The flexibility of a molten salt thermal energy storage (TES)-integrated coal-fired power plant

Integrating molten salt thermal energy storage (TES) into a coal-fired power plant can improve its operational flexibility. Existing research has primarily focused on the changes in the plant's load range, i.e., the magnitude of flexibility, while the plant's ramp rate, i.e., the velocity of flexibility, has not been carefully studied. This study fills this knowledge gap by investigating the dynamic operation of a molten salt TES-integrated power plant. A system-level dynamic model of an integrated system was developed and validated. The validated model was used to simulate load-variation processes between 30 %PN and 100 %PN, at target ramp rates from 2 %PN/min to 5 %PN/min. Results indicate that, compared to the standalone plant, the TES-integrated system achieves higher exergy efficiency at load rates below 45 %PN (based on validation mean absolute percentage error < 4 %). Moreover, the RTE of the molten salt TES varies from 49.4 % to 62.3 %, depending on the plant's load range and ramp rate. In addition, the integration of a molten salt TES unit remarkably improves the plant's capability in providing flexibility services, certified by the integrated system's responses to one-hour automatic generation control (AGC) commands.