Preliminary assessment of sCO2 cycles for power generation in CSP solar tower plants

This work discusses a preliminary thermodynamic assessment of three different supercritical CO2 (sCO2) power cycles applied to a high temperature solar tower system, with maximum temperatures up to 800 °C. The thermal power is transferred from the solar receiver to the power block through KCl-MgCl2 molten salts as heat transfer fluid, therefore an indirect cycle configuration is considered assuming a surrounded field as the one of Gemasolar plant. The most promising cycle configuration in terms of solar-to-electric efficiency is selected, optimizing the cycle turbine inlet temperature to achieve the best compromise between cycle and receiver performance: the highest efficiency at design conditions is achieved by the Recompression with Main Compression Intercooling (RMCI) configuration with a solar to electric efficiency of 24.5% and a maximum temperature of 750 °C. The yearly energy yield of the proposed power plant is estimated with a simplified approach and results in the range of 18.4%: the performance decay from design to average yearly conditions is mostly due to the optical and thermal efficiencies reduction (−10.8% and −16.4%, respectively).