Study Of Wind Energy Harvester For Self-powered Sensor Nodes

The south-to-north water diversion is a strategic project of our country.In order to ensure water quality and the safety of dams,electronic fences need to be built near dams based on vibration and tilt wireless sensor nodes.However,it is a big problem to power the sensor nodes widely distributed in the place without human and power.Wind energy harvesting is identified as a feasible way for powering wireless sensor nodes(WSNs).Wind energy harvesters used for powering WSN are required small size and high output.Some existing miniature vibration wind energy harvesters can meet the requirement of volume,but they always have high resonant frequency and low voltage output.Rotary wind energy harvesters usually have high power output while the weaknesses are large volume and complicated structure.For the reasons above,this paper proposed two kinds of wind energy harvesters to power different kinds of WSNs installed on the electronic fences of dams.They are double(single)-blades vibration hybrid wind energy harvesters(DBV-HH,SBV-HH)and turbine-rotation electromagnetic wind energy harvester(TR-MH).The DBV-HH and SBV-HH are designed with blade-cantilever structures and the vibrations are induced by flutter effect and Karman vortex,respectively.The blade-cantilever structure can break the limitation of cantilever's resonance frequency and amplify the vibration and voltage output of device.Meanwhile,the DBV-HH and SBV-HH are combined with triboelectric and piezoelectric mechanisms.Hence the volume power density is improved.These devices are suitable for powering temperature and humidity sensor nodes.For the TR-MH,instead of using gear growth box,a diffusion channel is designed to increase the rotate speed of turbine.Hence the structure is simplified and the output performance is still outstanding.This device is suitable for powering vibration and tilt sensor nodes.Besides,a self-powered tilt sensor system is built based on TR-MH to monitor the state of fences.The main contents of this paper are listed as follows:(1)In order to improve the vibration amplitude and voltage output of the miniature vibration wind energy harverters,a double-blades vibration hybrid wind energy harvester is demonstrated.The design of blade can amplify the vibration of cantilever,so that the power can be generated from both piezoelectric and triboelectric parts.The size and connection position of blade are optimized experimentally.Test results show that the vibration amplitude and voltage outputs of the DBV-HH are improved greatly comparing with the existing miniature vibration wind energy harvesters.(2)A single-blade vibration hybrid wind energy harvester is demonstrated to improve structure defects of the DBV-HH.The stability and power output of device are enhanced by optimizing the shapes of blade and outer frames.The vibration principle of the SBV-HH is researched by theoretical study and FLUENT simulation.The output performance of the improved wind energy harvester is further enhanced.The maximum power densities of triboelectric and piezoelectric parts are 748 ?W/cm3 and 8.57 ?W/cm3 respectively at 10 m/s,which is higher than most existing vibration wind energy harvesters.The DBV-HH can be used to power low-consumption temperature and humidity sensor nodes.(3)In order to further improve the power output of wind energy harvester,a turbine-rotation electromagnetic wind energy harvester with simple structure is proposed.The fluid speed is accelerated by diffusion channel so that the power output of the device is improved.The working principle of diffusion channel is researched by theoretical analysis and simulation.The best position of turbine is determined by the simulation results.The shape and size of the turbine are optimized experimentally.The maximum power output of TR-MH is 10.5 mW at 10 m/s,which can power vibration and tilt sensor nodes.(4)A tilt sensor system powered by the TR-MH is built to monitor the state of fences in south-to-north water diversion Project.The tilt sensor nodes and the data receiving module are designed based on STC89C52RC MCU.High efficient power management circuit is designed so that the TR-MH can power the tilt sensor nodes intermittently.