Alternative Caloric Energy Conversions - Magnetocaloric Energy Conversion: From Theory to Applications - page 423

Fig. 10.19 A self-sustaining pyroelectric energy harvester, a The engine chamber is in thermal
contact with the heat source, b The engine chamber is in thermal contact with the heat sink (see
also Ravindran et al. [ 69 ])

details about the dimensions of the samples and the time-averaged power density
achieved. Therefore, a direct comparison with other systems is not possible.
Ravindran et al. [ 69 ] presented a prototype of a self-sustaining pyroelectric
energy converter (PEG). The device is schematically presented in Fig. 10.19 .It
consists of a heat sink, a heat source, a pyroelectric material and the so-called
engine chamber. In the centre of the engine chamber, there is a sealed cavity lled

with a working uid. The bottom of the sealed cavity is made of a bi-stable

membrane. When the engine chamber is in physical contact with the heat source
(Fig. 10.19 a), the heat is transferred from the heat source to the engine chamber by
means of heat conduction. As a result, the working

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uid heats up, the pressure in
the cavity increases and the bi-stable membrane moves the engine chamber
up. Now the engine chamber is in physical contact with the pyroelectric element
(attached to the heat sink) and the heat is transferred from the engine chamber
through the pyroelectric element to the heat sink (Fig. 10.19 b). As a consequence,
the pyroelectric element heats up. On the other hand, the engine chamber is cooled
down in this process and as a certain temperature it reached it moves back to its
original position. Since the engine chamber and the pyroelectric material are now
no longer in contact, the pyroelectric element cools down and the cycle can repeat

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