Performance of beam-type piezoelectric vibration energy harvester based on ZnO film fabrication and improved energy harvesting circuit

Abstract

We demonstrate a piezoelectric vibration energy harvester with the ZnO piezoelectric film and an improved synchronous electric charge extraction energy harvesting circuit on the basis of the beam-type mechanical structure, especially investigate its output performance in vibration harvesting and ability to generate charges. By establishing the theoretical model for each of vibration and circuit, the numerical results of voltage and power output are obtained. By fabricating the prototype of this harvester, the quality of the sputtered film is explored. Theoretical and experimental analyses are conducted in open-circuit and closed-circuit conditions, where the open-circuit mode refers to the voltage output in relation to the ZnO film and external excitation, and the power output of the closed-circuit mode is relevant to resistance. Experimental findings show good agreement with the theoretical ones, in the output tendency. It is observed that the properties of ZnO film achieve regularly direct proportion to output performance under different excitations. Furthermore, a maximum experimental power output of 4.5 mW in a resistance range of 3 kΩ–8 kΩ is achieved by using an improved synchronous electric charge extraction circuit. The result is not only more than three times the power output of classic circuit, but also can broaden the resistance to a large range of 5 kΩ under an identical maximum value of power output. In this study we demonstrate the fundamental mechanism of piezoelectric materials under multiple conditions and take an example to show the methods of fabricating and testing the ZnO film. Furthermore, it may contribute to a novel energy harvesting circuit with high output performance.