Magnetic Liquefaction of Hydrogen
The ability to induce a reversible temperature change in a magnetic material by changing the magnetization is called the magnetocaloric effect (MCE) and has been known for over 100 years. Magnetic cooling is a process that uses the MCE to reduce the temperature of another substance and was originally employed to produce temperatures lower than those possible with liquid helium (LHe). Since the early 1970s, advancements in materials (magnetic refrigerants, superconductors, permanent magnets) and our understanding of the thermodynamics of magnetic cycles have led to increased interest in using magnetic cycles for a variety of applications. One area of particular interest is the liquefaction of hydrogen. Although no commercial liqueers using the MCE currently exist, the potential for high efciencies at smaller scales and lower cost than conventional gas expansion cycles is a driver of research and development activities. In addition, future energy systems in which hydrogen is used as an energy carrier require logistical chains for transmission, distribution, and storage. For this to happen, the need for hydrogen liquefaction will grow substantially from current levels.