Design Issues and Future Perspectives for Magnetocaloric Energy Conversion - Magnetocaloric Energy Conversion: From Theory to Applications - page 353

8.6 A Note on Magnetocaloric Power Generation

Imagine a realistic system with a low-enthalpy heat source with a temperature of
120 ° C and a heat-sink temperature of 30 ° C (i.e. such can be used by Organic

—

Rankine Cycle ORC). A 90 K temperature difference: This of course is not much

for some other technologies, but the present knowledge in magnetocaloric energy
conversion does not provide an ef cient solution to develop a market-ready

application. This kind of development will actually demand a longer period than
magnetic refrigeration or magnetic heat pumping. Therefore, despite the fact that
magnetocaloric power generation can represent an important future power-gener-
ation application, the high-temperature difference that is required simply represents
at the moment a too large obstacle. This, of course, is not a statement to discourage
future developments. However, it makes sense that the new emerging technology

rst enters market domains in which it can become well established. Despite this
fact and because of studies that show good future potential, we have made below a
short review on the existing work in this particular domain.

8.6.1 How to Perform Magnetocaloric Power Generation?

The answer is given by the temperature dependency of the magnetization of the
magnetocaloric material. For instance, if the magnetocaloric material is in the
ferromagnetic state, it will be attracted towards the higher magnetic

eld. Imagine
now an opened thermodynamic cycle, where a disc of magnetocaloric material is
partially placed in the high-magnetic- eld region and partially in the low-magnetic-

eld region. Of course, if no temperature gradient is applied, the disc will stay at
rest. Now let us introduce the heat source and the heat sink. The heat sink will be
provided in the low (or no

eld region. However, the heat source will be
provided in the region before the disc exits the magnet eld. Therefore, the mag-
netocaloric disc will have a temperature gradient in the magnetic

eld)

eld. It will be less

attracted to the magnetic eld at its exit, and more attracted to the magnetic eld

region at its entrance. This will create the rotation of the disc.

8.6.2 Review of Magnetocaloric Power Generation

The rst to start investigation of the phenomenon of magnetocaloric power gen-

eration were Tesla [ 3 ] and Edison [ 4 ]. Much later, in the 1950s, researchers were
analysing the idea of magnetocaloric power generation by applying magnetocaloric
suspensions as working

uids [ 5 , 6 ]. However, some work was additionally done
by Brillouin and Iskenderian [ 7 ], Van der Voort [ 8 ], Chilowsky [ 9 ] and Elliott [ 10 ],
but no evidence of actual prototypes from that time exists.

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