Design Issues and Future Perspectives for Magnetocaloric Energy Conversion - Magnetocaloric Energy Conversion: From Theory to Applications - page 359

8.7.6 Power Generation

As already mentioned in the section on power generation, the major problem of
performing such processes is in need for a very large number of layers of mag-
netocaloric material (in the case of La- or Mn-based materials, for low-enthalpy
sources with temperature at about 120 25 layers of

materials with different Curie temperatures). This is why we propose the devel-
opment of these systems after the market applications in the eld of magnetic
refrigeration, heat pumping and air-conditioning.

160 ° C, this means about 20

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8.7.7 General Characteristics of Future Magnetocaloric
Devices

Table 8.1 shows some of the predicted features that future magnetocaloric devices
will have. As shown in Table 8.1 , we predict that future magnetocaloric devices
will apply permanent magnets up to a heating or cooling power of 300 kW. Above
this range, the application of superconducting magnets makes sense. Therefore,
large-scale chillers and heat pumps with cooling or heating power above 300 kW
and up to a few MW will be based on superconducting magnets. Also, in power
generation, it is expected that micro units will not be developed, but rather larger
superconducting systems operating with a low enthalpy source of heat. Note,
however, that the operation with low-enthalpy heat sources, even if the power
generator operates with the Carnot ef

ciency (100 % exergy ef ciency), such a

device will have a thermodynamic ef ciency of the heat-to-power conversion in the

range from 10 to 30 %. Therefore, a power unit which converts 1 MW of heat with
the thermodynamic ef

ciency of 50 % will
generate 50 kW of mechanical power or electricity. Note also that the permanent
magnets, especially Nd

ciency of 10 % and the Carnot ef

B are quite sensitive to high temperatures. With regard
to the frequency of the operation, one can expect for the 40 K temperature dif-
ference and the ef

Fe

- -

ciency of at least of that of compressor units, that devices with
the AMR principle will reach 5 Hz. In the case of AMR principles with some

Table 8.1 Predicted general features of future magnetocaloric devices depending on the magnetic
eld source
Target market/
target of design

Small scale
refrigerators

Small scale
air
conditioners

Chillers/
heat
pumps
<300 kW

Large-
scale heat-
ing and/or
cooling
>300 kW

Power
generation
>50 kW el

Permanent
magnets

✔ ✔ ✔

Superconducting
magnets

✔ ✔