Static Mixers for Enhanced Reactant Distribution in Redox Flow Cells Nicholas Gurieff, Declan Finn Keogh, Chris Menictas, Victoria Timchenko School of Mechanical and Manufacturing Engineering, UNSW Sydney, NSW, Australia ICESI 2020, 1-4 March, Sydney, Australia
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Polarisation Problem
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 Current limited by reactant availability
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 Concentration overpotential a function
 Mass transfer requirements balanced against parasitic pump work  Mechanical cell architecture
Potential
of flow rate and concentration
Concentration Overpotential
innovations can help Time
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Multiphysics Modelling Modelling of electrochemistry and fluid dynamics Validated models with high performance computing Single cell geometries with flowthrough porous felt electrodes
Static Mixers MIXER
MEMBRANE
FELT
POSITIVE HALF-CELL NEGATIVE HALF-CELL CURRENT COLLECTOR
ENDPLATE
Address internal concentration gradients to improve electrolyte and electrode utilisation
1-ELEMENT
2-ELEMENTS
V3+ Concentration Minimum (mol/m^3)
Number of Elements 50 40 30 20 10 0
3-ELEMENTS
0
1
2
Mixer Elements
Gurieff, N. et al. (2019). Enhanced Reactant Distribution in Redox Flow Cells. Molecules, 24(21), 3877.
3
Half-cell modelling for sensitivity studies
POSITION
V3+ Concentration Minimum (mol/m^3)
Mixer Position 50 40 30 20 10 0 Ref
1/3 Position
1/2
2/3
Helical Mixers Shift from blade to helical style mixers to reduce parasitic pressure drop at higher flow rate
Blade vs Helical Mixers Pressure (Pa) 150
160
170
180
190
200
Uniform
Minimum V3+ Concentration
Blade
Differential Pressure
Helical
0
10
20
30
Concentration (mol m^-3)
40
50
Distribution at ¼ Depth Concentration profiles for unmixed and mixed cells mol m-3 UNIFORM
BLADE
HELICAL
Distribution at Outlet Concentration profiles for unmixed and mixed cells mol m-3
Mixer Assemblies Blade and helical mixer elements assembled for manufacturing and use in laboratory cells
Additive Manufacturing Blade and helical mixer assemblies 3D printed in rigid and flexible materials
Experiment Preparation Mixer assembly prepared for experimental testing in digitally manufactured lab cell
Efficiency and Capacity Mixers >1% voltage improvement Wedge cell 1% voltage improvement resulted in 15% energy efficiency improvement at 120 mA cm-2 and usable capacity increase
Voltage (V)
2.0 1.5 1.0 0.5 0
1 Time (hours)
2
3
4 Flat
5 Wedge
Gurieff et al. (2019). Performance enhancing stack geometry concepts. In The International Flow Battery Forum. Lyon, France.
Summary Decrease pressure differential Reduce concentration polarisation Improve energy efficiency Increase usable capacity Enhance value
Nicholas Gurieff UNSW Sydney, Australia n.gurieff@unsw.edu.au
Acknowledgements This research is supported by an Australian Government Research Training Program Scholarship