Design, Simulation and Experiment for a Vortex-Induced Vibration Energy Harvester for Low-Velocity Water Flow

Piezoelectric vibration energy harvesting has attracted considerable attention because of its prospects in self-powered electronic applications. There are a many low-velocity waters in nature, such as rivers, seas and oceans, which contain abundant hydrokinetic energy. In this paper, an optimal geometric piezoelectric beam combining magnetic excitation is identified and applied to a vortex-induced vibration energy harvester (ViVEH) for low velocity water flow, which is composed of a continuous variable-width piezoelectric beam carrying a cylindrical bluff body. The finite element simulation and experiment are first carried out to study the harvesting characteristics of the designed variable-width beam ViVEH without considering the magnetic excitation. The influence of the width-ratio and flow velocity on the harvesting voltage is studied in detail. The optimal structure, a ViVEH equipped with triangular piezoelectric beam, is then obtained by the superior energy harvesting performance for low velocity water flow. From the experimental results, at a flow velocity of 0.6 m/s, the highest root mean square (RMS) voltage and RMS voltage per unit area are 19.9 V and 0.07 V/mm(2), respectively. Furthermore, magnetic excitation is introduced to improve the scavenging performance of the optimal triangular beam ViVEH, different polarity arrangements are compared, and the optimal case, the arrangement of horizontal repulsion and vertical attraction (HR-VA), is obtained. This case can scavenge the highest power of 173 mu W at a flow velocity of 0.5 m/s, which is increased by 127% compared to a conventional constant-width beam ViVEH with no magnetic excitation.