Enhanced metal hydride canister employing multi-structure metamaterial for efficient hydrogen storage

Abstract

Metal hydride (MH) as a material for storing hydrogen has a substantial limitation in its wide use in the mobility sector, which is its low gravimetric hydrogen storage density. A novel canister design utilizing the optimized gyroid structure for MH-based hydrogen storage is proposed to enhance reactor strength and capacity, increasing its utilization outside stationary applications. The canister employs a multi-structure metamaterial to achieve enhanced heat transfer between the heat transfer fluid (HTF) and MH bed chambers. A nonsymmetrical triply periodic minimal surface gyroid chamber is set bigger than the other chamber by altering the surface numerical function. The larger chamber is assigned for the MH bed, while the smaller chamber is assigned for HTF during hydrogen charging and discharging. To induce more heat transfer towards the middle part of the MH bed, another metamaterial structure is embedded inside the MH bed chamber as an insert. The cell size parameter of the metamaterial insert influences the charging rate but at the cost of MH bed volume. This study employs a numerical model to assess hydrogen absorption and canister mechanical strengths. The numerical model for absorption accuracy is confirmed by comparing its results with data from prior experiments. Furthermore, a fluid pressure drop experiment is employed further to provide clarity on the approach of parameter arrangement to reach the optimum canister design. For the proposed scenario, it is found that a ratio of MH to HTF chambers of 5:1 with 40 mm insert cell size can absorb 80 % of hydrogen capacity under 2000 s by using charging pressure as low as 0.8 MPa. The structure also has a compression capacity of 5000 N, making it a prime approach to store hydrogen in a frame, replacing part to increase further the MH hydrogen storage system's overall gravimetric density.