Multimodal piezoelectric wind energy harvesters

We investigated energy harvesting from wind to electrical power using piezoelectric films. Commercial films with different areas (from 3 to 30 cm(2)) and thicknesses (40-64 mu m) were used. The generated energy was rectified through a diode bridge and delivered to a storage capacitor. Two different wind flows were investigated: laminar flow from a wind tunnel and turbulent flow from a dryer using three different setups and two wind incidences (parallel and normal). Piezofilms oscillating in wind flows were recorded using video cameras and electrical signals monitored with an oscilloscope. They were found to be stressed by travelling waves of different frequencies induced by wind turbulences. We propose a simple model based on sinusoidal current generators working at different frequencies. We studied the geometrical dependence of the piezofilm on the power generation. Power generation was found to be of the order of 0.2 mu W for these particular sensors. Guidelines to significantly improve power generation are provided, taking into account a convenient geometrical design to match the piezofilm resonance frequency to the vortex generation frequency.