By Josh Perry, Editor
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Researchers at Saarland University (Saarbrücken, Germany) created a prototype of a new air conditioner that uses nickel-titanium (nitinol), which is a shape-memory material that releases heat when loaded in a superelastic state and absorbs heat when unloaded.

Researchers have used shape-memory alloys to make an efficient, environmentally-friendly air conditioner. (Wikimedia Commons)

According to a report from the university, using nitinol, which is also referred to as muscle wire, allowed the researchers to make the heating and cooling system environmentally-friendly and two to three times as efficient as conventional devices.

“The EU Commission and the U.S. Department of Energy have both assessed the new process and consider it to be the most promising alternative technology to existing vapor-compression refrigeration systems,” the report stated.

Researchers created a patent-pending cam drive that rotates bundles of 200-micron-thick nitinol wires. The rotation alternately loads and unloads the wires to transfer heat efficiently. “Air is blown through the fiber bundles in two separate chambers: in one chamber the air is heated, in the other it is cooled,” the report explained. “The device can therefore be operated either as a heat pump or as a refrigerator.”

The prototype is the result of years of work by several teams to optimize the wire loading level, ideal rotational speed, and the number of wires to include in the bundle. Through the team’s research, there is a range of parameters to meet specific thermal needs.

“Depending on the alloy used, the heating or cooling power of the system is up to 30 times greater than the mechanical power required to load and unload the alloy wire bundles,” the article added. “That already makes the new system at least twice as good as a conventional heat pump and three times better than a conventional refrigerator.”