The future of home refrigerators: magnetic cooling

Perhaps someday we will have refrigerators at home that do not use chemical components and industrial coolers. They will work on the basis of magnetic cooling systems, which, in turn, will use about the same magnets that many of us played with in childhood - they hooked them to large metal objects and raised small metal objects with them.

When magnets hit metal objects, we were actually unconsciously heating those metal objects. And not just because they held these objects in their hot hands. This is because magnetic fields can heat metal. And this phenomenon is called the magnetocaloric effect.

When a metal is at rest and is not affected by external stimuli, then its electrons move in any possible direction. However, it is worth bringing a magnet to it, and the metal is exposed to a magnetic field - the electrons actually line up in the same direction. This is a change in entropy, or, in other words, the limitation of electrons in the possibility of free movement.

However, this limitation is not constant. Yes, now electrons cannot move in any directions in which they "want", but they can still move in other directions. In this case, entropy increases by increasing the vibration of atoms. And the vibration of atoms, or rather the energy of their vibration, or movement, has a more generalized name - heat. Therefore, if we bring a magnet to the metal, it starts to heat up. The heating effect when using most metals is practically negligible, but there are metals that are very hot in this case. Such metals include, for example, gadolinium.

It would seem that the magnetocaloric effect is more suitable for cooking food, and not for freezing it. However, this effect can also have the opposite effect. If a piece of metal is under the influence of a magnetic field and this field is then removed, then the metal begins to cool.

Most magnetic refrigerators currently being tested in scientific laboratories can cool small objects in this way. A special substance, most often helium, is applied to a metal under the influence of a magnetic field. This substance picks up excessive heat, the metal is cooled, and then the magnetic field is removed, which makes the metal very cold. Cold enough to be used as a cooler.

The principle of magnetic cooling has been known for a long time, but using it at home seems like a pipe dream. Hopefully, eventually the capabilities of magnetic refrigeration systems, their efficiency, quietness and reduced need for chemical refrigerants can one day bring them to market.