PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf ·...

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PR TON PR TON PEM Fuel Cell Design, Engineering, PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues Modeling and Diagnostic Issues Frano Barbir Director of Fuel Cell Technology and Chief Scientist Proton Energy Systems 50 Inwood Road, Rocky Hill, CT 06067 e-mail: [email protected] www.protonenergy.com NSF Workshop on Engineering Fundamentals of Low-Temperature PEM Fuel Cells, Arlington, VA, November 14-15, 2001 Hydrogen A ir Co llector P lat e M embran e x y z Cathode catalyst G as d iffuse r Anode catalyst G as d iffuser Co llector P late G as channel Gas channel 0.5 Current Density (A/cm ) -1 0 1 Z (m m ) 0 2 4 6 8 X (cm) 0.85 0.76 0.67 0.58 0.49 0.41 0.32 0.23

Transcript of PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf ·...

Page 1: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

PR TONPR TON

PEM Fuel Cell Design, Engineering, PEM Fuel Cell Design, Engineering, Modeling and Diagnostic IssuesModeling and Diagnostic Issues

Frano BarbirDirector of Fuel Cell Technology and Chief ScientistProton Energy Systems50 Inwood Road, Rocky Hill, CT 06067e-mail: [email protected]

NSF Workshop on Engineering Fundamentals of Low-Temperature PEM Fuel Cells, Arlington, VA, November 14-15, 2001

Hydrogen

Air

Collector Plate

Membrane

x

y

z

Cathode catalyst Gas diffuser

Anode catalyst Gas diffuser

Collector Plate

Gas channel

Gas channel

0.5

Cur

rent

Den

sity

(A/c

m2 )

-10

1 Z (mm)

0

2

4

6

8

X(cm

)

0.850.760.670.580.490.410.320.23

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yes

design

fabricate

test

requirements Knowledge:materialsprocessesinteractions

material characterizationquality control

Does it work?no

Fuel cell development processFuel cell development process

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design

fabricate

test

model

Knowledge:materialsprocessesinteractions

requirements

diagnostics

Should it work?

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Role ofRole ofmodeling andmodeling anddiagnostics indiagnostics infuel cell fuel cell development development processprocess

Page 4: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

Major componentsMajor components

MEA

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Bi-polarplate

end platebus plate

bi-polar collector plates

tie rod

MembraneCatalystCatalyst supportCatalyst layerGas diffusion layerGaskets/framesFlow fieldSeparator/connectorBus plates/terminalsEnd platesClamping mechanismFluid connectionsManifoldsCooling plates/arrangementsHumidification section (optional)

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Stack design/engineering issuesStack design/engineering issues

Uniform distribution of reactants to each cellUniform distribution of reactants inside each cellUniform temperature distribution in each cellMinimal resistive losses

• good electrical contacts• selection of materials

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• Electro-osmotic drag removes water from the anode side. With thicker membranes, back diffusion of water is difficult - the anode side loses water content.0.0

0.2

0.4

0.6

0.8

1.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

HF

RES

ISTA

NC

E (o

hm c

m2)

or C

ELL

VO

LTA

GE

(V)

CURRENT DENSITY (A/cm 2 )

Fg 3, TF69,109,74,117 Ox's

IncreasingMembraneThickness

(NeatOxygenCathodes)

Cell Resistance and Performance:PEM Thickness Effects

Materials Science and Technology DivisionPEFC Overview

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electronic

cell resistancein-situ

(current interrupt)

100-150 mΩcm2

ionic40-60 mΩcm2

ex-situ20-30 mΩcm2

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Cell resistanceCell resistance

Page 8: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

F

F

gold plate

sample

backing

backing

gold plate

press

press

mV

I

Electronic resistancemeasurement(ex-situ)

R = A VI

A

(mΩcm²)

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force

resi

stan

ce

contact resistance

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Resistance is a function of clamping forceResistance is a function of clamping force

Page 10: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

electronic

ex-situcontact

bulk<1 mΩcm2

cell resistancein-situ

(current interrupt)

