Why We Should Reconsider Geothermal Energy

| 12/24/2009 11:15:17 AM

Geothermal SpringsIronically, our pursuit of fossil fuels has brought us closer and closer to a much larger, more sustainable source of energy. The interior of our planet is a giant nuclear power plant. The solid rock and soil on which we live our lives is essentially a thin skin of cool solids on top of a big ball of extremely hot rock. On the continents, the Earth’s solid “crust” is less than 20 miles deep.[1] At the bottom edge of the crust the temperature of the rock is at least 1,000 degrees, Fahrenheit.[2] Deeper, it just gets hotter. As we drill for oil and gas, we come closer and closer to an energy source that makes our tiny reservoir of fossil fuels seems pathetic in comparison.

Most of that heat is generated by the decay of radioactive elements[3], and they are scheduled to keep on generating heat for billions of years.

Twenty miles is not far to drive in a car, but it’s a long way to drill through solid rock. The crust of the Earth is not so thick everywhere, however. The floors of our deepest oceans may be only a couple of miles from the outer mantle of 1,000-degree rock. Oil and gas wells are often that deep. And in places between the tectonic plates the crust is much thinner, or even breached. Molten rock flows out on the surface from volcanoes. Scalding steam shoots from geysers where cool surface water makes contact with the planet’s hot interior.

The total heat stored in the Earth’s interior is hundreds of thousands of times greater than our most aggressive projections of our power needs. The energy under our feet dwarfs our wildest notions for power consumption. If we could efficiently harness geothermal energy to heat steam and drive turbines, every building, vehicle and machine on Earth could be powered by geothermally generated electricity forever.

Simple applications of geothermal power are already in use in millions of buildings around the world. A few of them can draw hot air or steam directly from the Earth. Where very hot geothermal energy is near the surface — Iceland, for instance — hot groundwater can be piped into radiators and swimming pools. Reykjavik is warmed by hot groundwater pumped through radiators throughout the city, then circulated below the streets and sidewalks to keep them free of ice and snow.[4] 

Of course that sort of obvious geothermal resource isn’t available in most locales. “Ground-source” geothermal pumps are useful everywhere. They push air or liquid through underground pipes to warm or cool a building from season to season. Because the underground temperature is stable year-round — warmer than the external temperature in winter and cooler in summer — ground-source heat pumps save some of the energy that furnaces and air conditioners would use in heating or cooling. Any place in the world where you might want the inside of your home to be warmer or cooler than the outside, ground-source geothermal works. In the most conducive locations, it can reduce the consumption of energy for heating and cooling by 75 percent. Chances are there’s someone in your neighborhood already reducing their energy bill with a ground-source system.

2/4/2010 4:24:27 PM

I never understand the 75-80% estimates on energy costs geothermal will replace. My home is 100% heated and cooled by surface geothermal.

Mary Saunders_3
2/1/2010 3:24:55 PM

It amazes me that people who minimize the potential of solar, on the basis that it is not 24/7, seem not to understand that heated water, by the sun, can then be stored underground not that far, to be released for heat when needed. There are vast underground caverns that have been pumped out for fossil fuel use. Cooled water can be stored there for use as a cooling source as well. Oregon Polytechnic Institute has used geothermal power for years also. Minerals accumulating on the inside of pipes is a maintenance issue, but it is my understanding, from Janine Benyus's talks on TED, that there is now an efficient way to deal with scaling, based on how shellfish handle their building/rebuilding issues.

1/2/2010 10:47:51 PM

The only criticism that i can give the author of this article is that the interior heat of the Earth is not fully due to radioactive decay,good heavens you'll get everyone in a panic.A small part is of course like anything but most astrophysicists very well know that this planetary interior heat is present in nearly all large solid planetary bodies,including our Moon to a scaled degree of course.No most of this heat is very much due to the effect of gravitation on large masses of matter.We circle the Sun at over 17,000 MPH and with that we a rotatonal speed.All this gravitational motion plus the Earth's weight of 6.6 sextillion tons(including atmosphere,not including the Moon)generates heat at the center of gravity of an object,an example being the internal heat of a large pile of dirt,or coal piles that have to stay a certain legal size or they will combust.Compessed matter produces heat from the compression of molecules.

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