Piezoelectric Energy Harvesting from Wind Using Coupled Bending-Torsional Vibrations

Energy harvesting using Polyvinylidene-fluoride (PVDF) piezoelectric beams from fluid-induced flutter was studied. Vibration tests were performed to compare the power output of a piezoelectric beam subject to bending, and coupled bending-torsion loading conditions. A piezoelectric, harmonic computational analysis was done to further investigate the effect of the bending-torsion loading condition. It was evident that by inciting bending and torsion in the beam simultaneously, higher power outputs were achieved. However, when the tests were conducted in a wind tunnel with fluid forcing as opposed to steady-state vibration, the power output of the combined bending and torsion case was much lower than the bending-only case. High-speed image data indicated that the configurations subjected to bending-torsion flutter had lower bending deformations and were more prone to chaotic flapping, which inherently resulted in reduced power outputs. Finally, a vertical stalk configuration was examined, which produced five times more power compared to the horizontal stalk configuration at 8m/s wind speed due to excessive non-linear bending.