Heat transfer enhancement in metal hydride hydrogen storage: A comprehensive review of phase change material and hybrid thermal management approaches

Metal hydride (MH) systems are promising hydrogen storage technology, yet performance is severely limited by poor heat transfer. This review systematically evaluates the evolution of Metal Hydride Reactor (MHR) designs integrating Phase Change Materials (PCMs) to overcome thermal conductivity limitations via advanced hybrid systems. The analysis covers a spectrum of configurations, from baseline reactors to systems enhanced by passive methods (Metal Foam (MF), nano-additives, and fins) and active Heat Transfer Fluid (HTF). Quantitative benchmarks demonstrate a performance hierarchy: advanced basic geometries achieve up to 81.5% reduction in reaction time, while optimized 30-fin copper configurations and metallic foams reach peak improvements of 97.3% and 84%, respectively. Active HTF systems exhibit effectiveness ranging from 33.5% to 94%. By synthesizing numerical (2D/3D) and experimental findings, this work highlights a trend toward structurally complex, hybrid designs and assesses trade-offs between kinetics, complexity, and storage capacity, providing a roadmap for next-generation systems.