Representation and comparative study of electromagnetic-piezoelectric galloping energy harvesters

Abstract

The modeling and performance improvement of galloping-based energy harvesting when using both piezoelectric and electromagnetic transduction mechanisms are studied. To this end, a piezoelectric and an electromagnetic transducers are attached in the transverse degree of freedom of a prismatic cylinder in order to convert galloping vibrations to electrical power. A coupled lumped-parameter model is developed which relates the motion of the oscillating prismatic structure to the generated voltage from the piezoelectric layer(s) and the induced current from the stationary coil. A nonlinear quasi steady approximation is used to model the aerodynamic force created by the flowing wind over the bluff body. The influences of the electrical load resistances in both circuits on the coupled damping and onset speed of galloping are investigated. Based on a linear analysis, the results show that these external load resistances strongly affect the onset speed of galloping with the existence of optimum values. To study the effects of the external load resistances on the performance of the hybrid harvester, a parametric study is carried out. The results show that, for a well-defined wind speed, there exists optimal values of the external load resistances at which the outputs power in the electromagnetic and piezoelectric circuits are optimum. In order to determine the impacts of these transducers on each other, a comparative analysis is performed. The results show that designing hybrid energy harvesters is beneficial to simultaneously operate two low-power consumption devices. On the other hand, it is demonstrated that the existence of both transducers lead to an increase in the onset speed of galloping and a reduction in the levels of power in both circuits. This result is due to the appearance of additional shunt damping in the piezoelectric-electromagnetic energy harvester.