Size-dependent behavior of micro piezoelectric VIV energy harvester: Parametric study and performance analysis

Abstract

Implementation of self-powered MEMS units by converting wind and flow stream energy into electrical energy has gained substantial interest in recent years. A bluff body vortex induced vibrations (VIV) in combination with micro scale piezoelectric device can be designed to harvest the demanded power. In the present study, the mechanical performance of a piezoelectric micro energy harvester beam attached to a tip cylinder is numerically simulated. In order to increase the accuracy of the modeling, the elastic and piezoelectric micro-beam governing equations are derived based on strain gradient theory instead of the conventionally used classical theory. The actuating aerodynamic lift force due to the vortex shedding downstream of the cylinder, is simulated by the modified van der Pol wake oscillator equation. Using the mode summation and Galerkin method, the three coupled time dependent governing equations are solved. The accuracy of the van der Pol equation is examined by a moving object computational fluid dynamics (CFD) simulation on the basis of the cantilever beam tip deflection and great agreement is achieved. The effect of length scale parameter, beam length, cylinder diameter and mass, load resistance, piezoelectric thickness as well as the fluid velocity on the produced power density is studied. Findings revealed that increasing the length scale parameters, the device stiffness and frequency increases as well as the harvested power is increased at specific fluid velocities. In other words, increasing the length scale from 0 to 2μm, increases the power density up to 77%.