Pre-Cooling and Communication Requirements for 70MPa Hydrogen Fueling

All major vehicle OEMs are transitioning their light-duty fuel cell vehicle fleets to 70MPa (10,000 psi) on-board storage.  This shift allows greater hydrogen mass stored on vehicles without increasing the outer volume of the storage system.  The rapid fueling of these 70MPa fuel systems is a key barrier to the entry of fuel cell vehicles to the market.  The automotive industry have created a fueling document which specifies a  3 minute fueling for vehicles with 5 kg of hydrogen storage at 70MPa.

Rapid fueling of hydrogen at 70MPa is possible, but the heat generated is significantly greater than has been seen in 35MPa fueling.  As such, greater investigation into fueling thermodynamics has been made. 

The design of fueling stations must account for the variations in fuel system design and ambient conditions.  Active means to reduce fueling time and gas temperature may be necessary.   For example, station-side pre-cooling of the inflowing hydrogen gas will lower the peak temperature reached in the vehicle, where as communication allows the station to continuously monitor vehicle conditions to both improve the efficiency of the fill and to ensure an unsafe condition in not reached.   Also, active flow control may help eliminate temperature spikes caused by rapid changes in flow rate.

This paper will focus on an analysis of data generated during fueling trials conducted on real world vehicle fuel systems at 70MPa, examining the potential benefits of pre-cooling, communication, and active flow control.