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Li Xiaojin (Associate Professor)
Dalian Institute of Chemical Physics, Chinese Academy of
Science
Shanghai 26th, October, 2010
COMSOL Multiphysics application in modeling PEMFC transients
1
2010 Comsol Conference Presented at the COMSOL Conference 2010 China
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Main content
Principle of PEMFC and transient characteristics
Study on PEMFC transient characteristics
Develop the PEMFC transient model
Air stoichiometry change on PEMFC transient
Water transport on PEMFC transient
Modeling high temperature PEMFC
Conclusion 2
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Principle of PEMFC & application
PEMFC
H2 → 2H+ + 2e-
1/2 O2 + 2H+ +2e- → H2O Cathode:
Anode:
High efficiency
Environment friendly
High power density
Fast startup
Advantages
3
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Bottleneck of FC technology
Commercialization
System stability & reliability
System cost
Environment adaptability
Transient characteristics
4
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Water transport in FC
FC water transport principle Experiment observation
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Model assumptions 1. The gravity effect is neglected ; 2. The gas mixture is an incompressible ideal gas; 3. The flow in the gas channel is laminar; 4. The diffusion layer, catalyst layer and membrane are isotropic
and homogeneous, and the membrane is impermeable to gas species;
5. The contact resistance between any two parts in the fuel cell is neglected;
6. The dissolved reactive gas in electrolyte phase of catalyst layer is neglected;
7. It is considered that water exits in the gas phase at the electrodes as well as in the liquid phase within the membrane. In channels, existence of liquid water is in a small volume fraction and in finely dispersed droplets so that it dose not affect the gas flow.
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Main content
Principle of PEMFC and transient characteristics
Study on PEMFC transient characteristics
Develop the PEMFC transient model
Air stoichiometry change on PEMFC transient
Water transport on PEMFC transient
Modeling high temperature PEMFC
Conclusion 7
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Procedures
Assumptions Geometry
Parameters Governing Equation
Boundary Conditions
Solver
Result Analysis
COMSOL Multiphysics
Postprocess
8
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Model equations mu S
eff
i v g i iD C u C S
Continuity:
Momentum:
Species:
Water in membrane:
Energy:
Electron:
Proton:
effe e eS
eff
m m mS
( ) 0dw w
n ID c
F
2
1uuu p S
T( ) Sp fc u T k T
9
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Source term for model equations
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Model geometry & mesh
x
y
1 2 7 6 4
3 5
Model geometry:1anode flow channel, 2anode gas diffusion layer, 3anode catalyst layer, 4membrane, 5 Cathode catalyst layer, 6 Cathode gas diffusion layer,
7 Cathode flow channel
Comsol Multiphysics 3.5 11
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Main content
Principle of PEMFC and transient characteristics
Study on PEMFC transient characteristics
Develop the PEMFC transient model
Air stoichiometry change on PEMFC transient
Water transport on PEMFC transient
Modeling high temperature PEMFC
Conclusion 12
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PEMFC transient model
Model geometry:1anode flow channel, 2anode gas diffusion layer, 3membrane, 4Cathode gas diffusion layer, 5 Cathode
flow channel
mSut
Mass conservation
Momentum conservation
uSpuut
u
11
Species conservation
kk
eff
kkk ScDcut
c
cell act ohm concV E
Cell potential:
13
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0 2 4 6 8 10
0.60
0.65
0.70
0.75
0.80
0.85
V
olta
ge
/V
Time/s
stoichiometry 1.3 to 2.5 model
stoichiometry 1.3 to 2.5 experiment
Comparison between model and experimental cell voltage evolution
Q. Shen, M. Hou, et. al J. Power Sources. 2008, 179: 292–296
Model validation
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Air stoichiometry change on PEMFC transient 阴极计量比的变化速率
0 1 2 3 4 5 61.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
A1 stoichiometry A2 stoichiometry A3(base case) stoichiometry averge current density
time, s
Cat
hode
sto
ichi
omet
ry
0
1000
2000
3000
4000
