the available H2 at a rate required by a particular application or rehydrogenate it within a specified fill time. This limitation has been addressed in several modeling and experimental studies. For example, a full-scale hydride tank operated at 120 ºC and 220 ºC was demonstrated using 86 kg NaAlH4 to store 3.0 kg hydrogen. Graphite was added (~9 wt%) to improve heat transport, as prior investigations showed that mixing hydrides with materials such as expanded natural graphite (ENG) and carbon nanotubes can dramatically increase thermal conductivity. However, such additives reduce storage capacity, as this represents dead (i.e. non hydrogen-absorbing) mass, as discussed previously. Moreover, they may not address unfavorable thermodynamics and kinetics, which can reduce usable capacity when H2 must be burned to bring the hydride bed to a temperature that generates the minimum pressure required by a fuel cell (5 bar). Finally, physical mixtures of hydrides with other highly thermally conducting materials may segregate upon cycling, thereby reducing usable capacity over time as the thermal conductivity degrades. Both the unfavorable desorption thermodynamics and kinetics of metal hydrides and their poor thermal conductivity can be addressed by nanoconfinement within a nanoporous host material, such as porous carbon or a metal-organic framework (MOF). This is a vigorous area of hydrogen storage research and was recently reviewed. Nanoporous carbon hosts are also expected to improve thermal conductivity, but so far this speculation lacks experimental confirmation. In the only example of altered thermal conductivity by a metal hydride within a nanoporous host we are aware of, MgH2 encapsulated in reduced graphene oxide (rGO), the carbon host increased the thermal conductivity by only ~20%. This was likely due to the insulating properties of GO and the poor thermal contact with the packedpowder sample. However, MgH2 nanoparticles supported on graphene do have thermal conductivity ~100 times higher than unsupported nanoparticles. Nanoconfinement has additional advantages compared to physical mixtures of hydrides and thermally conducting carbons prepared, for example, by ball milling, as the hydride would be in intimate contact with host and could even be chemically bound to it. This should minimize agglomeration of hydride nanoparticles but a detailed investigation of LiBH4 supported on nanoporous carbon demonstrates that, at least for this hydride, capacity loss occurs when the dehydrogenation product LiH diffuses out of the pores. The integrated benefits of nanoscaling for a storage system are not easily quantified, however, as they depend on both the properties of the material and the specifics of the storage system. Consequently, models designed to predict either material properties or the performance of a storage system cannot be used in isolation.