Cabrera Cano, Enrique May 2014 Assignment Project M.Sc. Energy Systems, FH Aachen

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Introduction

Objectives

Theoretical Background

Experimental Settings ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Results ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Conclusions

Appendix

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Membrane electrode assembly (MEA)

Gaskets and End plates

Bipolar Plates

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1. Bendzulla, Anne: Von der Komponente zum Stack: Entwicklung und Auslegung von HT-PEFC-Stacks der 5 kW-Klassen; Forschungszentrum Jülich GmbH Zentralbibliothek (2010); ISBN: 978-3-89336-634-7

Distribution of gases,

Prevention of gas leakage,

Separation of the fuel and oxygen/air,

Collection of electrical current produced

Chemical, mechanical and thermal stability

4 6/11/2014 7:27 PM

1. Bendzulla, Anne: Von der Komponente zum Stack: Entwicklung und Auslegung von HT-PEFC-Stacks der 5 kW-Klassen; Forschungszentrum Jülich GmbH Zentralbibliothek (2010); ISBN: 978-3-89336-634-7

5

Nr. Requirement Target Unit

1 Electrical resistivity ˂ 0.01 Ω cm

2 Corrosion resistance ˂ 16 µA/cm²

3 Thermal conductivity ˃ 10 W/mK

4 Compression strength 42 bar

5 Density (Weight/Volume) ˂ 5 g/cm3

6 Costs ˂ 0.0045 US$/cm²

6/11/2014 7:27 PM

1. Bendzulla, Anne: Von der Komponente zum Stack: Entwicklung und Auslegung von HT-PEFC-Stacks der 5 kW-Klassen; Forschungszentrum Jülich GmbH Zentralbibliothek (2010); ISBN: 978-3-89336-634-7

2. Methta, Vial; Smith, Joyce: Review and analysis of PEM fuel cell design and manufacturing; Journal of Power Sources 114 (2003) 32-53

Introduction

Objectives

Theoretical Background

Experimental Settings ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Results ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Conclusions

Appendix

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1. Analysis of Electrical properties of three different Bipolar plate materials

◦ 70%, 75%, 80% weight percentage of graphite, rest of polypropylene

2. Influence of the manufacturing process on the measured material

3. Influence of applied pressure on the total resistance

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Introduction

Objectives

Theoretical Background

Experimental Settings ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Results ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Conclusions

Appendix

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Resistance depends on:

I. The type of material

II. The length

III. The thickness

IV. The temperature

For a given material at constant temperature

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3. Mc Tavish, J.P.: Foundation Electrical Engineering; Prentice Hall International (UK) Ltd. (1996); ISBN: 0-13-309931-8

𝑹 ∼𝒍

𝑨

Constant of resistivity (ρ) takes into account the type of material:

𝑹 = 𝝆𝒍

𝑨

Conductivity (σ ) reciprocal of resistivity

𝑮 =𝟏

𝑹[𝜴]= 𝑺 𝑮 = 𝝈

𝑨

𝒍

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3. Mc Tavish, J.P.: Foundation Electrical Engineering; Prentice Hall International (UK) Ltd. (1996); ISBN: 0-13-309931-8 4. Maxfield, Clive: Electrical Engineering, Elsevier Inc.,United States of America (2008); ISBN: 978-1-85617-528-9

Pure Graphite 6 ◦ Electrical conductivity

◦ Thermal conductivity

◦ sophisticated & costly processing

◦ unsuitable for reasons of stability

1. Electro graphite 2. Carbon – carbon composite 3. Sheet Metal 4. Flexible graphite foil 5. Graphite polymer composite 6

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Proportion between graphite and polymer 1: ◦ 75% - 80% of graphite

◦ Balance: electrical conductivity and mechanical stability

1. Bendzulla, Anne: Von der Komponente zum Stack: Entwicklung und Auslegung von HT-PEFC-Stacks der 5 kW-Klassen; Forschungszentrum Jülich GmbH Zentralbibliothek (2010); ISBN: 978-3-89336-634-7

6. Middelman, E.;Kout, W.; Vogelaar, B.;Lenssen, J.; de Waal, E.: Bipolar plates for PEM fuel cells; Journal of Power Sources 118 (2003) 44 – 46

