+1.613.822.3040 info@allianceme.ca

Elastocaloric process achieves 20°C temperature differences sans harmful refrigerants, surpassing conventional tech in energy efficiency.

Article Source: Interesting Engineering

Article Link: https://interestingengineering.com/innovation/worlds-first-refrigerator-run-by-flexing-artificial-muscles-revealed

Researchers have introduced the world’s first refrigerator which cools with artificial muscles made of nitinol – a nickel-titanium alloy.

The refrigerator developed by the team at Saarland University and the Center for Mechatronics and Automation Technology (ZeMa) is a small, compact prototype showcasing the new cooling technology.

The system works based on the elastocaloric principle: heat is removed from an area by stretching wires and releasing them again. The shape-memory wires composed of super-elastic nitinol, also called “artificial muscles,” collect heat within the cooling chamber and release it into the surrounding air.

According to researchers, compared to existing techniques, this energy-efficient cooling and heating technology is much more environment-friendly.

“Our elastocaloric process enables us to achieve temperature differences of around 20 degrees Celsius without using climate-damaging refrigerants in a far more energy-efficient manner than today’s conventional technologies,” said Professor Stefan Seelecke, who conducts research at ZeMa, in a statement.

The team will display the technology with the refrigerator at Hannover Masse, one of the world’s largest trade fairs, in Germany.

A promising alternative for the future

In light of climate change, energy scarcity, and the increasing need for both cooling and heating, elastocaloric materials offer a highly promising solution for the future. Their efficiency surpasses current air conditioning systems and refrigerators by more than tenfold.

Engineers currently demonstrate elastocalorics within small cooling chambers, yet these materials have the capacity to extract heat from and supply it to much larger spaces.

According to researchers, the utilization of superelastic wires enables effective heat transfer for heating applications as well. Thus, elastocaloric technology presents a transformative approach to address pressing environmental and energy challenges.

The researchers harness the unique “superpower” of the nitinol-based artificial muscles – shape memory – to transfer heat. This alloy’s wires can remember their original configuration and return to it after being stretched or distorted.

They can tense and release, just like muscles flexing. They can also become lengthy and then short again. This is because nitinol has two crystal lattices, or phases, that can change into one another deep within. The wires absorb heat and then release it at these crystalline structure phase transitions.

“The shape-memory material releases heat when it is stretched in a superelastic state and absorbs heat when it is released,” said Professor Paul Motzki, who holds a cross-institutional professorship at Saarland University and ZeMa, where he heads the Smart Material Systems research group, in a statement.

When multiple wires are bundled together, the effect is amplified. Their increased surface area allows them to absorb and release more heat, intensifying the overall impact.

Innovating cooling with elastocalorics

While the principle may seem straightforward, researchers claim that constructing a cooling circuit poses complex research questions. At Hanover, a research team is set to showcase a mini-fridge where a patented cam drive rotates bundles of 200 micron-thin nitinol wires around a circular cooling chamber.

As the wires move, they alternate between being mechanically loaded and unloaded, absorbing heat from the circulating air inside the chamber. The cooled air then circulates around unloaded wires. The rotating wires release heat outside the chamber when stretched.

Engineers in Saarbrücken investigate the drive’s continuous motion, optimal airflows, efficiency, wire bundling, and stretching levels for specific cooling targets. They also develop software for customizable heating and cooling technologies and study the entire cycle, including material production and recycling.

The team is just starting its journey with the refrigerator. “We want to leverage the innovative potential of elastocalorics in a wide range of applications, such as industrial cooling, electric vehicle cooling to advance e-mobility and also household appliances,” said Motzki.

Engineers have developed a continuous cooling and heating demonstrator in various research and doctoral dissertation projects, showcasing the air conditioning capabilities of elastocalorics.