Comparative investigation on the thermodynamic performance of coal-fired power plant integrating with the molten salt thermal storage system

Abstract

One of the most critical challenges facing China is enhancing the operational flexibility of coal-fired power plants (CFPPs), given the increasing reliance on renewable energy for power generation. This study focuses on analyzing and comparing the molten salt thermal storage systems integrated in CFPP in consideration of peak-shaving capacity, equivalent round-trip efficiency, heat consumption rate, and exergy efficiency. Five charging schemes integrating thermal energy storage (TES), power to heat (P2H) and combination of TES and P2H are proposed and tested via their thermodynamic models. Results show that all five integrated molten salt thermal storage systems can enhance the peak shaving capability of the CFPP. When integrating P2H system, CFPP has the potential to achieve a zero-power output. Furthermore, comparing to the other four schemes, P2H-only integrating scheme has the highest equivalent round-trip efficiency of 36.23 % and the lowest heat consumption rate of 8288.87 kJ·(kW·h)−1. However, its exergy efficiency decreases to 36.51 % due to the electric heater experiencing the highest exergy loss of 132.56 MW, in contrast to the TES-coupled system which shows a higher exergy efficiency of 39.58 %. The P2H-only scheme boasts the largest investment of $33,353,100 and the longest repayment time, while also earning the highest compensation for peak shaving. This study provides a promising approach for molten salt thermal storage system designs in enhancing flexibility for CFPPs.