A Thermal Energy Harvester Using LaFeSi Magnetocaloric Materials

A thermomagnetic generator (TMG) using a Halbach structure as a field source and a first-order LaFeSi magnetocaloric material (MCM) from Vacuumschmelze as the active substance is presented. The MCM, suspended on a cantilever beam, self-oscillates between a hot source and a heat sink. The mechanical energy associated with the oscillation is harvested and converted into electricity using the piezoelectric materials. This system is working between an 18 °C cold end and a 56 °C heat source (i.e., over a temperature difference between the reservoirs ΔTres= 38 °C) and shows a power of 0.12 μW (6.8 μW per 1 cm3of MCM). We present and discuss a detailed analysis of the thermodynamic cycle underpinning the device mechanism, relying on the direct measurements on the working prototype and on a full laboratory characterization of the MCM. Although our system shows a state-of-the-art power output, our analysis gives useful clues toward further performance improvements.improvements.