Abstract
In many fuel cell applications metal hydride tanks offer an interesting method of storing hydrogen as an alternative to compressed or liquefied hydrogen due to low pressure requirements and high volumetric capacity. Nevertheless, the weight fraction of hydrogen in the total storage system is less than 2 wt.% with today’s standard materials. This
prevents metal hydride storage tanks from being broadly used, especially in mobile and portable applications.
Helmholtz-Zentrum Geesthacht in Germany has been working on metal hydride materials with a storage capability of up to 11wt.%. Such a high value suggests reconsideration of
this technology. However, the high hydrogen absorption capability comes together with a high temperature required to enable hydrogen release (>300°C).
Coupling this type of storage with a high temperature fuel cell, though, offers an opportunity of accessing the high storage capacity through the use of the off-heat of the fuel cell and at the same time exploiting the high conversion efficiency of the SOFC system of around 60% net.
Questions arise, though, on the sizing of the system components and the transient behaviour during start-up.
JÜLICH and Helmholtz-Zentrum Geesthacht have teamed up in analysing basic system properties for an application in rail buses or boats where an APU is required, but weight is of marginal importance.
