Captured CO2 + geothermal = ultra-clean power 


Posted by Susan Kraemer, EarthTechling

 

In a novel combination of carbon sequestration used in conjunction with geothermal power production, a South Dakota geothermal firm will use sequestered carbon dioxide instead of geothermal fluids to produce geothermal power.

Rapid City-based Heat Mining Company can use the carbon dioxide captured in carbon capture and storage (CCS) process as the underground working fluid to extract geothermal heat for additional electricity production and/or district heating, according to a report at Sustainable Business.

In the process, the CO2 can be permanently stored underground, resulting in a geothermal power plant with not only a neutral, but even a negative carbon footprint.

The Carbon Plume Geothermal (CPG) technology used by the company is expected to produce renewable electricity far more efficiently than conventional geothermal systems, all while effectively sequestering the carbon dioxide far underground. It is a win-win for developing much more renewable geothermal power and reducing excess carbon dioxide in the atmosphere, by sequestering it.

CPG technology holds huge promise, even just for improving geothermal production so that it is viable in many more regions than now, which means that it establishes a real market for the carbon captured by CCS. Although the Feds recently invested $1 billion into CCS the lack of a market income has been the weak spot that holds back its development.

That is because, using the carbon dioxide processed from carbon sequestration, geothermal development in the US would have the potential to produce at least 150 gigawatts (GW) of power, far more potential than traditional geothermal has now.

By 2009 the U.S. had only 3 GW of geothermal power, and while the Obama administration stimulus bill added another 8 GW to the U.S. grid, that still adds up to just 11 GW. But because the new CPG technology can be used in regions where traditional geothermal production using water would not make sense technically or economically, this process allows much more geothermal to be developed.

Geothermal is among the few renewable sources of electricity that can produce baseload power or provide peak-load power, thus serving as not just a renewable source, but as a back-up for the intermittent renewables.

CO2 actually has many advantages over water in geothermal production. It travels more easily than water through porous rock, so it can extract heat more readily. This means additional geothermal extraction from traditional fields, which means additional income to pay for the costs of CCS, which has been the hurdle so far.

"This is probably viable in areas you couldn't even think about doing regular geothermal for electricity production," said postdoctoral Fellow Jimmy Randolph, one of the inventors of the technology at the University of Minnesota. "In areas where you could, it's perhaps twice as efficient."

The company was granted exclusive, worldwide rights.

Their research was funded by a $600,000 grant from the University of Minnesota and a $1.5 million grant from the U.S. Department of Energy to explore the subsurface chemical interactions of the process. The approach was invented by earth sciences professor Martin Saar, mechanical engineering professor Thomas Kuehn, and Jimmy Randolph. It was patented by the university in 2009 and licensed to Heat Mining Company in a worldwide exclusive patent.

This could be the beginning of a very key industry, with abundant supply and demand.

"This technology sits at the convergence of two conflicting demands in our society," says Kenneth Carpenter, managing partner of Heat Mining Company. "The ongoing need to burn fossil fuels for the foreseeable future and the desire to reduce atmospheric carbon dioxide emissions."

Supply is hardly going to be a problem. A typical coal-burning power plant produces 3.5-5 million tons of carbon dioxide a year, and it's possible to retrofit existing plants, and design new plants, that capture the CO2 and sequester it underground. And the greatly expanded geothermal market they see has enough storage potential to slake demand.

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

Stay tuned for the results of the first test projects of this potentially game-changing technology. Negotiations are under way in Canada and in Texas.

* Susan Kraemer, EarthTechling