HyDRA: A large-scale test bench for magnetic hydrogen liquefaction

Magnetic refrigeration at cryogenic temperatures represents a promising cleaner-production approach to reduce the energy intensity of hydrogen liquefaction. Experimental development of cryogenic active magnetic regenerators (AMRs) has been limited by the scarcity of magnetocaloric materials (MCMs), complex fluid–solid interactions, and the challenges of scaling up laboratory prototypes. Here, we present HyDRA, the largest hydrogen liquefaction AMR test bench to date, designed to achieve large temperature spans while using minimal MCM and supporting scalable regenerator geometries. Using holmium as the MCM, a maximum temperature span of 16.5 K at 9 T was achieved, representing the highest value reported for a single-layer cryogenic AMR. Internal temperature measurements reveal phase-shifted profiles caused by helium compressibility, providing new insight into fluid–solid thermal interactions under cryogenic conditions. The test bench enables adaptive optimization of flow and operating parameters, achieving high thermal efficiency with minimal parasitic losses. This scalable, material-efficient platform establishes a foundation for cleaner, lower-energy hydrogen liquefaction technologies.