Research On Micro Linear Generator For Ocean Wave Energy Conversion

As a strategic renewable energy source,wave energy technology has received great attention from all over the world.The basic principle of current wave power plants is to convert wave energy into pneumatic energy,hydraulic energy or potential energy,and then transmit it to a gas turbine,a water turbine,or a gearbox to drive a rotary generator to generate electricity.The characteristics of these power generation systems are that the transmission is complex,large in size and large in investment.The linear generator is directly driven by the up and down reciprocating motion of the wave to avoid complicated transmission system.It has many advantages such as simple structure,convenient maintenance,low loss and low cost.The shortcoming of linear generator direct drive power generation is that the moving speed of the mover is slow,so the power generation efficient is low,and it can not work smoothly.When the waves are small,both the cost and the energy conversion efficient of the current power generation are relatively poor.In order to overcome the shortcomings of the current power generation technology for poor adaptability of small waves and to realize the miniaturization of power generation devices,in this paper a micro linear generator for marine wave energy conversion was proposed,which is driven by pressurized air and moving coil type was adopted so that reduce the mass of the mover and increase the running speed.Another characteristic of the linear generator is that the coil is air core to reduce the weight of the coil and reduce the interact force between the coils and the magnets.Firstly,the structure design of the linear generator driven by pneumatic system was described,then numerical modeling and analyzing were carried out using finite element method,finally,the prototype is designed and its power generation performance is tested and analyzed.The main research contents of the project include: working mechanism of linear generator;structural design of linear generator;design of pneumatic control system;related electromagnetic field theory and numerical modeling and analysis for linear generator;analysis of the influence factors of structural parameters on the electromagnetic performance;fundamental test of generating electricity.The research results show that the rod-less cylinder can drive the mover coil stably and highspeed power generation,and the generator structure is compact;the air core coil significantly reduces the force of the mover and the magnetic field,the coil mover has small running resistance and runs smoothly;The small magnet spacing can optimize the magnetic field waveform and reduce the harmonic components;when the cylinder works in the gas expansion phase,the air pressure will gradually decrease,which will cause the moving speed of the mover to decrease,therefore result in the degradation of power generation voltage.The creative researches or contributions of this paper are mainly as follows: the linear generator's mover is driven by a rod-less cylinder to ensure the high running speed and high power generation efficiency,and in the meantime to keep compact size;numerical model and analysis was carried out using the vector magnetic potential based finite element method for the linear generator,and the influence of structural parameters on the magnetic field distribution characteristics was analyzed,in particular,the axial and radial components of the magnetic field were analyzed.