A magnetically coupled bistable piezoelectric harvester for underwater energy harvesting

This study presents a new magnetically coupled bistable piezoelectric energy harvesting approach for underwater applications. The flextensional piezoelectric transducer is used to harvest the energy of fluid induced vibration by magnetic coupling. Because of non-contact mechanical energy transfer, vulnerable key components can be packaged without affecting the normal operation. In addition, the magnetically coupled system has nonlinear bistable characteristics, which are beneficial to enhance the performance of the flow energy harvester. The magnetic excitation force can be amplified and uniformly applied to the piezoelectric layer through the flextensional structure, thereby exhibiting a higher equivalent piezoelectric coefficient and improved reliability. The prototypes were fabricated to verify the advantages of the design and a series of tests were carried out in a water tunnel. At a flow rate of 4 m/s, the peak-to-peak voltage and maximum power of the 390 kΩ load resistor were 26 V and 450.5 μW, respectively. The magnetically coupled bistable piezoelectric energy harvester exhibited stable power output performance after 144 h in the water (approximately 50% of the time in the working state). The results indicate that the magnetic coupling and flextensional mechanisms have great potential for energy harvesting in harsh environments such as underwater.