Safe hydrogen storage methods for underwater vehicles

The transition of underwater shipbuilding to fuel cell power systems requires solving the key problem of the low density of gaseous hydrogen and the associated explosion and fire hazards in confined compartments. Known hydrogen storage methods (compressed gas, cryogenic liquid, metal hydrides, liquid organic hydrogen carriers (LOHC), adsorption, chemical donors) have been developed primarily for land or surface applications and do not account for the strict constraints of underwater vehicles in terms of volume, mass, stealth, and safety during long-term autonomous navigation. This work, for the first time, systematically evaluates these methods specifically against the criteria of underwater technology, revealing not isolated advantages but the fundamental impossibility of meeting all requirements with any single method. As a result of a comparative analysis of six approaches, it was found that the highest volumetric density (108–150 kg H₂/m³) and long-term storage safety are provided by chemically bound forms—ammonia, LOHC, and metal hydrides; however, metal hydrides have low gravimetric efficiency and slow gas release, while ammonia requires high-temperature cracking. Compressed and cryogenic hydrogen, in contrast, allow rapid fuel delivery but are associated with continuous leakage or the risk of catastrophic failure. Based on the obtained data, a hybrid scheme is proposed that is absent from known analogues: the main hydrogen reserve is stored as ammonia or LOHC (high density and safety), while peak loads during maneuvering are compensated by rechargeable batteries that are recharged during the mission by the electrochemical generator. From reading the full text of the article, the reader learns for the first time a quantitative justification for precisely such a hybrid architecture for manned underwater vehicles, including recommendations for selecting buffer systems and directions for further development of low-temperature dehydrogenation catalysts.