Piezoelectric Energy Harvesting Device Optimization by Synchronous Electric Charge Extraction

Abstract

This article presents a nonlinear approach to optimize the power flow of vibration-based piezoelectric energy-harvesting devices. This self-adaptive principle is based on a particular synchronization between extraction of the electric charge produced by the piezoelectric element and the system vibrations, which maximizes the mechanical to electrical energy conversion. An analytical expression of the optimal power flow is derived from a simple electromechanical model. An electronic circuit designed to perform the synchronous charge extraction is proposed. Theoretical predictions confirmed by experimental results show that the new principle increases the harvested power by 400% as compared with a quasilinear impedance adaptation optimization method.

Efficiency of energy conversion for a piezoelectric power harvesting system

“…Note that (5) is identical with that derived by [39,43,44]. We next need to find out u 0 to determine V c .…”

“…This is equivalent to assuming that the coupling is very weak and the term V p can be dropped from (1). On the other hand, if the coupling is not so weak, Guyomar et al [43] and Lefeuvre et al [44] have provided another approach to estimate the displacement magnitude by assuming that the external forcing function and the velocity of the mass are in phase. Recently, Shu and Lien [34] have proposed a new method for determining u 0 without the uncoupled and in-phase assumptions.…”

“…If the modal density of such a device is widely separated and the structure is vibrating at around its resonance frequency, we may model the power generator as a mass+spring+damper+piezo structure, as schematically shown in figure 1 [33,39,44]. It consists of a piezoelectric element coupled to a mechanical structure.…”

“…We next need to find out u 0 to determine V c . There are two approaches to estimating it in the case of ac-dc power harvesting system in the recent literature [39,43,44]. The first one models the piezoelectric device as the current source in parallel with its internal electrode capacitance C p [5,9,11,39].…”

“…It is based on the principle of load impedance adaptation by tuning the load impedance to obtain a higher power flow. Related work based on the synchronous electric charge extraction can be found in [41][42][43][44].…”