An Inertial Piezoelectric Energy Harvester Excited by Flow-Induced Vibration in Low-Velocity Flowing Water

Low-velocity water flow in oceans and rivers contains abundant energy that can be harnessed. In this article, energy from low-velocity flow is converted into the vibration of an underwater tube, which is elastically supported by two springs and can move along two guiding slots. Piezoelectric cantilever beams are mounted inside the tube to harvest the inertial vibration energy. Unlike other flow-induced vibration converters, in which the converters are perpendicular to the flow direction, in this article, an inclined converter structure is applied. It is found that the inclined structure is beneficial for exciting the vibration of the tube and offers a frequency up-conversion mechanism for the piezoelectric energy harvester. The theoretical analysis is developed and guiding equations are derived. To verify the design and analysis, a low-speed circulating water channel is designed and manufactured for experiments. The voltage and power outputs of the piezoelectric energy harvester are tested under different flow speeds, with different end masses. It is found that an optimal flow speed exists for the energy harvester. Experimental findings reveal that at a flow speed of 0.351 m/s, the peak-to-peak piezoelectric open-circuit voltage can reach 41 V and the generated power with one piezoelectric element is up to 57.3 μW.