Geothermal energy system would use CO2

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MINNEAPOLIS, June 6 (UPI) -- U.S. researchers say a new method to tap heat below Earth's surface for energy could produce renewable energy while reducing atmospheric carbon dioxide.

Researchers at the University of Minnesota Department of Earth Sciences developed the technique, dubbed a CO2-plume geothermal system, or CPG.

Current methods for generating electricity using Earth's inner heat involve extracting hot water from rock formations several hundred feet below the surface at the few natural hot spots around the world, and then using the hot water to drive power-producing turbines, a UM release reported Monday. In contrast, the CPG system uses high-pressure CO2 instead of water as the underground heat-carrying fluid.

CPG provides a number of advantages over conventional geothermal systems, UM graduate student Jimmy Randolph said.

CO2 travels more easily than water through porous rock, so it can extract heat more readily and be used in regions where conventional geothermal electricity production is not feasible from a technical or economic standpoint.

CPG also offers the benefit of preventing CO2 from reaching the atmosphere by sequestering it deep underground, where it cannot contribute to climate change, the researchers said.

"Part of the beauty of this is that it combines a lot of ideas but the ideas are essentially technically proven, so we don't need a lot of new technology developed," Randolph said.