Fan-structure wind energy harvester using circular array of polyvinylidene fluoride cantilevers

A fan-structure piezoelectric energy harvester was proposed and tested in order to collect wind energy. Polyvinylidene fluoride was chosen due to its flexibility and longevity when compared to lead zirconate titanate. The impact-induced piezoelectric energy harvester consists of a stator and a rotor and a circular array of four cantilevers, utilize the rotor blades' periodic impact on the free end of the cantilevers to generate oscillatory motion of cantilevers. A circular array of polyvinylidene fluoride cantilevers was fixed around the rotor in order to increase output power, save space at the same time. Static and transient characteristics of different cantilevers were investigated using finite element method and the result showed that polyvinylidene fluoride triangular cantilever performs the best in output voltage and power. Under the condition of optimal impedance and optimal overlap distance, a sum AC output power of four cantilevers without connection to each other approach to 0.75mW was measured at the wind speed of 7 m/s when the blade number of rotor is 7 or 9. Two branches 0.27mW DC output power was obtained when each two cantilevers in parallel connection in the case of full-wave rectification of each cantilever at the wind speed of 7 m/s.