Modeling hydrogen storage at room temperature: Adsorbent materials for boosting pressure reduction in compressed H2 tanks

Energy storage systems are required for an efficient integration of renewables into the grid to achieve a net zero energy system. Hydrogen compressed at 700 bar, is one of the key energy storage technologies. This study evaluates the effectiveness of solid-state hydrogen storage, particularly physisorption in porous materials, to enhance storage performance and safety at room temperature by reducing the operating tank pressure. We model dynamically the entire storage system, comparing adsorbent materials to traditional compression in terms of maximum tank pressure and round-trip storage efficiency. Different energy system applications with varied cycle frequencies and discharge durations were examined. Results indicate that porous material-based systems exhibit higher efficiency for long-duration energy storage services than the compressed hydrogen. Notably, bulk density plays a pivotal role in storage performance. For instance, IRMOF-1 with a bulk density of 500 kg/m3, shows a 70 % pressure reduction compared to compressed hydrogen systems. In contrast, when its bulk density is reduced to 130 kg/m3, the maximum tank pressure is even 30 % higher than the compressed tank. We emphasize the need for comprehensive material characterization, highlighting the significance of parameters like bulk density for determining the most performing hydrogen adsorbent material in terms of maximum tank pressure and efficiency. As general outcome, the best performing material depends on the specific target or system requirements, such as pressure, volume, cost, or weight.