Numerical and experimental studies of stack shunt current for vanadium redox flow battery

• A coupled three-dimensional model of VRB cell stack is developed.
• Shunt current of the stack is studied with the model and experiment.
• Increased electrolyte resistance in channel and manifold lowers the shunt current.
• Shunt current loss increases with stack cell number nonlinearly.

The stack shunt current of VRB (vanadium redox flow battery) was investigated with experiments and 3D (three-dimensional) simulations. In the proposed model, cell voltages and electrolyte conductivities were calculated based on electrochemical reaction distributions and SOC (state of charge) values, respectively, while coulombic loss was estimated according to shunt current and vanadium ionic crossover through membrane. Shunt current distributions and coulombic efficiency are analyzed in terms of electrolyte conductivities and stack cell numbers. The distributions of cell voltages and shunt currents calculated with proposed model are validated with single cell and short stack tests. The model can be used to optimize VRB stack manifold and channel designs to improve VRB system efficiency.