A Multipurpose Hydrogen Storage System Using AB5– and AB2–Type Metal Hydrides for Flexible Hydrogen Storage and Delivery

Metal hydrides can safely store hydrogen in the solid state at high volumetric density under moderate temperature and pressure. Their hydrogen sorption characteristics are represented by pressure–composition–temperature (PCT) curves. AB5–type metal hydrides, which have low plateau pressures, store and release hydrogen at low pressures. AB2–type metal hydrides, which have high plateau pressures, store and release hydrogen at relatively high pressures. Compared with AB5–type metal hydrides, AB2–type metal hydrides generally have lower raw material costs and higher hydrogen storage capacity. This makes them more suitable for storing large quantities of hydrogen. Green and blue hydrogen are produced using commercial alkaline water electrolyzers and natural gas reformers, respectively. After downstream purification, this hydrogen is typically supplied at pressures below 1 MPa. However, the high plateau pressures of AB2–type metal hydrides make it difficult to store this low-pressure hydrogen directly. AB5–type metal hydrides can store it but release it only at low pressures. A single hydride type therefore operates within a narrow pressure range for both storage and delivery. In this study, a multipurpose hydrogen storage system (MHSS) using AB5– and AB2–type metal hydrides was proposed to broaden the applications of metal hydride-based systems. The feasibility of the MHSS was experimentally evaluated through lab-scale tests. The AB5 and AB2 modules were first tested as standalone units. The integrated MHSS was then tested assuming that waste heat was continuously available. The MHSS can store a large quantity of low-pressure hydrogen and deliver it across a wide pressure range. This range covers diverse end uses, from fuel cells at 0.5 MPa to hydrogen pipelines at 4.0 MPa.