A coupled piezoelectric–electromagnetic energy harvesting technique for achievingincreased power output through damping matching

Abstract

Vibration energy harvesting is being pursued as a means to power wireless sensors andultra-low power autonomous devices. From a design standpoint, matching the electricaldamping induced by the energy harvesting mechanism to the mechanical damping in thesystem is necessary for maximum efficiency. In this work two independent energyharvesting techniques are coupled to provide higher electrical damping within the system.Here the coupled energy harvesting device consists of a primary piezoelectric energyharvesting device to which an electromagnetic component is added to better match thetotal electrical damping to the mechanical damping in the system. The first coupleddevice has a resonance frequency of 21.6 Hz and generates a peak power output of∼332 µW, compared to257 and 244 µW obtained from the optimized, stand-alone piezoelectric and electromagneticenergy harvesting devices, respectively, resulting in a 30% increase in poweroutput. A theoretical model has been developed which closely agrees withthe experimental results. A second coupled device, which utilizes thed33 piezoelectric mode, shows a 65% increase in power output in comparison to thecorresponding stand-alone, single harvesting mode devices. This work illustrates the designconsiderations and limitations that one must consider to enhance device performancethrough the coupling of multiple harvesting mechanisms within a single energy harvestingdevice.