Effect of bypass current on coulombic efficiency of vanadium redox flow battery
In order to improve the performance and efficiency of the battery in vanadium redox battery(VRB)system,a multi-stack equivalent loss circuit model is developed based on the composition and principles of VRBs,which includes electrochemical,hydrodynamic,temperature,bypass current,and vanadium batteries.Moreover,the effects of pumping loss and bypass current on vanadium batteries in the pipeline system of all-vanadium flow batteries are investigated.The relationship between pumping loss and pumping current,the bypass current model,and the equivalent circuit model of vanadium battery with multiple stacks connected in series are established,and the core mechanism of the vanadium battery taking into account the dynamic response is elaborated by transforming each model into a whole.The key factors involved in modelling of the VRB,including the pumping loss and bypass current,are discussed in detail.The influencing factors of battery performance and efficiency are also analyzed.The results show that,parameters such as the length and cross-sectional area of the pipeline affect the pipeline resistance,and the resistance of longer main and branch pipes will reduce the bypass current but increase the pumping loss current.Longer and thicker pipelines are conducive to the simultaneous reduction of both the bypass current and the pumping loss,which improves the energy efficiency of the battery.The research provides an idea for design of the manufacturer's pipeline.
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