Compression molding

Injection molding

Two-component injection molding

Preform molding

Advantages ◦ Automated production,

◦ Short cycle time and

◦ Accurate size

Disadvantages

◦ Excessive mold wear

◦ Limited size of thickness ratio and

◦ Could affect conductivity

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6. Middelman, E.;Kout, W.; Vogelaar, B.;Lenssen, J.; de Waal, E.: Bipolar plates for PEM fuel cells; Journal of Power Sources 118 (2003) 44 – 46

Bulk resistance ◦ Ohmic resistance of the

component or material

Contact resistance ◦ Resistance at the interface of

two different surfaces in contact with each other

Total resistance: ◦ Contact resistance + bulk

resistance of the individual components

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5. Prakash, C. Ghosh; Dey Tapobrata; Singdeo, Debanand: Contact resistance between bipolar plate and gas diffusion layer in high temperature polymer electrolyte fuel cells; International Journal of Hydrogen Energy 39 (2014) 987-995

𝑹𝐓𝐎𝐓 = 𝑹𝟏/𝟐 + 𝑹𝟐/𝟑 + 𝑹𝟑 + 𝑹𝟐 + 𝑹𝟏

Introduction

Objectives

Theoretical Background

Experimental Settings ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Results ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Conclusions

Appendix

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25mm

38mm

2.1mm

Thirty samples made from three different materials each in equal number

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Two different configurations were designed: • in-plane and

• through-plane

Two different orientations: 1. in the injection direction

2. perpendicular to the injection direction

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Parameter Value Unit

Current flow area of

injection direction

orientation

0.525

𝑐𝑚2

Current flow area of

perpendicular to injection

direction orientation

0.798

𝑐𝑚2

Electrical Current 0.85 A

Sample

Multimiter

Multimiter

Power supply

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V R

I

ΔX=2cm

I

a

b

c

I

1 2 3

a = 6.25 mm

b= 12.5 mm

c= 18.75 mm

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ΔX=2cm

I

a

b

c

I

4 5 6

a = 9.50 mm

b= 19.00 mm

c= 28.50 mm

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Voltage measurement

Current measurement

Beam

Weight

Power supply

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Pressure distribution analysis

Parameters

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Parameter Value Unit

Reference measurement

area (45mm*45mm)

20.25 𝑐𝑚2

Sample measurement area

(38mm*25mm)

9.50 𝑐𝑚2

Current 1.00 A

Determination of total force ‘F2’ and pressure from a 5.13kg mass

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𝐹2 = 𝐹0 + 𝑖 ∗ 𝑚 ∗ 𝑔

𝐹2 = 410𝑁 + 32 ∗ 5,13𝑘𝑔 ∗9.81𝑚

𝑠2= 2,020.41𝑁

𝑃 =𝐹

𝐴=

2,020.41𝑁

0.00095𝑚2= 2126747.37𝑃𝑎 = 21.27𝑏𝑎𝑟

𝑀1 = 𝑀2

𝐹1 ∗ 𝑥 + 𝑦 = 𝐹2 ∗ 𝑥

𝑖 =𝐹2

𝐹1=

𝑥+𝑦

𝑥=

484𝑚𝑚

15𝑚𝑚= 32.26

Ratio of the output force to the input force (i)

𝑅𝑇𝑂𝑇 = 𝑅𝐶𝑃/𝑆𝐹 + 𝑅𝑆𝐹 + 𝑅𝑆𝐹/𝐺𝐷𝐿 + 𝑅𝐺𝐷𝐿 +𝑅𝐺𝐷𝐿/𝑆 +𝑅𝑆 +𝑅𝐺𝐷𝐿/𝑆 +𝑅𝐺𝐷𝐿 +𝑅𝑆𝐹/𝐺𝐷𝐿 +𝑅𝑆𝐹 +𝑅𝐶𝑃/𝑆𝐹

𝑅𝑇𝑂𝑇 = 2𝑅𝐶𝑃/𝑆𝐹 + 2𝑅𝑆𝐹 + 2𝑅𝑆𝐹/𝐺𝐷𝐿 + 2𝑅𝐺𝐷𝐿 +2𝑅𝐺𝐷𝐿/𝑆 +𝑅𝑆

As 𝑅𝐺𝐷𝐿 ≈ 0, it is negligible and hence,

𝑅𝑇𝑂𝑇 = 2𝑅𝐶𝑃/𝑆𝐹 + 2𝑅𝑆𝐹 + 2𝑅𝑆𝐹/𝐺𝐷𝐿 +2𝑅𝐺𝐷𝐿/𝑆 +𝑅𝑆

The following total resistance was determined:

