Design and performance evaluation of a new thermal energy storage system integrated within a coal-fired power plant

Thermal power plants are required to enhance operational flexibility to ensure the power grid stability with the increasing share of intermittent renewable power. Integrating thermal energy storage is a potential solution. This work proposes a novel system of molten salt thermal storage based on multiple heat sources (i.e., high-temperature flue gas and superheated steam) integrated within a coal-fired power plant. To evaluate the performance of the thermal energy storage system, simulation models were established, and exergy analysis was conducted. Results show that the integration of molten salt thermal storage achieves the synergistic improvement of operational flexibility and thermal efficiency of the thermal power system. When the boiler keeps steady combustion, the minimum power load decreases from 30% to 14.51% of the rated load during the charging process because of the integration of the thermal energy storage system. To decrease the power load of the coal-fired power plant, the surplus heat is stored in the thermal storage system to be used later. The equivalent round-trip efficiency of the thermal energy storage system is up to 85.17%, which is achieved by the appropriate match between the heat sources and the thermal storage media.