Numerical modelling and in-depth analysis of multi-stack vanadium flow battery module incorporating transport delay

The flow battery module comprised of multi-stack is commonly constructed for use in large-scale electrical energy storage applications. In such a multi-stack module, the transport delay associated with electrolyte flow in the piping systems inevitably exists that can impose a significant impact on module design and operation performance. In this paper, a complete dynamic model incorporating transport delay is developed for the multi stack vanadium flow battery module. Based on the model, the module performance and capacity utilization are comprehensively analyzed for different module designs and various operational conditions. Simulation results demonstrate that the transport delay can cause uneven concentration distributions along the piping and lead to a poor stack voltage uniformity in the module, which can subsequently result in premature voltage cut-off in operation and a degraded capacity utilization. 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. Such an in-depth simulation analysis considering the transport delay not only offers a cost-effective way to analyze a multi-stack flow battery system, but also provides a deep insight into design and optimization of the large-scale flow battery module that can allow both high system efficiency and superior capacity utilization to be achieved.