The tightening emissions regulations across the globe pose significant challenges to vehicle OEMs. As a result, OEMs are diversifying their powertrain solutions e.g., CNG/Propane based conventional powertrains, BEVs, H2 ICE, FCEV, etc. to meet these regulations. More recently, the ‘CARB Advanced Clean Trucks’ and ‘EPA GHG Phase 3’ regulations are forcing manufacturers to increasingly adopt zero tailpipe emission solutions. While passenger vehicle applications are trending towards a single consensus i.e., BEVs, the heavy-duty on-road applications are challenged with unique requirements of high payload capacity, higher range, lower sales volumes, higher durability, short refueling time, etc. These requirements are driving manufacturers to consider FCEV as an alternative powertrain solution to BEV specifically for higher payload capacity, and range applications.
Previously, the authors have published numerous model-based powertrain architecture optimization studies comparing different conventional, hybrid, and alternate powertrain solutions for heavy-duty applications [1,2]. While the suitability of a particular solution, e.g., BEV or FCEV, depends significantly on the type of application i.e., urban, regional, or long haul, it is important to conduct a thorough system level powertrain optimization study of each architecture for sound decision making on concept selection and component sizing. This study focuses on model-based propulsion system optimization of a fuel cell electric Class 8 long haul truck using GT-SUITE and MATLAB/Simulink.
A 1-D model of a class 8 heavy-duty truck with a conventional diesel powertrain was first developed and validated against on-road test data. The model was then adapted for a fuel cell powertrain which included fuel cell stack, fuel cell balance of plant loads, high-power LTO high-voltage battery pack, e-axle, thermal system and electrified accessories. To ensure optimal control for each powertrain configuration and size, an ECMS-based control strategy was developed for determining the optimal power split between the fuel cell and high-voltage battery. Powertrain component models for fuel cell, high-voltage battery, e-axle motor, e-axle geartrain, H2 tank etc., were parameterized to perform sizing optimizations and identify the optimal component specifications which would meet the vehicle performance requirements while maximizing efficiency, range and battery life for a given estimated vehicle direct manufacturing cost increase.