Piezoelectric Vibrational Energy Harvesting

Abstract

Piezoelectric vibration energy harvesting can provide a sustainable source of
energy for low-power sensors. The vibrational energy is converted to electrical energy by piezoceramic cantilevers. Replacing batteries by vibrational energy harvesters, reduces the footprint of the device and no continuous replacement of batteries is required cutting down the maintenance costs. However, the greatest issue preventing these system from being widely used is their poor reliability. The main failure mechanisms identified are ageing, temperature degradation, humidity degradation and most of all mechanical degradation. In the aim to maximise the power output, the piezoceramic cantilevers are resonating at
the eigenfrequency close to the point of the fracture strength. It is found that too large tensional deformations result in fractures in the active piezoceramic material. Experiments show that fractures significantly drops the power output and reduces the eigenfrequency. Literature suggest that tapered piezoceramic cantilevers are a reliable replacement for the conventional rectangular piezoceramic cantilevers. Experiments confirm the severity of fractures in the piezoceramic cantilevers reduction of power output as low as 75% have been measured. Tapered cantilevers show to have a higher electrical power output per unit area compared to rectangular cantilevers. Therefor less deformation is needed to achieve the same electrical output. It can be concluded that tapered cantilevers increase the reliability of the vibrational energy harvester.