Thermo-economic analysis of a carnot battery integrated with coal-fired power plant and thermochemical energy storage

To markedly enhance renewable-energy penetration and expedite the decarbonisation of coal-fired power stations, a Carnot-battery concept that synergises high-temperature thermochemical storage with an existing coal unit is proposed. The architecture adopts an inverted supercritical CO₂ Brayton cycle. Calcium-oxide/calcium-hydroxide (CaO/Ca(OH)₂) serves as the reversible thermochemical medium for thermal energy retention. In the energy release system, the reheated steam absorbs the heat released from the hydration reaction to replace part of the boiler heat load. Aspen Plus is employed to model the system, and its accuracy is verified using actual operational data. The results of the thermodynamic analysis show that the optimised round-trip efficiency of the coupled system under design conditions is 62.4%. Under the off-design condition, the coupled system has the maximum round-trip efficiency when the electricity storage capacity is about 40 MW. Deployment of the Carnot-battery system is projected to cut coal use by over 7.3%. Economic modelling indicates a levelised electricity cost of 1.18 RMB kWh1 and a dynamic pay-back horizon of 25 years for the integrated plant.