Energy scavenging from ambient sources based on ferroelectric materials

This paper addresses the problem of piezoelectric conversion enhancement from mechanical to electrical energy and illustrates this improvement on vibration control and health monitoring applications. Considering a mechanical structure equipped with piezoelements, it can be shown that a non-linear processing (SSHI) of the piezoelement output voltage improves significantly the energy conversion. This non-linear processing simply corresponds to short-circuit the voltage for a brief period of time when the voltage reaches a maximum or minimum. Technically, a non-linear switch is added in parallel with the piezoelement, thus the piezovoltage, in front of the rectifier, increases and consequently more energy flows to the storage capacitance. The harvested energy is nine times higher than the standard approach. The influence of piezo-material characteristics will be described. Extension of the non-linear approach to harvesting in the pulse regime leads also to a performance increase specifically for low coupled structure which is mostly the case. After an overview of the basic principles, the presentation will go over new extensions of the SSHI approach to increase the output power, to make it independent of the resistive load or to minimize the voltage drop effect in the rectifier. The SSHI extension to heat harvesting will be also introduced.