Study On The Blue Wave Energy Harvester Towards The Ocean Buoy Applications

The ocean buoy is a floating automatic monitoring platform for marine monitoring and acquisition of marine data.It can provide all-weather observation services for maritime military activities,marine economy,marine climate prediction and so on,which is of?g'eat significance to the national economy,people's livelihood and national security of coastal countries.However,long-term automated data collection,labeling and transmission of ocean buoys consumes a lot of energy.And carrying high-capacity battery packs and reducing the system energy consumption are not enough to guarantee their endurance.Therefore,it is necessary to obtain energy from the marine environment or feed back energy from the system to extend the working life of ocean buoys.Ocean wave energy refers to the kinetic energy and potential energy of the ocean surface wave.It has the advantages of green environmental protection,wide distribution and abundant reserves.It is the most direct energy source available for marine equipment.The blue wave energy harvesters convert ocean wave energy into electrical energy,making long-term unattended work of marine equipment possible.It is an important development direction for the supply of marine equipment.Aiming at the characteristics of ultra-low frequency and complex waveform of ocean waves,this paper designed an efficient complex pendulum based wave energy harvester.The device takes the compound pendulum as energy capture mechanism,and converts the ultra-low frequency and irregular wave motion into the swing of compound pendulum through the inertia action of the non-resonant pendulum.By using the gear speed increasing mechanism,the low-speed swing of complex pendulum is converted into the high-speed rotation of rotor to realize the high power density output of the device.In addition,this paper also designed a power monitoring circuit and a power management circuit that matches the output characteristics of the device.Finally,the in-lab test and the sea buoy carrying test were completed.And the output performance of the device was analyzed and verified.The main research contents of this paper include the following points:(1)Design and optimization of ocean wave energy harvesterAn electromagnetic wave energy harvesting device based on the compound pendulum is designed for ultra-low frequency and complex wave characteristics of ocean waves.The device utilizes the fan-shaped compound pendulum and the gear speed increasing mechanism to eonvert the ultra-low frequency wave motion into a high-speed rotation of the rotor in the electromagnetic power generation module.And based on the Faraday electromagnetic induction law,the electromagnetic coil generates an induced electromotive force.Firstly,based on the Lagrangian dynamic equation,the compound pendulum dynamics model was established and the optimal design of the compound pendulum structure was carried out in Simulink.According to the simulation results and the actual buoy integration requirements,the double-sector compound pendulum structure was finally designed.The sector radius is 4 cm,and the sector arcs are 1200 and 600,respectively.At the same time,the optimization simulation of the electromagnetic power generation module was carried out in the software JMAG.When the curvature and thickness of the stator magnet are 1400 and 1.8mm respectively,and the thickness of the rotor core top and the core root width are both 1.5mm,the electromagnetic power generation module can achieve the highest output voltage.(2)Design and testing of the power management circuitThe performance of the power management module directly affects the energy collection and utilization efficiency of the entire energy harvesting system.This paper designed a power management circuit based on the polymer lithium battery.Through using it,the irregular output voltage of the energy harvester can be rectified,filtered,and stored in a lithium battery or powered to an external load.The circuit is divided into a rectifier circuit,a charging circuit,and a discharging circuit.The charging circuit is based on the LTC4071 chip,which is used to protect the lithium battery from overcharging and overdischarging.The discharge circuit uses the LTC1540 and MAX4685 to control the discharge voltage range of the lithium battery and extend the discharge time.In order to carry out the buoy test for a long time and obtain the lithium battery charging information during the test period,a power monitoring module based on the MAX 17043 chip was designed.Under the control of the STM32F103 chip,the fuel gauge module reads the lithium battery charge in real time and stores it in the SD card.(3)Experimental testing and analysis of ocean wave energy harvesterThe experimental test platform was built,and the ocean wave energy harvester was tested in the laboratory test and sea buoy carrying test.In the laboratory test,the output characteristics of the device under different sea conditions were simulated and the kinetic model was verified.When the amplitude is 30cm,the period is 1s,and the external resistance is 122? the maximum output voltage,the maximum power output and the corresponding output power density of the device is 8.6V,610mW and 0.97mW/cm3,respectively.In the sea buoy carrying test,12 hours of open circuit voltage test was conducted.In the case of large waves,the maximum output voltage peak-to-peak value,the maximum output power and the corresponding output power density is 15.9V,259mW and 0.41mW/cm3,respectively.The test of ocean wave energy harvester proves that the device can harvest ultra-low frequency and irregular wave energy,and has the high output performance.Additionally,the integration of ocean buoy and wave energy harvester is realized,which lays a foundation for improving the life of marine buoys.