Assessing and Modeling Direct Hydrogen and Gasoline Reforming Fuel Cell Vehicles and Their Cold-Start Performance

This paper analyzes fuel economy benefits of direct hydrogen and gasoline reformer fuel cell vehicles, with special focus on cold-start impacts on these fuel cell based vehicles. Comparing several existing influential studies reveals that the most probable estimates from these studies differ greatly on the implied benefits of both types of fuel cell vehicles at the tank-to-wheel level (vehicle-powertrain efficiency and/or specific power), leading to great uncertainties in estimating well-to-wheel fuel energy and/or greenhouse gas (GHG) emission reduction potentials. This paper first addresses methodological issues to influence the outcome of these analyses. With one exception, we find that these studies consistently ignore cold-start and warm-up issues, which play important roles in determining both energy penalties and start-up time of fuel cell vehicles. To better understand cold-start and warm-up behavior, this paper examines approaches and results based on two available U.S. Department of Energy and USCAR funded National Laboratory vehicle simulation models - PSAT and ADVISOR. Our analysis reveals that the predicted cold-start effects are influenced by assumed choices concerning trade-offs between maximizing warm-up rate vs. minimizing wasteful energy during cold-starts, time to achievement of full power capability, and different modeling approaches. It appears that different cold-start warm-up strategies could result in a wide range of (1) vehicle performance capabilities as a function of time from start-up and (2) associated cold-start net energy penalties.