Study on the thermodynamic performance of a coupled compressed air energy storage system in a coal-fired power plant

Coupled energy storage can improve flexibility levels, increase renewable energy consumption, and alleviate the energy crisis of thermal power systems. In this article, 11 coupling schemes for the CAES and CFPP systems are proposed, and a mathematical model for the coupled system is established. An optimal coupling scheme is determined through simulation analysis and comparison by using the heat rate and energy utilization coefficient as evaluation indicators. In the energy release stage, the energy utilization coefficient of the coupled system increases by 2.842 %, and the heat rate in the energy storage stage decreases by 50.546 kJ · (kWh) ⁻¹, with a return water temperature of 120 °C. The effects of key parameters, such as compressor inlet air temperature, storage chamber pressure, and expander inlet temperature, on the thermodynamic performance of the coupled system are explored, and the NSGA-II multiobjective optimization algorithm and TOPSIS optimization algorithm are used to optimize the key parameters and obtain the optimal performance-related parameters of the system: a compressor inlet air temperature of 35 °C, expander inlet air temperature of 105.4 °C, and storage pressure of 9.105 MPa. At this time, the RTE of the system is 55.573 %, and the η_he value is 1.59. The results indicate that the coupled CAES energy storage stage can assist the CFPP in absorbing renewable energy, and the energy release stage can alleviate the pressure of its high electricity load demand, effectively improving its flexibility.