Progress in magnetic refrigeration and future challenges

Since a regenerative magnetic cooling cycle was first demonstrated in 1976, many developments have been made in the areas of system modeling, magnetocaloric materials and system design. Systems have gone from laboratory demonstrators using superconducting magnets to near commercial systems using more practical permanent magnets and use multi-material regenerators. Novel magnetocaloric material systems show potentially higher magnetocaloric properties than gadolinium and its alloys while reducing the cost of the raw materials. Detailed numerical models have been developed and show that magnetic refrigerators have the potential for high efficiency. However, reported device COPs for laboratory devices are still well below commercially available vapor compression systems. In order to significantly improve AMR efficiency, several loss mechanisms must be reduced and other aspects of system design, such as the drive system, must be better understood. Here, some major loss mechanisms are presented and modeling tools and design solutions are presented. Other challenges that must be overcome before the technology can become commercially viable are also discussed.