A Novel Piezoelectric Energy Harvester Using the Macro Fiber Composite Cantilever with a Bicylinder in Water

A novel piezoelectric energy harvester equipped with two piezoelectric beams and two cylinders was proposed in this work. The energy harvester can convert the kinetic energy of water into electrical energy by means of vortex-induced vibration (VIV) and wake-induced vibration (WIV). The effects of load resistance, water velocity and cylinder diameter on the performance of the harvester were investigated. It was found that the vibration of the upstream cylinder was VIV which enhanced the energy harvesting capacity of the upstream piezoelectric beam. As for the downstream cylinder, both VIV and the WIV could be obtained. The VIV was found with small L/D, e.g., 2.125, 2.28, 2.5, and 2.8. Additionally, the WIV was stimulated with the increase of L/D (such as 3.25, 4, and 5.5). Due to the WIV, the downstream beam presented better performance in energy harvesting with the increase of water velocity. Furthermore, it revealed that more electrical energy could be obtained by appropriately matching the resistance and the diameter of the cylinder. With optimal resistance (170 kΩ) and diameter of the cylinder (30 mm), the maximum output power of 21.86 μW (sum of both piezoelectric beams) was obtained at a water velocity of 0.31 m/s.