Vibration Energy Harvesting with Multi-Frequency Array of Nonlinear Piezoelectric Converters

This work proposes a piezoelectric energy harvester where the combination of the multi-frequency and nonlinear approaches is explored in a unique device. The harvester exploits four piezoelectric cantilevers with lead zirconate titanate (PZT) films deposited by screen-printing on ferromagnetic stainless-steel substrates. Nonlinear behavior of the cantilevers is achieved by exploiting the interaction between a magnet and the steel substrates. Two configurations have been analyzed where the magnet is either fixed, or elastically suspended through a spring on the harvester base. The fabricated prototype has been experimentally characterized employing band-pass filtered white- noise mechanical vibrations in the range 10-100 Hz with amplitude in the range 0.1-2.2g. The results show that the nonlinear configurations can increase the open-circuit output voltage up to 215 % over the same array operated in linear regime, i.e., without the magnet.