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Nonlinear dynamics of the bi-stable piezoelectric wind energy harvester

A nonlinear piezoelectric wind energy harvester is proposed which has a low startup wind speed and is not restricted to a specific wind speed. By using the piezoelectric transduction mechanism, the gearbox is eliminated from the system and the start up speed is improved. Permanent magnets are placed in the blade part of the windmill. The interactions between the rotating magnets, positioned on the blades, and the tip magnets mounted on the piezoelectric beams directly and parametrically excite the beams. The nonlinear magnetic 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. An analytic model is developed which is verified by the experimental results and explains the nonlinear phenomena captured by the experimental investigations.