Development of an innovative hydrogen liquefaction technology

   NIMS, Kanazawa University and the National Institute of Technology, Oshima College have developed a magnetic refrigeration system capable of operating at extremely low temperatures to liquefy hydrogen and demonstrated its practical suitability for this purpose. This result is expected to facilitate the development of cost- and energy-efficient hydrogen liquefaction plants.

   The use of hydrogen energy has been increasing in Japan in an effort to meet the national goal of achieving carbon neutrality by 2050. To store and transport large amounts of hydrogen, it needs to be liquefied using refrigeration systems capable of cooling it to its liquefaction temperature of approximately 20 K (-253°C). The hydrogen liquefaction efficiency of the vapor-compression refrigerators currently in use is no greater than 25%. This process accounts for one third of hydrogen production costs. To reduce hydrogen supply cost to a level at which a hydrogen economy can be achieved, liquefaction efficiency needs to be dramatically improved.

   Magnetic refrigeration may potentially be used to liquefy hydrogen with substantially higher efficiency. This technology is able to cool a target gas by repeatedly applying and removing a magnetic field to/from a magnetic refrigerant, causing it to cyclically absorb and release heat. A magnetic refrigerator does not require a compressor—a main energy consumption source in vapor-compression refrigeration—making it theoretically possible to achieve liquefaction efficiencies greater than 50%.

   However, all previously tested magnetic refrigerators for hydrogen liquefaction had narrow cooling temperature ranges of only a few degrees centigrade. These ranges needed to be widened in order for the refrigerators to be put into practical use. To address this, active magnetic regenerative refrigeration (AMRR) had been proposed. Although the use of AMRR in air conditioners and other household appliances that operate at ambient temperatures has been extensively researched and great progress has been made, its use at cryogenic temperatures to liquefy hydrogen had been unsuccessful.

   This research team recently developed an energy-efficient magnetic cooling mechanism (i.e., AMRR) in which a magnetic refrigerant is repeatedly moved into and away from a magnetic field generated by an optimized superconducting magnet. The team also developed a heat exchanger optimized for use with an AMRR system and improved the shape of the magnetic refrigerant. Combining these elements, the team realized a stable AMRR cycle capable of cooling hydrogen across a wider temperature range, and succeeded in liquefying hydrogen by AMRR for the first time in the world.

   The team plans to improve the output- and energy-efficiency of this magnetic refrigeration system, which can be used to develop cost- and energy-efficient hydrogen liquefaction plants.

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   This project was carried out by a research team consisting of Koji Kamiya (Leader of the Magnetic Refrigeration System Group (MRSG), Center for Green Research on Energy and Environmental Materials (GREEN), NIMS), Akiko Saito (Chief Researcher, MRSG, GREEN, NIMS), Takenori Numazawa (Special Researcher, MRSG, GREEN, NIMS), Hiroyuki Takeya (Special Researcher, MRSG, GREEN, NIMS), Koichi Matsumoto (Professor, Kanazawa University) and Shinji Masuyama (Professor, National Institute of Technology, Oshima College). This work was conducted as part of another project entitled, “Development of an advanced hydrogen liquefaction system using magnetic refrigeration technology” (project leader: Nobuyuki Nishimiya) supported by the JST-Mirai Program.

   This research was published in the online version of Applied Physics Express at 3:00 pm on April 11, 2022.