Design and thermo-economic analysis on molten salt thermal energy storage system integrated within coal-fired power plant: Co-storing energy from live and reheat steam

With the increasing penetration of renewable power within the power grid, the operational flexibility of coal-fired power plants (CFPPs) should be enhanced. The integration of thermal energy storage (TES) systems can decouple the energy flow from the boiler to turbines, and then enhance the operational flexibility of coal-fired power plants (CFPPs). The TES co-storing energy from live and reheat steam is a potential way, and appropriate system configurations are critical for good thermo-economic performance. In this study, three TES modes, including series, parallel, and hybrid modes, co-storing energy from live and reheat steam were proposed. In series and parallel modes, molten salt is heated by reheat and live steam in turn and parallel, respectively. The hybrid mode applies two charging stages in which the heating method of series and parallel modes are comprehensively used. Thermo-economic models were developed, and thermodynamic performance and techno-economic feasibility of the proposed system were evaluated. The results show that the minimum output power ratio of the CFPP can be reduced from 30 % to 19.02 %. The series mode has the highest equivalent round-trip efficiency at 58.92 %, followed by the hybrid and parallel modes with 45.08 % and 39.33 %. The payback period in series, parallel, and hybrid modes is about 3.7, 2.8, and 3.6 years, respectively.