Saw-tooth type piezoelectric multi-modal energy harvester

Abstract

The paper presents results of numerical and experimental investigations of a new design piezoelectric energy harvester based on a saw-tooth type cantilever array. The proposed energy harvester has multi-modal operation principle and allows to harvest mechanical vibrations energy in narrow frequency range. Moreover, the multi-modal operation principle of the harvester enable summation of bending strains of several cantilevers and allows to improve efficiency of the harvester. The proposed multi-modal energy harvester consist of four cantilevers that are connected rigidly to each other at 30° angles. Cross-sections of the cantilevers were modified by cylindrical gaps in order to increase bending strain. Seismic masses were placed at each corner of the harvester in order to reduce values of natural frequencies and to create additional rotation moment. Numerical investigation revealed that the energy harvester has five resonance frequencies in the range from 20 Hz to 135 Hz. The numerical investigation of electrical characteristics showed that voltage density of 48.39 mV/mm3 and energy density of 61.25μJ/mm3 was obtained. Experimental investigations confirmed the results of numerical investigation and showed that voltage and energy densities reached 55.65 mV/mm3 and 52.56 μJ/mm3, respectively.