Climate-friendly cooling technology without harmful refrigerants

Magneto-, electro- and elastocaloric systems

More and more air-conditioning systems are being installed all over the world. They generally operate with refrigerants which are harmful to the environment and also require a great deal of energy. Magnetocaloric cooling technology could make far more energy-efficient cooling systems, which do without harmful refrigerants, possible in future.

Magnetocalorics

It is possible to develop particularly energy-efficient cooling systems that operate on the basis of the magnetocaloric effect – entirely without harmful refrigerants. They are based on so called magnetocaloric (MC) materials. MC materials are magnetizable materials which heat up when exposed to a magnetic field and cool down again accordingly when the field is removed. This is how it is possible to implement a cooling cycle: The heated MC material is connected to a heat sink so that heat can be dissipated. If the magnetic field is removed, the material cools down again and is at a lower temperature than at the start of the cycle. The MC material is now connected to the system to be cooled and is able to absorb heat. Magnetocaloric cooling systems achieve up to 30 percent higher efficiencies by comparison with compressor-based systems.

Electrocalorics

The principle of electrocaloric cooling is similar to that of magnetocaloric cooling: A reversible heatflow is produced in the electrocaloric material when exposing it to an electric field. With intelligent system integration, this effect can be used to establish efficient cooling systems without harmful refrigerants.

Elastocalorics

Elastocaloric materials are already known in other applications as »shape memory alloys«. In these alloys, the material changes shape when heat is applied. By applying force to the material to generate reversible heat, the opposite effect can also be used. Just as with magnetocaloric or electrocaloric materials, this method can be integrated into a system to create a cooling system.

 

The principle of magnetocaloric cooling

© Fraunhofer IPM
The magnetocaloric material is heated (Step 1) by applying a magnetic field (H field). In Step 2, the MC material is connected to a heat sink so that the heat produced (Q) can be dissipated. If the magnetic field is removed (Step 3), the MC material cools down again and is at a lower temperature than it is at the start of the cycle. The MC material is now connected to the system to be cooled and can absorb heat (Q) (Step 4).