Fracking may increase geothermal energy availability

MIT Technology Review : Geothermal power plants require a combination of hot rock and large amounts of underground water that can be pumped to the surface. However, if the rock is not porous enough, the water can’t be recirculated back to the source. Some companies have been attempting to use hydraulic fracturing to increase the porosity of rock in geothermally active areas. The process entails plugging one part of a well to boost pressure at other parts when fluid is forced through. But traditional techniques for plugging wells don’t work in heated rock and don’t accommodate the larger flow of water that results. Now a company called AltaRock from Seattle, Washington, has demonstrated a special polymer plug that works despite the heat. AltaRock plans to drill a second well where they demonstrated their plug so that they can pump heated water out of the fractured rock. The company still has to overcome several problems, however, including those having to do with flow rate: Either the water doesn’t get hot enough or some of it disappears through unknown cracks in the rock. Until those problems are resolved, geothermal will remain a very small part of energy generation.