Fuel cells have been shown to reduce vehicle or tailpipe emissions and increase efficiency for the heavy-duty transportation application. Successful on-board hydrogen production from liquid fuels significantly enhances the ability of fuel cell vehicles to meet the application requirements for extended operation, energy density, etc. The U.S. DOE, DOT (FTA), and DOD have funded four development projects managed through Georgetown University for liquid-fueled, fuel cell systems utilizing on-board hydrogen production for the transit bus application.

Phase 1 consisted of a 50 kW, low temperature (250-300ºC) methanol steam reformed, Phosphoric Acid Fuel Cell (PAFC) system in a hybrid arrangement with 100 kW of Saft Ni-Cad batteries to power a 30’ transit bus. The low temperature methanol reformer had a long time constant, requiring approximately 4 minutes to transition from 25% to 100% power output. The slow transient response required a large battery capacity, which negatively impacted the weight and performance of the vehicle.

For Phase 2, a 100 kW, high temperature (800-850ºC) methanol steam reformed PAFC system was used with approximately 100 kW of lead-acid batteries to power a full-sized 40’ transit bus. The high temperature reformer, due to improved design and reaction kinetics, significantly lowered the time constant and the transition from 25% to 100% power output was achieved in 5 seconds. This paper details the improved performance and resulting benefits from incorporating a high temperature steam reformer with low-temperature shift converter. Figure 1 shows the nearly constant reformer temperature with changes in load, highlighting the improved design and control.