Design And Performance Regulation Of Structure-specific Hybrid Nanogenerator And Its Energy Harvesting For Wind And Raindrop Energy

In the new era of Internet of things,in order to satisfy the rapidly growing energy demand for portable electronic micro-nano devices,lots of research work has been carried out to explore renewable energy.The access to tens of thousands of sensors and portable electronic devices bring a huge demand for electric power.In contrast,the traditional decentralized energy uses disposable batteries as energy supplies,causing large environmental pollution.Sustainable energies such as solar energy,water energy,heat energy,mechanical energy have been developed rapidly.Mechanical energy as a huge and widespread resource in natural environment has been collected by electromagnetic generator?EMG?,triboelectric nanogenerator?TENG?and piezoelectric nanogenerator?PENG?.Among those mechanical energy collection techniques,TENG and PENG dominated by the second term of Maxwell displacement current has been proven to become powerful tools for capturing low-frequency and universal mechanical energy in the environment with advantages of low-cost,light-weight and wide range of materials.TENG can collect all kinds of mechanical motion energy and its structure design is complex and diverse,while the device structure of PENG is relatively simple.Recently,hybrid tribo/piezoelectric nanogenerators?TPENG?have gradually become one of the research hotspots in the field of nanogenerators and have attracted great interesting because they can collect many different forms of energy and improve energy conversion efficiency.This master thesis mainly focuses on the design,performance regulation and application exploration of hybrid nanogenerators.The main research contents are as follows:In the first work,we fabricated a unique two-terminal TPENG,which uses a metal-to-metal point contact design that can make both piezoelectric and triboelectric appear in one cycle.The BaTiO₃ ceramic sheets and commercial PTFE films were used as piezoelectric and triboelectric layers,respectively.Meanwhile,a small hole is formed on the PTFE film as the conductive channel to transport piezoelectric charges.The interaction between triboelectric charge and piezoelectric charge is promoted by adjusting the direction of ferroelectric polarization of the BaTiO₃.The TPENG can deliver the maximum open-circuit voltage?VOC?of 45 V and short circuit current density?JSC?of 10.4 ?A/cm² under an operating frequency of 2 Hz.The triboelectric and piezoelectric effects are studied from the perspective of the output electric energy through the V-Q plot,which shows that the triboelectric and piezoelectric effects of TPENG with point contact are simply superimposed,and no coupling between the triboelectric and piezoelectric charges.The qualitative theoretical analysis conducted by finite element simulation is consistent with the experimental results,which proves the rationality of the current experimental design.This work provides new insights into the understanding of the piezoelectric and triboelectric effects in TPENG.In the second work,a hybrid triboelectric nanogenerator inspired by the louver was proposed and designed in order to effectively collect environment energy such as wind energy and water droplet simultaneously.Low-speed winds are extensively distributed in low altitude environment,and raindrop with low or medium-frequency can be seen in rainy days,which make them suitable to be captured by TENG to efficiently convert into electric energy.In this structure design,the water droplet nanogenerator located at the upper end adopts working mode of double electrode.Compared with the traditional water droplet nanogenerator with single-electrode contact mode,the output power of the updated water droplet nanogenerator is significantly improved.The droplet nanogenerator with two-electrode can generate VOC of 95 V,ISC of 25 ?A and the maximum instantaneous output power of 1.2 mW.Compared droplet nanogenerator with one-electrode,the VOC and ISC of the droplet nanogenerator with two-electrode increased by 190 times and 64 times,respectively.The wind triboelectric nanogenerator?W-TENG?under bottom end adopts freestanding working mode to harvest wind energy by using the swing under gust.The VOC and ISC of the W-TENG can reach 57.6 V and 4 ?A,respectively.The hybrid TENG can charge the capacitance of 10 ?F to 7.8 V within 11 s by using the rectifier circuit,which can also monitor the frequency of droplet.It is found that output current of the W-TENG shows a linear relationship the wind speed,presenting potential for employing in wind speed sensor.The advantage of this hybrid structure is that water droplet energy collection and wind energy collection don't affect with each other and don't vulnerable to environmental impacts.It will provide great convenience for people in a harsh environment.It is expected to provide electric energy for portable micro-nano devices in the environment of wind and rain,where the traditional battery is not easy to function.