As the planet warms, the race for sustainable cooling technologies is heating up. In Slovenia, researchers are developing a revolutionary cooling system that skips toxic gases and instead uses recyclable nickel-titanium alloy to keep things chill. Their method?
It’s called elastocaloric cooling—and it could transform how we air-condition homes and buildings without harming the planet. Unlike traditional systems that use hydrofluorocarbons (HFCs)—greenhouse gases thousands of times more potent than CO₂—this method doesn’t rely on liquid-to-gas phase changes. Instead, it leverages a solid-state material, nitinol, which heats up when mechanically stressed and cools down when the pressure is released.
“A mass of only one kilogram of refrigerant with a GWP of 10,000 causes as much global warming as 10 tons of CO₂,” says Jaka Tušek, principal investigator of the project at the University of Ljubljana. “We want to replace them with solid refrigerants based on shape memory alloys.”
The project, E-CO-HEAT, is part of the European Union’s broader mission to decarbonize heating and cooling—a sector that accounts for 10% of global electricity use. This research could help phase out toxic coolants, reduce fire risk, and improve efficiency, especially as climate change accelerates.
“Our device has no moving parts in the cooling loop and uses less energy,” the team notes. “It can become a highly efficient alternative to vapor compression cooling.
“Ironically, the more we cool, the greater the demand for cooling.” he explains. “The International Energy Agency estimates that the number of air conditioners worldwide will rise from 1.6 billion today to 5.6 billion by the middle of the century.
“At this rate of increase in cooling demand, energy use for cooling will exceed total energy use for heating by 2060 and by the end of the century by more than 60%. Among the alternative technologies, elastocaloric cooling and heating technology, based on exploiting the elastocaloric effect during cyclic loading of shape memory materials, has shown great potential in recent years,” says Tušek.
Read more on Green Prophet about the hidden climate cost of air conditioners and efforts to design buildings that don’t need cooling at all.
Metal-Based Cooling Could Cut Carbon and Slash Energy Use
Tušek’s team is working with partners from Ireland, Germany, and Italy under the project SMACool, which aims to deliver a working prototype of a metal-based air conditioner by 2026. Though still at 15% efficiency, researchers expect to surpass that soon, potentially beating standard vapor compression units that max out at 30%.
The technology avoids the flammable or toxic properties of so-called “natural refrigerants” like isobutane or ammonia, which come with their own risks—especially in hot climates where performance drops.
“We are building an advanced elastocaloric device that can replace today’s harmful cooling systems and have a measurable impact on climate goals,” Tušek says.
But change won’t be instant. This kind of leap forward faces resistance from an industry heavily invested in HFC-based infrastructure. Still, the benefits—zero-emissions refrigerants, higher safety, and better performance—are hard to ignore.
As Tušek puts it: “We’re not only developing a device. We’re shaping a safer, cooler future.”
Check out Green Prophet’s coverage of other clean tech frontiers like solar cooling in deserts and AI-powered climate solutions.
