Performance analysis on a compressed air storage system deeply coupled with coal-fired unit

To enhance the operational flexibility of conventional coal-fired units, a novel power generation system that deeply couples adiabatic compressed air energy storage (AA-CAES) with a 600 MW coal-fired unit is proposed, achieving system efficiency improvement through cascade energy utilization. A bidirectional coupling mechanism of “condensate cooling + extraction steam heating” is established: during the energy storage phase, unit condensate is utilized to cool the compressed air; during the energy release phase, extraction steam from the fifth low-pressure heater of the steam turbine is employed to heat the stored compressed air, and energy recovery is realized by matching the heat-exchanged return water with the regenerative system. An analysis model for a new coal-fired power generation system based on compressed air energy storage is constructed based on Ebsilon software, focusing on the effects of storage tank pressure, inlet flow rate, and other parameters on heat rate, cycle efficiency, and exergy loss. The research results indicate that with the integration of the compressed air energy storage system and the coal-fired unit, as the storage tank pressure increases, the heat rate of the coupled system gradually rises, while the system cycle efficiency and energy utilization coefficient initially increase and then decrease, reaching optimal performance at a storage tank pressure of 10 MPa with a cycle efficiency of 50.66% and an energy utilization coefficient of 47.86%. As the inlet air flow rate of the compressor increases, the energy utilization coefficient and heat rate decrease, whereas the system cycle efficiency increases. Analysis is the most direct method to reflect system losses. Under rated conditions, the exergy efficiency is 77.39%, with the maximum exergy loss occurring at the throttle valve, accounting for 5.69%. When the load decreases, the system heat rate increases by 11%, the cycle efficiency decreases by 3.2%, and the energy utilization coefficient drops by 6%. The thermal and cold storage devices of the compressed air system are optimized, achieving dual benefits of enhanced unit peak-shaving capability and reduced investment costs. A new technical pathway is provided for the flexibility retrofitting of traditional coal-fired power, effectively lowering the investment cost of the coupled system and improving the economic performance of coal-fired units.