Full-range performance analysis of a Carnot battery system coupled thermochemical energy storage and coal-fired power plant

The Carnot battery is a promising energy storage technology. Integrating it with coal-fired plants enables energy storage and enhances flexibility. However, existing research primarily focuses on design conditions, lacking full-range performance analysis. Furthermore, the critical impact on boiler thermal balance is rarely considered, which may lead to unrealistic results and safety risks. This study proposes a Carnot battery system integrating a coal-fired plant with Ca(OH)₂/CaO thermochemical energy storage and a supercritical CO₂ reverse Brayton cycle, aiming for energy storage, coal consumption reduction, and operational flexibility enhancement. An Aspen-Matlab co-simulation model is developed for full-range analysis. Two energy release strategies—Mass-Based and Time-Based—are proposed. Crucially, the system's impact on boiler thermal balance is examined and the analysis shows original boiler design causes excessively high main steam temperature and low reheat steam/flue gas temperatures under off-design conditions. A boiler retrofit scheme is proposed and subsequent analysis shows that within 20-100 MW storage capacity, cumulative coal savings reach 7.7%-17.8%, with round-trip efficiency of 31.0%-53.7%. Finally, a peak-raising strategy using hydration heat to replace extracted steam is proposed, providing up to 89.2 MW additional capacity and extending the unit's operating range to 0-125% THA. Under the design condition, the system achieves a levelized cost of storage of 0.74 RMB/kWh, and a net present value of 69.96 million RMB. This research advances practical deployment of renewable energy-storage-thermal power integration.