Shape memory alloys: a promising elastocaloric prototype

German researchers have developed an environmentally friendly, highly efficient air-conditioning device based on the elastocaloric effect.



In 2016, a team of researchers from the University of Saarland published its first research on a shape memory alloy. Composed of nickel-titanium (also called "nitinol" alloy), this material seemed able to produce cold or heat thanks to the elastocaloric effect (see IIR news 18117).

In 2019, the same team made a prototype using this alloy. This one is often compared to a muscle in the different articles that deal with it. Indeed, it absorbs or rejects heat according to its deformations: when it is mechanically loaded in its eslastocaloric state, it releases heat. When it returns to his original form, it absorbs heat.

According to Felix Welsch, who worked on the project, pre-stressed nitinol wires can cool down by as much as 20°C, when discharged at room temperature.

The main innovation in this system is that it is able to operate continuously, thanks to a cam drive (patent pending). Its rotation ensures that the bundles of nitinol wires are alternately charged and discharged and provide efficient heat transfer. Air is blown through the fibre bundles in two separate chambers: in one of them, air is heated, in the other, it is cooled. The system can therefore be used as a heat pump or as a refrigerator.

The team is currently working on optimisation of heat transfer within the system.

This promising and environmentally friendly technology (it does not require any refrigerant) will be exhibited at the Hannover Messe in April.