Locating Shunt Currents in a Multistack System of All-Vanadium Redox Flow Batteries

An all-vanadium redox flow battery (VRFB) system, with multiple stacks, is typically used for large-scale electrical energy storage applications. In a VRFB system, pumps deliver positive and negative electrolytes, through a piping system, to each stack. Because the electrolytes are electrically conductive, shunt currents can occur within a multicell stack and within the piping system, connecting the stacks due to the voltage differences between cells and between stacks. Shunt currents cause energy loss and are affected by the number of cells in a single stack, the number of stacks, and the piping system dimensions. In this study, we develop a mathematical model, based on Kirchhoff’s law, to locate shunt currents in a multistack system. Using this model, we estimate the charge efficiency with various numbers of stacks. The results show that the shunt currents in the central stacks are larger than the currents in other stacks. In addition, the piping system dominates the distribution of the electrolytes, and the shunt currents gradually shift from inside the stack to the piping system.