Design of Thermal Management System Based on Phase Change Material for Fuel Cell Hybrid Electric Vehicles: A Numerical Study

Abstract

In this study, a numerical analysis of the thermal management system for a fuel cell hybrid electric vehicle (FCHEV), based on the second‐generation Toyota Mirai, has been conducted. Within the scope of the model, the fuel cell stack, electric motor, high‐voltage battery, cabin heating/cooling system, and phase‐change material (PCM) based thermal storage unit have been considered as a single integrated system. Hydrogen consumption, component temperatures, battery state of charge, the effect of regenerative braking, cabin thermal behavior, and waste heat recovery have been analyzed for summer and winter operating conditions within the WLTC Class 3 driving cycle. In the proposed model, while the fuel cell is regarded as the primary energy source, the battery functions as a secondary energy storage system, used to meet sudden power demands and to store energy recovered from regenerative braking. The control strategy is designed to recover waste heat energy generated by the fuel cell and electric motor for cabin heating and PCM charging. The model also considers dynamic battery SOC behavior, fuel‐cell load‐following operation, cabin thermal behavior, and PCM charge/discharge behavior. The results obtained demonstrate that the proposed integrated thermal management approach can utilize fuel cell and electric motor waste heat to support cabin heating, particularly in winter conditions. The simulated hydrogen consumption is 0.944 kg/100 km under WLTP‐like conditions, within 6% of the certified value of 0.89 kg/100 km, rising to 0.989 and 1.007 kg/100 km under summer and winter HVAC loads, respectively. In winter, 29.2% of the powertrain waste heat is recovered; the pre‐charged PCM unit delivers 1204 Wh of cabin heat, covers 73.9% of the delivered heating during the first 10 min of the cold start, and reduces the PTC consumption by 58.4% and the hydrogen consumption by 5.8% compared with the no‐PCM baseline In conclusion, the PCM‐assisted integrated thermal management system offers a measurable improvement in energy efficiency and cabin heating performance in fuel cell vehicles, but its effectiveness depends strongly on the control strategy, the initial thermal state of the storage, and the sizing of the PCM unit.