Heat transfer improvement in metal hydride hydrogen storage systems: State of the art review and bibliometric analysis

• To investigate heat transfer improvement in metal hydride hydrogen storage. • To highlight research gaps in metal hydride alloy development and tank design. • To provide insights into future research directions in metal hydride storage. Hydrogen storage is an important challenge in the advancement of hydrogen-based technology. This review provides a comprehensive overview of hydrogen storage in metal hydrides (MHs), with a particular focus on important topics such as sintering effect, additives, metal foam, fins, heat transfer fluid and phase change material configurations, and integration with power systems. Also, this review aims to identify emerging research trends, highlight existing gaps, and provide insights into future research directions in both MH alloy development and tank design through a combined bibliometric and systematic approach. A bibliometric analysis was performed to analyze research trends in this field by considering co-occurrence frequencies of the 2277 articles. The results showed that, in the field of MH alloys, enhancing thermal conductivity, reducing cycle stability duration, and improving storage capacity are the main challenges. For the MH tanks, it was observed that for low-temperature MH tanks, the storage capacity and absorption/desorption time are important for the integration with the fuel cell system, and for high-temperature MH tanks, the shape of the heat transfer fluid pipe, thermal conductivity of the MH bed and phase change material are important for integrating with power cycles. The findings revealed that these systems could achieve maximum energy and exergy efficiencies of 77.1% and 59.5%, respectively.