Mechanical integration of a PEM fuel cell for a multifunctional aerospace structure

284 Pages·2017·14.63 MB·English

Loughborough University
Institutional Repository
Mechanical integration of a
PEM fuel cell for a
multifunctional aerospace
structure
ThisitemwassubmittedtoLoughboroughUniversity’sInstitutionalRepository
by the/an author.
Additional Information:
• A Doctoral Thesis. Submitted in partial fulfilment of the requirements
for the award of Doctor of Philosophy of Loughborough University.
Metadata Record: https://dspace.lboro.ac.uk/2134/21513
Publisher: (cid:13)c Wasim Bhatti
Rights: This work is made available according to the conditions of the Cre-
ative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
(CC BY-NC-ND 4.0) licence. Full details of this licence are available at:
https://creativecommons.org/licenses/by-nc-nd/4.0/
Please cite the published version.
LOUGHBOROUGH UNIVERSITY
Mechanical integration of a PEM fuel cell for

a multifunctional aerospace structure

By

Wasim Bhatti

Submitted as partial fulfilment of the requirements for the award of Doctor of Philosophy of
Loughborough University

2/6/2016

© Wasim Bhatti 2016
Acknowledgments

This research project has been a rollercoaster ride, with challenge, after challenge,
both personal and professional, a game of endurance and shear will power. The
journey could not have been completed without God almighties (Allah s.w.t) guiding
hand.
I’m a firm believer that everybody has a place in life and people come in and out of
one’s life for a reason, to guide you, to support you, to believe in you, and sometimes
not too. I would like to acknowledge and express my appreciation and gratitude for
those supervisors, academics, and people of knowledge and experience who have
worked with me, lent their ear, and contributed in any way small or large to the
success of this project.
I would like to thank the various academic institutions, industrial companies, and
research funding groups for their support over the years.
I would specially like to thank those people (and industrial companies) who
contributed to this project simply because they wanted to help a research student out
or had an interest in the research area but did not specifically gain anything in return.
I would like to thank all my friends and family for believing in me, encouraging me,
and backing me over the years.

To those who believed in me
And to those who did not
Please read on

1
Contents
Abstract ................................................................................................................... 12
Introduction ............................................................................................................ 13
Chapter 1 Literature review ................................................................................... 15
1.1 Fuel cell fundamentals ...................................................................................... 15
1.2 PEM fuel cell arrangement ................................................................................ 17
1.3 Bipolar plates ................................................................................................... 18
1.4 Membrane electrode assembly (MEA) ............................................................... 19
1.5 MEA – Electrode ............................................................................................... 20
1.6 Fuel cell polarisation curves ............................................................................. 21
1.6.1 Activation polarisation .......................................................................................................... 23
1.6.2 Ohmic polarisation .................................................................................................................. 24
1.6.3 Concentration polarisation .................................................................................................. 25
1.6.4 Other losses................................................................................................................................ 27
1.7 Hydrogen production road map ........................................................................ 28
1.8 Fuel cell systems for UAVs ................................................................................ 32
1.8.1 Thermal management ............................................................................................................ 34
1.8.2 Hydrogen storage .................................................................................................................... 35
1.8.3 Hydrogen generator ............................................................................................................... 37
1.8.4 Anode purge .............................................................................................................................. 38
1.8.5 Weight breakdown .................................................................................................................. 39
1.8.6 Clamping pressure .................................................................................................................. 42
1.8.7 Fuel cell shape ........................................................................................................................... 43
1.9 Structural power .............................................................................................. 45
1.9.1 Multifunctional fuel cells ...................................................................................................... 45
1.9.2 Pultruded and VARTM fuel cell .......................................................................................... 47
1.10 Wing rib loads ................................................................................................ 49
1.11 Summary and knowledge gap ......................................................................... 53
Chapter 2 Structural fuel cell development ............................................................ 55
2.1 Current fuel cell systems .................................................................................. 55
2.2 Structural fuel cell concept ............................................................................... 56
2.3 Structural fuel cell ............................................................................................ 57
2.4 Structural fuel cell design and development ...................................................... 58

