| Amidst the rising development of information industry with the core of Internet of Things(Io Ts),personal mobiles and other sensor devices were evolved in the direction to the concepts of miniaturization,intelligence,information sharing and device networking,which will gradually infiltrate into various fields such as medical caring,environmental monitoring,AI interaction and national defense security.However,the traditional power supply method with battery cannot meet the requirements of growing sensor network or adapt the working environment,which will be an urgent challenge to drive these enormous numbers of sensors.Since 2012,the emergence of triboelectric nanogenerator(TENG)to harvest various types of ambient mechanical energy into electricity brings about an alternative way for energy conversion and application.The research on TENG has been one of the frontier research topics in the field of renewable clear energy,and has made a great progress in the field of self-powered application.The self-powered system based on TENG will greatly promote the development of Io Ts,even become a new development orientation in electronic information age based on the Io Ts.Therefore,the in-depth study of TENG is of relatively high theoretical as well as practical value.Triboelectric nanogenerator as a new type of electromechanical energy conversion device is characterized by features of simple structure,light weight,low cost,diverse material selections and high conversion efficiency.Various forms of energy in environment can be easily collected and effectively converted into electricity through its working modes.Among all the four working modes,the freestanding working mode in which the friction layer and electrodes are independently assembled without interactions exhibits more advantages in applications.In this thesis,on the basis of freestanding working mode,we will propose different TENG designs in structures and principles for harvesting wind energy,water wave energy and environmental vibration energy,which are the most common energy source for this mode of TENG.Then,the output performances and the influencing factors of TENG are studied.Meanwhile,the structural parameters of TENG were optimized through experiments and simulations.Finally,self-powered systems were build up based upon the designed TENGs,and the related performances for systems were also systematically studied.The main innovative achievements of this paper are as following:(1)For wind energy harvesting,the structure design and working principle for wind driven TENG based on freestanding mode were proposed.In the designs of structure and working principle,a sandwich structure for device and nanowire structure for dielectrics were adopted and constructed to enhance the output voltage and charge.Meanwhile,a new wind energy collecting structure and soft friction mode were also introduced to enhance the dynamic performance and durability of the device.The electrical performances such as output performance and load performance of TENG were studied afterwards.According to its unique performances,a self-powered high-voltage plasma discharge system and a self-powered Ag~+ions recovery electrochemical system was respectively constructed.In the self-powered plasma discharge system,the basic discharge characteristics of plasma for different discharge forms were obtained,and the influences of different parameter configurations on discharge characteristics in different discharge forms were also obtained.Thus,an electrode distance of 0.2 mm and a gas flow rate of 1000 sccm were obtained as the optimal parameter configurations for this plasma discharge platform.While in the self-powered electrochemical system,the reaction efficiencies for the mixed solutions were obtained,which were positively correlated with the equivalent resistance in mixed solutions,but had a negative relation with the Ag~+ions concentration.Moreover,the influence mechanism of equivalent resistance on reaction efficiency was analyzed and an appropriate range of equivalent resistance in electrolyte was proposed for TENG as electrochemical power source.(2)For water wave energy harvesting,the structure design and working principle for hybrid water wave driven TENG based on freestanding mode were proposed.In structure design,TENG and EMG were combined into one device to expand the effective working area into a wide operating frequency as well as loading range through the complementary output characteristic of both generators.In principle design,contact-separation mode was innovatively incorporated into the freestanding mode,making the system owns the merits of both working modes.The output performance as well as the operating frequency range and loading range were obtained.Moreover,the influencing factors such as topology structure,operating condition and polymer dielectric on the output performance were further studied.In the study of topology structure,the energy loss mechanism in energy conversion process was disclosed,that is the energy loss is determined by energy collection efficiency and energy storage efficiency.In the study of polymer dielectric,the metal-polymer contact electrification mechanism was disclosed,that is the interfacial electrons need to overcome the interfacial barrier to transfer,and move from the metal surface to the lowest unoccupied molecular orbital on the polymer surface,forming a partition area where the local electric field at the interface is continuously enhanced.Finally,a self-powered system based on wave energy was constructed with its average output power and capacitor charging characteristics studied in whole operating frequency band.Furthermore,the optimal operating frequency of TENG and EMG were also studied.(3)For vibration energy harvesting,the structure design and working principle for vibration-driven TENG based on freestanding mode were proposed.In structure design,an annular tubular structure was adopted which ensures the inner liquid not easily to be lost in the long-term operation,and also realizes the DC type output with the adoption of electric brush structure.In principle design,the isolated freestanding mode was adopted to avoid the instability of the output signal caused by the irregular flows of liquid.The output performance of TENG was tested,and the related influencing factors such as structural parameters,working conditions as well as liquid dielectrics were studied.Thus,a diameter of 6 mm and an electrode length of 25 cm were obtained as the optimal structural parameters for FEP tube,and a rotation speed of 70 rpm and a liquid volume of 7 m L were considered as the optimal working condition.In the study of liquid dielectrics,the contact electrification mechanism of liquid-polymer dielectrics was analyzed from both macroscopic and microscopic aspects.That is,the contact electrification is determined by the effect of contact angle at the macro level and the polarity at the micro level,and the amount of charge generation is positively correlated with these two factors.Finally,a self-powered system for power generation as well as self-powered chemical analysis system based on vibration energy were respectively constructed,the power supply can deliver multi-phase output signals with adjustable pulse width and movable phase difference,while the self-powered chemical analysis system provides a very simple and passive method to detect the components of the liquid dielectrics or moisture content of the known liquid. |
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