Green Fridges...

Using the "magnetocaloric effect" to build a low-temperature magnetic refrigeration device. (Courtesy: Shutterstock/Spectral-Design)

A large, rotational magnetocaloric effect – which could be used as the basis for a low-temperature magnetic refrigeration device – has been observed in crystals of the compound HoMn2O5, according to research carried out by scientists in Canada and Bulgaria. This finding expands our knowledge of magnetocaloric materials, adding to our progress towards a practical and environmentally friendly magnetic cooler that might be usable in a domestic setting.

In recent times, the potential of magnetic refrigeration techniques as an alternative to traditional, vapour-compression solutions has been attracting considerable attention. This is mainly thanks to the lower energy demands of the technique, and the fact that it is not reliant on hazardous fluids. Such devices take advantage of the magnetocaloric effect – a phenomenon in which certain materials change temperature in response to an externally applied magnetic field. Such fields cause the magnetic dipoles of the atoms within magnetocaloric compounds to align. To balance out this decrease in entropy – and thereby satisfy the second law of thermodynamics – the motion of the atoms also becomes more disordered, and the material heats up. In contrast, when the applied field is removed, the process reverses and the material cools. In magnetic refrigerators, these temperature changes can be harnessed, using a fluid or gas, to drive a heat pump.

This relates to the ozone layer and how we could use technology to reduce the size of the hole over the Antarctic. UV radiation is filtered by it to make our existence possible. Kind of an important thing, since Monday's post on warp drive technology - though inspiring - is still in the theory stage. The only spaceship we currently have is under our feet.

Physics World: Using magnetic cooling for 'green' refrigeration
#P4TC: "An Extremely Bold Op-Ed," November 19, 2010