Hybrid piezoelectric-electromagnetic energy harvester for scavenging energy from low-frequency excitations

Abstract

Capturing mechanical energy from our living environment is an effective approach for implementing self-sustained electronics. One of the key challenges is how to generate more electricity from the low-frequency and multi-directional excitations. To address this interesting issue, this paper reports a hybrid energy harvester (HEH) that consists of a piezoelectric energy harvester (PEH) and an electromagnetic energy harvester (EMEH), which can scavenge energy from both low-frequency and bi-directional excitations. The PEH is composed of two piezoelectric cantilever beams, each of which can deliver a peak power of approximately 0.13 mW when excited directly by a harmonic vibration of 0.8 g. A spherical magnet is utilized to not only trigger the PEH to function, which endows the PEH with bi-directional energy-harvesting capability, but also induce the coil to generate electricity, achieving the integration of EMEH with PEH. When the magnet is subjected to a sinusoidal excitation of 1.24 g, each beam of the PEH generates a peak power of 0.058 mW at 7 Hz and the coil outputs a peak power of 2.94 mW at 7.2 Hz. The HEH exhibits a better charging performance than the PEH or EMEH for charging a capacitor, and the fabricated HEH prototype can light up tens of light-emitting diodes (LEDs) when excited by hand-shaking vibrations.