Research On Ocean Wave Energy Harvesting System Based On Triboelectric Nanogenerator

Energy issue is essential to national economy,which closely related to the interests and lives of the people.The ocean covering 71%areas of the earth's surface has enormous energy,however the development of ocean energy and energy harvesting technologies have lagged far behind.Traditional ocean energy harvesting technology applies electromagnetic induction generator,but its high construction and maintenance costs,low conversion effi ciency and unsatisfactory reliability and stability make it limited in collecting irregular and low-frequency energy.Triboelectric nanogenerator(TENG)with the merits of light weight,low cost,and high energy conversion efficiency,showing promising application potential in ocean energy harvesting.This thesis proposes a marine wave energy harvesting system based on TENGs and aims to improve the electrical output performances,stability as well as durability of power generation system toward large-scale ocean blue energy harvesting.Based on Maxwell's displacement current theory,the mathematical model of vertical contact-separation triboelectric nanogenerator is established using a capacitance model.The COMSOL Multiphysics software is used to simulate the mathematical model of the triboelectric nanogenerator,the following theoretical results are obtained through analyzing the simulation results:1)The dielectric constant is linearly related to the TENC's electrical output performances;2)The film thickness is inversely proportional to the TENG's electrical output performances;3)The gap distance is linearly proportional to the TENG's output potential difference.The simulation analysis reveals that the Maxwell displacement current is the fundmental of TENG and establishes the theoretical basis for improving the output performance of TENG.A flexible and wearable TENG is fabricated based on polydimethylsiloxane/polyvinylidene fluoride dielectric composite films(PDMS/PVDF,PPCF).Through systematically investigating and optimizing the dielectric property of composite film,film thickness and surface architectures,an instantaneous maximum power density of 832.05 mW/m2 is registered by the champion TENG.Moreover,highly stable Voc output is obtained after continuous operation over 2200 cycles,implying the outstanding ability of structural retention and fatigue resistance during wearing the TENG.Stimulating by knee bending,arm swing and elbow bending,a self-powered TENG is successfully realized with multi-adaptability and compatibility with various fabric clothes,demonstrating the great application potential as wearable electronics for mechanical energy harvesting,pressure sensing and human-machine interfacing without external energy supply.A multi-track swing-structured integrated TENG(MS-TENG)based on freestanding triboelectric-layer working mode is proposed for effectively harvesting ocean wave energy with excellent low-frequency performance.The results are as follows:1)The optimized connection approach of the internal swing units are in parallel connection;2)The simulated results of nylon ball's diameter of MS-TENG is consistent with the experimental results,the optimal diameter is 30 mm for the first layer,25 mm for the second and third layer;3)The maximum open-circuit voltage(Voc)of 507 V is reached at an agitation frequency of 0.21 Hz and amplitude of 7.5 cm with excellent stability and durability;4)The instantaneous power density of MS-TENG is 217.33 mW/m2 at an external load resistance of 150 M?.A tribo-electromagnetic hybrid generator(TEHG)is fabricated toward wave energy harvesting.The conclusions are as follows:1)A Voc of 800 V and an Isc of 1.74 ?A at frequency of 0.21 Hz and amplitude of 60 mm are achieved of TEHG;2)The optimal number of grid electrodes is 3,and the average power density of TEHG is 333.21 mW/m2;3)The Voc,Isc and power density of the electromagnetic generator are 1.35 V,1.46 mA and 65.72 mW/m2,respectively at frequency of 1.25 Hz and amplitude of 50 mm;4)The maximum power density of TEHG is 76.97 mW/m2 with 70 LEDs lighted up simultaneously and drive a electronic timer without battery.Based on reviewing large number of scientific articles and theses at home and abroad,this thesis delivers a comprehensive and systematical study on ocean wave energy harvesting system based on triboelectric and electromagnetic induction effects,aiming at the shortcomings of the current ocean energy generating devices.The key issues and parameters of optimizing the elecrtcal output perforamcnes of TENG are studied by variable control methodology to obtain the optimal dielectric film.The outcomes of the thesis show that the two systems have excellent environmental adaptability and stability under different wave conditions,and present promising application potential for effectively exploiting large-scale low-frequency blue energy.