Researchers from Germany and Japan have built a miniaturized cooling system that needs no electricity at all, instead running on the waste heat produced by the very devices it's meant to cool. The Karlsruhe Institute of Technology and the University of Tsukuba published their findings in Nature Energy on Friday, showing that their solid-state elastocaloric technology achieved measurable temperature drops in lab tests. The breakthrough could eventually help datacenters cut energy use and water consumption, both of which have surged as facilities expand to support AI and cloud computing.
The prototype relies on a pair of ultra-thin nickel-titanium foils with opposite functions. One foil contracts when exposed to heat, creating movement that converts into mechanical energy and serves as its own actuator. That mechanical energy transfers to the second foil, which loads and unloads to trigger a phase shift that generates the cooling effect. In laboratory experiments, the system produced a temperature span of 12.9 K at the refrigerant film level and 4.0 K at the device level when powered by Joule heating at 86°C. Even when subjected to an external heat source of 130°C, the device maintained a temperature span of 2.2 K at the device level.
"For us, the decisive moment was seeing measurable cooling for the first time, actually generated by a heat-driven system," said Yi-Ting Hsiau, a KIT PhD candidate and lead author of the paper. The researchers noted in their report that traditional thermoelectric solid-state cooling systems, while compact, still require energy and run at only a quarter of the efficiency of modern compression cooling. Hsiau added that the results showed "the principle doesn't just work on paper."
The timing matters because energy generation for powering and cooling facilities like datacenters is climbing, as is their water footprint, partly tied to cooling demands. According to the International Renewable Energy Agency, heating and cooling combined now represent more than 40 percent of global energy-related carbon dioxide emissions. Traditional compression cooling depends on environmentally damaging refrigerants and substantial electricity use, while climate change makes keeping electronics and people cool an even bigger concern. Elastocaloric cooling sidesteps both problems by using shape-memory alloys that change temperature when mechanically loaded and unloaded through a phase transition, eliminating the need for harmful refrigerants or constant power input.
The team plans to build larger experimental units to optimize cooling performance now that the concept has been validated at a basic, single-pair-of-films level. Jingyuan Xu, who leads KIT's ZEco Thermal Lab focused on zero-emissions and eco-friendly heating and cooling technology, said the researchers believe "this is just the beginning." The lab aims to scale up the technology to develop compact cooling systems that tap into abundant heat sources for sustainable cooling. Addressing the datacenter energy and water challenge hinges largely on solving the cooling problem, and while this research remains in early stages, it could become a valuable tool for shrinking the tech industry's energy footprint. If the approach proves scalable beyond the laboratory, facilities could theoretically redirect the heat their servers generate into a self-sustaining cooling loop, turning a liability into an asset and reducing reliance on grid electricity for temperature control.