Interstage water flow rate regulation in thermal power unit coupled with two-stage steam-driven compressed air energy storage system under design conditions

Abstract With the expansion of the grid-connected scale of renewable energy, enhancing the peak shaving flexibility of Thermal Power Units (TPUs) has become a crucial requirement. This paper focuses on the thermal power-coupled two-stage steam-driven Compressed Air Energy Storage (CAES) system, concentrating on the influence of regulating the return water flow rate of the inter-stage heat exchangers on the thermodynamic performance and thermo-economic efficiency of the system. Based on the EBSILON platform, a model is constructed, and with the thermo-economic indicators and heat exchanger heat transfer parameters as optimization objectives, a collaborative optimization method for the return water flow rate of the inter-stage heat exchangers is proposed. The results show that during the energy storage stage, when the water mass flow of the heat exchanger is optimized to 165.5 t/h, the heat transfer capacity of the inter-stage heat exchanger reaches its peak, and the minimum value of the instantaneous heat rate of the coupled system drops to 8311.75 kJ/kWh. During the energy release stage, when the water mass flow is in the range of 380-412 t/h, the total power generation of the system approaches 775.998 MW, and the instantaneous heat rate remains at 6882.56 kJ/kWh.