5000
Averge current density, A
/m2
0 1 2 3 4 5 60.62
0.64
0.66
0.68
0.70
0.72
0.74
0.76
0.78
0.80
0.82
0.84
Ce
ll P
ote
ntia
l, V
time, s
A1 A2 A3
0.64V
0.65V
0.66V
Qu Shuguo, Li Xiaojin, etc., J Power Sources 185 (2008), 302-310 15
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Reactant starvation under different conditions
A1 A2 A3
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Main content
Principle of PEMFC and transient characteristics
Study on PEMFC transient characteristics
Develop the PEMFC transient model
Air stoichiometry change on PEMFC transient
Water transport on PEMFC transient
Modeling high temperature PEMFC
Conclusion 17
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Experiment study on water dynamic transport
Aim:Study water transport in fuel cell under different humidity on cell potential and as model validation
Conditions: Current:step from 0.05 to 2.5A Air flow:parabolic pattern 22-110ml/min Hydrogen flow:fixed Humidity:100% 62%
工作站
空气入口
针型调节阀
氢气入口
空气增湿
罐 氢气增湿
罐
5cm2燃料电池
针型调节阀
空气出口 氢气出口
电子负载
开关阀
稳压阀
开关阀
稳压阀
压力表
流量计
流量计
流量计
分水器
分水器
压力表
流量计
程序控制
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Average current density & cathode inlet velocity change
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Experiment results
For same relative humidity, the lower the change rate, the greater the cell potential undershoots.
For different relative humidity, the magnitude of cell potential undershoots increased as the relative humidity decreased
The steady state cell potential also decreased as the relative humidity was decreasing
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Model geometry
Model geometry:1anode flow channel, 2anode gas diffusion layer, 3membrane, 4Cathode gas diffusion layer, 5 Cathode
flow channel
Continuity
Momentum
Species
Water in
membrane
Electrons
Protons
eff eff
i i v g i iC D C u C St
eff
e e eS
eff
m m mS
( ) 0w dm w w
c n ID c
t F
uSpuut
u
11
g g g mu St
Comsol Multiphysics 3.5求解 21
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Model validation
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Water content change at membrane/electrode interface
RH=100% water content at membrane/electrode interface
RH=62%water content at membrane/electrode interface
Qu Shuguo, Li Xiaojin, etc.,J Power Sources 195 (2010), 6629-6636 23
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Main content Principle of PEMFC and transient characteristics
Study on PEMFC transient characteristics
Develop the PEMFC transient model
Air stoichiometry change on PEMFC transient
Water transport on PEMFC transient
Modeling high temperature PEMFC
Conclusion 24
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x
y
1 2 7 6 4
3 5
Model geometry:1anode flow channel, 2anode gas diffusion layer, 3anode catalyst layer, 4membrane, 5
Cathode catalyst layer, 6 Cathode gas diffusion layer, 7 Cathode flow
channel
mu S
eff
i v g i iD C u C S
Continuity:
Momentum:
Species:
Water in membrane:
Energy:
Electron:
Proton:
effe e eS
eff
m m mS
( ) 0dw w
n ID c
F
2
1uuu p S
T( ) Sp fc u T k T
2-D nonisothermal HT-PEMFC model
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Species distribution in HT-PEMFC
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Temperature distribution in HT-PEMFC
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Potential distribution in electrode and membrane
Cathode electrode potential
Anode electrode potential Membrane potential
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Main content Principle of PEMFC and transient characteristics
Study on PEMFC transient characteristics
Develop the PEMFC transient model
Air stoichiometry change on PEMFC transient
Water transport on PEMFC transient
Modeling high temperature PEMFC
Conclusion 29
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Conclusion
Modeled fuel cell transient characteristics using COMSOL Multiphysics and the model result validated by experiment; Carried out fuel cell dynamic simulation using Comsol and closer to real operation conditions; Studied the effect of reactant transport and membrane water transport on the PEMFC cell potential under transient air flow and load change using COMSOL Multiphysics; Modeled the high temperature PEMFC based on Nafion/SiO2 composite membrane using COMSOL Multiphysics .
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Thank You!