Wednesday, April 27, 2011

Geothermal Senior Moment

Geothermal Senior Moment
By Rob Watson

A web search on Geothermal... whatever, usually generated twenty million hits on air conditioners. After going to the advanced search you can eliminate nearly half of them. What I am looking for is real information on using Geothermal heat to generate power.

You, and I, know that wherever you are, if you dig deep enough you find heat. The problem being, if you end up in solid rock and start drawing heat from it, the rock cools off. The eventual recovery rate of energy is equal to the rate of heat transfer into the area from which you are drawing heat, thermal differences, total area of contact, etc. etc. etc.

Having spent a few years in the oil exploration business, I recalled the seismic data reflections from underground formations. Unfortunately without drilling into the formation you could not distinguish oil and gas from water. The up side is there is a huge library of data (my former employer, Geophysical Service Inc. had ancient files in huge libraries.) that tells you where to look for pools of something. Checking the records should tell you where the drillers found oil, gas, and water.

If memory serves, these data plots recorded information for 6 seconds. At 5 miles per second (speed of sound in rock) that could get you down to the hot rocks. This brings up the question of how deep you can drill. My friends in Louisiana report BP has gone one mile through water and an additional 7 miles through rock. If memory of the thermal gradient in the earth is correct, that oil should be pretty warm.

My thought was to drill into the opposite ends of a formation, one down 20 or 30 thousand feet down, where it is nice and warm. Pump water from one well to the other and use this extracted heat to generate electricity. If the formation is large (tens of miles), now you have a huge surface area and an enormous fluid medium. Pollution is not a problem because the extracted water is returned to the source. And, the other problem of where to get water is also solved. (some former experiments pumped surface water into porous formations and had the water disappear... Real geologists know that some such formations could swallow the Great Lakes without yielding a bucket full of hot water) The worst down side is you strike oil and/or gas  instead of water. (now, wouldn't that be a heart breaker?)

Now remember, friends, when they finally find this is a practical solution to the nation's energy future, you heard it first here... I think.

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