Comparative Study of Kilowatt-Scale Vanadium Redox Flow Battery Stacks Designed with Serpentine Flow Fields and Split Manifolds

Abstract

A low-pressure drop stack design with minimal shunt losses was explored for vanadium redox flow batteries, which, due to their low energy density, are used invariably in stationary applications. Three kilowatt-scale stacks, having cell sizes in the range of 400 to 1500 cm2, were built with thick graphite plates grooved with serpentine flow fields and external split manifolds for electrolyte circulation, and they were tested over a range of current densities and flow rates. The results show that stacks of different cell sizes have different optimal flow rate conditions, but under their individual optimal flow conditions, all three cell sizes exhibit similar electrochemical performance including stack resistivity. Stacks having larger cell sizes can be operated at lower stoichiometric factors, resulting in lower parasitic pumping losses. Further, these can be operated at a fixed flow rate for power variations of ±25% without any significant changes in discharge capacity and efficiency; this is attributed to the use of serpentine flow fields, which ensure uniform distribution of the electrolyte over a range of flow rates and cell sizes.

Power and Energy Rating Considerations in Integration of Flow Battery with Solar PV and Residential Load

“…Furthermore, 1.6 M vanadium electrolyte, procured from Oxkem, UK in an oxidation state of 3.5 is used as the electrical energy storage medium. In all the experiments, a constant flow rate of electrolyte, which corresponds to a stoichiometric factor of 9 at a current density of 60 mA/cm 2 , was maintained on each side [22,39]. Comprehensive testing over a range of flow conditions and state of charge (SoC) shows that, over a wide range of SoC, the stack can deliver 1200 W in charging and 750 W in discharging when operated at a current density of 100 mA/cm 2 .…”

Model for Rating a Vanadium Redox Flow Battery Stack through Constant Power Charge–Discharge Characterization

“…The VRFB stack shown in Figure 1 has 22 cells, with each cell having a nominal electrode area of 1500 cm 2 active area. It was built in the same way as the 8-cell stack reported previously in [15]. Activated graphitized carbon felt of 4.6 mm thickness, which was procured from SGL Ltd., was used as an electrode, and an untreated Nafion 117 membrane, which was soaked in de-ionized water for 24 h, was used to serve as the proton conductor and separator of the positive and negative electrolytes.…”

“…Vanadium salt was dissolved in a 5 M H 2 SO 4 solution to make a 1.6 M VOSO 4 electrolyte. Other redox species (V 5+ , V 3+ , and V 2+ ) were generated in the dissolved form using the dual step charging approach [15]. A total of 35 L of the electrolyte were used in all studies, both on the positive and negative sides.…”

“…Park et al [14] showed testing of a kW-scale stack of 31 cells with a 2714 cm 2 active area and reported EEs of 76% and 70% at operating current density of 60 and 90 mA/cm 2 , respectively. Gundlapalli and Jayanti [15] studied three kW-scale stack configurations with different cell areas to bring out the effect of cell size on stack efficiency.…”

Electrolyte circulation effects in electrochemical performance for different flow fields of all‐vanadium redox flow battery

“…10 Commercially available VRFB systems and their performance were also reviewed by Alotto et al 11 Some investigations have been reported on stack-level studies for the VRFB systems. Gundlapalli and Jayanti 12 investigated the 8 cell stack at kilowatt-scale by using the serpentine flow field design. Reed et al 13 employed 3 cell stacks of 1 kW by using different interdigitated flow field designs.…”