Research On Micro Water Wave Energy Harvester And The Self-Powered System

Energy plays an important role in our country for aspects of livelihood,construction,development,environment and so on.Our country’s energy structure is dominated by fossil energy consumption,and the development and utilization of new-type energy is relatively low.The development of renewable energy is of great significance to solve the energy shortage and carbon emission in our country.China’s water area is vast,and there is abundant wave mechanical energy in natural waters.The energy can not only be used as new renewable energy to generate electricity,but also provide energy supply for electronic equipment such as wireless sensor network on water,which realizes in-situ utilization of energy.Traditional wireless sensor systems use batteries as the main power source.For the wireless sensor system with very limited volume and weight,the capacity of the battery that can be carried is limited.When the energy is exhausted,the node system needs to be recycled to replenish the energy.The wireless water quality sensor network with a large number of nodes and a wide range of distribution needs a lot of human resources to maintain their power source,and the abandoned batteries have tendency to pollute the environment.Wave undulation is common in water environment.Converting the mechanical energy contained in the waves into the direct current energy required by the wireless sensor system can realize the real-time supplement of energy,which could extend the battery life,or even completely replace the battery.However,the harvesting and utilization of wave energy is still immature,and there are still deficiencies in the output power density,power management efficiency and load application.Aiming at the problems existing in the key components of wave energy collection and utilization,such as power generation,power management and load system,this paper designs the core components from theoretical analysis,modeling optimization and system design,and finally constructs a small wave-energy self-powered wireless sensor system with full package.The research content is as follow:In terms of energy,the selection of the working position and evaluation of the energy transfer effect of the energy harvester are realized by the‘particle-wave’model and‘fluid-solid-electromagnetism’coupled model which could simulate the output response of the energy harvester.The motion characteristics of the equivalent water point of point absorption structure at different depths are analyzed.Mechanical response of float vibration and output performance of the energy harvester under wave action are simulated.According to the characteristics of vibration generation,the eccentric pendulum energy converting structure and electromagnetic power generation structure which can work under such low frequency vibration are designed,which forms the simple and compact basic architecture of the energy harvester.The generation mechanism and output response of the energy collector under low frequency vibration environment are analyzed by establishing the finite element analysis model of electromagnetic field,which verifies its feasibility of working in low frequency water wave environment.Aiming at the problems existing in the current wave energy harvester,such as complex structure,large volume,weight and low power density,the wave energy harvesting unit with high power density,low working frequency,high vibration sensitivity and compact package is designed and implemented in this paper.The electromagnetic field design parameters of the energy harvester are further optimized by using the multi-physical field coupling model,and the processing and assembly methods are studied to form the prototype.A test platform for quantitative control of vibrational frequency and intensity is built to test the output performance of the energy harvester in detail.The results show that the center frequency of the energy harvester is 1.8Hz.The maximum effective output power and peak output power are9.4m W and 114.4m W respectively.The volume and weight power densities are1.06m W/cm~3 and 0.61m W/g respectively.In terms of power management,this paper establishes an energy management system model based on rectifying and storing energy for efficient rectification and charge storage of energy harvester.In different energy storage states,the energy storage voltage characteristics of each output cycle of the energy harvester are analyzed,and the optimal working voltage range of the energy harvester is obtained.The power control strategy of the power management system is designed according to the results.In the aspect of hardware implementation,this paper designs the circuit level design for the operation logic of energy management system and establishes the system level power consumption analysis model,which determines the detailed power consumption and cold start-up conditions of the energy management system in its operating state and verifies its functionality through energy harvester input and low impedance load output.The AC-DC conversion efficiency of the power management system achieved in this paper is 77.62%and the maximum load current is 180.6m A.The average power consumption of the system is 57μW and the layout area is 4.36cm~2.In the aspect of load system and energy application,a low power wireless sensor system is designed according to the output characteristics of the designed power system composed of energy harvester and power management system.The acquisition of water quality and temperature parameters powered by wave energy is realized due to low power design in both software and hardware.The package structure and anchor structure of the self-powered system are designed according to the structural characteristics of the sensor system,the power management system and the energy harvester.The output performance and self-powered wireless sensing function are tested in the simulating water-wave environment in a flume,which verifies the feasibility of self-powered wireless water quality and temperature acquisition.