| Intelligent agriculture is a technology that combines modern science and technology with agricultural planting,to realize unmanned,automatic and intelligent management of farmland.The monitoring of agricultural production environment in smart agriculture are realized by collecting real-time information of growing environment in farmland through a large number of sensor nodes placed in farmland.The sensors distributed in farmland have the characteristics of large quantity and low power consumption,and their working power generally ranges from tens of microwatts(μW)to tens of milliwatts(m W).Traditional battery power supply not only requires a lot of manpower to replace batteries,but also improper recycling of waste batteries will pollute the soil and water.Using aboveground or underground power lines will lead to serious aging of the wires and difficulties in maintenance.Therefore,new energy acquisition methods need to be developed to power sensors widely distributed in the field.It is a feasible solution to capture mechanical energy from the environment around the sensor and convert the captured mechanical energy into electricity to power the sensor and the sensor connected transmitter.Solar energy,wind energy,water energy and other energy exist widely in farmland.If a small device can be used to collect these energy and convert them into electricity to power the Internet of Things system required by smart agriculture,it will be a very good solution.Triboelectric nanogenerator(TENG)as a new energy harvesting technology that can collect different forms of mechanical energy,such as wind energy and water flow energy,from the environment where the sensor works and directly convert it into electricity.The self-powered intelligent agriculture based TENG has attracted the attention of many researchers,and many self-powered wireless agricultural sensing systems based TENG have been reported in recent years.The researchers designed the TENG with various structures to collect wind or water flow in the field to power the sensor and transmit the collected farmland environment information through wireless transmission methods such as Bluetooth and WiFi.Through comparison,we found that these reported wireless agricultural sensing systems still have some shortcomings.First,the whole system is applied in farmland,but the triboelectric layer of TENG is mostly polymer plastic film,which is easy to pollute the farmland environment.Second,agriculture will be large-scale in the future.The transmission distance using Bluetooth,Wi Fi and other wireless transmission methods is only 10-100 m,which is difficult to meet the needs of large-scale agriculture.Therefore,there is an urgent need to develop TENG,which uses biodegradable materials,as well as a new type of self-powered wireless agricultural sensing system that uses new sensing methods for long-distance data transmission.In chapter 2,a self-powered multichannel wireless agricultural sensing system based on pulsed triboelectric nanogenerator of corn husk composite film(CH-Pulsed-TENG)is developed.Corn husk has the advantages of wear-resisting,moisture-proof,pollution-free,and biodegradable,and CH-Pulsed-TENG has an output voltage and transferred charge of 3.2 k V and 300 n C,respectively.By integrating CH-PulsedTENG,passive power management circuit(PMC),voltage regulator circuit(VRC),sensors,signal transmitter and receiver,a self-powered multichannel wireless agricultural sensing system is developed.The energy storage efficiency of the passive PMC can reach 54.5%.Four different signals of temperature,humidity,light intensity,and soil moisture of the farmland can be simultaneously collected and transmitted,reaching a maximum wireless transmission distance of 1.7 km.Also,the self-powered sensing system is demonstrated to be driven by wind energy.The self-powered agricultural sensing system can not only continuously detect the environmental information of farmland,but also recycle the abandoned crops,having potential application in developing intelligent green agriculture.In Chapter 3,a self-powered wireless agricultural sensing system based on a fully degradable triboelectric nanogenerator with friction layer is developed.Soft triboelectric is introduced through the use of rabbit hair,which greatly improves the output stability of the TENG and the wear resistance of the friction layer material.The FD-TENG has a transfer charge of 979.74 n C,a short circuit current of 11.10 u A and an open circuit voltage of about 5 k V at the rotation speed of 120 rpm,and a peak output power of 28.90 m W when the external circuit resistance is 500 MΩ.Finally,a power management circuit with pin-pin discharge switch is designed.Under the new power management circuit,the 10 mF capacitor can be charged from 0 V to 5.5 V in 98 s,and the 22 m F capacitor can also be charged from 0 V to 5.22 V in 180 s.Finally,the selfpowered wireless agricultural sensor system based on FD-TENG was demonstrated with a 0.1 F supercapacitor.The data transmission interval was 7 minutes every two times,which further improved the practicability of the self-powered wireless agricultural sensor system and the timeliness of information collection.In this paper,the triboelectric layer material of TENG,which is used in a self-powered wireless agricultural sensor system,is not degradable and the transmission distance of the system is close.We designed two TENGs made of degradable materials,one is CH-Pulsed TENG made of corn husk as positive triboelectric layer material,the other is FD-TENG made of rabbit hair and calcium alginate film as triboelectric layer,and a multi-channel wireless agricultural sensing system with transmission distance of 1.7km was also designed.The multi-channel wireless agricultural sensor system designed in this paper for the triboelectric-layer degradable TENG and ultra-long transmission distance provides a new scheme for the development of smart agriculture. |
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