Performance analysis and optimization study of a new supercritical CO2 solar tower power generation system integrated with steam Rankine cycle

Currently, the supercritical CO2 solar tower power generation (S-CO2 STPG) has become a research hotspot, but due to S-CO2 Brayton cycle characteristics, the solar energy utilization rate of the system is low. Therefore, a new S-CO2 STPG system integrated with steam Rankine (SR) cycle is first proposed. The SR cycle absorbs the waste heat of the S-CO2 Brayton cycle, and the introduction of the SR cycle can increase the solar energy utilization rate. The research is based on the simulation results, the system model is developed by Ebsilon, and system operation calculation is developed by MATLAB. The daily and monthly performances of the new S-CO2 STPG system integrated with SR cycle are compared with those of conventional S-CO2 STPG system in detail. The system location is Bakersfield. The comparative analysis results show that compared with the conventional system, the monthly power output for the new system rises significantly, especially in summer. The new system can effectively improve the solar energy utilization rate. The effect of SR cycle power output on new system performance is studied. Increasing SR cycle power output can improve the thermal energy storage subsystem and solar field subsystem performances. The optimal SR cycle power output is related to the solar radiation level. The Fargo, Bakersfield and Phoenix are selected as three places representing low-direct normal irradiance (DNI), medium-DNI and high-DNI districts, respectively. For the medium-DNI and high-DNI districts, the SR cycle power outputs corresponding to the optimal thermal performance and optimal economic performance are 20 MW and 15 MW, respectively; for the low-DNI district, those are 15 MW and 5 MW, respectively.