Design and Modeling of a Magnetic-Coupling Monostable Piezoelectric Energy Harvester Under Vortex-Induced Vibration

Vortex-induced vibration (VIV) is used by piezoelectric energy harvesters to generate electricity from wind and water flow. In this study, we introduce the nonlinear magnetic force into piezoelectric energy harvesters and develop a nonlinear monostable piezoelectric VIV transducer. We build a distributed-parameter model based on the Euler-Bernoulli beam theory and Kirchhof's law to analyze the dynamic responses of the magnetic-coupling piezoelectric energy harvester (MCPEH). Model results show that the performance of the MCPEH varies greatly with the increase of the load resistance and the length of the used PZT. There are two optimal resistance values for the MCPEH. When $R<; 31.6~\text{k}\Omega $ , both the external load resistance and the PZT length affect the maximum power output. The little optimum resistance value will dwindle with the increase of the PZT length, whereas the large optimum resistance value still fixes at 1.78 $\text{M}\Omega $ with the increase of the PZT length. Due to the resistive shunt damping effect and the kinetic energy of wind, the resonance domain becomes wider in these ranges of load resistance smaller than 31.6 $\text{k}\Omega $ and larger than 316 $\text{k}\Omega $ comparing that when the load resistance is larger than 31.6 $\text{k}\Omega $ and smaller than 316 $\text{k}\Omega $ . Besides, the performance is enhanced by the monostable nonlinear magnetic force, which can be improved by decreasing the value of the distance between moving magnets and fixed magnets. The energy harvester shows a maximum power output of 0.21 mW under excitation of wind velocity is 1.6 m/s when the cylindrical diameter is 20 mm, the PZT length is 30 mm and the load resistance is 0.5 $\text{M}\Omega $ .