Design And Optimization For Flow Battery Module

Flow battery commonly constructed by a certain number of large-scale modules consisting of multi-stack is considered to be one of the most appropriate electrochemical technologies for use in large-scale electrical energy storage applications.The design,optimization and performance improvement of the flow battery module are therefore of great significance for its wider implementation.In this work,all-vadamium flow battery,as a technology nearing commercialization and being widely used is selected to be the carrier for the study on the characteristics of large-scale multi-stack flow battery module under the influences of transport delay,module layout and module thermal behavior by conducting both the dynamic dynamic module model and the experimental validation.This study can not only offer an deep insight into high-performance large-scale flow battery design and operation,but also assist in promotion of flow battery implementation in grid-scale applications as well as further penetration into electrical energy storage market.The contents of the thesis are summarized as follows:First of all,dynamic models of the module are developed on the basis of the conservations of mass and energy,which successfully extends the existing flow battery models from single stack to multi-stack scale,thus offering an effective way to provide a deep insight into design and optimization of large-scale flow battery module by simulations.Secondly,transport delay is proved to be existed in flow battery module by both simulation and experiment.Simulation results demonstrate that the transport delay can cause uneven concentration distributions along the piping,thus leading to a poor stack voltage uniformity in the module,and lowering the electrolyte utilization and battery efficiency.Meanwhile,the analyses also prove that the transport delay and its negative effect on the module can be effectively reduced by optimizing the electrolyte feeding mode in addition to adopting a high variable flow rate and a small pipe radius.Then,an in-depth investigation is further conducted to understand the effects of module layout on performance.Based on experimental measurements,the correlation of module layout to performance is firstly revealed on both the eight-stack 250 kW module and a laboratory mini-module.Subsequently,35 different layouts are specified for the 250 kW module and their performances are fully evaluated by means of development of dynamic models for the module.Simulation results prove that the module charging capacity can be effectively improved by grouping stacks with similar resistances into the same branch and can even be further promoted by optimizing the flow rate for the stack with the largest resistance.Last but not the least,the thermal behavior of flow battery module is revealed for the first time on an eight-stack 250 kW module,especially the module temperature variation and its influential factors during operation.Simulation results show that the module temperature variation consists of three phase of fast rising,slow rising and keeping.In addition lowering the applied current,extending the storage time,reducing the surrounding air temperature,enlarging the surface area of the tanks and rise up the flow rate are applicable to improve the module thermal behavior and help to moderate the module temperature rising.