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Publication

A Method for Determining the Optimal Delivered Hydrogen Pressure for Fuel Cell Electric Vehicles

Publication Type
Journal
Journal Name
Applied Energy
Publication Date
Page Numbers
183 to 194
Volume
216

Fuel cell electric vehicles (FCEVs) are considered an important long-term technology strategy to reduce petroleum use and greenhouse gas emissions from transportation. The advantages of FCEVs compared to other zero emission vehicles include short refueling time and long driving range, both of which are related to the onboard hydrogen storage system and the underlying storage capacity and pressure. The onboard nominal working pressure (NWP) can affect the vehicle tank design, infrastructure design and logistics, hydrogen station costs, and the driving range, ultimately affecting consumer acceptance. Conceptually, the delivered hydrogen pressure (DHP) from the station could match or be less than the NWP in order to lower the associated cost of the infrastructure. This study developed and utilized the Hydrogen Optimal Pressure (HOP) model to systematically identify the optimal DHP among 350, 500, and 700 bar with the lowest total consumer cost and analyze how the optimal DHP may be affected by attributes of the driver, the vehicle, and the hydrogen refueling station. The analysis varied the DHP from the station while assuming the vehicle onboard hydrogen pressure remained consistent at a nominal working pressure (NWP) of 700 bar for all DHP variations. A lower DHP reduces the delivered hydrogen cost and the vehicle driving range. While the inconvenience of a reduced driving range can be compensated for with the deployment of more stations, the increase in the number of stations may result in a lower average station utilization, which leads to a higher delivered hydrogen cost. Station utilization can be increased with smaller capacity stations, but the diseconomy of scale also leads to a higher delivered hydrogen cost. These intertwined relationships are quantitatively captured in the HOP model. It is found that the
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optimal DHP is sensitive to regional context, fuel economy, driving pattern and time value. The DHP of 700 bar was found to be a robustly better choice than 350 bar or 500 bar for different regional contexts, different driver types, time values, and fuel economies, although the urgency for pressure upgrades is less with a Cluster Strategy than with a Region Strategy for station deployment.