Tuesday, October 22, 2013

Fracking for Geothermal Heat

A startup to watch - building on the fracking technology originally developed for oil and gas (Wired via Instapundit):

The main problem is that conventional geothermal plants rely on a rare combination of geological features. Hot rock has to be accompanied by large amounts of hot water or steam that can easily be pumped to the surface, where it would drive steam turbines to generate electricity. The rock formation needs to be porous enough that the water can be continuously recirculated and reheated to keep a power plant running. (Geothermal pumps are sometimes used to heat and cool homes, but these are inadequate for generating electricity because they work at much lower temperatures.)

Although such formations are rare, the amount of heat underground is actually huge (see “Abundant Power from Universal Geothermal Energy”). There’s enough heat trapped under the United States within drilling distance (as deep as 10 kilometers) to supply its energy needs for thousands of years. AltaRock is one of several companies trying to figure out how to access more of that heat (see “Cracking Rock to Get More from Geothermal Fields” and “Using CO2 to Extract Geothermal Energy”).

The basic idea is to modify the rock to allow water to flow through it (researchers call the resulting reservoirs enhanced geothermal systems, or EGS). This involves pumping cold water into rock in just the right way to trigger existing fractures in the rock to expand and allow water to flow through. It’s been tried many times in the past—with efforts stretching back for decades. But it’s been hard to get enough hot water flowing to justify the expense of drilling a well and building a power plant.

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