Lowering the resonance frequency of a two-dimensional high-power piezoelectric energy harvester with reducing the stiffness of the harvester

Abstract

Generating more power in lower frequencies is one of the most challenging purposes in designing cantilever beam energy harvesters. Using geometrically symmetric two-dimensional beam shapes is one of the most effective ways that has been proposed to increase the output power of harvesters. With symmetry in the geometry, torsional forces on piezoelectric elements eliminate. Consequently, the output power of the harvester increases. However, the resonance frequency of these designed harvesters is still high for some applications. In this work, we demonstrate a strategy to decrease the stiffness of a two-dimensional harvester named Elephant type, without changing in its output power. The output power and the resonance frequency of our proposed harvester are calculated using a finite element simulation. The finite element model is in a good agreement with the analytical and experimental data for the Elephant type harvester. The finite element model predicts lower resonance frequency for our model compared to Elephant type, without a major drop in the output power. Finally, we propose a dimensionless parameter to evaluate the performance of piezoelectric harvesters which have a direct relation with the output power and an inverse relation with the resonance frequency of the harvester.