Slovenian scientists spearheading revolution in cooling tech

by Lea Udovč

Ljubljana, 31 August - Slovenian scientists are spearheading efforts to make cooling, which is still based on a century-old technology, more environment friendly and energy efficient through finding alternative technologies to the all-present vapour-compression technology.

To this day, all cooling appliances such as refrigerators and air conditioners use the same technology that was used in the first commercial refrigerators launched by the US General Electric more than 100 years ago.

But this technology is becoming inefficient in terms of energy it uses for cooling, as the amount of energy used for cooling could surpass the amount of energy used for warming within 20 or 30 years if the demand for cooling, fuelled by the needs of rapidly developing countries such as China and India, and global warming, continues to grow at the current pace.

Moreover, cooling agents that are used in the vapour-compression technology produce a thousand-times larger greenhouse effect than carbon dioxide when released into the environment, noted Jaka Tušek, a researcher at the Ljubljana Faculty of Mechanical Engineering.

While it has advanced over time, the technology has topped its potential in recent years. This has in turn encouraged research into alternative solutions, with caloric-based technologies using ferroic materials showing the most potential.

Alternative cooling technologies

Caloric cooling technologies are based on magnetocaloric, electrocaloric, barocaloric or elastocaloric effect, using ferroic materials. Because these are solid materials and cannot leak into the environment like the gasses used in the vapour-compression technology, these technologies have the potential to be far more eco-friendly.

At present, magnetic refrigeration is the most advanced among them. While around 100 refrigerator prototypes using it exist in the world today, it has a major setback as it is extremely pricey due to the value of required materials and thus cannot compete with the vapour-compression technology.

While not on the same level of development as magnetic refrigeration, elastocaloric refrigeration has emerged as the more promising technology recently, with the US Department of Energy and the European Commission identifying it as potentially replacing the vapour-compression technology in the next ten years.

Elastocaloric refrigeration

This technology is based on elastocaloric materials, super-elastic materials with shape memory effect which are capable of stress-induced reversible phase transformations during which latent heat is released or absorbed. The most widely used electrocaloric material today is the nickel titanium alloy.

Theoretic models indicate that eleastocaloric technologies could be up to 30% more efficient than the vapour-compression technology. "Caloric effects in some materials have no irreversible loss, which means, in theory, they could be nearly 100% efficient, if we exclude other systemic losses," said Tušek.

According to the young scientist who has recently received an EUR 1.4m ERC Starting Grant from the European Research Council to pursue work on his SUPERCOOL project concerning elastocaloric refrigeration, these materials can be recycled and reused, which makes this an extremely sustainable technology.

ERC project aimed to facilitate transition of technology from labs to real life

While pursuing postdoctoral studies in Denmark, Tušek and his colleagues managed to transfer the logic of magnetic refrigeration to elastocaloric refrigeration.

The effort proved to be a success as the very first prototype surpassed all alternative cooling technologies in terms of cooling characteristics.

Tušek will continue to research the technology as part of his five-year project. He and six PhD students and researchers will try to find solutions to the two key challenges of the technology that Tušek and his Danish colleagues pointed to in a 2016 article in the Nature Energy magazine.

At first, they will try to develop an elastocaloric structure that will have an adequate lifespan and at the same time ensure suitable transfer of heat to make it viable.

The other challenge is developing a power system that will put stress on elastocaloric materials as efficiently as possible.

The final goal is to develop an elastocaloric cooling device that would be considered the first major breakthrough in cooling technology in 100 years.

"If we manage to show the effectiveness and the potential of this technology at least to some degree, it will be comparable to electric cars. It is a revolution in the field of cooling technology," Tušek said.

Technology with potential for versatile application

According to Tušek, the existing refrigerators and air conditioners will not be replaced by the new technology in the next few years, but he believes it could become widespread in time.

It has huge potential in many fields, spanning from micro-cooling to industrial cooling, while it could also play a major role in electric cars, he believes.