Energy harvesting from large force vibrations using a piezoelectric wafer-stack harvester

This paper presents a novel piezoelectric harvester to convert ambient vibrations into usable electrical energy. Unlike the normal cantilever beam structure, the piezoelectric harvester developed in this paper is based on the wafer-stack configuration, which is appropriated for large force vibrations. Firstly, two electromechanical models (without and with a rectifier circuit), considering both the mechanical and electrical factors of the harvester, were built to characterize the harvested electrical power across the external load. Exact closed-form expressions of the electromechanical models have been given to analyze the maximum harvested power and the optimal resistance. It was shown that the harvested electrical power depends on the external vibration characteristics, the natural frequency, the mechanical damping factor, the normalized electrical load, the stiffness of the harvester and the overall electromechanical coupling coefficient of the harvester. Finally, a shake table experimental testing was conducted to evaluate the feasibility of the proposed piezoelectric wafer-stack harvester under standard sinusoidal loadings. Experimental results show that the harvester can generate a maximum 16 mW DC electrical power for sinusoidal loading with 3040 N amplitude and 2 Hz frequency, and the harvested electrical power is proportional to the strength of the exciting vibration.