Modeling and evaluation of a plug-in hybrid fuel cell shuttle bus

The Center for Electromechanics at The University of Texas at Austin acquired a plug-in hybrid fuel cell bus for demonstration and model development under a program funded through the USDOT-FTA. The purpose of this program was to evaluate the performance and use of the bus while developing a model that could predict overall performance and energy consumption on daily driving routes. A model of the fuel cell bus was developed using PSAT (Powertrain Analysis Toolkit). The model development involved verifying component characteristics and a parametric study of drivetrain efficiencies to relate predicted to measured vehicle energy consumption data from on-road testing. The PSAT model was able to predict net energy consumption to within 5% over varying route profiles and vehicle conditions. Further investigations with advanced energy storage were performed to evaluate the benefits of ultracapacitor assisted batteries by using the correlated PSAT model. Ultracapacitors act as an additional load leveling device in the hybrid vehicle for peak propulsion and braking vehicle loads, thereby reducing stress on the batteries. The model simulation results show that ultracapacitors can increase overall vehicle economy by 2 to 4% and deliver a net increase in battery efficiency of 3 to 4%.