Simulation model for adsorption-based hydrogen storage

Abstract In this work a 0D simulation model of the adsorption behavior of hydrogen on activated carbon AX-21 TM has been created, employing the modified Dubinin-Astakhov model, to perform parameter studies on the influences of the adsorption isotherms, the operation temperature, the temperature control and the mass flow, on the inside pressure, the total hydrogen storage capacity, the hydrogen mass distribution (adsorbed and in gas phase) and the filling time. The structure of the simulation framework will be explained in detail and the interdependency of the system parameters will be worked out for different scenarios. It is shown that the operation of an adsorption storage tank at cryogenic temperatures (77 K) significantly enhances the total storage capacity, compared to operation at room temperature. Optimizing the temperature control with regards to the thermal conductivity results in a more effective heat dissipation and leads to operation temperatures closer to the target temperature. Different mass flows have only very little influence on the filling time when loading the tank fully, due to a self-limiting thermal behavior, while for partial tank filling, higher mass flows result in much faster filling times. It is also shown that the adsorption time constant used in the linear driving force model greatly influences the mass distribution (the ratio of stored adsorbate to stored gas phase) and represents the crucial factor concerning the accurate representation of the adsorption kinetics of a real system.