Investigations on the presence of electrical frequency on the characteristics of energy harvesters under base and galloping excitations

The characteristics and performance of piezoelectric energy harvesters concurrently subjected to galloping and base excitations when using a complex electrical circuit are studied. The considered energy harvester is composed of a bilayered cantilever beam with a square cylindrical structure at its tip. Euler-Bernoulli beam theory, nonlinear quasi-steady hypothesis, and Galerkin method are used to develop a reduced order model of this system. The electrical circuitry of the harvester consists of a load resistance, a capacitance, and an inductance. The impacts of the electrical components of the harvester's circuitry, the wind speed, and the base excitation frequency and acceleration on the broadband characteristics of the harvester, quenching phenomenon, and appearance of new nonlinear behaviors are deeply investigated and discussed. Different methods were used to characterize the new nonlinear phenomena that took place due to mechanical electrical interaction like the power spectrum and time history. When both coupled frequencies of electrical and mechanical types exist and are far from each other, it is shown that the quenching phenomenon is only related to the coupled frequency of mechanical type. It was also proven that this configuration results on high harvested power with low displacement near the electrical frequency. On the other hand, for a well-defined choice of the electrical components, the results show that a broadband configuration of the harvester can be designed. It is also indicated that the quenching phenomenon interacts with the appearance of hysteresis regions that depends on the value of the base acceleration and initial conditions. Moreover, it was shown that the presence of this inductance may result in broadband system harvesting more power from both galloping and base excitation.