Hydrogen storage adsorbent systems acceptability envelope

A methodology was developed to determine the range of coupled material parameters and operating conditions that allow an adsorbent based hydrogen storage system to meet performance targets. The range of acceptable parameters forms a multi-dimensional volume, or envelope. For this reason, the methodology is referred to as the Adsorbent Acceptability Envelope. The model evaluates the performance of the overall storage tank, comprised of the adsorbent material, the heat transfer system and the pressure vessel. Two cases were analyzed, both based on the flow-through cooling approach providing the cooling power required to charge hydrogen, with results presented and discussed. The first application (the forward problem) analyzed the gravimetric and volumetric performance of MOF-5 (R) based hydrogen storage beds, under various operating conditions. Results demonstrated that the system can reach a gravimetric capacity of approximately 4 wt% and volumetric capacity of about 20 g/L within 200 s during the absorption process. The second application (the inverse problem) identified the range of selected material parameters, required to meet the U.S. Department of Energy targets for gravimetric and volumetric capacity. Results showed that the most important parameters are the maximum capacity and the density of the material. Adsorbents having a density on the order of twice that of nominal powder form MOF-5 (R) can meet the 2020 DOE targets (i.e. system gravimetric capacity of 0.045 kg(H2)/kg(System) and system volumetric capacity of 0.030 kg(H2)/L-System). A density of about 3-4.5 times the nominal value is required to meet the DOE 2025 targets (i.e. system gravimetric capacity of 0.055 kg(H2)/kg(System) and system volumetric capacity of 0.040 kg(H2)/L-System,). Likewise, a material with a maximum adsorption capacity approximately equal to three times that of nominal MOF-5 (R) can meet the 2020 DOE targets, while a maximum capacity about 4.5 times the nominal value is required to meet the 2025 DOE targets. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.