Improve efficiency of harvesting wind energy by integrating bi-stability and swinging balls

Scavenging wind energy from ambient environment to power wireless sensors has attracted more and more attentions in recent years. However, for the weak and varying-speed winds, the classical harvester can't keep a high output. A new concept of harvesting energy from weak and varying-speed winds with introducing swinging balls and bi-stability is proposed and investigated for the first time. In a wind field, driven by the incoming flow, the swing of balls will lead the beam to oscillate and execute snap-through between two stable equilibrium positions, thus generating large electric output. The velocity and pressure distributions near the two balls are obtained and illustrated. The effects of spacing distance between the tip and fixed magnets are studied through potential energy analysis. The experiments are conducted to investigate the vibration characteristics and harvesting performance. The results show that this harvester achieves a significant improvement in electric outputs, due to its ability to realize frequent snap-through motions over a wide range of wind speed. The presented harvester is simple in structure and cheap in cost, so this study may open a new way to extensively harvest wind energy in the nature environment.