Design, fabrication and characterization of a wind-isolated galloping energy harvester via an embedded piezoelectric transducer

Harvesting energy from wind-induced vibration utilizing piezoelectric mechanism has attracted much attention for enabling energy-autonomous wireless sensor systems over the past decade. To offer a promising solution for low reliability, poor environmental adaptability and narrow operating bandwidth of existing piezoelectric wind energy harvesters, a wind-isolated galloping energy harvester with an embedded piezoelectric transducer (EPT-WGEH) is proposed in this paper. Unlike previous most directly-excited piezoelectric wind energy harvesters, the EPT-WGEH was characterized by an indirectly-excited shelter-structure, which isolates the embedded piezoelectric transducer (EPT) from the flow environment. Meanwhile, the horizontal swing of the hollow cylinder and the elastic pendulum beam is transformed into the vertical swing of the EPT mounted in the hollow cylinder under wind excitation. Therefore, this 2-DOF indirectly-excited EPT-WGEH could possess both high reliability and small volume. A CFD simulation model was established to analyze the influence of structural parameters on the vibration characteristics of EPT-WGEH. To verify the feasibility of the principle and design regarding the proposed EPT-WGEH, a prototype of the EPT-WGEH was fabricated and tested in terms of electrical output and operating bandwidth. The results showed that the length of elastic pendulum beam, proof mass, and wind speed brought significant effects on the electrical output, minimum working wind speed and operating bandwidth. The maximal output voltage increased with the decreasing length of elastic pendulum beam or the increasing proof mass. Meanwhile, there existed some optimal combinations of parameters to minimize the minimum working wind speed of EPT-WGEH. Besides, the optimal output power of EPT-WGEH could reach 2.4 mW at load resistance of 600 kΩ. The EPT-WGEH could light up 75 series-connection commercial blue LEDs simultaneously at the wind speed of 15 m/s and demonstrated its practical power supply capability by charging capacitors.