Geothermal power, which taps heat from the earth’s interior to generate electricity, could soon get a major technological upgrade. Because it consumes no fuel, geothermal is clean and almost endlessly abundant. Right now, though, it generates just 0.4 percent of the electricity in the United States. A big obstacle is that traditional, high-temperature geothermal plants require drilling as much as three miles into the earth’s crust. Such digging is costly and may even carry the risk of triggering an earthquake, a possibility that scuttled a major project in Switzerland this past December.
Low-temperature systems are cheaper to build. They generate energy from heat just below the surface; water pumped down there is used to warm fluids with low boiling points, releasing vapor that turns a turbine to make electricity. Typically, these systems are also much less efficient, but environmental engineer Peter McGrail at the U.S. Department of Energy’s Pacific Northwest National Laboratory may have found a simple way to improve them. He is experimenting with metal-organic heat carriers, extremely fine particles that can allow fluids to absorb more heat. On the basis of his lab measurements, he says, systems incorporating the particles could show “efficiency improvements of 20 to 30 percent,” enough to match a high-temperature system. McGrail is building a small prototype to test the metal-organic particles with various fluids. He plans to acquire a commercial-scale geothermal system so he can run larger tests later this year.