Harvesting low-speed wind energy by bistable snap-through and amplified inertial force

One of current research focuses in wind energy harvester (WEH) design is improving electric output in low-speed wind environments. A desired WEH should work efficiently and produce large output in low-speed wind conditions. For this aim, a novel piezoelectric harvester is presented, which introduces multi-stability and applies amplified inertial forces on the piezoelectric material to improve the WEH's performance for low-speed wind. Under the action of wind, galloping will drive the cantilever beam to oscillate, and multi-stability will increase its response amplitude. Finally, the resulted inertial force will be amplified by two branches and act on the piezoelectric sheets to produce electric outputs. The theoretical model is established, and corresponding analyses are carried out. The results prove that a desired potential energy function can be obtained by adjusting the distances between magnets. The validation experiments are conducted in a wind tunnel. The experimental results prove that the harvester can start the snap-through motion from a relatively low wind speed of 1.30 m/s and keeps it in a low-speed area (1.30 m/s-1.85 m/s). Especially, the force's acting mode on piezoelectric material and the attraction between magnets can improve the harvester's reliability and sustainability.