Redox flow batteries (RFB) hold great potential for large-scale stationary energy storage to be integrated with solar and wind power plants. However, their low energy density (compared to other energy storage systems) must improve for large-scale feasibility. Electrolyte flow distribution affects current density distribution; providing a uniform current density distribution is one way to improve RFB performance. Additionally, reducing the power consumption of the electrolytes’ pump as a sink of energy in RFB systems increases their efficiency. Investigating both subjects requires analysis of the fluid dynamics in RFB cells.A computationally cost-effective hydraulic-electrical analogous model (HEAM) was developed to study fluid dynamics by implementing scaling analysis on Navier-Stokes and modified Darcy’s equations. The HEAM was compared with experimental data and shown to be accurate. The HEAM demonstrated the deficiencies of flow distribution in interdigitated flow fields (IFFs) and suggested that lower viscous resistance at the flow distribution manifold or higher resistance in the parallel channels remedies the flow maldistribution. Designing wider flow field ribs, wider manifold, shorter channels, or more compressed electrodes are all suitable improvements that will enhance flow distribution in IFFs; however, the most appropriate modification would be to use a wider manifold due to the decrease in the overall pressure drop.Further analysis showed that RFBs with IFFs need lower pump power to operate than those with single-channel serpentine flow fields (SSFFs) and three-channel serpentine flow fields (3SFFs) with similar properties. Moreover, the HEAM predicted that the electrolyte flow penetrates more above the channels and penetrates deeper above the ribs in carbon felts than in carbon papers, giving the reactants more exposure to the electrode and hence enhancing reaction progress in each cycle.In closing, the HEAM suggested that designing flow fields with thinner ribs, deeper channels, and less compressed electrodes are desirable to lower the pump work in an RFB cell. However, this analysis needs to be coupled with electrode transport and kinetic modeling to ensure that better flow field designs in RFB cells will also lead to enhanced performance.

Development of a Computationally Cost-Effective Model of Fluid Flow in Redox Flow Batteries

Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2021/volume/85284

ASME 2021 Fluids Engineering Division Summer Meeting (FEDSM2021)

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