Load cycling rate of power-to-heat molten salt thermal storage and power generation system: Dynamic modeling and performance evaluation

To develop a low-carbon power system with high renewable energy penetration, this study proposes a novel power-to-heat energy storage and power generation (P2HES-PG) system, which utilizes molten salt thermal storage technology to achieve flexible heat-power decoupling and rapid load regulation. By establishing dynamic models, the rapid load cycling dynamic characteristics and exergy destruction evolution of the P2HES-PG system under different load ranges were investigated. The results demonstrate that, within a 25% THA amplitude, the maximum load down rates in the high, medium, and low load ranges are 15%, 12%, and 11% P_e min⁻¹, respectively, while the maximum load up rates reach 17%, 14%, and 11% P_e min⁻¹, exceeding the ramping rate of conventional power units. During load cycling processes, significant fluctuations in molten salt circulation flowrate were observed, directly affecting the thermal storage/release dynamics of the steam generator (SG) and the system's thermal performance. Dynamic exergy analysis indicates the condenser maintains a stable 20% exergy destruction share, while turbine and mechanical contributions increase with higher loads, and the regenerative system peaks at 13.97% during the low-load range loading down process. The SG exhibits lower exergy destruction than ideal conditions during the loading down process and higher destruction during the loading up process, providing a theoretical basis for optimizing system control strategies and improving system variable load energy efficiency.