An underwater piezoelectric energy harvester based on magnetic coupling adaptable to low-speed water flow

The rapid development of the fifth-generation mobile networks (5G) and the Internet of Things (IoT) is inseparable from a large number of miniature, low-cost, and low-power sensors and actuators. To solve the problem of self-powered underwater wireless sensor nodes (WSNs), this paper proposes a magnetically coupled piezoelectric energy harvester (MPEH) based on fluidinduced vibration (FIV) to achieve high-efficiency performance in low-velocity water environments. The results show that compared with the non-magnetic PEH, the initial vibration velocity, velocity bandwidth, and maximum output voltage of the magnetic attraction coupling piezoelectric energy harvester (MAPEH) are increased by 18.42%, 41.38%, and 5.79% respectively. Besides, it is also shown that the vertical distance between the magnets, the diameter, and the mass of the vibrating column have a significant effect on the vibration characteristics, water velocity bandwidth, and performance of the magnetic repulsion coupled piezoelectric energy harvester (MRPEH). The initial vibration velocity of the MRPEH is reduced by 42.1%, and when the water speed is 0.2 m/s, its output voltage is 12.21 times that of the classical configuration. This proposed structure can provide a reference for the optimization of underwater FIV-based PEH, and also lay a foundation for further interconnection of underwater self-powered sensors.