Spatially decoupled self-circulating metal hydride-phase change material dual-storage system: Study on heat transfer enhancement and energy conversion

Conventional integrated phase change material–metal hydride hydrogen storage systems are constrained by direct heat exchange at the reaction wall, resulting in limitations such as the inability to independently regulate thermal and hydrogen storage capacities, large heat transfer dead zones, and poor modular scalability. In response, this study proposes spatially decoupled linear-type and O-type dual-storage systems, which achieve physical separation of the hydrogen and thermal storage units through a circulating fluid loop, fundamentally resolving the technical bottlenecks of integrated reactor designs. The results demonstrate that, under equivalent radial space and metal hydride inventory, the decoupled system improves cumulative heat storage by 5.85% and reduces the equilibrium bed temperature by 28.36 K compared to the integrated configuration, attributed to the sustained latent heat storage regime throughout absorption. Among the two variants, the O-type dual-storage system exhibits superior performance, with a liquid fraction 8.82% higher than that of the linear-type dual-storage system and a 12.89% reduction in the time required to reach 90% hydrogen absorption fraction. Furthermore, a non-uniform corrugated fin structure and a cascaded phase change thermal storage mode are proposed to address the spatiotemporal non-uniformity of axial melting in the O-type dual-storage system. The dual-stage configuration increases the equilibrium bed temperature by 4.52 K while extending the time to reach 90% hydrogen absorption fraction by only 2.21%, achieving an effective trade-off between hydrogen storage performance and high-grade thermal energy storage. This study provides theoretical support for the construction of hydrogen–thermal synergistic systems in practical distributed energy supply scenarios.