| Energy storage system is an essential technology to reform a new type of power system,which is significant to promote the utilization of renewable energy,increase the flexibility of power system,and achieve the goal of "carbon neutrality".Vanadium Redox Flow Battery(VRB)has the advantages of high safety long service life,flexible design,and friendly-to-environment.A well-designed cell structure can enhance the uniformity of electrolyte distribution,reduce overpotential and pumping losses.However,the conventional flow channel designs of vanadium redox flow batteries ignore the consideration of the electrode compression effects on cell performance.Therefore,to improve the performance of the vanadium redox flow battery,this thesis is to optimize the battery design in the following aspects: the flow channel design and the electrode compression to fully consider the influence of cell structure on overpotential,pressure drop and uniform concentration distribution.Firstly,a three-dimensional multi-physical field coupled model of vanadium redox flow battery is developed.The three-dimensional multi-physical field of the vanadium redox flow battery is established based on various complex partial differential equations such as mass conservation equation,momentum conservation equation,charge conservation equation and reaction kinetics equation.The model is divided into three sub-models,respectively,electrochemical field model,flow field model and concentration field model,and the accuracy of the simulation results is verified by charging/discharging experiments.Secondly,this thesis investigates the effects of different flow channels on the cell performance.Three common flow channels are analyzed: the parallel flow channel,the serpentine flow channel and the interdigitated flow channel.The distribution of overpotential,pressure drop and concentration distribution inside the cell during the operation of the three flow channels are investigated.The results indicate that each of the three flow channels has its own advantages and disadvantages under different performance indexes.The parallel flow channel has better pressure drop performance,but the overpotential and concentration uniformity distribution are poor.The serpentine flow channel shows excellent overpotential and uniform concentration distribution,but the pressure drop is too high and the pumping loss is large.The interdigitated flow channel exhibits good overpotential and uniform concentration distribution,while the pressure drop performance is better than that of the serpentine flow channel.Finally,this thesis considers the effect of uneven electrode compression on the cell performance under different flow channels.Since the mechanical stress can cause electrode compression during assembly,this paper considers this phenomenon and investigates the effects of different flow channels and electrode compression on the overpotential,pressure drop and concentration distribution of the cell under five kinds of uneven electrode compression The results show that increasing the electrode compression can reduce the overpotential and improve the concentration uniformity distribution,but will increase the pressure drop.By evaluating the above three indicators,the interdigitated flow channel with 45% compression shows the best cell performance. |
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