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

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

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

Bottleneck of FC technology

Commercialization

System stability & reliability

System cost

Environment adaptability

Transient characteristics

4

Water transport in FC

FC water transport principle Experiment observation

5

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

Procedures

Assumptions Geometry

Parameters Governing Equation

Boundary Conditions

Solver

Result Analysis

COMSOL Multiphysics

Postprocess

8

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

Source term for model equations

10

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

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

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

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

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

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

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

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

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

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！