Geothermal
I don't know much about geothermal power, but I do know I don't hear much talk about it of late. Anthony Watt thinks this is a mistake, and discusses the potential. To some extent, the problem with geothermal's acceptance is that it breaks our current centralized power model in favor of distributed power. There are few spots where geothermal potential is large enough to run a big power plant, but apparently many where there is the ability to heat a single building.
Dr. T:
Looking at the map of geothermal regions with water temperatures above 100 degrees centigrade, one finds that Nevada could generate lots of geothermal power. The mountainous area that extends from northeast California through central Washington also has high temperature water, but mostly in poorly accessible regions. Some of those regions (eg: Cascade Mountains in Washington) already have hydroelectric power.
I don't see as much potential as Mr. Watt (great name for someone interested in electric power). Iceland has the most experience with geothermal power, and Icelanders use the large power plant model instead of the individual building model. Some individual buildings heat water geothermally, but they get their electricity from the big geothermal power plants.
June 7, 2008, 3:50 pmJim:
Geo Thermal power uses water that is full of dissolved rock. This rock falls out of solution in the pipes of the power plant. This kills the thermal conductivity and blocks the pipes. The water pressure in the rocks also causes earthquakes according to the Swiss government (www.swissinfo.org/eng/front/detail/swissinfo.html?siteSect=105&sid=7407138)
June 7, 2008, 7:26 pmMike Giberson:
Geothermal can also be used directly for heating and cooling, for example using a geothermal heat pump. (See also this discussion of a geothermal HVAC system.) These kinds of systems don't require quite the high temperature differences that geothermal power generators typically need.
To Jim: a system that pumps hot underground water to the surface might have that problem, but closed loop systems either use water that always remains in the pipe and then doesn't have the problem you describe, or use some other liquid to carry heat from/to the earth.
From the article, it looks like the particular technology employed was responsible for creating the tremors (pumping water underground using high pressure with a goal of fracturing underground hot rock formations which then heats the water producing steam to drive a generator. As the article notes, it is the first use of the technology; other geothermal projects don't work in quite the same way.
June 7, 2008, 8:07 pm