Study of the energy conversion chain in a thermomagnetic generator.

Thermomagnetic generators designed to scavenge electrical energy from a heat flow can be designed following different conversion chains. Here we numerically study a device based on a three steps conversion, from magnetic towards kinetic, and eventually electrical energy. This chain is assured by a magnetocaloric material (MCM) as active substance moving between the heat reservoirs on an elastic beam (polypropylene :60.6 x 26.6 x 1.2 mm3) designed to obtain an auto-oscillating system. The cantilever kinetic energy is recovered using piezoelectric patches (PZT 5a). After optimization of the patches size, our simulations give an output energy density of 0.03 mJcm-3. To achieve a further optimization we investigate the possibility to use the piezoelectric material both as a transducer and as an actuator to have a better control of the working thermodynamic cycle. In this way we show that an energy density up to 60.46 mJcm-3 can be achieved.