Earth’s molten mantle is a potentially inexhaustible source of energy that could meet 10 percent of the nation’s energy needs, but cost and safety concerns have hampered the growth of geothermal energy. Last week, Scientific American reported that researchers at the Pacific Northwest National Lab have announced plans to test a more efficient way to tap into safer, low-temperature geothermal stores through cagelike nanostructures.
Obama has promoted geothermal energy as a component for kicking the nation’s fossil fuel habit and reducing greenhouse gas emissions. Last week, the Bureau of Land Management auctioned geothermal energy rights on nearly 1,000 square kilometers of public land in the Southwest and expects 111 new geothermal plants by 2015.
These traditional geothermal power plants – which currently account for just 0.5 percent of the nation’s energy supply – tap into hot springs miles beneath Earth’s surface that contain water superheated to between 150°C and 370°C. These springs arise when magma from the outer mantle, about 50 kilometers beneath the surface, intrudes into the crust, heating rock and water. At most power plants, as this high-pressure water is extracted from the reservoir, it expands and turns to steam, powering the plant’s generator turbines.