Sub-zero Celsius elastocaloric cooling via low-transition-temperature alloys

Elastocaloric cooling using shape-memory alloys (SMAs) is a promising greenhouse gas (GHG)-free alternative to conventional vapour-compression refrigeration that relies on high global warming potential (GWP) gas refrigerants^1-4. However, existing elastocaloric systems have not yet reached sub-zero Celsius temperatures, which restricts their application in various freezing scenarios^5,6. Here we constructed a compression-based, regenerative elastocaloric cooling device using low-transition-temperature tubular NiTi units in a cascaded configuration. The selected NiTi alloy exhibited superelasticity and substantial entropy changes down to -20 °C. Moreover, low-freezing-point aqueous calcium chloride solution was used as the heat-transfer fluid, ensuring effective flow at low operational temperatures. Our desktop device achieved a heat-source temperature of -12 °C from a room-temperature heat sink, paving the way for next-generation green elastocaloric freezing technologies.