Effect of electrolyte convection velocity in the electrode on the performance of vanadium redox flow battery cells with serpentine flow fields

Sufficient convective velocity in the electrode is essential for the good performance of a flow battery. The present study is concerned with identifying how this condition is attainable for a given size of a vanadium redox flow battery cell. To this end, detailed experimental investigations of fluid dynamic and electrochemical characteristics with serpentine flow fields have been done in cells with active area of 416, 918 and 1495 cm2, and optimal operating conditions of reasonably high efficiency, discharge capacity and energy density have been identified for each size. Investigations using calibrated computational fluid dynamics simulations show that optimal performance condition for each cell size corresponds to the case where the local convective velocity in the electrode is the same and is of the order of Reynolds number ~2. Based on this condition, a model has been developed to determine the optimal electrolyte circulation rate for a given cell size and operating current density.