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For the reference measurement, the total resistance was determined:

𝑅𝑇𝑂𝑇,𝑅𝑒𝑓. = 𝑅𝐶𝑃/𝑆𝐹 + 𝑅𝑆𝐹 + 𝑅𝑆𝐹/𝐺𝐷𝐿 + 𝑅𝐺𝐷𝐿 +𝑅𝑆𝐹/𝐺𝐷𝐿 +𝑅𝑆𝐹 +𝑅𝐶𝑃/𝑆𝐹

𝑅𝑇𝑂𝑇,𝑅𝑒𝑓. = 2𝑅𝐶𝑃/𝑆𝐹 + 2𝑅𝑆𝐹 + 2𝑅𝑆𝐹/𝐺𝐷𝐿 + 𝑅𝐺𝐷𝐿

As 𝑅𝐺𝐷𝐿 ≈ 0, it is negligible and hence,

𝑅𝑇𝑂𝑇,𝑅𝑒𝑓. = 2𝑅𝐶𝑃/𝑆𝐹 + 2𝑅𝑆𝐹 + 2𝑅𝑆𝐹/𝐺𝐷𝐿

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𝑅𝑇𝑂𝑇 − 𝑅𝑇𝑂𝑇,𝑅𝑒𝑓. = 2𝑅𝐶𝑃/𝑆𝐹 + 2𝑅𝑆𝐹 + 2𝑅𝑆𝐹/𝐺𝐷𝐿 +2𝑅𝐺𝐷𝐿/𝑆 +𝑅𝑆 − (2𝑅𝐶𝑃/𝑆𝐹 + 2𝑅𝑆𝐹 + 2𝑅𝑆𝐹/𝐺𝐷𝐿)

𝑅𝑇𝑂𝑇 − 𝑅𝑇𝑂𝑇,𝑅𝑒𝑓. = 2𝑅𝐺𝐷𝐿/𝑆 + 𝑅𝑆

Sample resistance:

Introduction

Objectives

Theoretical Background

Experimental Settings ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Results ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Conclusions

Appendix

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0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

30% PP 25% PP 20% PP

In p

lan

e R

esis

tivi

ty /

Ωcm

Material

Perpendicular to injectiondirection

Injection Direction

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0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

30% PP 25% PP 20% PP

In p

lan

e C

on

du

ctiv

ity

/ S/

cm

Material

Perpendicular to injection direction

Injection Direction

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Introduction

Objectives

Theoretical Background

Experimental Settings ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Results ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Conclusions

Appendix

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0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

70% graphite-30%PP 75% graphite-25%PP 80% graphite-20%PP

Thro

ugh

-pla

ne

Re

sist

ivit

y /

Ωcm

Materials

4,32

6,44

13,07

21,27

30,02

38,26

[bar]

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0.0000

0.0500

0.1000

0.1500

0.2000

0.2500

0.3000

0.3500

0.4000

70% graphite-30%PP 75% graphite-25%PP 80% graphite-20%PP

Thro

ugh

-pla

ne

Co

nd

uct

ivit

y /

S/cm

Materials

4,32

6,44

13,07

21,27

30,02

38,26

[bar]

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Introduction

Objectives

Theoretical Background

Experimental Settings ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Results ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Conclusions

Appendix

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1. A change from 70% graphite to 80% graphite increases all conductivities measured by a factor of 7 approximately

◦ The mechanical properties were not analyzed in this measurement

2. The injection direction orientation shows 18 to 29% higher electrical conductivity than the perpendicular to injection direction orientation

3. An increase of pressure from 4.32 bar to 38.26 bar shows an improvement on the total conductivity by a factor of 2.2 – 2.5

