Investigation of energy harvest and storage by using curve-shape piezoelectric unimorph

A curve-shape piezoelectric unimorph is used for energy harvest. Deformation of the unimorph will gain electricity via piezoelectric direct effect. In this study, a cantilever unimorph encountered with external force at various vibration frequencies to generate electricity and save into a storage circuitry is investigated. Modeling of the unimorph and storage circuitry is derived. The analytical computation and experimental result are in a good agreement. Both outcomes verify that vibration frequency nearer the resonant frequency will gain more energy and the load resistance of a RC storage circuitry matching the equivalent impedance of piezoelectric ceramics will gain maximum storage energy. Efficiency of electromechanical conversion and energy storage is examined. As compared to other previous works using piezoelectric ceramics, the curve shape unimorph performs better. In experiment, for instance, by using a load resistor of 3kΩ ideally equal to the impedance of ceramics and an arbitrarily chosen capacitor of 470µF at vibration frequency of 135.59Hz for 25 seconds, electric power of 48mW is obtained and electromechanical efficiency of about 18.49% is achieved.