dsorptive storage of hydrogen is being examined as one of the
approaches for safe and economical storage of hydrogen, in order to address
this key challenge in widespread application of hydrogen economy. The focus
of this work is a theoretical analysis of adsorptive storage of hydrogen on
adsorbents (such as metal-organic frameworks, i.e., MOFs) for distributed
power applications. MOFs are considered as promising adsorbents for their
large hydrogen storage capacities, well-defined structures and high pore
volumes. Modeling of hydrogen adsorption has been extensively studied over
a wide range of scales: From ab initio and molecular-level to characterize
the adsorption process and energetics, to entire system level to
investigate discharge and refueling dynamics. However, a multi-scale
approach, which combines analysis over scales ranging from molecular to
device level is missing. First, a critical analysis of device-level model
is presented for 2D model of refueling hydrogen storage tank containing
MOF-5 adsorbent under cryogenic and room temperature conditions. Adsorption
isotherm model was confirmed to be a critical parameter, whereas the effect
of other assumptions (such as ideal gas law or Darcy’s approximation for
the porous bed) was observed to be less important. Since pellets of MOF-5
are used in practical applications, the interaction between pellet level
mesoscale with system-level macroscale is investigated and the effect of
diffusional resistances in pellets analyzed. The “1D-Plus-1D multiscale
pellet-and-bed model” developed to study the effect of diffusional
resistances of the pellet packed bed on refueling dynamics of hydrogen
storage. Later the “1D-Plus-1D” model applied for bed packed with compacted
and expanded natural graphite (ENG) added MOF-5 pellets and observed
improvement in the refueling time and storage capacity. To understand the
hydrogen adsorption behaviour, estimation of binding energies and finding
preferential adsorption sites density functional theory calculations (DFT)
carried out for ZIF-8 and ZIF-67 adsorbent systems.