Optimal Design Of Off-grid Seawater Desalination System By Using Wind-solar Hybrid Energy

In recent years,countries around the world accelerated the process of developing the coastal islands to make use of marine resources.The construction of the islands in the south China sea is in our country's current plan as well.Because the developed islands are far away from the mainland and lack of power and fresh water,now the obtain of fresh water is realized through the ship transport or the seawater desalination equipment which will increase the cost of development and environment pollution of the islands.With the technology of wind and solar power developing,using renewable energy to provide green power for seawater desalination equipment is able to solve the problem of supplying fresh water to the remote islands.Now the combination of the wind or solar energy with the seawater desalination is studied by many research institutions in order to obtain double benefits of green power and water supply.Due to instability of wind or solar energy,it is usually store the power generated by wind or solar to the battery first,and then through the battery to supply power for the seawater desalination equipment.Because the power of the seawater desalination equipment is very high,it needs to be configured with large capacity batteries,which not only increase the system cost but has a huge power loss in the battery charging and discharging process.It will cause the efficiency of the off-grid seawater desalination system lower by using wind-solar hybrid energy.The introduction of structure characteristics and main technical parameters of the horizontal and vertical wind driven generators and the design points of the solar power station are presented in this paper so as to provide the design basis of the power supply module for the off-grid seawater desalination system by using wind-solar hybrid energy.By elaborating the technological process of seawater desalination and analyzing the technical parameters of key components in the seawater desalination equipment,the foundation for the seawater desalination design is laid.According to the seawater quality and the statuses of wind and solar energy in Xiamen,the1t/d seawater desalination equipment,which include the pretreatment module,high-pressure pump,reverse osmosis membrane components and post-processing module,is designed this paper.And according to the energy consumption of the 1t/d seawater desalination equipment,the capacity of photovoltaic module and wind power module is designed.A power buffer equilibrium controller is developed to monitor the power of the power generation module anddeploy the charge and discharge process of the small capacity batteries.The power is supplied through the combination of wind-solar hybrid energy and the small capacity batteries,which is able to solve the power fluctuation caused by wind-solar hybrid module and ensure the seawater desalination equipment running in rated power.Under different climate conditions,the property of system power units,energy buffer equilibrium controller and the seawater desalination equipment are tested through the test platform.The experimental result indicated that the power buffer equilibrium controller can effectively solve the power fluctuations,ensuring the seawater desalination equipment operated safely and stably under various climate conditions as well as reduce the charge and discharge times of small capacity batteries.The water produced by the seawater desalination equipment meets the drinking water standards.Because the system running randomly in different climate conditions,it is difficult to monitor the system by people.Besides,there is no energy recovery in the system to recover the pressure,which results in a higher power consumption.To the difficulty of monitoring the system by people that revealed in the experiment process,according to the control plan of seawater desalination,the automation of the 1t/d seawater desalination test platform is ameliorated by using wind-solar hybrid energy in this paper.Because the power consumption of the system is very high,through counting the power of emitted high pressure seawater,the increase of energy recovery device in the middle-sized seawater desalination system is proposed which owns the ability of reduce the energy consumption for producing fresh water.