Temperature threshold tuning of a thermal harvesting switch

This paper presents an original energy harvester making use of a temporal variation of temperature and converting it to electricity. Such a device combines piezoelectric and magnetic materials in order to be able to react to small and slow variations of temperature. Therefore it can be integrated for powering nodes in a wireless sensor network. We report here how to tune the behavior of such generator. By modifying the gap between the hard magnet and the soft magnetic material, it is possible to finely control the hysteresis between the two thresholds but also the position of those thresholds. Finally, like for the electrical load, there is an optimal gap which allows the harvesting of a maximum power.