Performance of Molten Salt Thermal Energy Storage System Based on Reheat Steam Extraction from Coal-fired Power Plants

A coupled system based on reheated steam extraction and molten salt thermal storage was presented, and the operation processes and efficiency of the system were analyzed. In order to match the main steam temperature, electric heating was used to elevate the molten salt temperature after heat exchanging with extracted steam during the charging process. On this basis, the effects of average temperature difference in charging process, temperature difference of pinch point in discharging process and lower storage temperature of molten salt on system performance parameters were studied. Results show that with a fixed temperature difference of 10 K of the charging process, increasing the temperature difference of pinch point from 5 K to 15 K, the maximum equivalent round-trip efficiency reduces from 88.2% to 85.0%, and the optimal heat storage temperature will increase from 314 ℃ to 324 ℃. With fixed pinch point of 10 K, the round-trip efficiency decreased from 89.5% to 85.8% when the average temperature difference of the charging process increased from 5 K to 15 K. With both temperature differences of 10 K, the maximum equivalent round-trip efficiency is 87.1%, and the minimum load of the unit is reduced from 30% to 24.3%.