On Efficiency of Two-Degree-of-Freedom Galloping Energy Harvesters with Two Transducers

Abstract

This paper examines the energy efficiency of three variations of the two-degree-of-freedom transverse galloping energy harvester. These variants differ in the number and placement of electromechanical transducers. By utilizing the harmonic balance method, the limit cycles of mathematical models of the devices were determined. Analytical expressions derived from the models were then used to formulate the efficiency of the systems. It was demonstrated that efficiency depends on flow speed and can be comprehensively characterized by the following criteria parameters: peak efficiency, denoting the maximum efficiency of the system, and high-efficiency bandwidth, which describes the range of flow speeds within which the efficiency remains at no less than 90% of peak efficiency. The values of these parameters are heavily reliant on two other parameters: the speed at which the system achieves peak efficiency, referred to as the nominal speed, and also the flow speed at which the system undergoes Hopf bifurcation, namely the critical speed. Comparative analysis revealed that only the device equipped with two electromechanical transducers can potentially outperform a simple one-degree-of-freedom system. For selected parameters, this gain reached nearly 10%.