2
2.5 Cantilever concept and terminology .................................................................. 59
2.6 Conceptual design ............................................................................................ 60
2.6.1 Bipolar plates ............................................................................................................................ 60
2.6.2 End plates ................................................................................................................................... 62
2.6.3 Initial FEA ................................................................................................................................... 63
2.7 Structural fuel cell design ................................................................................. 66
2.7.1 Bipolar plate and Gasket ....................................................................................................... 68
2.7.2 Gas inlet/out sealing............................................................................................................... 69
2.7.3 Gasket ........................................................................................................................................... 70
2.7.4 Membrane Electrode Assembly (MEA) manufacture ................................................ 71
2.7.5 GDE misalignment ................................................................................................................... 74
2.7.6 Electrical insulation ................................................................................................................ 75
2.7.7 Gas tightness .............................................................................................................................. 76
Chapter 3 - Experimental setup and results ........................................................... 79
3.1 Fuel cell operating conditions ........................................................................... 79
3.1.1 Consumption of Oxygen ........................................................................................................ 80
3.1.2 Consumption of Hydrogen ................................................................................................... 82
3.1.3 Water production .................................................................................................................... 83
3.2 Water management .......................................................................................... 84
3.3 Humidification ................................................................................................. 86
3.4 Thermal management ...................................................................................... 88
3.5 Experimental parameters ................................................................................. 93
3.6 Experimental apparatus ................................................................................... 96
3.7 Experimental loads........................................................................................... 99
3.7.1 Manual application of loads ................................................................................................. 99
3.7.2 Digital image correlation – Bending .............................................................................. 101
3.7.3 Digital image correlation – Tip ........................................................................................ 105
3.7.4 Digital image correlation – Torsion ............................................................................... 108
3.8 Strain measurements ..................................................................................... 111
3.8.1 Strain comparison with and without clamping bolts ............................................. 113
3.9.1 Actuator accuracy ................................................................................................................. 118
3.10 MEA activation ............................................................................................. 122
3.10.1 Initial MEA polarisations ................................................................................................ 123

3
3.10.2 Investigation ........................................................................................................................ 128
3.10.3 Experimental apparatus .................................................................................................. 128
3.10.4 MEA manufacturing procedure .................................................................................... 129
3.10.5 Hot pressing ......................................................................................................................... 130
3.10.6 Interfacial contact resistance ........................................................................................ 132
3.10.7 Performance benchmark comparison ....................................................................... 135
3.10.8 MEA- Quality and repeatability .................................................................................... 137
3.10.9 Conclusion of investigation ............................................................................................ 138
3.11 Experimental results .................................................................................... 139
3.11.1 Experimental procedure ................................................................................................. 139
3.11.2 Static bending – Cathode compression ...................................................................... 142
3.11.3 Static bending – Anode compression ......................................................................... 145
3.11.4 Static torsion ........................................................................................................................ 148
3.11.5 Dynamic bending – 3mm deflection ........................................................................... 151
3.11.6 Dynamic bending – 5mm deflection ........................................................................... 156
3.11.7 Dynamic bending – 7mm deflection ........................................................................... 161
3.11.8 Dynamic torsion – 3.4° ..................................................................................................... 168
3.11.9 Dynamic torsion – 5° ........................................................................................................ 172
3.12 Discussion .................................................................................................... 177
3.12.1 Dynamic bending comparison ...................................................................................... 177
3.12.2 Dynamic torsion comparison ........................................................................................ 180
3.12.3 MEA recovery ...................................................................................................................... 183
3.12.4 MEA examination ............................................................................................................... 185
Chapter 4 - Corrosion of bipolar plates ................................................................ 188
4.1 Initial test run ................................................................................................ 188
4.2 Investigation .................................................................................................. 188
4.2.1 SEM and EDS ........................................................................................................................... 190
4.2.2 Anode surface analysis – figure 4.3 ............................................................................... 195
4.2.3 Cathode surface analysis –figure 4.4 ............................................................................. 195
4.2.4 MEA surface analysis – figure 4.5 ................................................................................... 196
4.2.5 Overall analysis ..................................................................................................................... 197
4.2.6 Results post corrosion protection .................................................................................. 199
4.2.7 Conclusion ............................................................................................................................... 212

4
Chapter 5 - Finite element analysis ...................................................................... 214
5.1 Further finite element modelling .................................................................... 214
5.2 Coordinate system.......................................................................................... 214
5.3 Initial simplified model ................................................................................... 215
5.4 Material specification ..................................................................................... 215
5.5 Boundary conditions ...................................................................................... 215
5.6 Loading and additional constraints ................................................................. 215
5.7 Simplified model results ................................................................................. 218
5.8 Detailed model ............................................................................................... 220
5.8.1 End plates and bipolar plates ....................................................................... 220
5.8.2 Contact behaviour ................................................................................................................ 222
5.8.3 FE sensitivity analysis ......................................................................................................... 223
5.8.4 Boundary conditions and steps ....................................................................................... 226
5.8.5 Clamping bolt constraints ................................................................................................. 227
5.8.6 Detailed model ....................................................................................................................... 228
5.9 Model validation ............................................................................................ 242
5.9.1 Strain values ........................................................................................................................... 242
5.9.2 Load verses displacement ................................................................................................. 244
Chapter 6 – Conclusions and future work............................................................. 246
6.1 Conclusions .................................................................................................... 246
6.2 Future works ................................................................................................. 249
Publications ......................................................................................................... 251
References ............................................................................................................. 252

