Energy Storage for Flexibility of Thermal Power Plants: Integration Strategies and Environmental-Economic Implications

The increasing penetration of wind and solar power, together with their intermittency and uncertainty, has increased the demand for flexible regulation in power systems. However, peak shaving and frequency regulation can reduce the efficiency of thermal power units, intensify thermal stress, accelerate equipment degradation, and complicate pollutant emission control. Energy storage integration therefore offers a promising pathway for enhancing thermal power flexibility while alleviating unit-level operational burdens. This review examines energy storage technologies for thermal power flexibility, focusing on electrochemical energy storage, molten salt thermal energy storage, flywheel energy storage, and gravity energy storage. Their operational characteristics, application scenarios, and roles in frequency regulation and peak shaving are compared. The impacts of energy storage integration on unit efficiency and peak-shaving capability are further analyzed by considering the operational characteristics of thermal power units. In addition, different energy storage pathways for peak shaving and frequency regulation are evaluated in terms of environmental and economic impacts. Finally, future research priorities are discussed, including deeper thermodynamic integration, multi-energy and multi-timescale coordination, economic value realization, engineering reliability, and life-cycle sustainability.