Scientists are developing a new type of geothermal power plant that will store unwanted carbon dioxide (CO2) underground and use it as a mechanism to improve electric power generation by relatively 10 times in comparison to existing geothermal power.
The technology to execute this design already exists in various industries, so the scientists are hopeful that their new approach could broaden the use of geothermal energy in the U.S. much beyond the handful of states that can take advantage of it now.
The new power plant design comes across as a cross between a typical geothermal power plant and the Large Hadron Collider. It features a sequence of concentric rings of horizontal wells deep underground. Inside those rings, CO2, nitrogen and water disseminate separately to haul heat from below ground up to the surface, where the heat can be used to rotate turbines and produce electricity.
The design exhibit contrasts with conventional geothermal plants, says 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 underground, 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 draws heat more efficiently than water, he added.
According to computer simulations, this method, using concentric rings that disseminate multiple fluids, builds upon the idea to use CO2 which was developed by Martin Saar and others at the University of Minnesota, and can be at least twice as efficacious as conventional geothermal power.
The scientists say that the resulting multifluid design will capacitate geothermal power plants to stock energy away, may be hundreds of gigawatt hours for many days or even months, so that it can be availed whenever the electricity grid needs it. The underground geothermal formation could stock hot, pressurized CO2 and nitrogen, and discharge the heat to the surface power plant when the demand for electricity is more. During times of low power demand the plant could also suspend heat extraction from the subsurface, or when there is already a surplus of renewable power on the grid.
The current research team includes Ohio State, the University of Minnesota and Lawrence Livermore National Laboratory.