Off-design performances of a dry-cooled supercritical recompression Brayton cycle using CO2–H2S as working fluid

The dry-cooled supercritical CO2 recompression Brayton cycle is a promising power generation technology for concentrated solar power plant. Since the critical temperature of working fluid acts as a limitation to heat rejection, H2S can be introduced into pure CO2 to improve the cycle's adaptability to high ambient temperature. The purpose of this study is to recognize the off-design behaviors of the dry-cooled supercritical recompression Brayton cycle using CO2–H2S mixture as working fluid. The detail component models of a 50 MWe power plant as well as the CO2–H2S physical property models are developed. The impacts of heat resource and ambient temperature on cycle performances are evaluated by varying turbine inlet temperature and compressor inlet temperature. The results show that the dry-cooled supercritical CO2–H2S recompression Brayton cycle remains excellent thermodynamic performance even at ambient temperatures up to 50 °C. Under design load, the thermal efficiency decreases by 1.2% points per 5 °C increment in the compressor inlet temperature range of 35 °C–65 °C, and increase 6.4% points when turbine inlet temperature increases from 500 °C to 650 °C. The impact of turbine inlet temperature on split ratio and main shaft speed is lower than that of compressor inlet temperature. •A detail model for dry-cooled sCO2-H2S recompression Brayton cycle is developed.•The off-design behaviors at varying TIT and CIT are investigated.•The sensitivity analysis of operating parameters are carried out.•The sCO2-H2S recompression Brayton cycle shows excellent performance at ambient temperatures up to 50 °C.