Piezoelectric energy harvester featuring a magnetic chaotic pendulum

Chaos is usually accompanied by broadband properties of nonlinear energy conversion. To investigate the effects and potential of chaotic vibration in enhancing energy harvesting technologies, this study presents a piezoelectric wind energy harvester with a magnetic chaotic pendulum. The proposed structure is mainly composed of a piezoelectric clamped-clamped beam and a magnetic chaotic pendulum attached to a radial wind turbine. A chaotic pendulum is a double pendulum consisting of two pendula that swing freely in the vertical plane and are connected by a pin joint. The magnet is fixed at the end of the second pendula. When the chaotic pendulum rotates with the wind turbine, the magnetic interaction between the magnet of the second pendula and the magnet in the middle of the clamped-clamped piezoelectric beam produces chaotic beam vibration for nonlinear energy harvesting. Since the energy harvesting system of the proposed structure is chaotic, particle swarm optimization combined with a neural network was adopted to optimize the output power of the proposed structure. The results showed that the proposed structure automatically adapts to the natural wind environment. The working flow velocity range can be increased compared to that of an energy harvester with a traditional single pendulum. An experimental maximum output power of 1.25 mW can be achieved at 557.31 rpm in the investigated flow velocity range.