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Today's fuel cell powered vehicles typically utilize compressed hydrogen storage systems with a nominal working pressure of either 35MPa or 70Mpa. This coexistence of working pressures has, in a large part, developed in isolation, in that automakers have primarily considered vehicle side issues when choosing the storage system pressure. This study looks at hydrogen fueling from a holistic perspective by considering both vehicle side and station side issues with the goal to determine an optimum hydrogen working pressure. The approach utilized is to first conduct a data driven study of vehicle fueling at different working pressures and ambient temperatures to determine the vehicle and thermodynamic considerations of hydrogen fueling. This data is then contrasted with the hydrogen station hardware required to perform fueling at these temperatures and pressures.

With the increasing prevalence of fuel cell vehicles, hydrogen consumption during fuel economy certification needs to be measured in an accurate and convenient manner. Typically, consumption is measured by weighing hydrogen cylinders before and after testing and calculating the amount of depleted hydrogen by the difference in weight. This method is theoretically highly accurate but time-consuming. This paper describes a new method developed to measure hydrogen consumption using a flow meter system. With a flow meter input pressure of 2MPa, and a minimum flow rate of 4NL/min, this new system achieves a level of error that is within 0.5% of the weight measurement method, but is far simpler and reduces the measuring time by approximately 130 minutes.