In a recent post - It's Always Something - I argued that for seemingly every renewable option, there is a trade-off. In that particular essay I was discussing a recent report that suggested that jatropha curcas - which I have written about as an intriguing option for renewable, liquid fuels - has very large water requirements. It is also poisonous, and was banned as an invasive species by the Western Australian State government. So as the title suggested, there always seems to be a catch with any of these options.

Geothermal energy is one of the most promising renewable energy technologies. There are a number of commercial geothermal plants already in operation (the U.S. is the world leader in geothermal energy), and the economics are much more favorable than some of the other choices. Geothermal electricity makes a much larger contribution to the electricity mix than does solar power, and does not suffer from the intermittency issue. A 2006 report from NREL (PDF warning) concluded that the potential for domestic geothermal energy at a depth of 2 miles (3 kilometers) is 30,000 times all current annual U.S. energy usage.

But while the current plants in operation utilize geothermal energy that is close to the surface, tapping deeper into the earth would hugely increase the geothermal potential. The only problem is that this sort of deep drilling can cause earthquakes. From the New York Times:

Deep in Bedrock, Clean Energy and Quake Fears

BASEL, Switzerland — Markus O. Häring, a former oilman, was a hero in this city of medieval cathedrals and intense environmental passion three years ago, all because he had drilled a hole three miles deep near the corner of Neuhaus Street and Shafer Lane. He was prospecting for a vast source of clean, renewable energy that seemed straight out of a Jules Verne novel: the heat simmering within the earth’s bedrock.

All seemed to be going well — until Dec. 8, 2006, when the project set off an earthquake, shaking and damaging buildings and terrifying many in a city that, as every schoolchild here learns, had been devastated exactly 650 years before by a quake that sent two steeples of the Münster Cathedral tumbling into the Rhine.

Hastily shut down, Mr. Häring’s project was soon forgotten by nearly everyone outside Switzerland. As early as this week, though, an American start-up company, AltaRock Energy*, will begin using nearly the same method to drill deep into ground laced with fault lines in an area two hours’ drive north of San Francisco.


The New York Times article goes into a lot of detail about why the deeper geothermal techniques cause earthquakes, but it also gives a good overview of the geothermal potential. I think the solution to this - if they can't come up with techniques that don't spawn earthquakes - is to only tap geothermal in relatively uninhabited locations. There are lots of places in the Western United States that have very low population densities, but very high geothermal potential.

Regardless, geothermal is one of those options that I think is around for the long haul, and won't require endless subsidies in order to be competitive.

* As a footnote, AltaRock Energy is a company that Vinod Khosla has invested in. AltaRock also has some information at their site about how geothermal works.



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