Wind energy harvester for sensors based on gravity-driven magnet self-resetting

Abstract Wind energy has characteristics of abundant reserves and wide distribution. It is a feasible solution by collecting wind energy to supply sustainable power for sensors. The proposed wind energy harvester mainly consists of a wind-induced rotating unit and some electromagnetic units (EMUs). The inner permanent magnets (PMs) rotate under the drive of the wind-induced rotating unit, while the outer PMs in the EMUs move under the action of magnetic repulsion. The EMUs are evenly distributed along the circumference, and the coil fixed-magnet moving structure is adopted to reduce the difficulty of lead layout. The PMs are installed inside the coil at an inclined angle, and can achieve self-reset under the action of gravity when magnetic repulsion force is less than gravitational component along the slope. In order to explore the mechanism of the magnet reciprocating cutting magnetic flux lines in EMUs, the magnetic force changes during magnetic repulsion and self-reset movement are analyzed. The finite element method is used to analyze the influence of magnet layout on magnetic induction intensity to determine the optimal number configuration of EMUs. The experimental results show that the circumferential layout of 5 EMUs is more reasonable and the energy collected is larger, and the optimal number ratio is two inner PMs and three outer PMs, respectively. When wind speed is set to 5.5 m s −1 , the harvester can output a power of 6.16 mW with a load of 10 Ω and the efficiency is 13%, which significantly reduces 25%–40% reset energy loss commonly associated with traditional spring-based mechanisms.