A miniature generator using piezoelectric bender with elastic base

Nowadays green energy devices such as vibration generators attempt to harvest energy from environment. A lot of studies dealing with vibration generators put emphasis on mechanism designs or power generation methods, but few on lowering the resonant frequency of power generation systems. This study proposes that elastic bases attached to vibration generators can lower natural frequencies, so as to make natural frequencies closer to ambient vibration frequency. Therefore, this study investigates miniature electric generators consisting of piezoelectric benders and elastic bases. To install the elastic base, this work uses a spring with prescribed stiffness and a board with given mass between the piezoelectric bender and a vibration source to make the resonant frequency of piezoelectric benders close to the frequency of ambient vibration. Analytical derivation is carried out to obtain optimal mass and stiffness. Accordingly, more electric power can be generated from piezoelectric generators using an elastic base with appropriate mass and stiffness. According to experimental results, using an elastic base increases 376 times generated power compared with no elastic base. In the presence of the elastic base, the power increases 132% when a point mass is added.