Washington: Scientists are developing a new kind of geothermal power plant that will lock away unwanted carbon dioxide (CO2) underground and use it as a tool to boost electric power generation by at least 10 times compared to existing geothermal energy approaches.
The new power plant design resembles a cross between a typical geothermal power plant and the Large Hadron Collider: It features a series of concentric rings of horizontal wells deep underground. Inside those rings, CO2, nitrogen and water circulate separately to draw heat from below ground up to the surface, where the heat can be used to turn turbines and generate electricity.
The design contrasts with conventional geothermal plants, explained study co-author Jeffrey Bielicki from Department of Civil, Environmental and Geodetic Engineering and the John Glenn School of Public Affairs at The Ohio State University.
"Typical geothermal power plants tap into hot water that is deep under ground, pull the heat off the hot water, use that heat to generate electricity, and then return the cooler water back to the deep subsurface. Here the water is partly replaced with CO2 or another fluid - or a combination of fluids," he said.
CO2 extracts heat more efficiently than water, he added.
This approach, using concentric rings that circulate multiple fluids, builds upon the idea to use CO2 originally developed by Martin Saar and others at the University of Minnesota, and can be at least twice as efficient as conventional geothermal approaches, according to computer simulations.
The Researchers believe that the resulting multifluid design will enable geothermal power plants to store energy away - perhaps hundreds of gigawatt hours - for days or even months, so that it is available when the electricity grid needs it.
The underground geothermal formation could store hot, pressurized CO2 and nitrogen, and release the heat to the surface power plant when electricity demand is greatest. The plant could also suspend heat extraction from the subsurface during times of low power demand, or when there is already a surplus of renewable power on the grid.
The study was presented at the American Geophysical Union meeting.