Heat-driven elastocaloric cooling with shape memory films

Efficient thermal management is critical for next-generation energy systems. Elastocaloric cooling with shape memory alloy (SMA) films offers rapid heat transfer, high specific cooling capacity and simple solid–solid heat exchange, but current devices rely on bulky, electrically powered actuators that limit scalability and efficiency. Here we demonstrate a thermally powered shape memory actuator that drives elastocaloric cooling in tailored SMA films, establishing a heat-driven cooling system that can use waste heat or solar thermal energy with reduced electricity demand. Our prototype achieves a temperature span of 12.9 K at the refrigerant film level and 4.0 K at the device level under Joule-heated actuation at 86 °C. When driven by an external heat source, the system maintains a device-level temperature span of 2.2 K, confirming the feasibility of heat-driven elastocaloric cooling. These results mark a step towards electricity-minimized elastocaloric cooling technologies that transform heat into useful cooling.