An enhanced performance scythe-shaped bending-torsion coupling wind energy harvester excited by magnetic force

Piezoelectric energy harvesters leveraging wind energy provide a solution for autonomous power in wireless electronic devices, driving advancements in wireless sensor networks and IoT technologies. This work presents a magnetic-excited scythe-shaped wind energy harvester (S-WEH) inspired by traditional scythes. The piezo oscillator comprises a vertical piezo beam and a horizontal auxiliary beam, mimicking the silhouette of a scythe. The motion of auxiliary beam impacts the piezo beam, inducing torsion during first-order vibration and bending during second-order vibration. Consequently, this work focuses on the influence of the auxiliary beam on the vibration response and power generation performance of the piezo beam. A combination of theoretical modelling and finite element analysis is employed to streamline the complex magnet-solid-electric multi-physics finite element calculations, with the method's validity and applicability validated through experimental results. Findings indicate that, with an auxiliary beam length, La, of 20 mm-50 mm, and a tip mass, ma, of 8.4 g, increasing the length of auxiliary beam reduces the average voltage at the first-order resonance by 83.8 %, but boosts it at the second-order resonance by 166.1 %. Besides, at a wind speed of about 9 m/s, the S-WEH successfully transmitted temperature data to a mobile device after charging a Bluetooth temperature sensor for 5 s.