[Objective] To meet the increasing demand for deep peak -shaving capability of coal -fired power plants(CFPP) under the “dual-carbon” targets, this paper proposes a novel liquid carbon dioxide energy storage system (LCES) integrated with a coal-fired power plant, aiming to improve both operational flexibility and overall energy utilization efficiency. 

[Methods] A 1 000 MW ultra-supercritical coal-fired power plant coupled with a liquid CO₂ energy storage system is selected as the research object . Using the EBSILON platform, a comprehensive thermodynamic and economic model is developed. During the charg ing process, compression heat is effectively recovered by utilizing condensate water from coal-fired power plant. During the discharging process, a cascaded heating strategy is adopted, in which CO₂ is preheated using both low-temperature and high-temperature feedwater to improve the turbine inlet condition and increase power output. Various coupling configurations, including different return water locations and feedwater extraction positions, are systematically investigated to determine the optimal integration scheme. In addition, the effects of key parameters, such as high- and low-pressure tank pressures, 2 throttle valve pressure drop, and mass flow rate, on system performance are analyzed in detail. 

[Results] The results indicate that, under the optimal c oupling scheme, the proposed system significantly outperforms the stand -alone LCES system. Specifically, the electrical efficiency increases by 11.41%, while the energy density improves by 3.32 kW·h/m³. Meanwhile, the levelized cost of electricity (LCOE) d ecreases from 0.091 dollar/(kW·h) to 0.082 dollar/(kW·h), demonstrating enhanced economic performance and cost competitiveness. Moreover, the load regulation range of the coal -fired unit is expanded to 93.26% ~102.82%, indicating substantially improved operational flexibility and wider load adjustment capability. Among all system components, turbomachinery contributes the largest share to the total investment cost and plays a critical role in determining both thermodynamic and economic performance. Parametric analysis further reveals that the high-/low-pressure tank pressures, throttle valve pressure drop, and mass flow rate have significant and sometimes competing effects on system performance, providing important guidance for system optimization and parameter selection. 

[Conclusions] The proposed coupled system enables efficient recovery of compression heat and multi-stage feedwater heating during the discharging process without relying on large-scale external thermal storage devices. By achieving effective thermal integration and cascade utilization of energy, the system significantly enhances the flexibility and efficiency of coal-fired power plants. This study provides valuable insights and practical guidance for the engineering application, system design, and large-scale integration of CO ₂-based energy storage technologies with conventional thermal power systems, contributing to the transition toward low-carbon and flexible energy systems.