Optimal Gear Selection and Lifetime-Aware Fuel-Cell Power Allocation for a Hybrid Multi-Fuel-Cell Heavy-Duty Truck

Hybrid heavy-duty vehicles powered by multiple fuel cells (FCs) offer opportunities to improve energy efficiency and support sustainable powertrain operation through powertrain-level optimization. This study investigates optimal gear shifting to reduce the electrical-power demand of the electric machine (EM) and optimal power distribution among multiple FCs with different ageing states. A longitudinal vehicle model determines the wheel power demand and propagates the operating point backward through the drivetrain. An optimization-based gear-selection strategy identifies the gear that minimizes the required EM power, while a closed-form optimization method optimally distributes a given total FC power demand among multiple FCs according to the specific electrical energy output and remaining useful life of each FC. An active-set procedure enforces FC operating limits. The methods are evaluated using a Paris–Munich ESCALATE drive cycle and several FC age configurations. Depending on the operating point, optimal gear selection reduces EM power demand by up to 50 kW, while optimal FC power distribution reduces hydrogen-consumption rate by up to $3.1\%$ and $3.3\%$ compared with equal power distribution for dual and three-FC configurations, respectively. The optimized allocation may also have implications for long-term FC ageing and maintenance planning, providing an additional perspective for future assessments of powertrain sustainability.