As a young engineering student considering the management of his doctoral research, Jaka Tušek knew that he wanted to push the limits of science. “I wanted to work on breakthroughs, attack something new that has never been done before.”
Today, the Slovenian researcher is at the dawn of the first major breakthrough in cooling technologies in the past 100 years. His work consists in resolving one of the fundamental challenges of our time: staying cool in a world warming without polluting it more.
Change time
Vapor compression technology commonly used by refrigerators, air conditioners and other cooling technologies has more than a century and is relatively ineffective and bad for the environment.
While the most damaging refrigerants have been prohibited since 1989, those who replaced them – the hydrofluorocarbons – proved to have a greenhouse effect Hundreds of thousands of times higher than CO2.
“If a kilogram of such a refrigerant evaporates in the atmosphere, it has roughly the same greenhouse effect as driving a car for about 30,000 kilometers,” said Tušek.
For this reason, hydrofluorocarbons are also removed. But natural alternatives such as ammonia and isobutane come with their own set of problems, toxicity and explosiveness to poor efficiency in hot climates.
A solid solution
Based on the discoveries of a research project funded by the EU named Supercol, which took place at the Slovenia University of Ljubljana from 2019 to 2023, the Tušek team develops a system with a fundamentally different approach. It replaces toxic refrigerants with metal tubes.
Although these solid state cooling technologies are still at their beginnings, thought is that they will be able to provide safer cooling devices that work quietly and more efficiently, without polluting the environment.
Researchers at the University of Ljubljana are now trying to put this new technology on the market. They prepare a patent and develop an industry adoption plan as part of E-Co-Heat, another research initiative funded by the EU, which took place until early 2026.
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No one wants to work in a heat at 50 degrees and 90% humidity.
Making the heating and cooling technologies more efficient and more sustainable is at the heart of the EU heating and cooling strategy, which is a vital segment of the European Green Agreement.
Cooling currently represents 10% of global electricity demand, according to the International Energy Agency (AIE). Worse, the need for cooling technologies increases exponentially, due to the increase in temperatures and growing demand in developing countries.
“No one wants to work in a heat at 50 degrees and 90% humidity,” said Tušek.
There are about 2 billion air conditioning units worldwide today, a figure that the IAI plans almost triple by 2050.
“This growth, combined with the fact that they are relatively ineffective and harmful to the environment, could lead to an environmental disaster,” he said.
The quest for efficiency
The cooling depends on the basic chemistry of phase changes, when the material changes from a state (solid, liquid or gas) to another.
With traditional refrigerants, the transformation of gas and vice versa liquid is what feeds the cooling cycle. But some materials, such as an alloy of nickel-titanium known as Nitinol, can go through a phase transformation while remaining solid.
“In simple terms, when you put a mechanical constraint there, they heat, when you relieve it, they cool,” said žiga Ahčin, project researcher. The technology is called elastocaloric cooling, caloric in this case referring to heat.
Unlike traditional refrigerants, these materials are not harmful to people or the environment. In fact, Nitinol’s sons are biocompatible and commonly used in medicine. In theory, the system could also be much more effective, although it still has a way to go.
“Our prototype is currently at 15% of maximum efficiency possible, while steam compression has an efficiency of 20 to 30%,” said Tušek.
“But we have been developing this technology for less than 10 years, while steam compression technology has been on the market for more than a hundred, so I think we still have a room for maneuver.”
A first world
In theory, elastocaloric cooling could reach 70% Efficiency, but there is a major problem. Nitinol’s sons deteriorate quickly when they are stretched several times to induce a phase change, a phenomenon known as fatigue.
“Let’s say that the device works for 10,000 load cycles. It’s two to three days, and you’ve finished,” said Ahčin. It didn’t look promising.
But then, he explained, Tušek had the idea of compressing the materials instead of stretching them, reducing the physical constraint on the wires.
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It’s cool to think that this technology could one day be everywhere.
The resulting prototype was a first world, reaching new levels of heating and cooling performance without degrading the materials on which it depended.
“We have proven that the lifespan of these materials can be practically unlimited,” said Tušek. “At the same time, our prototype was the first in the world with a range of more than 30 degrees Celsius, which is the key for practical cooling and heating applications.”
From the laboratory to the world
Researchers at the University of Ljubljana have teamed up with universities in Germany and Italy, as well as a technological company in Ireland, to develop an advanced technology air conditioner. This collaboration, named Smacool, has also received funding from the EU.
“We are progressing more quickly when we work in this interdisciplinary way,” said Tušek, noting that each university contributes to a different field of expertise. It is optimistic that technology could reach the market over the next 5 to 10 years.
“It’s cool to think that this technology could one day be everywhere,” said Ahčin. “And my children could say that their father developed it.”
Research in this article was funded by the Horizon program of the EU. The opinions of those questioned do not necessarily reflect those of the European Commission. If you liked this article, please consider sharing it on social networks.