Thermodynamic study on coupled system of concentrated solar power and pumped thermal energy storage based on supercritical CO2 Brayton cycle

As the intermittent and fluctuating characteristics of renewable energy sources such as solar power become increasingly prominent, the pumped thermal energy storage (PTES) system emerges as a key peak-shaving technology and a potential solution. This study proposes a coupled system of the PTES system and the supercritical CO 2 Brayton cycle for a concentrated solar power (CSP) system with a preheating thermal storage and a bypass heating discharging cycle. Based on typical daily operating conditions, a quasi-steady-state thermodynamic model of the system is developed. The results indicate that there are optimal values for the high-temperature compressor inlet temperature, the low-temperature compressor pressure ratio, and the compressor inlet pressure that maximize system performance. The compressor isentropic efficiency, the compressor inlet pressure, and the expander isentropic efficiency significantly affect system performance. The heat exchanger pressure drop exerts a greater impact than energy conversion efficiency, whereas direct normal irradiance has a greater impact on the system than ambient temperature. Under the summer operating condition, the maximum power ratios of the CSP input and PTES output are 58.96% and 29.86%, respectively. Under the winter operating condition, they are 60.20% and 28.87%, respectively. The maximum round-trip efficiency and energy density under the summer operating condition are 60.62% and 26.78 kWh/m 3 , respectively, which are 0.32% and 4.18 kWh/m 3 higher than those under the winter operating condition. Under both operating conditions, the round-trip efficiency and energy density are highly sensitive to the isentropic efficiency and inlet pressure of the low-temperature compressor, and the isentropic efficiency of the high-temperature expander.