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 W 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%.