Lifetime powertrain optimization of a fuel cell electric truck including components’ ageing, cooling requirements and tractor packaging constraints

The current work compares numerical design optimization of a long haul fuel cell electric truck for minimizing lifetime total costs, carbon footprint and H2 consumption. Lifetime powertrain optimization considers the impact of fuel cell and battery ageing induced replacements by employing a nested co-design algorithm. The outer design layer explores possible fuel cell system, eDrive and battery dimensions with suitable power change rate limit and battery operating temperature. The inner EMS layer assures a fair energetic comparison of all evaluated cases through end-cycle SoC sustenance. It also performs iterative convergence between changing H2 tank capacity affecting vehicle mass and the corresponding varying fuel consumption impacting the required tank size. The effect of components’ sizing on traction load and powertrain efficiency were investigated including variations in cooling power and aerodynamic drag. A comparison of 700 bar and 350 bar H2 storage considering European tractor packaging space and mass limitation showed that powertrain sizing got significantly space constrained when employing the 350 bar tanks. For this 5-dimensional design search space with varying packaging limitation, over the 1.5% savings from manual tuning, numerical optimization of the fully loaded FCEV found 9.2%, 3.7%, 6.3% H2 fuel, total costs and carbon footprint savings for long haul and 10.6%, 15% and 12.9% for regional delivery mission. Freeing of packaging space with denser 700 bar tanks allowed larger powertrain dimensions and increased percentage savings to 15.1%, 12.6%, 13.1% for long haul and 14.8%, 14.7%, 13.8% for regional delivery. When carrying a nominal 13840 kg instead of the maximum 25000 kg payload, even with the improved efficiency of larger 700 bar powertrain designs, no significant lifetime benefit could be found over the 350 bar solutions.