Bi-resonant structure with piezoelectric PVDF films for energy harvesting from random vibration sources at low frequency

This paper reports on a bi-resonant structure of piezoelectric PVDF films energy harvester (PPEH), which consists of two cantilevers with resonant frequencies of 15 Hz and 22 Hz. With increased acceleration, the vibration amplitudes of the two cantilever-mass structures are increased and collision occurs which causes strong mechanical coupling between the two subsystems. The experimental results show that the operating bandwidth is widened to 14 Hz (14-28 Hz) at an acceleration of 9.81 m/s2, and the peak output power can be 0.35 μW at a relatively low operation frequency of 16 Hz. Simulation and experiments with piezoelectric elements show that the energy harvesting device with the bi-resonant structure can generate higher power output than that of the sum of the two separate devices from random vibration sources at low frequency, and hence significantly improves the vibration-to- electricity conversion efficiency by 40-81%.