Part-load performance analysis and comparison of supercritical CO2 Brayton cycles

The system that integrates solar power tower, molten salt thermal storage, and supercritical CO2 (S-CO2) Brayton cycle has emerged as a promising technology to provide a dispatchable power output following the power demand. Studying the part-load performance of the S-CO2 Brayton cycle is crucial to achieve an efficient system operation during power load adjustment. In this work, the performance of four typical S-CO2 Brayton cycles including simple recuperative cycle, reheating cycle, recompression cycle, and intercooling cycle are analyzed and compared under part-load conditions. The optimal cycle layouts under different power demand scenarios are revealed. Results show that the reheating cycle achieves higher efficiency than the simple recuperative cycle, and the recompression cycle and intercooling cycle perform better than the reheating cycle under part-load conditions. However, the intercooling cycle is more efficient than the recompression cycle only when the load exceeds 60%. Given that the relative reduction in the reheating cycle efficiency is minimal as the load decreases, this cycle shows the best response to the requirement of wide-range load adjustment. When the ratio of the actual total electricity generation to the maximum total electricity generation in a certain period is lower than 62.5%, the recompression cycle performs better. When this ratio is higher than 68.3%, the intercooling cycle performs better. In general, the efficiency of intercooling cycle is not significantly improved compared with that of the recompression cycle under the load-following scenarios.