Heat-driven prototype cools with two nickel-titanium films

At an actuator temperature of 86°C, the prototype at the Karlsruhe Institute of Technology (KIT) produced a 4°C temperature difference at component level, while its elastocaloric refrigerant reached a temperature change of nearly 13°C—reported in Nature Energy as up to 12.9 K.

The design separates two jobs that earlier elastocaloric systems assigned to an electric actuator. The first shape-memory film shrinks when heated, converting thermal energy directly into mechanical work. That motion loads and unloads the second film, whose reversible crystal-structure changes generate cooling.

The result is a heat-driven system rather than one that needs an electric motor to create the required force. The researchers also tested it with an external heat source at 130°C, showing that the principle can work with heat supplied from outside the device. The work was led by Yi-Ting Hsiau, a doctoral researcher at KIT's Institute of Microstructure Technology, with Jingyuan Xu leading the ZEco Thermal Lab's Young Investigator Group.

Potential uses include supplying the input with waste heat or solar heat, while the films provide cooling for processors or sensitive automotive electronics. Cooling and heating account for nearly half of global energy consumption, according to the report, so recovering heat that would otherwise be unused could reduce the electricity needed for some cooling tasks. The sources do not provide a cooling-capacity figure, efficiency comparison or commercial timetable.

Concretely, the technology is at the prototype feasibility-study stage. The team says the current setup is not optimized for maximum cooling capacity and is testing parallel film arrangements to increase it. The measured temperatures establish that heat-driven elastocaloric cooling works in the laboratory; they do not yet show how much cooling a practical system could deliver.