| The development of the Internet of Things has triggered people’s desire for smart cities and smart life.Currently,wireless sensors are an important component of the Internet of Things,but there are still problems with their sustainable power supply.Environmental energy harvesting is the conversion of energy in the natural environment into electrical energy to realize self-powered sensing,which has the advantages of convenience,energy saving,environmental protection and sustainability.Among them,small wind energy harvesting systems have a compact structure,long service life and no maintenance,which mean that they can replace batteries to power small electronic devices for self-powered sensor systems and wireless sensor networks.However,the wind energy in the environment is random,wide and irregular in wind speed.If it is directly collected and converted into electrical energy through traditional electromechanical conversion methods,it will result in low conversion efficiency,poor adaptability and even damage to equipment.In order to improve the performance of small wind energy harvesters,this paper explores the improvement through dynamic regulation methods.The main contents are as follows:(1)Aiming at the problems of low starting wind speed and narrow working wind speed range of the galloping wind energy harvesting system,the boundaries regulation mechanism of the triboelectric nanogenerator is proposed,and the galloping wind energy harvesting method combining piezoelectric and triboelectric is invented.The proposed boundaries regulation can not only prevent the piezoelectric sheet from being damaged due to excessive wind speed,but also realize the cooperative work of the triboelectric nanogenerator and piezoelectric energy harvesting under high wind speed.Establish a theoretical model that characterizes the dynamics and electrical characteristics of piezoelectric-triboelectric coordinated galloping wind energy harvesting;In order to verify the superiority of the design,the prototypes with and without boundaries regulation are compared by experiments.The experimental results show that the piezoelectric energy harvesting with boundary regulation can start working at low wind speeds and protect the piezoelectricity at high wind speeds.The film is not damaged and can still work effectively.The simulation results show that: 1)As the thickness increases,the initial working wind speed of the triboelectric nanogenerator increases sequentially;and as the thickness increases,a greater wind speed is required to make the beam contact the boundary;(2)Analyze the impact of key design parameters on the dynamics and electrical performance of the composite energy harvesting system.Design different thicknesses of cantilever beams and different distances between cantilever beams and the boundaries,and discuss their performance on galloping wind energy harvesters.2)Under the condition of the same beam parameters,the smaller the distance,the smaller the wind speed can make the beam contact with the boundary,and the triboelectric nanogenerator will start to work;When the beam and the boundary start to contact,under the same wind speed,the smaller the distance,the smaller the distance the beam needs to move in contact with the boundary,and the higher the operating frequency in the same time.The piezoelectric-triboelectric synergistic galloping wind energy harvester with the optimal parameters is experimentally verified.At a wind speed of 14 m/s,the total average output power of the principle prototype of the piezoelectric-triboelectric synergistic galvanizing wind energy harvester is 0.24 m W.It is 2.3times that of the piezoelectric energy harvester alone.The boundary regulation obviously expands the effective working wind speed range and improves the output performance at high wind speeds.(3)Reveal the influence of the boundary of the triboelectric nanogenerator on the flow field around the wind energy harvesting system,and develop a vertical piezoelectric-triboelectric composite galloping energy harvesting method.First,the advantages of the vertical structure are explained through simulation and experiment,and the vertical structure is compared with the horizontal structure.Through the CFD computational fluid dynamics simulation in ANSYS software,a parameterized two-dimensional flow field simulation of the two situations is carried out,and it is found that the vertical structure avoids the interference of the object behind the bluff body on the flow field.Study the influence of key design parameters on the electrical performance of triboelectric nanogenerator,design three different beams and curved boundary widths,establish electromechanical coupling dynamics models,and conduct experimental verification.The results show that the increase of the boundary width can increase the working area of the triboelectric nanogenerator and the output power at high wind speeds,but the greater the stiffness,the higher the wind speed at which the triboelectric nanogenerator starts to work.Comparing the wind energy harvester with or without boundary,the output power with boundary regulation is 180% higher than that of the traditional piezoelectric energy harvesting at a wind speed of 6 m/s.(4)Aiming at the problems of large triboelectrical resistance and extremely easy to wear when the rotating wind energy harvester is working,an adaptive dynamics regulation mechanism is proposed,and an adaptive wind energy harvesting method is invented.By reasonably designing the centrifugal force and magnetic force,the separation,contact and contact degree of the triboelectric power generation pair can be automatically adjusted under different wind speeds,and the reliability of the wind energy harvester can be effectively improved.Based on the energy method,the electromechanical coupling model of the high-robust and wide-speed wind energy harvester is established,and the performance of the wind energy harvester with three different permanent magnet initial center distances and fan-shaped plate mass configurations is studied by simulation and experiment.The results show: 1)When the initial center distance of the permanent magnet remains unchanged,the smaller the mass,the smaller the centrifugal force received at low wind speeds,and the magnetic force is greater than the centrifugal force,making it require a higher wind speed to make the functional material contact.At high wind speeds,the voltage of the collector increases as the mass decreases,because the device with a small mass rotates faster and the peak voltage is high.2)Under the same mass,as the initial center distance of the permanent magnet decreases,the magnetic force will increase,so the adaptive telescopic arm needs a higher wind speed to make the two functional materials contact.After contact,the smaller the magnetic distance,the greater the magnetic force,the smaller the triboelectrical force that the fan-shaped plate receives during the movement,and the faster the rotation speed,so the smaller the magnetic distance,the higher the voltage.The performance is best when the magnetic spacing is 0.021 m and the mass of the sector plate is 7.2 g,the peak voltage is up to558 V,and the average power is 2.79 m W.(5)Design a wind energy harvester with self-adjusting electromagnetic-triboelectric composite mechanism,and establish an electromechanical coupling dynamic model of electromagnetic and triboelectric composite mechanism.When the initial center distance of the permanent magnet is 0.021 m and the mass of the fan-shaped plate is 7.2 g,the magnet disk and the coil disk of the same size are added,and the electromagnetic energy harvesting and the triboelectric nanogenerator can work at the same time without interfering with each other.The simulation results show that the output voltage of the 8 coils with a diameter of 30 mm is higher.Comparing the single triboelectric generator system and the composite generator system,it is found that the composite mechanism can greatly improve the output performance of the collector.When the wind speed is 12 m/s,the average power of the electromagnetic-triboelectric composite mechanism is 6.1 times that of the triboelectric nanogenerator alone. |
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