Abstract
Description of electrolyte fluid dynamics in the electrode compartments by mathematical models can be a powerful tool in the development of redox flow batteries (RFBs) and other electrochemical reactors. In order to determine their predictive capability, turbulent Reynolds-averaged Navier-Stokes (RANS) and free flow plus porous media (Brinkman) models were applied to compute local fluid velocities taking place in a rectangular channel electrochemical flow cell used as the positive half-cell of a cerium-based RFB for laboratory studies. Two different platinized titanium electrodes were considered, a plate plus a turbulence promoter and an expanded metal mesh. Calculated pressure drop was validated against experimental data obtained with typical cerium electrolytes. It was found that the pressure drop values were better described by the RANS approach, whereas the validity of Brinkman equations was strongly dependent on porosity and permeability values of the porous media.
Highlights
Research and development in redox flow batteries (RFBs) has thrived due to the need for large- and medium-scale energy storage devices for renewable sources [1]
RFBs utilize membrane-divided, electrochemical filterpress flow reactors to store energy into a pair of redoxactive substances dissolved in recirculating electrolytes [2]
The analysis presented in this work is chemistry agnostic, i.e., it can be readily applied to other RFB chemistries needing similar electrodes
Summary
Research and development in redox flow batteries (RFBs) has thrived due to the need for large- and medium-scale energy storage devices for renewable sources [1]. While hefty upfront costs are being abridged by electrolyte leasing schemes, the improvement of reliability, cycle life cost and energy efficiency ought to be addressed by a renewed consideration of electrochemical engineering in these devices [3,4]. Through a combination of realistic experiments and mathematical modelling, the following desirable general features should be understood and optimized: (1) Uniform and developed electrolyte flow through the porous electrodes; (2) A reduction of pressure drop and its associated pumping energy cost; (3) An increase in the mass transport of electroactive species to electrode surfaces; (4) Control of cell potential losses (kinetic, ohmic and mass transport related); (5) Effective reactant conversion per pass in batch recirculation vs time; (6) Prediction of state of charge and cell potential during cycling
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