Compression-based elastocaloric cooling: advances in materials and systems*

The open challenge in caloric cooling technologies at large is the scale-up in terms of capacity and performance, while keeping the cost of materials and driving mechanisms to a manageable level. We have been pursuing different materials and device designs for compression-based elastocaloric cooling. It has been shown that in compression geometries elastocaloric NiTi can survive over 1 million cycles, opening the door to long-term applications. Commercial superelastic NiTi tubes are useful for implementing them in a variety of compression configurations. Our four-bundle multi-mode elastocaloric system can be operated in a high-utilitization mode as well as the active regenerator mode. It has produced 260 W in delivered cooling in the high-utility mode and the temperature lift of 22.5 K in the active-regeneration mode. When implemented in a multi-stage regenerator, we have been able to achieve a temperature lift of 27.5 K to date. We are now working toward developing cascade regenerators where different NiTi parts of the device have varying Af temperatures. We are also working with Cu-based elastocaloric materials, whose main advantage is a significantly reduced critical stress compared to NiTi. Comparison of recent advances in elastocaloric cooling with other caloric cooling technologies will be discussed. This work is carried out in collaboration with David Catalini, Nehemiah Emaikwu, Jan Muehlbauer, Suxin Qian, Jun Cui, Huilong Hou, Sumio Kise, Kenjiro Fujimoto, Yunho Hwang, and Reinhard Radermacher.