Hybrid Fuel Cell Systems for Heavy-Duty Trucks: Configuration, Heat Rejection and Performance

Although low-temperature (LT) polymer electrolyte membrane (PEM) fuel cell (FC) systems can be more efficient than diesel engines, heat rejection in Class-8 heavy duty FC trucks is an issue because of a higher radiator heat load for the same rated power and lower operating temperatures. This work explores 400-kWe FC-battery hybrid (FCH) platforms and operating strategies to manage heat rejection without enlarging the frontal area of the radiator. The LT-PEMFC is generally operated at 60-80oC for 25,000-h lifetime and sporadically at 90oC or higher temperatures during short transients where heat rejection is a challenge. Four maximum stack coolant exit temperatures () are identified. The platform features the smallest FC system (FCS) and satisfies all system and vehicle requirements at the end of stack lifetime at a  of  90oC: ≥750 mWe/cm2 stack power density (PD) at rated power, 175 kWe(net) FCS power at top speed, and 400 kWe  FCH power on a 6% grade. The FC stack in the FCH achieves the highest PD of 840 mWe/cm2 at a  of  95oC. The FCH includes the largest 275 kWe(net) FCS that can reach ≥750 mWe/cm2 PD at a  of 102oC. The platform becomes a stand-alone 400 kWe(net) FCS that has a 480 kWe stack with a lower PD of 460 mWe/cm2 at a  of 115oC.