Extreme weather, droughts, heatwaves, and soaring temperatures have become more intense and frequent as the planet’s warming more.

Per research published in the Journal of the American Meteorological Society, global warming has brought simultaneous large heatwaves. 

In the Northern Hemisphere, global warming has made heatwaves six times more likely over the past 40-year period.

Cooling is crucial for our comfort, health, and productivity, but it isn’t just for us humans’ benefits. 

It’s necessary in agriculture to ensure food security; hospitals and healthcare centers also need it to transport vaccines and other medical products.

But as we know, the cooling that comes from the current, conventional systems aren’t the best for our planet. 

However, new research might give us hope.

A team of professors led by Stefan Seelecke and Paul Motzki has made a refrigerator. It’s powered by artificial muscles made of a special nickel-titanium alloy.

Their groundbreaking mini prototype has made its debut at the Hannover Messe. It marked a significant step forward in making elastocalorics. Elastocalorics is a climate-friendly cooling and heating technology, a practical reality.

This innovative cooling and heating system is the result of collaborative research at Saarland University and the Center for Mechatronics and Automation Technology (ZeMa).

It operates on a remarkably simple principle: heat is absorbed from a space by stretching wires and then released again. 

These ‘artificial muscles’, crafted from super-elastic nitinol, extract heat within the cooling chamber and dissipate it into the surrounding environment.

Professor Stefan Seelecke from Saarland University and ZeMa explained that their elastocaloric process allowed them to achieve temperature differences of up to 20C. 

The process didn’t rely on environmentally harmful refrigerants, making it far more energy-efficient than conventional technologies.

For those who are new to this, experts suggest that the efficiency of elastocaloric materials surpasses that of current air conditioning systems and refrigerators by over tenfold. 

Both the US Department of Energy and the EU Commission vouch for it. They recognize the cooling technology developed in Saarbrücken as the most promising alternative to existing methods. 

This system can handle heat exchange in much larger spaces than the compact cooling chamber showcased at the Hannover Messe. That means it’s rather versatile for various cooling and heating applications.

Climate change and energy shortages have become increasingly challenging as humans need more cooling and heating. To address this, elastocalorics can offer a promising solution for the future.

It has the potential to revolutionize how we heat and/or cool any space efficiently and sustainably. 

The artificial muscles that can change the future

In their mission to transport heat efficiently, researchers leverage a remarkable feature of artificial muscles crafted from nitinol: shape memory. 

As mentioned, the muscles are made of a special alloy. It has the ability to recall and revert to their original shape after being stretched or deformed. More or less, it’s like flexing muscles; they can elongate and then contract, capable of both tension and relaxation.

 

 

Such a feature stems from the inner workings of nitinol. The nitinol possesses two crystal lattices–meaning that there are two phases that can seamlessly transition between each other.

Unlike water, which transitions between solid, liquid, and gaseous phases, both phases of nitinol are solid. 

During these phase transitions within the crystalline structure, the wires absorb and release heat after. 

Professor Motzki stated that the shape-memory material emitted heat when stretched in a superelastic state. It then absorbed heat upon release. 

This effect is magnified when numerous wires are bundled together. It’s due to the increased surface area which allows for greater heat absorption and dissipation.

Now, while the underlying principle may seem straightforward, constructing a cooling circuit gets intricate research challenges. 

In the miniature refrigerator presented at the Hanover presentation, a patented cam drive showed the continuous rotation of bundles of ultra-thin (200 micron) nitinol wires around a circular cooling chamber. 

Lukas Ehl, a PhD student working on the cooling system, explained that the wires rotated in a circular motion. 

As that happened, they underwent mechanical loading on one side—being stretched—and unloading on the other.

Air is directed past the rotating wire bundles into the cooling chamber, where the wires absorb heat from the air. This air then circulates around the unloaded wires within the chamber.

As the rotation persists, the wires transport heat out of the cooling chamber and release it when stretched outside.

“The cooling chamber cools to around 10-12 degrees Celsius using this method,” said Nicolas Scherer, a thesis student that contributed to the project’s efforts.

In Saarbrücken, engineers have been further developing their groundbreaking cooling system. 

They’ve also been exploring how to keep the wires in constant motion, optimizing air flows, enhancing efficiency, determining the ideal wire bundling configurations, and fine-tuning wire stretching for optimal cooling performance. 

Additionally, they’ve also developed sophisticated software to help the heating and cooling technology adapt for diverse applications. This will enable simulation and planning of cooling systems.

Their research spans the entire lifecycle—from material production and recycling to manufacturing.

But refrigerators are just the tip of the iceberg. 

Motzki wants to leverage the innovative potential of elastocalorics on various domains. The domains include industrial cooling and enhancing e-mobility with electric vehicle cooling and revolutionizing household appliances.

This cutting-edge technology is the result of over a decade of research, backed by multimillion-euro projects and noteworthy doctoral dissertations. 

 

 

Funding from the EU, the German Research Foundation (DFG), and the Federal Ministry of Education and Research, including a significant investment, has kickstarted their endeavors. 

And now, in collaboration with research institutions and industrial partners, the researchers aim to pave the way for new technology. Therefore, they can make their way to practical, widespread availability.

Because for now, the researchers have developed a continuous cooling and heating system in different research projects. They can keep showcasing the abilities of elastocalorics in real-time by doing that.

At the Hannover Messe the experts from Saarbrücken demonstrated the versatility of their shape memory technology. 

It was, in essence, a good glimpse of the future of cooling that gives us hope about dealing with the heat as time goes by.

Such a hope is important, because the current cooling systems contribute to 3.4% of global emissions, as experts say.

One can simply say that there should be more widespread sustainable or eco-friendly cooling methods or systems.

The International Energy Agency paints a hopeful picture: by embracing “Climate-friendly cooling,” we could potentially dodge over 460 billion tonnes of greenhouse gas emissions. That’s equivalent to around eight years’ worth of global emissions at 2018 levels.

But, there’s no universal solution for that. And the challenge is, some areas have got incredibly hotter that they’re in need of more cooling.

According to experts, to address such a challenge effectively, there needs to be a multifaceted approach. 

Some if not most of the time, initiatives from communities can be a great start to take a step towards a sustainably cooler future. 

At the same time, new innovations such as these artificial muscles can help if not boost such efforts.

Do you know any other cooling innovations or efforts to bring temperatures down in your community?

 

Sources

https://www.sciencedaily.com/releases/2024/04/240402192607.htm
https://climatechampions.unfccc.int/what-is-sustainable-cooling-and-how-can-it-help-tackle-the-climate-crisis/