks
is continually replenished by conduction of heat from the earth's deeper
interior.
But, if you're thinking about global warming, using all of that heat to
provide clean energy is obviously a way to go. Like the sunlight hitting the
earth every day, the energy available from the heat of the earth is enormous
and largely unused as a source of energy. If we could tap just a fraction of
the heat reaching the surface of the earth every year, we could provide all
of the heat and power needed to run our society, and avoid the potentially
tragic consequences of overusing fossil fuels.
Comments:
Karl, while geothermal electricity holds great potential, we seldom see any focus on geothermal heat pumps for both industrial and home use. The technology is mature and its application almost universally available. It would seem to me to be a no-brainer, and i don't understand why it is not well promoted and utilized.
john sykes
The areas on the Earth's surface which need high amount f Energy inputs for heating as well as Mechanical action are the coldest ones. Actual input of such high doses of Energy is actually one of the main reasons behind the Polar and other high Altitude melting of the ICE CAPS.This is not to ignore the impact of the CFC et al, but to keep in fcus one aspect rarely discussed.
C.S. Radhakrishnan
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