Development of magnetic refrigeration system for hydrogen liquefaction

Abstract

This paper reviews current status and future directions of magnetic refrigeration system for hydrogen liquefaction. Hydrogen promises to be one of the most important energy sources in the near future. Liquid hydrogen can be utilized for infrastructure construction consisting of storage and transportation. Consuming energy of hydrogen liquefaction becomes comparable with the energy required for compressing hydrogen to 70 MPa, when high efficient liquefier is developed. Magnetic refrigeration that uses the magneto-caloric effect has potential to realize liquefaction efficiency higher than 50%, and also to be environmentally friendly and cost effective. Our hydrogen magnetic refrigeration system consists of Carnot cycle for liquefaction stage and active magnetic regenerator (AMR) cycle for precooling stages. Various magnetic materials were studied for candidate refrigerants. For the Carnot cycle, we developed a liquefaction stage with liquefaction efficiency higher than 80% using the heat pipe. For the AMR cycle, we studied two kinds of displacer systems and confirmed that the AMR effect expanded the cooling temperature span several times larger than adiabatic temperature change. From our simulation, FOM of 0.47 was estimated for the magnetic hydrogen liquefaction plant of 10 kg/day.