Stack Design Considerations for Vanadium Redox Flow Battery

Abstract

In this paper we deal with strategic considerations in designing the stack of a vanadium redox flow battery. The design of the stacks is complicated by the presence of a number of parameters that can influence the performance. For a given stack power, the cell size and the number of cells are inversely related. As the cell size increases, concerns arise over uniform circulation of electrolyte over the cell and the pressure drop incurred in circulating a larger flow rate over a longer flow path. In the present paper, these issues have been studied experimentally and through model estimates. A short stack of four cells has been prepared by connecting them in series electrically and its electrochemical performance, including pressure drop, has been characterized over a range of important design parameters. It is shown that, for the same local electrochemical performance, increasing the cell size increases the gravimetric and volumetric efficiency of the stack. Although the cell pressure drop increases with increasing cell size, the pressure drop in the manifold is reduced as there are fewer number of channels. This leads to a decrease in the parasitic power consumption for electrolyte circulation. For large-powered stacks, further reduction in pressure drop can be achieved by making deeper grooves in the serpentine channels.