VIV-Based Energy Harvesting from Tandem Cylinders for Self-Sustained IoT Systems

Piezoelectric energy harvesters are considered a replacement for batteries because they are self-sustainable with low or no maintenance, and suitable for off-grid devices. In this study, two cylinders were placed in a flowing stream of water. The upstream cylinder of 25 mm diameter is fixed at the center of the stream while another cylinder of the same diameter, which is free to oscillate in the crosswise direction of the flow and is placed in the wake of that fixed cylinder. A piezoelectric flag is then placed in the wake of the vibrating cylinder and its distance from the vibrating cylinder was changed to observe the effect of wake length on the energy harvester. The energy harvesting potential of the system is explored for flow velocities ranging from 0.28 m/s to 0.36 m/s. The distance between the cylinders Gx, which is explored for the range of 2.5D–7D, and the distance between the piezoelectric membrane and the vibrating cylinder are expressed as Sx for the same range. The maximum power of 19.17 μW was produced at Sx = 2D and Gx = 3.5D. The maximum power for the baseline case, when two tandemly arranged stationary circular cylinders were used and a piezoelectric membrane was placed in their wake, is 10.24 μW; hence, an increase of 87.2% is observed under the same ambient conditions.