Parametrically excited nonlinear piezoelectric wind energy harvester

A nonlinear piezoelectric wind energy harvester is proposed which operates at low wind speeds and is not sensitive to the speed of the gusts. The piezoelectric transduction mechanism is used instead of DC generators to eliminate the gearbox in the windmill and thus reduces the friction. The reduced friction facilitates operation of the windmill at low wind speeds. Permanent magnets have been placed in the blade part of the windmill. The magnets axially repel another set of magnets which are positioned at the tip of the piezoelectric beams. As a result, when the rotating magnets pass over the piezoelectric beams they excite the beams and affect the type of their vibrations. The nature of excitations in the proposed design is therefore both parametric excitations and ordinary excitations. The nonlinear magnetic axial force makes the vibrations of the beams nonlinear and can make the beams bi-stable. This phenomenon is utilized to enhance the power output and to improve the robustness of the power production. Two designs are presented which incorporate parametric and ordinary excitations to generate electric power. The performance of each design is examined through experimental investigations.