Thermodynamic and techno-economic analysis of a novel compressed $ \mathrm{CO_2} $ energy storage system coupled with coal-fired power plant

Liquid \mathrm{CO_2} energy storage (LCES) offers advantages such as high energy storage density, compact equipment, and high safety, making them one of the most promising large-scale long-duration energy storage technologies. However, their relatively low cycle efficiency remains the primary factor limiting their development. To improve the cycle efficiency of the LCES system, this paper proposes coupling the coal-fired power plant (CFPP) with the LCES system. This integration optimizes LCES performance while eliminating thermal storage infrastructure requirements. Simultaneously, it increases the peak-shaving capacity of CFPP, enhancing grid stability amid high renewable penetration. This study investigates the coupling performance of the CFPP with LCES systems of different capacities under various operating conditions. The results show that under different operating conditions, the cycle efficiency of the LCES system coupled with the CFPP can reach over 60%. Among these, the best performance is achieved when the CFPP operates at 100% THA and the LCES system has double the capacity. At this point, the LCES system’s cycle efficiency can reach 67.49%.