Thermo - economic Performance of Retrofitting Decommissioned Coal-fired Power Plant by Carnot Battery Energy Storage

With the advancement of the double carbon goals, the repurposing of decommissioned coal-fired power plants has become a critical issue in energy system optimization. Based on the double carbon scenario and the retirement needs of coal-fired power plants, this paper proposes a scheme to retrofit the 135MW decommissioned power plant into Carnot battery by integrating the characteristics of Carnot batteries and coal-fired power plants. A thermodynamic model for the coupling of the power plant and Carnot battery is established, and the performance differences of different coupling schemes are clarified through thermodynamic analysis. Meanwhile, an economic analysis is conducted. The results show that the steam extraction location significantly affects the performance of the retrofitted system. When using the final-stage extraction steam from the intermediate-pressure steam turbine for thermal storage, the system achieves the highest round-trip efficiency of 54.2%. The most economical scheme involves using the first-stage extraction steam from the low-pressure steam turbine for thermal storage, with a total investment of approximately 496.8 million yuan. When the valley electricity price varies between 0.1-0.4 CNY/(kW·h), the static investment payback period increases from 4.9 years to 14.6 years.