期刊
ENERGY
卷 69, 期 -, 页码 409-418出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.energy.2014.03.032
关键词
Carbon dioxide; Geothermal energy; Carbon dioxide utilization; Thermosiphon; Renewable energy; Carbon dioxide plume
资金
- National Science Foundation [CHE-1230691]
- George and Orpha Gibson Endowment for the Hydrogeology and Geofluids Research Group in the Department of Earth Sciences at the University of Minnesota (UMN)
- Division Of Earth Sciences
- Directorate For Geosciences [1230691] Funding Source: National Science Foundation
CPG (CO2 Plume Geothermal) energy systems use CO2 to extract thermal energy from naturally permeable geologic formations at depth. CO2 has advantages over brine: high mobility, low solubility of amorphous silica, and higher density sensitivity to temperature. The density of CO2 changes substantially between geothermal reservoir and surface plant, resulting in a buoyancy-driven convective current - a thermosiphon - that reduces or eliminates pumping requirements. We estimated and compared the strength of this thermosiphon for CO2 and for 20 weight percent NaCl brine for reservoir depths up to 5 km and geothermal gradients of 20, 35, and 50 degrees C/km. We found that through the reservoir, CO2 has a pressure drop approximately 3- 12 times less than brine at the same mass flowrate, making the CO2 thermosiphon sufficient to produce power using reservoirs as shallow as 0.5 km. At 2.5 km depth with a 35 degrees C/km gradient the approximate western U.S. continental mean - the CO2 thermosiphon converted approximately 10% of the energy extracted from the reservoir to fluid circulation, compared to less than 1% with brine, where additional mechanical pumping is necessary. We found CO2 is a particularly advantageous working fluid at depths between 0.5 km and 3 km. (C) 2014 Elsevier Ltd. All rights reserved.
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