Experimental and Numerical Study of Electrolyte Mixing in the Tanks of Vanadium Redox Flow Batteries: Insights from Conventional and 3D-Printed Tanks

Abstract

Vanadium redox flow batteries (VRFBs) are a promising technology for large-scale grid energy storage. Despite extensive research on the electrochemical and fluid dynamic phenomena in the cells or stacks [1, 2], the impact of electrolyte flow and mixing in the tanks has received much less attention. Previous research has shown that the cell potential and battery capacity may substantially differ from those predicted under the perfect mixing assumption [3] (i.e., continuous stirred-tank reactor). Recent numerical simulations have detected the formation of segregated zones within the tanks that cause inhomogeneous electrolyte utilization and significant capacity decay [4]. The authors have confirmed these results by means of transient laminar numerical simulations [5] and experimental testing of an industrial VRFB system [6]. However, these first attempts should be carefully extended, using a well-controlled lab-scale system, so that the effects of the different components can be independently studied.In this study, we investigate the effect of electrolyte mixing on VRFB response using a medium-size lab-scale system. Two experimental campaigns were conducted to explore i) the impact of flow rate and applied current on the predicted fluid behavior, and ii) the performance of 3D-printed tanks designed for improving electrolyte mixing with reduced dead recirculation zones. In both campaigns, the transient response of the system was investigated to assess the effect of electrolyte mixing on battery performance. The experimental results were also compared with numerical simulations, which showed good agreement with the experimental data.This work makes a novel contribution to the field by using 3D-printed tanks to investigate the impact of electrolyte mixing on RFB performance. The results extend previous research on this topic and provide insights into the design of RFBs for improved energy storage. Specifically, the use of 3D-printed tanks could be a promising approach to address the issue of inhomogeneous electrolyte exploitation in RFBs. The findings of this study could serve in the design of RFBs for large-scale grid energy storage and facilitate the adoption of this technology as a sustainable energy storage solution.