Drs. Martin Saar and Jimmy Randolph have had a paper accepted to Geophysical Research Letters on the feasibility of developing an enhanced geothermal power plant system that generates electricity in low to intermediate heat flow regions like Minnesota while simultaneously sequestering carbon dioxide in the ground.
IREE supported this research via a $600,000 Large Grant, and the project has leveraged just over $1.7M.
Geothermal energy offers clean, renewable, reliable electric power with no need for grid‐scale energy storage, yet its use has been constrained to the few locations worldwide with naturally high geothermal heat resources and groundwater availability. We present a novel approach with the potential to permit expansion of geothermal energy utilization: heat extraction from naturally porous, permeable formations with CO2 as the injected subsurface working fluid.
Fluid‐mechanical simulations reveal that the significantly higher mobility of CO2, compared to water, at the temperature/pressure conditions of interest makes CO2 an attractive heat exchange fluid. We show numerically that, compared to conventional water‐based and engineered geothermal systems, the proposed approach provides up to factors of 2.9 and 5.0, respectively, higher geothermal heat energy extraction rates. Consequently, more regions worldwide could be economically used for geothermal electricity production. Furthermore, as the injected CO2 is eventually geologically sequestered, such power plants would have negative carbon footprints.
Randolph, J. B., and M. O. Saar (2011), Combining geothermal energy capture with geologic carbon dioxide sequestration, Geophys. Res. Lett., 38, L10401, doi:10.1029/2011GL047265.
Or, see: http://www.geo.umn.edu/orgs/geofluids/publications_home.html