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University Start-Up to Generate Power with Stored CO2

Coal plant (USGS.gov)

(USGS.gov)

A spin-off company from University of Minnesota is commercializing a process for generating electricity with geothermal energy from stored carbon dioxide captured at coal-fired power plants. Heat Mining Company LLC, in Rapid City, South Dakota, is based on a technology invented by Minnesota faculty Martin Saar (earth science) and Thomas Kuehn (engineering), and earth science postdoc Jimmy Randolph.

Heat Mining plans to generate electric power with heat extracted from underground, but with sequestered carbon dioxide instead of water as is normally done with geothermal power. The use of carbon dioxide (CO2) rather than water, says the company, allows electricity to be provided from many more sites than would be possible with conventional water-based systems and does it more economically.

Heat Mining calls its process CO2 plume geothermal (CPG) technology and says it’s an attractive solution for conventional power plants based on fossil fuels. In this technology, the CO2 is permanently stored underground, rather than emitted into the atmosphere, where it contributes to greenhouse gases. The geothermal power facility can produce baseload power or provide peak-load power and thus also serve as a type of high-efficiency back-up power source for intermittently available wind or solar power.

A typical coal-burning power plant produces between 3.5 and 5 million tons of CO2 per year, and it’s possible — but expensive — to retrofit existing plants, and design new plants, that capture the CO2 and sequester it underground. With a CPG system tapping into the underground CO2 and using it as a heat extraction fluid, power produced from earth’s underground heat can be used for CO2 injection pumps while revenue from additional geothermal electricity sales can offset the high costs of capturing the CO2 in the fossil-fueled power plant. Until now, the costs of retrofitting a plant have been a hurdle, making so-called carbon capture and storage economically unfeasible for energy providers.

“We have enough storage potential in the United States alone,” says Heat Mining’s president Stephen O’Rourke, “to store 100 percent of the carbon dioxide produced by fossil-fueled power plants for about a thousand years.”

The University of Minnesota submitted the technology for patents in March 2009 and licensed it exclusively to Heat Mining through the university’s technology transfer office. The CPG method has been demonstrated in computer simulations and details have been tested in the laboratory. The next step is to build a pilot plant to test it in the field.

Read more: Energy Dept. Scales Back FutureGen CO2 Capture Project

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