◦ Due to the reduction of contact resistance

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33 6/11/2014 7:27 PM

1. Bendzulla, Anne: Von der Komponente zum Stack: Entwicklung und Auslegung von HT-PEFC-Stacks der 5 kW-Klassen; Forschungszentrum Jülich GmbH Zentralbibliothek (2010); ISBN: 978-3-89336-634-7

2. Methta, Vial; Smith, Joyce: Review and analysis of PEM fuel cell design and manufacturing; Journal of Power Sources 114 (2003) 32-53

3. Mc Tavish, J.P.: Foundation Electrical Engineering; Prentice Hall International (UK) Ltd. (1996); ISBN: 0-13-309931-8

6/11/2014 7:27 PM 34

35 6/11/2014 7:27 PM

4. Maxfield, Clive: Electrical Engineering, Elsevier Inc.,United States of America (2008); ISBN: 978-1-85617-528-9

5. Prakash, C. Ghosh; Dey Tapobrata; Singdeo, Debanand: Contact resistance between bipolar plate and gas diffusion layer in high temperature polymer electrolyte fuel cells; International Journal of Hydrogen Energy 39 (2014) 987-995

6. Middelman, E.;Kout, W.; Vogelaar, B.;Lenssen, J.; de Waal, E.: Bipolar plates for PEM fuel cells; Journal of Power Sources 118 (2003) 44 – 46

Introduction

Objectives

Theoretical Background

Experimental Settings ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Results ◦ In-plane resistivity measurement

◦ Through-plane resistivity measurement

Conclusions

Appendix

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Nr. Name Weights (kg)

Total Weight

(kg)

Force

“F2” (N)

Pressure Reference

Measurement (bar)

Pressure at

sample surface

(bar)

1. 0 0 0 410.00 2.02 4.32

2. 1 0.643 0.643 611.85 3.02 6.44

3. 2 2.648 2.648 1241.26 6.13 13.07

4. 4 5.13 5.13 2020.41 9.98 21.27

5. 4+2 5.13+2.648 7.778 2851.67 14.08 30.02

6. 4+3 5.13+5.143 10.273 3634.90 17.95 38.26

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Injection Direction Perpendicular to injection direction

Material / Data

Resistivity

(Ωcm)

St.

Dev.

Conductivi

ty (S/cm)

St.

Dev.

Resistivit

y (Ωcm)

St.

Dev.

Conductivi

ty (S/cm)

St.

Dev.

70% graphite-

30%PP 0.901 0.121 1.134 0.188 1.168 0.176 0.880 0.162

75% graphite-

25%PP 0.299 0.040 3.404 0.481 0.385 0.052 2.647 0.388

80% graphite-

20%PP 0.130 0.013 7.742 0.751 0.155 0.022 6.579 0.974

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Material 70% graphite-30%PP 75% graphite-25%PP 80% graphite-20%PP

Pressure

(Bar)/Data

Resistivity

(Ωcm) St. Dev.

Resistivity

(Ωcm) St. Dev.

Resistivity

(Ωcm) St. Dev.

4.32 55.18 18.73 30.53 4.64 8.3623 1.3562

6.44 48.10 16.72 26.50 4.27 7.1594 1.0763

13.07 36.21 13.05 19.13 3.10 5.1281 0.6734

21.27 29.93 10.48 15.01 2.21 4.1027 0.5338

30.02 26.91 9.30 13.14 1.84 3.5917 0.4168

38.26 25.04 8.71 12.08 1.65 3.3262 0.3812

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Material 70% graphite-30%PP 75% graphite-25%PP 80% graphite-20%PP

Pressure

(Bar)/Data Conductivity (S/cm)

St.

Dev.

Conductivity

(S/cm) St. Dev.

Conductivity

(S/cm)

St.

Dev.

4.32 0.0194 0.0042 0.0335 0.0053 0.1229 0.0217

6.44 0.0224 0.0050 0.0387 0.0063 0.1429 0.0228

13.07 0.0299 0.0070 0.0536 0.0084 0.1983 0.0265

21.27 0.0360 0.0084 0.0680 0.0096 0.2480 0.0347

30.02 0.0400 0.0092 0.0775 0.0104 0.2826 0.0383

38.26 0.0430 0.0098 0.0842 0.0111 0.3045 0.0357

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