Performance enhancement of piezoelectric wind energy harvester using a flexible plate attached to an upstream cylinder*

We experimentally investigated piezoelectric wind energy harvesting utilizing the flow-induced vibration of a cantilevered flexible plate. A macro fiber composite piezoelectric sheet is glued on a thin flexible plate. The combined configuration is fixed to a lee side of a circular cylinder subjected to axial airflow. Two cases of this simple configuration consisting of only a piezoelectric sheet and a piezoelectric sheet fixed on flexible plates are studied. In particular, we performed parametric studies varying flow velocity and external load resistance in the range of 4 to 17 m/s and 5 to 100 kΩ, respectively to optimize the energy output. The dynamics of plate motion were examined by describing the displacement, frequency, phase plane, and oscillation envelopes. Additionally, voltage output and power generation are measured and illustrated. Based on the oscillation dynamics of the plate motion, mainly three regimes namely, initial excitation, transition, and lock-in are found. The lock-in is the most efficient regime for energy harvesting as the plate attains a periodic high amplitude limit cycle oscillation. There exists an optimum load resistance (order of mW) for the maximum power generation in the lock-in regime. The piezoelectric sheet fixed on the plate significantly improved power (1000 times) compared to only the piezoelectric sheet and therefore represents an efficient way of extracting power from wind. Furthermore, the harvested power is utilized to power multiple LEDs.