100-150 mΩcm2

20-30 mΩcm2

ionic40-60 mΩcm2

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Cell resistanceCell resistance

Page 11: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

force

resi

stan

ce

contact resistance example of pressure distribution

forc

e

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Resistance is a function of clamping forceResistance is a function of clamping force

Page 12: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

Stack design/engineering issuesStack design/engineering issues

Uniform distribution of reactants to each cellUniform distribution of reactants inside each cellUniform temperature distribution in each cellMinimal resistive losses

• good electrical contacts• selection of materials

PR TONPR TON

Account for thermal expansionNo crossover or overboard leaksMinimum pressure drop (reactant gases and coolant)No water accumulation pocketsDesign for manufacture/design for assembly

Page 13: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

Difference between single cell and stackDifference between single cell and stack

Flow distributionActive areaTemperature control (heating/cooling)Temperature distributionCompression/electrical contactsLeak pathsAdjacent cell interference

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Page 14: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

Modeling:Parameters and Processes (partial list)

O2H2Air

Flow-Fields - Convection -Two-Phase Flow

Gas Diffusion Layer - Gas Diffusivity - Porosity - Tortuosity - Electronic Conductivy - Gas Composition

Catalyst Layer - Ionic Conductivity - Electronic Conductivity - Gas Permeability - Reactant Solubility - Capacitance

Electro-catalyst - Exchange Current Density - Tafel Slope - Roughness Factor

Membrane - Water Content - Ionic Conductivity - Water Diffusivity - Electro-osmotic Drag - Hydraulic Permeability

Overall: Mass Balance - Heat Balance Cell Parameters

Fluid flowHeat transfer

Materials Science and Technology DivisionPEFC Overview

Page 15: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

Modeling as a design toolModeling as a design tool

A model is approximation of the real world.

Every model is wrong!

Any model is as good as the assumptions it is built upon are valid!

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Concentration at the boundary is known

Local current density is known

Isothermal conditions

Heat transfer by conduction in the gas phase in negligible

Pressure is constant

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Assumptions used in fuel cell modelingAssumptions used in fuel cell modeling

Page 17: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

1-D (y)2-D (x-y or z-y)2 2-D (x-y and z-y)3-D models (x-y-z)

One phaseTwo phase models

Hydrogen

Air

Collector Plate

Membrane

x

y

z

Cathode catalyst Gas diffuser

Anode catalyst Gas diffuser

Collector Plate

Gas channel

Gas channel

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Modeling Modeling domaindomain

DifferentDifferentmodels models

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When someone presents the modeling results no one trusts those except the presenter/person who did themodeling.

except the presenter/personwho performed the experiment.

When someone presents the experimental resultseveryone trusts those

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Truths and myths about Truths and myths about experimental and modeling workexperimental and modeling work

Page 19: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

0

500

1000

Y(X10

-3mm

)

-1

-0.5

0

0.5

1

Z (mm)

0

100

200

300

400

500

600

700

800

X (x10- 2 cm)

0.16800.14280.11760.09240.06720.0420

Oxygen mole fraction

Oxygen molar fractionconventional flow field vs. interdigitated flow field

0

0.5

1

Y(m

m)

0

0.5

1

1.5

2

Z (mm)

0

1

2

3

4

X (cm)

0.16800.12600.08400.0420

In

Page 20: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

Oxygen molar fraction contours

0.0890.0990.1100.1100.1200.130

0.1400.150

0.160

0.160

0.170

0.170

0.18

0

0.180

0.180

0.190

0.190

0.20

0

0.200

X (cm)

Y(m

m)

0 1 2 3 4 5 6 7 80

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Gaschannel

Diffuser

Catalyst

0.0680.087

0.106

0.106

0.124

0.124

0.143

0.1

0.161

0.1

0.180

0.1

Z(mm)

Y(m

m)

0 0.25 0.5 0.75 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Collector plate gaschannel

catalyst

gasdiffuser

across x-y direction

across y-z direction

Page 21: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

Current density distribution

0 . 5

Cur

rent

Den

sity

(A/c

m2 )

