A NOVEL, COMPACT AND LIGHTWEIGHT DESIGN OF A VANADIUM REDOX FLOW BATTERY STACK

Large-scale electrical energy storage systems are necessary to harness renewable energy sources to their full potential. These systems can absorb the inherent fluctuations in a renewable energy source, store the surplus energy, and deliver it later in high power demand. One such system that has seen fruition at an industrial scale is the vanadium redox flow battery (VRFB). The conventional VRFB stack is built with thick (>10 mm) graphite plates to accommodate the flow field needed for efficient electrolyte circulation through the stack. This thick plate design requires high-grade graphite and expensive machining, increasing the stack's weight. To address these issues, thin graphite plates (< 2 mm) along with thin flow frames (≤ 5 mm) in flow-through mode have been employed. However, the high pressure drop leads to a significant impairment of system efficiency. Against this background, we present a novel cell design that features thick flow frames which permit use of multiple feed holes to reduce pressure drop; electrolyte circulation in a flow-through mode that reduces mass transfer polarisation; and thin (< 1 mm) bipolar plates made of expanded graphite sheets that prevent electrolyte seepage.