A Hybrid Self-Powered System Based on Wind Energy Harvesting for Low-Power Sensors on Canyon Bridges

Canyon cross wind has great potential to be transformed into electricity to power for low-power sensors of the health monitoring devices in bridge field. In this paper, a hybrid wind energy harvesting system (WEHS), integrating piezoelectric and electromagnetic mechanisms, is proposed to supply power for low-power sensors on canyon bridges. Firstly, the S-rotor embedded with a one-way bearing converts wind energy into rotational mechanical energy. Then, the piezoelectric cantilever beam and coils simultaneously convert mechanical energy into electricity under the excitation of the rotational magnet array. For the piezoelectric transducer, the symmetrical poles arrangement of tip magnet reduces the starting wind speed and resistance torque during energy harvesting. In addition, the relationship between different number of excitation magnets and the output of the piezoelectric transducer is explored. Finally, the output electricity is stored in the capacitors to supply power for low power sensors. The experimental results showed that the symmetrical poles arrangement of tip magnet could effectively reduce the starting resistance torque and improve the output power at low wind speeds. Given a wind speed of 6.5 m/s, the maximum output power of the WEHS can reach 19.24 mW with corresponding electrical energy of 75.714 mJ in one sweep period (6 s). The field test results demonstrated that the WEHS could effectively charge for the capacitors and power for a hundred LEDs. Furthermore, the mechanical durability and stability of the WEHS are verified by introducing a self-powered low power sensor system.