Peak-shaving performance of a molten salt thermal energy storage system assisted by a CO2 Brayton-cycle heat pump

An innovative flexible peak-shaving scheme for coal-fired power plants (CFPPs)is proposed. A supercritical CO₂ Brayton-cycle heat pump system is integrated with a dual molten salt thermal energy storage (MSTES) configuration. In this scheme, a high-temperature CO₂ heat pump replaces conventional electric heaters. This substitution uses electrical work to upgrade heat supplied by the steam cycle to the molten-salt storage temperature, thereby reducing the direct electrical input required per unit of stored heat. Deep peak shaving is enabled by the coordinated control of turbine steam extraction and heat pump power consumption. Steady-state models of the heat pump and coupled unit are established to evaluate system performance. The role of main operating parameters in determining round-trip efficiency (RTE)and peak shaving capability is systematically analyzed. The findings indicate that, the minimum load can be reduced to 20.10%–21.18% THA in the optimized system. Meanwhile, the peak output power increases to 106.99% THA. The system achieves an RTE of up to 76.77%. At the matched comparison point, the RTE is 76.56%, compared with 56.31% for electric-heater-based MSTES, an increase of 20.25 percentage points. These results demonstrate that the proposed scheme provides an effective and technically feasible approach to improve the flexibility and efficiency of CFPPs.