1. Effects of Electrolyte Flow Rate, Flow
Channel Thickness, and Current Density
on the Regenerative Hydrogen-Vanadium
Flow Battery
By:
Christopher Graves
Master’s Candidate
580: Technical Review Presentation
2. Motivation
• The shift to renewable sources of power
requires a power storage method to store the
power that was generated during off peak
hours.
• Redox flow batteries have emerged as a
possible candidate for full scale
implementation.
• The all vanadium flow battery appears to be
the device closest to grid scale implementation
4. All Vanadium Flow Battery
• Vanadium has multiple oxidations states.
– 5 oxidation states
• Since vanadium is the only redox elements
in the system, cross contamination is not as
large an issue as in multiple electrolyte
batteries.
5. All Vanadium Flow Battery
• A major capital cost of the All Vanadium
Flow Battery is the cost of the vanadium.
9. Regenerative Hydrogen
Vanadium Flow Battery
• The Hydrogen Vanadium benefits:
– Decreased dependency on vanadium
• The Hydrogen Vanadium Battery retains all
of the benefits of the all Vanadium battery
10. Purpose
• Analyze 3 variables for effects on capital
cost of the Regenerative Hydrogen
Vanadium Flow Battery
– Electrolyte (vanadium) flow rate
– Flow Channel thickness
– Current density
11. Method
• Three variables were selected to be varied
in a simulation.
• The project was presented as the capstone
project for the senior class.
• The students used a previously developed
model to determine the device parameters
and device cost.
• The sizing method was determined by
Moore et al.
12. Method
• The technology was costed using tables
and methods laid out in Dr. Gael Ulrich’s
textbook Chemical Engineering: Process
Design and Economics A Practical Guide
and information provided by Moore et al.
13. Assumptions
• The pressure drop due to the manifold spreading
the vanadium electrolyte into the cells would be
equal to the gains when the flows were rejoined.
• The cells were modeled as fully developed
linear flow infinite plates.
• The pressure drop in the different cells is
assumed the same, so the pressure drop of the
liquid flow through one cell is equal to the total
pressure drop.
14. Assumptions
• The costs and additional effects of enlarging the
flow channel are neglected.
• It is assumed the current density is independent of the
channel thickness.
• The flow rate of hydrogen is the flow rate required to
keep the hydrogen gas at 1 atm.
• Hydrogen is the dominant gas in the gas flow stream.
The presence of any other substance is negligible.
15. Electrolyte Flow Rate
• The flow rate of the vanadium electrolyte
has an effect on the overall efficiency of the
battery.
• In order to generate any power, and
consistently achieve positive voltage, a
minimum flow rate is required.
• The analyzed flow rates were 20 and 50
times the minimum theoretical flow rate.
16. Efficiency VS Flow Rate and
Current Density
1 1.5 2 2.5 3 3.5 4 4.5 5
x 10
4
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
FlowRateof Vanadium(L/s)
Efficiency(%)
100mA/cm2
200mA/cm2
300mA/cm2
400mA/cm2
18. Effects of Electrolyte Flow Rate
on Capital Cost
• The observed effects of the flow rate on the
price of the battery were minimal.
19. Flow Channel Thickness
• Traditionally the cost of pumps are a small
percentage of the total device cost.
• The analyzed flow channel thickness were:
0.5 cm, 1 cm, 1.5 cm, and 2 cm.
21. Effects of Flow Channel
Thickness on Capital Cost
• A small effect of the flow channel was
observed.
• The thicker flow channels resulted in the
smallest cost, however, the returns
diminished after the 1 cm thickness.
22. Current Density
• The current density is assumed to be
constant through all the stacks
• The current density is a parameter that
determines many other important
parameters such as flow rate and the total
number of required cells
23. Current Density
• An efficiency is associated with the 4
current densities that were analyzed
• The 4 current densities analyzed were: 100
mA/cm², 200 mA/cm², 300 mA/cm², and
400 mA/cm².
24. Current Density
Table 1. The efficiency of the due to electrical resistances at different
current densities.
Current Density
(mA/cm2
) Efficiency
100 93.54%
200 87.16%
300 80.77%
400 74.40%
27. Effect of Current Density on
Capital Cost
• The optimal current density is a function of
the power capacity of the battery
• The current density has the greatest effect
on the over cost of the device
28. Conclusions
• Flow rates have a small effect on the overall
efficiency.
• The flow rate has a small overall impact on
the overall cost of the device.
29. Conclusions
• The channel thickness had the least impact on the
overall device cost of the three variables analyzed.
• Larger flow channels resulted in decreased overall
costs.
• Extremely thin channel thicknesses will result in
drastically increasing costs.
30. Conclusions
• The current density had the greatest effect
of the three variables.
• The ideal current density is a function of the
power capacity of the battery.
– 200 mA/cm² for a 4 MW battery, 300 mA/cm²
for a 6 MW battery.
31. Conclusions
• The ideal current density would be
dependant on the desired power of the.
• The optimal flow channel is around a
thickness of 2 cm.
• The flow rate should be at least 20 times the
minimum theoretical flow rate.
34. References
• REFERENCES
• 1 D. Aaron, Z. J. Tang, A. B. Papandrew, and T. A. Zawodzinski, 'Polarization Curve Analysis of All-
Vanadium Redox Flow Batteries', Journal of Applied Electrochemistry, 41 (2011), 1175-82.
• 2 Christie John Geankoplis, Transport Processes and Separation Process Principles. 4 edn (Bernard Goodwin,
2003), p. 1026.
• 3 'Hydraulic Diameter of Ducts and Tubes', 2014) <
http://www.engineeringtoolbox.com/hydraulic-equivalent-diameter-d_458.html> [Accessed June 4 2014].
• 4 M. Moore, J. S. Watson, T. A. Zawodzinski, M. Q. Zhang, and R. M. Counce, 'Capital Cost Sensitivity
Analysis of an All-Vanadium Redox-Flow Battery', Industrial Electrochemistry and Electrochemical Engineering
(General) - 220th Ecs Meeting, 41 (2012), 1-19.
• 5 M. Skyllas-Kazacos, M. H. Chakrabarti, S. A. Hajimolana, F. S. Mjalli, and M. Saleem, 'Progress in Flow
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• 6 A. Tang, S. M. Ting, J. Bao, and M. Skyllas-Kazacos, 'Thermal Modelling and Simulation of the All-
Vanadium Redox Flow Battery', Journal of Power Sources, 203 (2012), 165-76.
• 7 A. Z. Weber, M. M. Mench, J. P. Meyers, P. N. Ross, J. T. Gostick, and Q. H. Liu, 'Redox Flow Batteries: A
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• 8 V. Yufit, B. Hale, M. Matian, P. Mazur, and N. P. Brandon, 'Development of a Regenerative Hydrogen-
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