THE PERFORMANCE OF IC ENGINE AND FUEL CELL HYBRID PROPULSION SYSTEMS IN LIGHT DUTY VEHICLES

The report On the Road in 2020 provided a methodology for analyzing the performance of future light-duty vehicles and offered a broad comparison among these vehicles. This study furthers On the Road in 2020 by investigating two issues: the impact of driving schedule on the performance of these vehicles and the performance of fuel cell vehicles based on more optimistic assumptions than those used in the original study. It focuses on three propulsion systems: internal combustion engines operating on gasoline, fuel cells operating on hydrogen created from steam reforming gasoline, and fuel cells operating on a direct hydrogen feed. In addition, it investigated hybrid forms of these three systems. Using a simulation package used in its parent report based on the more optimistic assumptions concerning fuel cells, this study found that vehicles with fuel cells consumed less fuel and energy than those with gasoline engines. Fuel cells operating on direct hydrogen feed exhibited lower fuel and energy consumption than those operating on gasoline-reformate. The choice in driving schedule affected the actual fuel consumption for a specific vehicle configuration. Comparing against the IC engine non-hybrid vehicle, the gasoline-reformate fuel cell vehicle reduced fuel consumption by typically 30-40% for most driving schedules, though the US06 schedule only improved the consumption by about 15%. Hydrogen fuel cell vehicles reduced fuel consumption by typically 50-60%, though the US06 schedule did so by only 35%. Comparing against the IC engine hybrid vehicle, reduction in fuel consumption was more consistent for fuel cell hybrid vehicles over all driving schedules tested (typically 20% for gasoline-reformate and 40% for hydrogen). Hybridization of all propulsion system types resulted in large reduction in fuel consumption (typically 35-50%) for European and Japanese schedules, but only about 5-15% for US06 schedules. Thesis Supervisor: John B. Heywood Title: Sun Jae Professor of Mechanical Engineering