Maximizing Direct-Hydrogen PEM Fuel Cell Vehicle Efficiency – Is Hybridization Necessary? 1999-01-0530

The question of whether or not direct-hydrogen fuel cell systems in automotive applications should be used in load following or load leveled (battery hybrid) configurations is addressed. Both qualitative and quantitative analyses are performed to determine the potential strengths and weaknesses of each option. It is determined that the amount of energy that can be recovered through regenerative braking has a strong impact on the relative fuel economy of load following versus load leveled operation. Further, it is demonstrated that driving cycles with lower power requirements will show an improvement in vehicle fuel economy from hybridization while those with higher power requirements will not. Finally it is acknowledged that the practical considerations of cost and volume must also weigh heavily into the decision between the two configurations.