Carbon dioxide (CO2) sequestration in deep saline aquifers and exhausted oil and natural gas fields has been widely considered as a means for reducing CO2 emissions to the atmosphere as a counter-measure to global warming. However, rather than treating CO2 merely as a waste fluid in need of permanent disposal, we propose that it could also be used as a working fluid in geothermal energy capture, as its thermodynamic and fluid mechanical properties suggest it transfers geothermal heat more efficiently than water. Energy production and sales in conjunction with sequestration would improve the economic viability of CO2 sequestration, a critical challenge for large-scale implementation of the technology. In addition, using CO2 as the working fluid in geothermal power systems may permit utilization of lower temperature geologic formations than those that are currently deemed economically viable, leading to more widespread utilization of geothermal energy. Here, we present the results of early-stage calculations demonstrating the geothermal energy capture potential of CO2-based geothermal systems and implications of such energy capture for the economic viability of geologic CO2 sequestration.
Bibliographical noteFunding Information:
Research support was provided by the Initiative for Renewable Energy and the Environment (IREE), a signature program of the Institute on the Environment (IonE) at the University of Minnesota, and by the U.S.A. Department of Energy (DOE) Geothermal Technologies Program under grant No. DE-EE0002764. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the DOE, IREE, or IonE. M.O.S. also thanks the George and Orpha Gibson endowment for their generous support of the Hydrogeology and Geofluids Research Group.
- Geothermal energy