In this study, a closed-loop geothermal system (CLGS) using downhole heat exchanger (DHE) was proposed to extract heat from the HDR resources in order to avoid the problems associated with the current EGS technology. An increasing-pressure endothermic power cycle (IPEPC), with an increasing-pressure endothermic process in the DHE and CO2-based mixture as working fluid, has been developed for the geothermal wells with depths ranging from 2 km to 4 km. The mixture types and mass ratio of the working fluid, and the operation parameters of the IPEPC have been optimized simultaneously. The power generation performance of the IPEPC has been compared with that of organic Rankine cycle (ORC) and that of flash-steam system under the same geothermal conditions. When the DHE length (L) is 2000 m, the net power output of the IPEPC is 17.5%, 98.4% and 120% higher than that of the t-CO2, SF and ORC respectively; whereas it is only 7.4%, 9.1% and 21.7% if the L is 3000 m. Results obtained in this study are of engineering guiding significance for hot dry rock power generation.
Keywords Integrated research, Power generation, Heat extraction, Increasing-Pressure Endothermic process, CO2-based mixtures