University of Southampton Ewan Fraser ef5g12sotonacuk Dr Richard Wills and Dr Ranga Dinesh Kahanda Koralage Contents Introduction Redox flow batteries S oluble lead flow battery Challenges ID: 1046875
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1. Simulating the Effect of a Change in Deposit Geometry on the Performance of a Soluble Lead Flow CellUniversity of SouthamptonEwan Fraser, ef5g12@soton.ac.ukDr Richard Wills and Dr Ranga Dinesh Kahanda Koralage
2. ContentsIntroductionRedox flow batteriesSoluble lead flow batteryChallengesModel setupMoving meshSimulation setupSimulation resultsCell potential Cell resistanceElectrolyte flow rateConclusions
3. Redox Flow BatteriesPositive ElectrolyteNegative ElectrolyteIon Exchange MembraneCurrent CollectorsElectrodesPumpPumpAaAa+zBbBb-zPower Source / SupplySecondary (rechargeable) battery>MW scaleHigh energy (>4 hours)Stationary applicationsEnergy is stored solely in the electrolytesPower is determined by the size of the stackTypically two tank, membrane divided configuration
4. Soluble Lead Flow BatteryElectrolytePumpCurrent CollectorsElectrodesSolid Lead MetalSolid Lead DioxidePb2+Power Source / SupplySingle electrolyteNo membraneSolid deposits at electrodesPb at negative electrodePbO2 at positive electrodeExisting lead supply chainMethanesulfonic acid“Green acid”
5. ChallengesStability of depositsAdherence to electrodesRough, uneven deposits+ve deposit not well understoodScale upHigh energy -> large depositsLarger deposits are less stableChanging cell geometry with SoCChange in cell resistancePower Source / Supply
6. GeometryThree domainsSolid positive electrodeSolid negative electrodeLiquid electrolyteElectrolyte inlet and outletNegative electrodePositive electrodeElectrolyteInletOutlet
7. Model setupModulesLaminar FlowNavier stokes & continuity equationsNo slip walls, 0 pressure at outlet, average velocity inletTertiary current distribution, Nernst-PlanckNernst-PlanckButler-Volmer kinetics
8. Model setupTertiary current distribution, Nernst-PlanckDissolving-Depositing speciesSide reaction Global ODE and DAEsElectrolyte concentration at inlet.Assumes perfect mixing
9. Model setup – Moving meshModulesGlobal DOEs & DAEsCoefficient form PDEsDeform inlet & outletDeformed geometryMoves electrode boundariesDeforms domainsMoving mesh not adaptive mesh ChargeDischarge-ve+ve-ve+ve-ve+veGie, 0Gie, cGie, dden, 0den, cden, ddep, 0dep, cdep, d
10. Simulation setupConstant current200 A m-2, 300 A m-2Two charge/discharge cycles1 hour chargeDischarge to 1.2 VImplemented using events300 KInitial [Pb2+] 1000 mol m-3Initial [H+] 500 mol m-3Inlet velocity 2.3 m s-1Volumetric flow rate varies
11. Results – Cell potentialIncreased overpotential with moving mesh.Difference increases with time20 mA cm-130 mA cm-1
12. Results – Cell resistanceChange in resistance due to :Electrolyte concentrationChange in electrolyte domain thicknessCell resistance change due to deposits is negligible
13. Results – Electrolyte flow rateSignificant variation in volumetric flowPumping or control implicationsAlternative is variation in electrolyte velocityImpact on mass transport
14. ConclusionsSuccessfully modelled the change in deposit geometry using a moving meshLeads to a significant decrease in cell resistanceLargely due to electrolyte resistanceIncrease in charging cell potentialSignificant variation in volumetric flow rateDirect applications for other metal deposition flow batteriesZn/BrZn/airZn/Ce, etc.