Simulation And Experiments Of Underwater Flow Induced Vibration Energy Harvester

With the development of wireless sensor network, sensor nodes are widely applied in real-time monitoring of oceans and rivers. Then, how to power the network nodes is a challenging problem. The traditional energy supply systems have a finite life span, require regular replacement and can not kept pace with the devices’ demands. Thus, the method of capturing energy from environmental is required. Currently, electrostatic, electromagnetic, piezoelectric transducers are the three used devices for underwater energy harvesting. And piezoelectric transducer achieves a widely attention among many options due to its simplicity, high energy, eco-friendliness, not affected by electromagnetism.The energy conversion efficiency of flexible piezoelectric vibrator (PV) is low in the placid waters. But in the vortex field, the vortex can mechanically strain flexible PV and generate larger deformation and higher efficiency of energy conversion. Therefore, in this paper, a new underwater flow induced vibration energy harvester of flexible piezoelectric vibrator (PVDF) based on the theory of the Karman vortex street is proposed.Firstly, according to the theory of Euler-Bernoulli beam, piezoelectric, vortex motion and theory of vibration etc, a mathematic model of flow induced vibration energy harvesting system is established.The nature frequency of PV in air and fluid, and the parameters of influencing frequency of vortex shedding are analyzed in COMSOL software. The simulation results indicate that the nature frequency of PV in fluid is smaller than in the air, and the frequency of vortex shedding is decrease with the diameter of bluff body and increase with the flow velocity.Finally, an experimental system is built to research the relationship between the energy harvesting performance of PV and the diameter of bluff body, flow velocity, dimensions of PV. The experimental results depicted that the performance of PV is in proportion to the diameter of bluff body, flow velocity, width and thickness of piezoelectric and inversely proportion to the length of PV.In conclusion, underwater flow induced vibration energy harvesting system has a high conversion efficiency and is an effective solution for energy powering of wireless sensor network nodes.