A multi-material cascade elastocaloric cooling device for large temperature lift

Elastocaloric cooling using shape memory alloys is a promising candidate for next-generation environmentally friendly refrigeration. The temperature lift (Tlift), that is, the ability of the cooling device to transfer heat from a low-temperature source to a high-temperature sink, is a critical performance indicator. However, increasing the Tlift of existing elastocaloric devices is difficult due to the narrow temperature window across which the individual elastocaloric materials exhibit superelasticity (for example, ≤50 K for commercially-available NiTi shape memory alloys). Here we construct a multi-material cascade elastocaloric cooling device using NiTi with three different temperatures at which the martensite-to-austenite transition is completed, also called austenite finish temperature. By matching the working temperature distribution of the NiTi units with their austenite finish temperatures, we expand the device’s superelastic temperature window to over 100 K and achieved a Tlift of 75 K on the water side. This work demonstrates the great potential of multi-material cascade elastocaloric regenerators for space cooling in the near future. Elastocaloric cooling, an emerging refrigeration technology, has so far yielded limited performance in devices. Zhou et al. increase the temperature lift of such devices to 75 K by combining three NiTi elastocaloric materials with different phase-transition temperatures.