COMPARATIVE STUDY OF GASEOUS HYDROGEN REFUELING PROCESS CONTROL APPROACHES

Sitra Colom, Frederic Barth

Air Liquide

Paris, France

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Abstract

A number of refueling stations for hydrogen vehicles have been put into service in the last years. However these stations are still at a demonstration stage and are designed for a limited number and variety of vehicles. Technical developments and standardization remains to be achieved for being able to operate as existing commercial stations capable of properly fueling any vehicle.

The objective is to transfer in the minimum time the right amount of hydrogen while remaining within the operating safety limits of the on-board hydrogen storage vessel. The accuracy and reliability of the refueling process control system is critical both to achieve a 100% fill and to avoid exceeding these operating limits. Apart from initial conditions and fuel gas temperature, vessel type and size determine the thermal behavior of the system for a given filling curve.

A refueling station must be able to safely supply high pressure hydrogen to a broad range of vehicles, each with their particular storage design. Furthermore, the fueling operation should be as easy and transparent as it is today with gasoline. Therefore

§  The control system has to be fully automatic so that the station can be used by anyone

§  The control system has to be able to deal with the differing behaviors of the storage systems of the vehicles coming to refuel.

Three different technical approaches are currently considered :

§  “No communication” : the stations carries out the refueling process without any information from the vehicle.

§  “Static communication” : a single set of data is communicated from the vehicle to the station at the beginning of the refueling process as input to the refueling process control.

§  “Dynamic communication” : a permanent data link is maintained between the vehicle and station throughout the fuelling process, thanks to which real time pressure and temperature values are communicated to the station as input to process control.

This paper details a comparative study of each approach based on work performed by Air Liquide and elsewhere.