Thermodynamic analysis of an improved coal-fired power plant coupled with compressed air energy storage and molten salt storage

In the context of carbon neutrality and large-scale integration of renewable energy, improving the flexibility and energy efficiency of coal-fired power plants has become a key research topic. This study focuses on a 600 MW coal-fired power plant and proposes a multi-energy complementary system integrating compressed air energy storage and molten salt thermal storage. The scheme replaces conventional electric heating with high-temperature steam heating. During charging, a two-stage, series-connected heat exchanger train comprising molten salt–air and water–air units is employed; during discharging, a hybrid heating scheme integrates a high-temperature molten salt tank, a medium-temperature tank, and turbine steam extraction. This configuration maximizes heat recovery from compression and enables cascade utilization. Five metrics evaluate the system: heat rate, coal consumption rate, exergy efficiency, thermodynamic resilience index, and round-trip efficiency. Relative to baseline operation, the system reduces heat rate by 12.68 kJ/kWh (charging) and 22.43 kJ/kWh (discharging), lowering coal consumption by 0.43 g/kWh and 0.77 g/kWh, respectively. Exergy efficiency increases by 0.60% (charging) and 0.32% (discharging). Regarding flexibility, the solution raises peak-shaving depth by 0.36%, increases maximum output power by 1.099 MW, and improves TERI by 0.026. Furthermore, the system achieves a round-trip efficiency of 62.8%, surpassing conventional compressed air energy storage. Economic analysis indicates a daily peak-shaving revenue of 186,400 yuan and a static payback period of approximately 5.8–6.5 years. This study offers a viable techno-economic pathway for the low-carbon transition of the power sector.