Image Courtesy: Ella Maru Studio

Researchers have developed a heat-driven cooling system that can use waste heat or solar energy to produce cooling, potentially offering a new approach to refrigeration without relying on an electrically powered motor.

The prototype was developed by researchers at the Karlsruhe Institute of Technology (KIT) and the University of Tsukuba in Japan. It uses two ultrathin nickel-titanium films, with one converting heat into mechanical motion and the other using that motion to generate cooling. The study was published August 28, 2026, in Nature Energy.

The technology builds on elastocaloric cooling, an emerging solid-state alternative to conventional refrigeration. Shape-memory alloys can cool when mechanical stress is released, but existing systems generally require electrically powered actuators to repeatedly apply that mechanical force.

The new design eliminates that requirement by using heat itself as the driving energy.

When heated, the first nickel-titanium film contracts because of its shape-memory properties. This converts thermal energy into mechanical work without an electric motor. The resulting movement loads and unloads the second film, causing reversible changes in its crystal structure that produce a cooling effect.

“The crucial innovation is that we combine two complementary functions of shape memory alloys,” said Jingyuan Xu, who leads the Young Investigator Group of the ZEco Thermal Lab at KIT. One film converts heat into mechanical work, while the other converts that work into cold.

Laboratory testing demonstrated that the concept can generate measurable cooling. At an actuator temperature of 86 degrees Celsius, the prototype produced a 4-degree Celsius temperature difference at the component level, while the elastocaloric refrigerant itself experienced a temperature change of nearly 13 degrees Celsius.

The researchers also successfully operated the system using an external heat source at 130 degrees Celsius, suggesting that the technology could potentially work with practical sources of waste heat.

Lead researcher Yi-Ting Hsiau said measuring actual cooling from the heat-driven system was a key milestone because it demonstrated that the principle works beyond theory.

The current prototype is designed primarily to establish feasibility rather than deliver large cooling capacity. The team is now exploring ways to connect multiple films in parallel to increase its output.

Potential applications include electronics that could use their own waste heat for cooling, as well as automotive systems that could recover heat from a vehicle’s drivetrain.

The researchers say the longer-term goal is to develop compact cooling systems powered by readily available heat sources, including industrial waste heat and solar energy.