An Efficient Carnot Battery System Based on Retired Coal-Fired Power Plant: Thermodynamic Analysis and Performance Evaluation

Abstract

A novel Carnot battery system has been proposed in this study, featuring a deep integration of retired coal-fired power plant and pumped thermal energy storage, with the aim of improving overall system performance and facilitating the low-carbon transition of the power grid. A compression heat pump subsystem is introduced into the system, which effectively enhances the ability of the system to capture low-grade heat from ambient. Additionally, the combination of the high-pressure heaters bypass operation strategy with the Solar salt-Hitec salt hybrid system results in a substantial augmentation of the exothermic temperature range of the system. Compared to the reference system, the proposed system increases the coefficient of performance by 0.09 and raises the round-trip efficiency by 3.00%, achieving 57.35% under identical electrical input. Annual carbon emissions decrease by approximately 8.93 × 105 t, while the net present value rises by 153.18 M$, and the dynamic payback period shortens by 2.06 years. Sensitivity analysis identifies an optimal recuperator inlet temperature of 50 °C and R245fa as the preferred working fluid. Further enhancement of compressor and turbine isentropic efficiencies markedly improves system performance, underscoring the potential of the proposed system for large-scale, low-carbon energy storage applications.

Keywords: Carnot battery, Pumped thermal energy storage, Molten salt, Coal-fired power plants, Thermodynamic analysis