Energy Harvesting using Non-linear Techniques

Abstract

Recent progresses in both microelectronic and energy conversion fields have made the conception of truly self-powered, wireless systems no longer chimerical. Combined with the increasing demands from industries for left-behind sensors and sensor networks, such advances therefore led to an imminent technological breakthrough in terms of autonomous devices. Whereas some of such systems are commercially available, optimization of microgenerators that harvest their energy from their near environment is still an issue for giving a positive energy balance to electronic circuits that feature complex functions, or for minimizing the amount of needed active material. Many sources are available for energy harvesting (thermal, solar, and so on), but vibrations are one of the most commonly available sources and present a significant energy amount. For such a source, piezoelectric elements are very good agents for energy conversion, as they present relatively high coupling coefficient as well as high power densities. Several ways for optimization can be explored, but the two main issues concern the increase of the converted and extracted energies, and the independency of the harvested power from the load connected to the harvester.

Particularly, applying an original nonlinear treatment has been shown to be an efficient way for artificially increasing the conversion potential of piezoelectric element applied to the vibration damping problem. It is therefore possible to extend such principles to energy harvesting, allowing a significant increase in terms of extracted and harvested energy, and/or allowing a decoupling of the extraction and storage stage.

The purposes of the following developments consist in demonstrating the ability of such microgenerators to convert ambient vibrations into electrical energy in an efficient manner. As well, when designing an energy harvester for industrial application, one has to keep in mind that the microgenerator also must be self-powered itself, and needs to present a positive energy balance. Therefore, in addition to the theoretical developments and experimental validations, some technological considerations will be presented, and solutions to perform the proposed processing using a negligible part of the available energy will be proposed. Moreover, the behavior of the exposed technique under realistic vibrations will be investigated.