THERMAL-ECONOMIC FEASIBILITY OF COAL-FIRED POWER PLANT INTEGRATED WITH POWER-TO-HEAT THERMAL ENERGY STORAGE SYSTEM

The new power system with renewable energy as the main body puts forward higher requirements for the operational flexibility of coal-fired power plants (CFPP). In this study, three systems of the CFPP integrated with molten salt thermal storage with power-to-heat heaters are proposed. To evaluate the thermodynamic performance of the integrated thermal energy storage system, simulation and thermodynamic models for a 600MW CFPP were developed. The molten salt thermal storage system (MSTES) was designed, and the maximum discharging power and the discharge duration of the MSTES are 312.2 MW and 2.8 h, respectively. Exergy analysis results show that the exergy loss of electrical heaters in the charging process is up to 44.02%, which is the largest exergy loss part in the power-to-heat-to-power cycle of the integrated system. Compared with the standalone CFPP, using molten salt thermal energy storage to replace part of the boiler heat load or extracting steam from turbines can enhance the system's thermodynamic performance. The largest equivalent round-trip efficiency (electricity to electricity) of the system is 48.89%. Then, an economic analysis model is developed to explore the power-to-heat thermal energy storage system’s economics. The scheme of heating feed water to live steam is a good integration option with the lowest LCOD of 160.54 USD/MWh.