Size optimization of conical piezoelectric energy harvesters

The optimal design of piezoelectric patches on a piezoelectric conical energy harvester is presented in this study. Based on the equivalent voltage source model, the power of the resistance load is derived firstly. The origin location of the piezoelectric patch is set at the peak points of the modal voltage. The piezoelectric patch is in the region formed by the zero lines where the modal voltage is zero. The location of the peak points and the zero lines are determined by the spatial distribution of the modal voltage and the open-circuit voltage. Three parameters are chosen to locate the piezoelectric patch, i.e. the circumferential width, the length from the origin to the minor end and the length from the origin to the major end. Solving the extremum of the power equation with respect to the three parameters yields the optimal size of the piezoelectric patch. Case studies are given to evaluate the power of the optimal piezoelectric energy harvester. The results indicate that with the origin located at the optimal location, the power of resistance load firstly increases with the width and the lengths until the maximum and then decreases. The optimal width of the piezoelectric patch is 75% of the half-wave length for all of the evaluated modes.