Design and Performance Analysis of a Thermal Energy Storage System With Steam Extraction and Electric Heating in a Coal‐Fired Power Plant

ABSTRACT To alleviate the impact of the instability of renewable energy power generation on the power grid, coal‐fired power plants (CFPPs) have to undertake peak shaving tasks, which puts forward high requirements for the flexibility of CFPPs. To enhance the flexibility of CFPPs to consume more renewable energy, this paper innovatively proposes a thermal energy storage (TES) model of the main and reheat steam extraction heating coupled with electric heating (mode 1) and compares it with the model only using electric heating (mode 2). During the discharging process, the heat stored in the TES system is utilized to generate the main steam returning to the unit. The results show that for mode 1, during a heat storage and release cycle, the unit can increase the peak shaving capacity of 113.3 MW and provide extra electric power of 74.2 MW. Besides, the comprehensive coal consumption is 327.74 g/kWh, reduced by 10.1 g/kWh, about 2.99%, compared with 30% turbine heat acceptance (THA) condition. The round‐trip efficiency is 53.22%, 18% higher than that in mode 2. In the charging process, the main steam condensate has the most significant influence on the steam/water thermal storage power, accounting for about 66%, with the latent heat exchanger having the highest proportion. Mode 2 has the highest load reduction ability but with the largest irreversible loss. The cold salt temperature and the mass flow of generated steam affect the molten salt mass flow in the charging and discharging processes, respectively. In the TES system, exergy losses mainly come from the electric heater, phase change heat exchangers, and steam ejectors. This study can provide some references for enhancing the flexibility of CFPPs.