Structural improvement and thermodynamic optimization of a novel supercritical CO2 cycle driven by hot dry rock for power generation

Abstract

Abstract Due to the higher thermal extraction rate, injection capacity and fluidity of supercritical CO2, supercritical CO2 as the circulating working fluid in the enhanced geothermal systemfor thermal utilization of hot dry rock resources will achieve higher energy efficiency. In view of the low power generation efficiency of the supercritical CO2 cycle and the decrease in the mass flow rate of the CO2 fluid in the cycle caused by dissolution and precipitation of CO2 fluid in rocks and minerals in fractures, a novel supercritical CO2 cycle with CO2 pressurization process is proposed. Based on the conventional supercritical CO2 cycle and CO2 pressurization process, the cycle configuration is optimized to improve the generation performance and reduce the power consumption. The optimization rate which compared to the conventional supercritical CO2 cycle and CO2 pressurization processis selected as the evaluation index to prove the improvement of the cycle performance after the improvement, and the main thermodynamic parameters that affect the cycle performance are optimized. The results show that the reduction of the condensation temperature in the supercritical CO2 cycle, the liquefaction pressureand cooling temperature in the CO2 pressurization process, will all lead to the improvement of the cycleoperation performance. Under the best operating conditions, the optimization rates of the proposed supercritical CO2 cycle and CO2 pressurization process are 19.8% and 4.3%, respectively.