Performance and Durability of Hybrid Fuel Cell Systems for Class-8 Long Haul Trucks

Abstract

We investigated hybrid fuel cell-battery configurations that overcome thermal management issues in fuel cell powertrains for heavy-duty Class 8 trucks. The battery is sized so that it has sufficient capacity to provide supplemental power and energy on a hill climb transient at end-of-life. A dynamic load sharing strategy is developed to distribute the power demand between the fuel cell system (FCS) and the energy storage system in a manner that optimizes their lifetimes. The FCS end-of-life is identified as the terminal point beyond which the stack cannot generate the rated power with target power density at 0.7 V and 40°C ambient temperature. Reaching the target lifetime with a-Pt/C cathode catalyst in one hybrid configuration requires voltage clipping to 813 mV, idle power limited to 50 kW, catalyst overloading to 0.45 mg/cm2 total Pt in anode and cathode, and 44% active membrane area oversizing. The stack and FCS drive cycle efficiencies decrease by 4.2 % and 5.4%, respectively, during the electrode lifetime. The FCS performance, durability and cost are compared with the targets of 68% peak efficiency, 0.30 mg/cm2 total Pt loading, 2.5 kW/gPGM Pt group metal (PGM) loading, 750 mW/cm2 power density, 25,000-h lifetime and $80/kW cost.