Researchers are developing a new kind of geothermal（地热的） 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 technology to implement¹ this design already exists in different industries, so the researchers are optimistic that their new approach could expand the use of geothermal energy in the U.S. far beyond the handful of states that can take advantage of it now.

 

At the American Geophysical Union meeting on Friday, Dec. 13, the research team debuted² an expanded version of the design, along with a computer animated³ movie that merges⁴ advances in science with design and cognitive⁵ learning techniques to explain the role that energy technologies can have in addressing climate change.

 

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, assistant professor of energy policy in the 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 efficiently⁶ 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.

 

"When we began to develop the idea to use CO2 to produce geothermal energy, we wanted to find a way to make CO2 storage cost-effective while expanding the use of geothermal energy," said Jimmy Randolph, postdoctoral researcher in the Department of Earth Sciences at the University of Minnesota.

 

"We hope that we can expand the reach of geothermal energy in the United States to include most states west of the Mississippi River," Bielicki said.

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