Energy conversion improvement in ferroelectrics: application to energy harvesting and self-powered systems

The proliferation of consumer electronics, combined with the constant progress in ultra-low power devices and increasing demand in terms of autonomous sensors and sensor networks, has enabled the conception of systems powered up using ambient sources such as vibrations, hence allowing the replacement of batteries that present maintenance issues and environmental problems. However, the power output of microgenerators is still limited from a few tens of microwatts to a few milliwatts. The topic addressed here exposes the conversion enhancement principles for piezoelectric generators, using a simple, low-cost, embeddable and truly self-powerable concept based on an intermittent switching of the piezoelement, allowing a great increase of the piezoelectric conversion abilities and thus of the performance of energy harvesters. Several schemes derived from this basic switching concept will be discussed, with a particular attention placed not only on the energy harvesting abilities of the microgenerators, but also on their realistic implementation and their use for powering up electronics devices (e.g., by considering the power output as a function of the connected load). The application of the conversion enhancement principles to semi-passive, self-powered or semi-active vibration control will be also presented, as well as its application to other conversion effects (e.g., pyroelectric). Finally, a truly self-powered wireless Structural Health Monitoring scheme using an efficient energy harvesting scheme will be described.