Abstract
Considering coil inductance and the spatial distribution of the magnetic field, this paper developed an approximate distributed-parameter model of a hybrid energy harvester (HEH). The analytical solutions were compared with numerical solutions. The effects of load resistances, electromechanical coupling factors, mechanical damping ratio, coil parameters and size scale on performance were investigated. A meso-scale HEH prototype was fabricated, tested and compared with a stand-alone piezoelectric energy harvester (PEH) and a stand-alone electromagnetic energy harvester (EMEH). The peak output power is 2.93% and 142.18% higher than that of the stand-alone PEH and EMEH, respectively. Moreover, its bandwidth is 108%- and 122.7%-times that of the stand-alone PEH and EMEH, respectively. The experimental results agreed well with the theoretical values. It is indicated that the linearized electromagnetic coupling coefficient is more suitable for low-level excitation acceleration. Hybrid energy harvesting contributes to widening the frequency bandwidth and improving energy conversion efficiency. However, only when the piezoelectric coupling effect is weak or medium can the HEH generate more power than the single-mechanism energy harvester. Hybrid energy harvesting can improve output power even at the microelectromechanical systems (MEMS) scale. This study presents a more effective model for the performance evaluation and structure optimization of the HEH.
Highlights
Vibration energy harvesting technology, which converts the ambient vibration energy into electric energy, has drawn much attention in recent years. It is considered as a promising solution to power the low-power portable microelectronic devices and wireless sensor networks
It is a challenge for researchers to design the vibration energy harvester (VEH) with a broad operating frequency bandwidth and outstanding energy density
It is clear that the output power first rises up and falls off with the increasing of one load resistance, when the other one is kept constant
Summary
Vibration energy harvesting technology, which converts the ambient vibration energy into electric energy, has drawn much attention in recent years. To improve the performance of the VEH, hybrid energy harvesting technology combining piezoelectric and electromagnetic mechanisms is proposed. It shows an increasing trend and attracts more and more attention from scholars. The effect of the coil inductance mostly is not taken into account It is disadvantageous for the performance evaluation and structure optimization of the HEH based on those theoretical models. The objective of this paper is to develop an approximate distributed-parameter theoretical model of the HEH by considering the coil inductance and spatial distribution of magnetic field and to analyze comprehensively the effects of key parameters on the generating performance
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