What if the heat produced by a computer, car engine, industrial machine or even sunlight could be used to create cooling instead of simply being released into the environment?
Scientists from the Karlsruhe Institute of Technology (KIT) in Germany and the University of Tsukuba in Japan have demonstrated a new cooling technology that could make this idea possible. In a prototype system, researchers used two ultra-thin nickel-titanium shape-memory films to convert heat into mechanical motion and then into cooling.
The concept could eventually lead to compact, electricity-free cooling systems powered by waste heat or solar energy. The research has been published in Nature Energy.
Why Do We Need a New Way to Cool Things?
Cooling is essential in modern life. Refrigerators preserve food, air-conditioning systems keep buildings comfortable, and data centers depend on powerful cooling systems to prevent computers and servers from overheating.
However, conventional cooling technology has a major drawback: it requires electricity.
For more than a century, refrigerators and air conditioners have mainly relied on an electrically powered compressor. The compressor moves a refrigerant through the system, allowing heat to be transferred from one place to another.
As temperatures rise and demand for air conditioning, refrigeration and electronic cooling increases, the amount of energy required for cooling is also growing.
Cooling and heating together account for a very large share of global energy consumption. At the same time, some conventional refrigerants can contribute significantly to global warming if they escape into the atmosphere.
This has encouraged scientists to search for alternative cooling technologies that consume less electricity and use more environmentally friendly methods.
One promising possibility is known as elastocaloric cooling.
The Strange Cooling Behavior of Shape-Memory Materials
Shape-memory alloys are special materials capable of changing their shape when exposed to heat or mechanical forces.
Certain shape-memory alloys also display an interesting thermal effect. When mechanical stress is applied and then released, the material can experience a temperature change. This phenomenon can be used to create cooling without relying on conventional refrigerants.
However, there has been a major limitation.
Existing elastocaloric cooling systems generally require an electric actuator or motor to repeatedly apply mechanical force to the material.
That means the technology still depends on electricity to operate.
The researchers at KIT and the University of Tsukuba have now proposed a different approach: instead of using electricity to create the mechanical force, why not use heat itself?
Two Films With Two Different Jobs
The key innovation is the combination of two extremely thin nickel-titanium films.
Although both films are made from shape-memory materials, they perform different functions.
The first film acts as a heat-powered actuator.
When this film is heated, it changes shape and begins to shrink. In doing so, it converts thermal energy directly into mechanical work.
Normally, a motor would be required to provide this mechanical movement. Here, the heat performs that job.
The movement of the first film is transferred directly to the second film.
The second film acts as the elastocaloric cooling element. As it is repeatedly loaded and unloaded, its crystal structure undergoes reversible changes. These changes produce a temperature variation that can be harnessed to generate cooling.
In simple terms, the system works like a chain:
Heat → mechanical motion → elastocaloric effect → cooling
This is what makes the concept particularly interesting.
Rather than consuming electricity to operate a motor, the system can potentially use heat that would otherwise be wasted.
Heat Becomes the Driving Force
According to Dr. Jingyuan Xu, who leads the Young Investigator Group of the ZEco Thermal Lab at KIT's Institute of Microstructure Technology, the crucial innovation is combining two complementary functions of shape-memory alloys.
One film converts heat into mechanical work, while the other converts that mechanical work into cold.
This approach could create a completely different way of driving solid-state cooling systems.
An important advantage is that the heat required to operate the system does not necessarily have to come from electricity.
Possible sources include industrial waste heat, solar thermal energy and heat generated by machines or vehicles.
That could make the technology especially attractive in situations where usable heat is already available.
The Prototype Actually Produced Cooling
The researchers did not stop at a theoretical model.
They constructed a prototype and tested whether the heat-driven mechanism could actually produce measurable cooling.
When the actuator was heated to approximately 86°C (187°F), the prototype produced a temperature difference of about 4°C at the component level.
Even more importantly, the temperature change within the elastocaloric refrigerant reached nearly 13°C.
These measurements provided experimental evidence that the heat-driven cooling principle works.
The researchers also tested the system using an external heat source at approximately 130°C (266°F).
The prototype continued to operate reliably under these conditions, demonstrating that the concept could potentially work with practical sources of high-temperature waste heat.
For the research team, measuring actual cooling from a system driven by heat was an important milestone.
Lead author Yi-Ting Hsiau, a doctoral researcher at KIT's Institute of Microstructure Technology, described the measurement of generated cold as the decisive moment that demonstrated the principle was more than a theoretical idea.
The Technology Is Still at an Early Stage
Despite the promising results, this technology is not yet ready to replace your home refrigerator or air conditioner.
The current prototype was designed primarily as a feasibility demonstration.
Its cooling capacity has not yet been optimized, and producing useful amounts of cooling on a larger scale remains a major engineering challenge.
The researchers are already exploring ways to solve this problem.
One approach involves connecting multiple shape-memory films in parallel. By increasing the number of active films, the team hopes to increase the amount of mechanical work generated and, consequently, the cooling capacity.
Scaling the system efficiently will be crucial if the technology is eventually going to be used commercially.
Computers Could Potentially Cool Themselves
One of the most fascinating possibilities is using this technology to cool electronics with the same heat they produce.
Modern processors generate substantial amounts of heat during operation. Today, fans, heat pipes, liquid cooling systems and other technologies are commonly used to remove that heat.
A future heat-driven elastocaloric system could potentially capture some of this thermal energy and use it to produce cooling.
In principle, this could create a system where waste heat from a processor helps power the mechanism responsible for cooling it.
The researchers also point to possible applications in automobiles. Sensitive electronic components could potentially be cooled using heat generated by the vehicle's drivetrain.
Beyond electronics, industrial facilities could potentially use their existing waste heat as an energy source for cooling.
Solar Energy Could Also Power the System
Another major opportunity is solar thermal energy.
Solar energy can be converted into heat relatively easily, and many systems already generate high-temperature thermal energy.
If that heat can directly drive a solid-state cooling system, it could provide an alternative route to cooling without first converting solar energy into electricity.
This could be particularly useful in locations where cooling demand is high but electricity supplies are limited or expensive.
A Different Future for Cooling
The research represents an early but important step toward heat-driven solid-state cooling.
The technology still faces challenges involving cooling capacity, efficiency, durability, scalability and practical system design. But the basic principle has now been experimentally demonstrated.
The most important idea is surprisingly simple: instead of treating waste heat as something that must be removed, use it as the energy source for cooling.
If researchers can successfully scale up the technology, future cooling systems could potentially operate using heat from industrial processes, vehicles, electronics or the Sun.
That would represent a significant change from today's electricity-driven cooling systems.
The prototype is small, but its underlying concept could have a much larger impact: using one of the biggest problems in modern technology—waste heat—as part of the solution to another major problem: the growing demand for cooling.
Reference: Hsiau, YT., Miyazaki, S., Kohl, M. et al. Heat-driven elastocaloric cooling with shape memory films. Nat Energy (2026). https://doi.org/10.1038/s41560-026-02122-6
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