Welcome to the scenic Mayacamas mountains of Northern California. Feel that shaking? It's an earthquake. There are about 40 of those a year. That's because the Mayacamas are home to the Geysers geothermal field, where geothermal power provides 1,500 megawatts of clean energy and has the unfortunate side effect of causing "natural" disasters.
The process works by pumping liquid into the ground at high pressures, which fracture rocks and get to the hot air underneath. But those fractures can increase the frequency and severity of earthquakes, especially in earthquake-prone zones like Northern California. Around the Geysers, it has become a large problem.
GTherm, a Connecticut-based startup, claims it has developed an EGS system that won't cause earthquakes. Instead of pumping liquids into wells at high pressures to fracture rock, GTherm's "heat nest" can be installed at the bottom of a well to draw out heat from the surrounding rock. Nice and non-shaky. According to MIT Technology Review, fluid travels down the well in a closed loop, bringing heat to the surface and creating steam that turns turbines.
The whole process requires very little water, which means GTherm can set up shop anywhere that there are ground temperatures between 250 °F and 300 °F--not just in places with water reservoirs. This includes thousands of used-up gas and oil wells around the U.S. that were previously off-limits for geothermal. Since we already dug all those holes in the ground, we might as well get some clean use out of them.
So when will this EGS solution hit a deep hole near you? Demonstration projects are expected to begin next year. This may prevent future earthquakes, but it won't be enough to save the Geysers.
[Image: Flickr user martinluff]