A Multi-Objective Framework for Optimal Sizing and Power Splitting in PEM Fuel Cell Hybrid Electric Vehicles

Fuel Cell Hybrid Electric Vehicles (FCHEVs) are promising solutions for reducing emissions, extending driving range, and reducing reliance on lithium. However, achieving optimal performance requires careful consideration of fuel cell and storage system sizing, battery aging, and energy management. This work proposes a co-design framework that simultaneously optimizes the weight, energy management, and battery lifespan of a fuel cell–battery–ultracapacitor power source. A single WLTP driving cycle is used for sizing, while battery aging is extrapolated over 1000 cycles. Multi-objective optimization is performed using both a Non-Sorted Harris Hawks Optimizer (NSHHO) and a Multi-Objective GreyWolves Optimizer (MOGWO), targeting total system mass (Mtot) and battery degradation metrics (capacity and resistance state-of-health, SOHcapand SOHres). The results indicate that the optimal total mass ranges between 215.4–223.4 kg, with a battery SOHcapdegradation of 0.091–0.0925 and SOHresdegradation of 0.09673–0.09676 over 1000 WLTP cycles. The selected medium solution (OS2) achievesMtot= 217.4 kg withfH= 0.0073 Hz, including 56 fuel cell cells, 63 battery cells, and 59 ultracapacitor cells. Battery EOL is predicted at 10,929 WLTP cycles for capacity and 10,337 cycles for resistance, representing a 36.6% improvement compared to literature values. The energy management strategy ensures accurate power sharing: the fuel cell covers low-frequency loads, the battery handles medium-frequency power, and ultracapacitors manage high-frequency peaks. Both NSHHO and MOGWO converge to consistent Pareto-optimal solutions, confirming the effectiveness and robustness of the proposed co-design framework.