| Rural all-vanadium liquid flow battery(VRB)micro-grid energy storage system can develop and store rural renewable energy to solve the problems of insufficient supply of rural power grid,low power supply voltage,high cost of grid architecture and so on.By optimizing the internal structure of VRB reactor and increasing the energy storage efficiency,the volume and weight of the energy storage system can be reduced to make it more suitable for agricultural environment.The main conclusions are as follows:(1)By calculating the resistance of vanadium batteries with different thicknesses,it is concluded that the resistance increases linearly with the continuous operation of the battery system.The energy efficiency of the 4 mm thick electrode is3.5% and 4% higher than that of the other two thicknesses,respectively.Charge and discharge efficiencies are 3% and 9% higher,respectively.Moreover,the electrode thickness of 4 mm is sufficient for the area providing a reaction site for electrolytes to meet the use of the reaction rate of the existing vanadium battery electrolyte.(2)The effect of different flow rate battery system performance was studied.Simulation results show that when the flow rate increases from 5 m L min-1 to 35 m L min-1,the concentration of V3+ ions and VO2+ ions in the electrode decreases by6.25%.The concentration of V2+ and VO2+ ions increased by 4%.Electrolyte potential increased by 1V;The rate of sulfuric acid dissociation will also increase.According to the calculation,when the battery system flow rate is 5 m L min-1,the energy efficiency reaches 83%,which is the highest efficiency.Charge and discharge efficiency reached 99.3%,higher than other flow rate.In the experimental flow range,the overall system efficiency of 5 m L min-1 is the highest.(3)The fluid flow frame with embedded electrodes was optimized,and the fluid simulation calculation of the two fluid flow frames before and after optimization was carried out.The pressure drop of the new fluid flow frame(double electrode fluid flow frame)was reduced by 61% compared with that of the single electrode fluid flow frame.According to the calculation,compared with the flow frame before optimization,the flow resistance of the optimized flow frame is reduced by 61%.According to the actual experiment,the current efficiency of the bipolar liquid flow frame battery is 2.6% higher than that of the single electrode liquid flow frame battery,and the energy efficiency of the bipolar liquid flow frame battery is 2% higher than that of the single electrode liquid flow frame battery.(4)A combination of serpentine flow channel and new flow channel(flat parallel flow channel)was designed,and the battery flow channel was innovated.The combined flow channel and new flat parallel flow channel were studied.The optimized combined flow channel has the advantage that the serpentine flow channel can evenly distribute the electrolyte,and keeps the advantage that the parallel flow channel can make the electrolyte resistance smaller.The pressure drop and flow resistance of the carbon felt serpentine flow channel are reduced by the new double plate flow channel.Experimental results show that the energy efficiency of the combined flow channel is up to 85.5%,and compared with the non-flow channel,the energy efficiency is improved by 2.28%.The new flow frame and combined flow channel design improved the performance of the battery system by 4.28%. |
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