Magnetic cooling is based on the magnetocaloric effect: the phenomenon that certain materials placed in a magnetic field heat up and then cool when the magnetic field is switched off.
This technique works as follows. First the material is placed in a magnetic field that regulates the magnetic spin, thus releasing heat. Then the heat that has been generated is fed through directly, or using a cooling medium, to the space or object that has to be heated. By then switching off the magnetic field, the regulation in the magnetic material is lost. Heat is required for this and it can be acquired directly or indirectly from the environment. This is the cooling effect.
The key features of magnetic cooling are:
TNO Built Environment and Geosciences also uses this technique for developing new equipment to climatise space.