- 10

1 Z ( m m )

0

2

4

6

8

X( c m

)

0 . 8 50 . 7 60 . 6 70 . 5 80 . 4 90 . 4 10 . 3 20 . 2 3

Hydrogen

Air

Collector Plate

Membrane

x

y

z

Cathode catalyst Gas diffuser

Anode catalyst Gas diffuser

Collector Plate

Gas channel

Gas channel

Page 22: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

Temperature profiles across the fuel cell

85

90

Temperature

( oC)

0

2

4

6

8

x

01

2y

92.7091.2789.8588.4286.9985.5784.1482.71

Temperature (oC)

0 0.5 1 1.5 2Y(mm)

80

82

84

86

88

90

92

94

Tem

pera

ture

(Co )

Near inletMiddle of channelNear exit

Cathode gas channel Anode gas channel

Diffuser

Diffuser

Membrane

Catalyst

Page 23: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

Polarization curveCurrent interruptAC impedancePressure dropPolarization curve hysteresisComparative polarization curvesCurrent density mapping

design

fabricate

test

model

Knowledge:materialsprocessesinteractions

requirements

diagnostics

Should it work?

design

fabricate

test

model

Knowledge:materialsprocessesinteractions

requirements

diagnostics

Should it work?

PR TONPR TON

Diagnostics as a design toolDiagnostics as a design tool

Page 24: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

Current density mappingCurrent density mapping

M. Potter, S.Shaw, P. Adcock, and J. McGuirk, Loughborough University,Computer Modelling of Solid Polymer Fuel Cells, 1998

Page 25: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

S.J.C. Cleghorn, C.R. Derouin, M.S. Wilson, and S. Gottesfeld, A Printed Circuit Board Approach to Measuring Current Distribution in a Fuel Cell, J. Appl. Electrochem., 1997

Current density Current density mappingmapping

Page 26: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

Polarization curveCurrent interruptAC impedancePressure dropPolarization curve hysteresisComparative polarization curvesCurrent density mappingTemperature mappingFlow visualizationNeutron imagingPost-mortem analyses

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Diagnostics as a design toolDiagnostics as a design tool

Page 27: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

Development of new membrane materialLess expensiveRetains water or does not rely on water for proton

conductance

Development of new (less expensive) catalyst material

Effect of catalyst layer structure on fuel cell performance

Engineering of catalyst layer structure

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Fuel Cell R&D OpportunitiesFuel Cell R&D Opportunities

Page 28: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

Investigation of surface quality and interface conductivity

Better understanding of thermal effects inside the fuel cell

temperature distributionphase change

Design of fuel cell as a heat exchanger

Design of a humidifier/heat exchanger

Investigation of 2-phase flow characteristics

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Fuel Cell R&D Opportunities Fuel Cell R&D Opportunities –– cont. (2)cont. (2)

Page 29: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

Understanding of fuel cell degradation/aging/failure

Development of methods for accelerated life-testing

Development of diagnostic methods and tools

Development of standardized methods for characterization of fuel cell materials/subcomponents (pre-installation & post mortem)

Development of advanced control algorithms

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Fuel Cell R&D Opportunities Fuel Cell R&D Opportunities –– cont. (3)cont. (3)

Page 30: PEM Fuel Cell Design, Engineering, Modeling and Diagnostic ...jmfent/NSF-Barbir_Diagnostics.pdf · PR TON PEM Fuel Cell Design, Engineering, Modeling and Diagnostic Issues. Frano

AcknowledgmentAcknowledgment

My thanks to Dr. Hongtan Liu, Department ofMechanical Engineering, University of Miamifor letting me use his slides for this presentation.I also used the slides or materials from:• Mahlon Wilson, Los Alamos National Laboratory,• Simon Cleghorn, W.L.Gore&Assoc., (formerly with LANL)• Marcus Potter, University of Loughborough.

PR TONPR TON