Scientists turn waste heat into cooling

September 01, 2026

Researchers in Germany and Japan have developed what they describe as the world’s first heat-driven elastocaloric solid-state cooling system, a technology that can generate cooling without relying on an electric motor or conventional refrigerants.

The breakthrough, created by scientists at the Karlsruhe Institute of Technology (KIT) and the University of Tsukuba, uses extremely thin shape-memory alloy films to convert thermal energy first into mechanical motion and then into cooling.

The technology could eventually allow waste heat from electronics, vehicles and industrial equipment — or even heat supplied by solar energy — to power cooling systems directly.

Turning heat into mechanical energy and cooling

At the heart of the new cooling concept are two complementary nickel-titanium alloy films, each performing a different function.

One film operates as a thermal actuator. When heated, the shape-memory alloy contracts and converts thermal energy directly into mechanical force.

That force stretches a second, superelastic film responsible for producing the cooling effect. When the mechanical load is released, reversible structural changes inside the material cause its temperature to fall.

In effect, the system follows a simple energy pathway:

Heat → mechanical motion → cooling

This design eliminates the need for the electric motors normally required to operate elastocaloric cooling devices.

Dr. Jingyuan Xu, head of the Young Investigator Group at KIT's ZEco Thermal Lab, said the key advance comes from combining two different properties of shape-memory alloys. One material converts heat into mechanical work, while the other uses that mechanical energy to produce cooling.

The researchers believe this approach could create new opportunities to use waste heat and solar thermal energy for refrigeration and thermal management.

Two ultra-thin alloy films power the system

Cooling and heating represent a major share of global energy consumption, while many conventional refrigeration and air-conditioning technologies continue to depend on chemical refrigerants that can contribute to global warming when released into the atmosphere.

Elastocaloric cooling has emerged as a potential alternative.

These systems use special alloys that undergo temperature changes when mechanical stress is applied and removed. Previous elastocaloric devices, however, typically depended on electrically powered actuators to stretch or compress the cooling material.

The KIT and University of Tsukuba system takes a different approach by using heat itself to create the necessary mechanical force.

Its thermal actuator consists of a 22-micrometer-thick one-way shape-memory alloy film, while the cooling component uses a 26.5-micrometer superelastic alloy film.

Despite its tiny dimensions, the actuator achieved a force-to-displacement ratio of 14.5 newtons per millimeter. According to the researchers, that is more than ten times higher than comparable commercially available electromechanical actuators.

Prototype produces cooling directly from heat

Laboratory experiments demonstrated that the concept can produce measurable cooling without an electrically driven mechanical actuator.

Using an actuator temperature of approximately 86°C (186°F), the researchers recorded a component-level temperature reduction of around 4°C (7.2°F). The elastocaloric material itself achieved a temperature change approaching 13°C (23.4°F).

The prototype also continued operating with external heat sources reaching temperatures of up to 130°C (266°F), highlighting its potential to recover thermal energy that might otherwise be wasted.

Yi-Ting Hsiau, the study's lead author and a doctoral researcher at KIT's Institute of Microstructure Technology, said observing cooling generated directly by the heat-powered setup was an important milestone because it demonstrated that the concept could work experimentally rather than only in theory.

Elastocaloric cooling could offer high efficiency

Efficiency is another potential advantage of the technology.

According to the researchers, elastocaloric cooling systems can achieve as much as 84% of their theoretical maximum cooling efficiency, potentially outperforming compact thermoelectric cooling technologies.

Unlike conventional vapor-compression refrigeration, solid-state cooling also offers the possibility of operating without traditional gaseous refrigerants.

That combination could make elastocaloric systems particularly attractive for applications where compact size, energy efficiency and reduced environmental impact are important.

Waste heat could one day cool computer chips

The existing prototype remains an early proof-of-concept system, and considerably more development will be required before the technology can be deployed commercially.

Researchers are now working to increase its cooling capacity. One strategy involves arranging multiple shape-memory alloy films in parallel, allowing the system to generate greater cooling power.

The technology could eventually be particularly useful in devices that already generate substantial amounts of waste heat.

High-performance processors, for example, might use part of their own thermal output to power cooling mechanisms. Instead of relying entirely on additional electricity to remove heat, future computer systems could potentially recycle some of that energy to help regulate chip temperatures.

Electric vehicles represent another possible application. Heat produced by drivetrain components could potentially be redirected to cool sensitive electronics and other vehicle systems.

Industrial machinery, renewable-energy installations and solar-powered cooling systems could also benefit from the concept.

A new route toward electricity-free cooling

The heat-driven elastocaloric system demonstrates a new way of approaching one of modern technology's largest energy demands.

Rather than consuming additional electricity simply to remove unwanted heat, future cooling devices could potentially turn that heat into part of the solution.

If researchers can successfully scale the technology while maintaining its efficiency and durability, heat-powered solid-state cooling could provide a new route toward cleaner thermal management for electronics, electric vehicles and industrial systems — transforming waste heat from an unwanted byproduct into a useful source of cooling energy.