A hybrid piezoelectric and electromagnetic energy harvester for scavenging low frequency ambient vibrations

This work presents a hybrid type piezoelectric and electromagnetic multi-degree of freedom (MDOF) energy harvester for low-frequency ambient vibrations. The proposed device is designed with unique MDOF mechanical structure that helps to obtain multiple resonant modes operation of the harvester at low frequency range. The mechanical design comprises of a clamped-clamped beam as primary beam and four secondary beams as cantilever array. During external excitation, the secondary cantilever beams vibrate simultaneously along with the magnetic proof mass that causes mechanical strain to the piezoelectric elements as well as relative motion between magnets and coils placed underneath of it. A prototype of the hybrid MDOF energy harvester has been fabricated, simulated, and experimentally verified. The frequency response of the prototype implies that the proposed hybrid MDOF harvester has four resonant modes which concentrate around 12, 16, 17, and 21 Hz, respectively. On the other hand, a maximum of 218μW and 204µW peak powers have been obtained across the respective optimal load resistances from a single piezoelectric and electromagnetic generator of the array at 3^rd resonance (17Hz) under 0.1g base acceleration. (paper)