Published on November 16th, 2009 | by Susan Kraemer3
Using CO2 to Extract Geothermal Energy
As part of developing new energy resources that don’t emit carbon dioxide, the DOE is funding 9 trials that use supercritical CO2 to extract more geothermal energy.
The idea started in 2000 at Los Alamos National Laboratory; when physicist Donald Brown thought of pumping geothermal fluid using supercritical CO2 – a pressurized form that is part gas, part liquid; instead of water. Theoretically this should flow more freely through rock than water, because it is less viscous than water.
Then, six years later; in modeling the technology Lawrence Berkeley hydro-geologist Karsten Pruess projected that not only should it perform as expected but that it would also yield a 50% hotter geothermal resource.
Now the DOE is funding this promising research with $16 million in nine trials to see if this will work in the real world.
The funding is to be shared by nine carbon dioxide-related projects led by Lawrence Berkeley National Laboratory and other national labs and universities, and the Californian combinatorial chemistry firm Symyx Technologies that screens about a million potential materials a year using advanced computer modeling.
Brown’s idea was that the density difference between the supercritical CO2 pumped down and the hotter gas coming up would make the gas cycle better by a siphoning action, so the pumping process would use less energy.
Symyx project leader and materials scientist Miroslav Petro wants to make sure that supercritical carbon dioxide plays nicely with rock and minerals. It could form a super-dissolving “acidic soda water” that dissolves minerals from rocks.
Sequestering the carbon would be the big bonus. It could be a large amount: 70 years worth of CO2 emissions from a 500 megawatt coal power plant.
Source: Technology Review