Smart interference galloping energy harvester with optimally tunable gap between the bluff body and interference

Abstract

This study focuses on the development of a piezoelectric wind energy harvester that utilizes the wake interference galloping phenomenon. We found that depending on the applied wind velocity, there exists an optimal gap distance between the oscillating bluff body and the interference, which produces the required wake interference galloping. Accordingly, we aimed to design a novel interference galloping–based energy harvester that can smartly adjust the bluff body location to its optimal position in response to the external wind velocity. The optimal gap distance between the two bodies for the wind velocity range considered in this study was found to be 9–15 mm, which strongly depends on the applied wind velocity. It was also observed that the phase delay of the lift force with respect to the displacement of the oscillating body plays a major role in determining the state of the system stability and that the wake interference galloping can also occur due to the memory effect. The phase angle of π/2 rad was found to be an important indicator for determining whether wake interference galloping occurs. The balance of forces on the bluff body is vital for determining the optimal location of the bluff body. The mathematical modeling was performed using the extended Hamilton principle, the Galerkin method, eigen- and multi-modal analyses, the extended Fourier theorem, and novel energy/power balance conditions that yielded the four additional equations required to compute the aerodynamic lift in an autonomous form. To identify the physical parameters for analyzing the proposed energy harvester system, a main experiment and several preliminary experiments were conducted. The analytical results were compared with the experimental data in terms of both the dynamic behavior and energy production, and they were observed to be sufficiently close (the maximum error in the averaged output power was 9.8%). The average output power from the proposed energy harvester was also compared with that from conventional interference galloping–based energy harvesters having an immobile bluff body; the results showed that the proposed energy harvester outperformed the conventional harvesters by up to 128.8%. Specifically, it generated an average output voltage of 71 V (rms) and an output power of 6.88 mW at a wind velocity of 10 m/s. © 2024 Elsevier Ltd