Thermodynamic Analysis of Energy Conversion Systems of CO2-based EGS

摘要

With an expanding economy and increased electrification of our society, China is concerned about its long term energy supply. Enhanced geothermal resources (EGS) have an enormous potential for supplying electricity extracting and utilizing the earth’s stored thermal energy. Most attempts to develop EGS have used water as the heat transmission fluid. However CO2 has certain physical and chemical properties that are advantageous for EGS systems, so CO2 can be instead of water as the heat transmission fluid; which would also provide geologic sequestration of CO2 as an ancillary benefit. This paper presents a series of CO2-based energy conversion systems designed for the temperatures and pressures of EGS reservoirs. However the thermal efficiencies of the CO2-based EGS power cycles are less than that of water-based EGS cycles. The thermal efficient of CO2-based EGS is improved with a combined cycle that makes full use of the thermal energy. The total thermal efficiency of the combined cycles is then increased to greater than that of water-based EGS for identical conditions.