Design and performance analysis of hybrid Carnot battery for LNG dual-fuel ship

To solve the energy waste problem of LNG dual-fuel ships, a hybrid Carnot battery system integrating engine waste heat recovery and LNG cold energy utilization is proposed in this study. The system uses R245fa and R1234yf as the working medium for heat storage and cold storage respectively, combined with supercritical carbon dioxide power generation cycle. Based on the steady-state thermodynamic model (validation assumptions include the compressor isentropic efficiency of 80% and the heat exchanger minimum temperature difference of 5°C), the energy flow, exergy loss and parameter sensitivity are analyzed. The simulation results show that the coefficient of performance (COP) of heat storage cycle is 6.607, and the round-trip efficiency is 112.96%. The EER of storage cycle refrigeration was 4.0243, and the round-trip efficiency was 77.04%. Evaporator (exergy loss 26.3%) and throttle valve (15.9%) are the main sources of irreversible loss. Parameter analysis shows that the efficiency can be increased by 5%-8% when the heat source temperature is raised to 92°C, and the equipment volume is reduced by 1/5-1/10 compared with the traditional system. The modular design and multi-energy complementary characteristics of the system are suitable for Marine scenarios, but the practicality needs to be further optimized through heat recovery and advanced control strategies.