modeling the behavior of a polymer electrolyte ... - comsol
TRANSCRIPT
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MODELING THE BEHAVIOR OF A POLYMER
ELECTROLYTE MEMBRANE WITHIN A FUEL CELL
USING COMSOL
PRESENTER: STEFAN BEHARRY
SUPERVISOR: DR. DAVINDER PAL SHARMA
(PHYSICS DEPARTMENT, UWI)
Excerpt from the Proceedings of the 2012 COMSOL Conference in Boston
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OBJECTIVES
To create a model of an acid-base blended Poly(1-
vinylimidazole) based membrane using COMSOL
Multiphysics 4.2a for a high-temperature proton
exchange membrane fuel cell (PEMFC).
Investigation of the electron and proton exchange with
respect to the velocity and electrolyte conductivity
phenomenon within the fuel cell using the developed
model has been done.
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PROTON EXCHANGE
MEMBRANE FUEL CELL
(PEMFC)
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THE PROTON EXCHANGE MEMBRANE FUEL
CELL (PEMFC)
Fig. 2 – Diagram of PEM Fuel Cell
At anode: 2H2 => 4H+ + 4e-
At cathode:
O2 + 4H+ + 4e- => 2H2O
Net reaction:
2H2 + O2 => 2H2O
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THE PROTON EXCHANGE MEMBRANE
FUEL CELL (PEMFC) CONT’D
This reaction only produces about 0.7 volts
in a single fuel cell.
In order to increase the voltage level, a fuel-
cell stack is made using bipolar plates.
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THE PEMFC MEMBRANE
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THE PEMFC MEMBRANE
The membrane of the PEMFC is one of the most fundamental parts of the cell as its properties have great impact on the cell’s output capability.
Most PEMFCs use hydrated membranes.
Membrane materials which could be used at temperatures higher than 80oC now had to be developed.
One such material is the Poly(1-vinylimidazole) (PVIm) polymer which was developed by the Fuel Cell Materials Research Laboratory in the Physics Department at UWI.
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POLY(1-VINYLIMIDAZOLE) COMPOUND
Fig. 3 – Diagram of chemical structure of PVIm
compound
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POLY(1-VINYLIMIDAZOLE) MEMBRANE
This polymer, when combined with triflic acid forms an acid-base ternary composite blend membrane.
It also utilizes PVDF-HFP as a polymer for its good mechanical properties which provide a stable hydrophobic backbone.
Includes nano-tubular titania to improve conductivity and morphology.
Does not require hydration.
Can operate at temperatures much higher than 80oC without degradation.
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EXPERIMENTAL DATA VALUES
The experimental data used to create the model
was obtained from experimentations completed by
research students at the Fuel Cell Materials
Research Laboratory at UWI.
The following table shows a sample of the various
parameter readings obtained from experimental
data performed on the membrane.
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Table showing the parameter values used in order to model the ternary
membrane.
Membrane thickness = 0.0542 cm
Table 3 – Parameters used in modeling
MATERIAL ELECTROLYTE
CONDUCTIVITY
(S/m)
DENSITY
(kg/m3)
DYNAMIC
VISCOUSITY
(Pa*s)
THERMAL
CONDUCTIVITY
(W/mK)
HEAT
CAPACITY
(J/kgK)
SPECIFIC
HEAT
RATIO
Graphite
sheet
3.3 x 102 - 0 25 710 1
Carbon fibre 1.25 x 103 1.80 0 1.2 4.77 1
Platinum 9.43 x 106 - 0 - - 1
Hydrogen
and Oxygen
5.5 x 10-6 - - - - -
PVIm 1.43 x 10-4 1.036 0.146 2.53213 x 105 3.7982 x 103 1
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METHOD OF MODELING FUEL CELL WITHIN COMSOL
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MODELING STEPS OF FUEL CELL USING COMSOL
Fig.5 Shows the modelling steps for the PEMFC
PHYSICS
PHYSICS
INTERFACES
MODEL WIZARD
AC/DC ACOUSTICS CHEMICAL
SPECIES
TRANSPORT
ELECTRO-
CHEMISTRY
FLUID
FLOW
HEAT
TRANSFER MATHEMATICS
STRUCTURAL
MECHANICS
TRANSPORT OF
CONCENTRATED
SPECIES
SECONDARY
CURRENT
DISTRIBUTION
POROUS
MEDIA AND
SUBSURFACE
FLOW
FREE AND
POROUS
MEDIA FLOW
BUILDING MODEL DEFINING DOMAINS
MESH APPLIED
TO MODEL
MATERIAL
RESULTS STUDY
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RESULTS
Fig.6: General model of the fuel cell.
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RESULTS (CONT’D)
Fig.7: Model with mesh
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RESULTS (CONT’D)
Fig. 8: Shows the velocity within the PEMFC (free and
porous media flow)
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RESULTS (CONT’D)
Fig.9:Shows the electrolyte potential in the PVI membrane (for
Secondary current distribution)
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RESULTS (CONT’D)
Fig.10: Magnified view of the electrolyte membrane
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CONCLUSION
Using data obtained from the fuel cell research laboratory a model of the ternary acid based PVIm membrane was developed within the PEM fuel cell. From this model, the exchange of the electrons and protons with respect to velocity was observed as well as the electrolyte potential of the membrane. When compared to the traditional membrane (0.7V) the PVIm membrane (0.95V) can be deemed to be successful.
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ACKNOWLEDGEMENTS
GOD
Dr. Davinder Pal Sharma - Supervisor
Ms. Kerrilee Stewart – Fuel Cell Lab, UWI
Mr. Jamin Atkins - VLSI Lab
Mr. Mats Gustafsson - COMSOL
Mr. Miguel Andrews - UWI, postgraduate
student