Hydrogen storage in an activated carbon bed: Effect of energy release on storage capacity of the tank

Thermal effects during dynamic charging of a two-liter, adsorbent, packed bed, hydrogen storage tank were studied through numerical modeling. For packed-bed materials having adsorption capacities smaller than 2 wt%, the conversion to heat of the mechanical work required to feed the tank produces more than 60% of the temperature increase that occurs during the charging process. However, for materials having adsorption capacities greater than 3 wt%, 60% of the heating is due to the adsorption process. The temperature increase for a material that would fulfill the DOE recommendation of 6 wt% storage capacity is 130 K. This reduces the storage capacity by 20% relative to what would be obtained from an isothermal charging process. Simulations showed that the limitation in the storage capacity can be reduced to less than 10%, if a packed bed having an effective conductivity of a few W m−1 K−1 can be used.