Thermal modeling of a sodium borohydride-based hydrogen storage system

On-board hydrogen storage has been identified as one of the most challenging technical barriers to the transition from gasoline- to hydrogen-powered vehicles. The Hydrogen-On-Demand system patented by Millennium Cell Inc. uses sodium borohydride as a hydrogen storage medium. Sodium borohydride generates hydrogen when it reacts with water in the presence of catalyst. This system is much safer than other types of storage methods, such as compressed hydrogen, liquid hydrogen and metal hydrides. Nevertheless, it suffers severe disadvantages of adding significant amount of additional heat load to the already challenging thermal management problem of fuel-cell powered vehicles. To make this hydrogen storage method attractive, innovative thermal management should be adopted. This paper models the thermal behavior of a sodium borohydride-based hydrogen storage system and considers various potential methods to reduce the on-board cooling load by increasing reactor pressure and decreasing fuel cell pressure.