5
Table of figures
Figure 1.1 - Electrochemical reaction within PEM fuel cells [19] ............................................. 16
Figure 1.2 - Components within a conventional single PEM fuel cell and a stack .............. 17
Figure 1.3 - Biologically inspired flow filed design [18] ............................................................... 18
Figure 1.4 - MEA component interaction ............................................................................................ 20
Figure 1.5 - A typical polarisation curve with voltage losses ..................................................... 22
Figure 1.6 - Breakdown of MEA layers ................................................................................................ 25
Figure 1.7 - Global hydrogen production [79] .................................................................................. 28
Figure 1.8 – Global CO production [81] ............................................................................................. 30
2
Figure 1.9 - Roadmap hydrogen production technology mix [81] ........................................... 31
Figure 1.10 - Fuel cell system based sodium borohydride [15] ................................................ 37
Figure 1.11 - Experimentally derived hydrogen purge [1] .......................................................... 38
Figure 1.12 - UAV system weight breakdown [1]............................................................................ 39
Figure 1.13 - Sodium borohydride fuel cell system [39] .............................................................. 40
Figure 1.14 - Assembly procedure of the cylinder shaped air-breathing PEMFC [14] ..... 43
Figure 1.15 - Polarization curves for planar PEMFC and Cy-PEMFC [14] ............................. 44
Figure 1.16 - Composite structural fuel cell [30] ............................................................................. 46
Figure 1.17 - Cross section of multifunctional composite fuel cell ........................................... 47
Figure 1.18 - Concept of pultruded fuel cell [35] ............................................................................. 48
Figure 1.19 - Key wing structural components [43] ...................................................................... 50
Figure 1.20 - Wing twisting and wing bending [42] ....................................................................... 51
Figure 2.1 - Chemical hydride based fuel cell system [37] .......................................................... 55
Figure 2.2 - Fuel cell replacement of the Rear Rib structure highlighted in red ................. 57
Figure 2.3 - Exploded view of a conventional fuel cell arrangement ....................................... 58
Figure 2.4 - Cantilever arrangement with terminology ................................................................ 59
Figure 2.5 - Structural fuel cell stainless steel bipolar plates ..................................................... 60
Figure 2.6 - Structural fuel cell aluminium end plates .................................................................. 62
Figure 2.7 - Finite element modelling steps ...................................................................................... 63
Figure 2.8 - End plate displacement ..................................................................................................... 64
Figure 2.9 - Redesigned structural fuel cell end plate ................................................................... 66
Figure 2.10 - Bipolar plate and Gasket re-designed ....................................................................... 68
Figure 2.11 - Gas inlet, end plate, and bipolar plate arrangement............................................ 69
Figure 2.12 - Application guide [52] ..................................................................................................... 70
Figure 2.13 - MEA and Gasket ................................................................................................................. 71
Figure 2.14 - MEA manufacturing process ......................................................................................... 73
Figure 2.15 - GDE misalignment ............................................................................................................ 74
Figure 2.16 - MEA7 Batch 3 ...................................................................................................................... 74
Figure 2.17 - Clamping bolts and short and long bolt insulation bushes ............................... 75
Figure 2.18 - Exploded view of the new structural fuel cell ........................................................ 76
Figure 2.19 - Structural fuel cell gas tightness achieved .............................................................. 78
Figure 3.1 - Production and transportation of water content [2] ............................................. 84
Figure 3.2 - Passive humidification with internal recirculation of water .............................. 85

6
Figure 3.3 - Humidify bottle and dual temperature controller .................................................. 86
Figure 3.4 - Humidifier gas outlet temperature / flow rate against dew point [78].......... 87
Figure 3.5 - Structural fuel cell with a flexible silicone heating element attached ............. 90
Figure 3.6 - Three heating elements bonded to each end plate ................................................. 92
Figure 3.7 - Gas humidifiers in close proximity to the structural fuel cell............................. 94
Figure 3.8 - Structural fuel cell experimental setup ....................................................................... 97
Figure 3.9 - Structural fuel cell mounted on the mechanical loading assembly .................. 98
Figure 3.10 - Manual application of loads ....................................................................................... 100
Figure 3.11 - Surfaces spray painted for digital image correlation ....................................... 101
Figure 3.12 - DIC image of structural fuel cell under bending loads of zero to 232N .... 102
Figure 3.13 - DIC image of structural fuel cell under bending loads of 276N to 365N .. 103
Figure 3.14 - DIC image of fuel cell tip under bending loads of 54N to 98N ...................... 105
Figure 3.15 - DIC image of fuel cell tip under bending loads of 147N to 365N ................. 106
Figure 3.16 - Bending loads against average DIC displacement measurements .............. 107
Figure 3.17 - Deformation magnitude and x-plane displacement - 1.6 degree of twist. 109
Figure 3.18 - Deformation magnitude and x-plane displacement ......................................... 110
Figure 3.19 - Strain gauges attached to the structural fuel cell. ............................................. 111
Figure 3.20 - Strain measurements - top and bottom end plate ............................................. 114
Figure 3.21 - Strain measurements - top end plate and bottom end plate ......................... 115
Figure 3.22 - Clamping bolts, horizontal rib, and strain gauge positons ............................. 116
Figure 3.23 - Gimson robotics GLA750 screw type actuator ................................................... 117
Figure 3.24 - Experimental setup for actuator accuracy measurements ............................ 118
Figure 3.25 - Actuator tested with structural fuel cell attached ............................................. 119
Figure 3.26 - Experimental setup for torsion loads and bending loads ............................... 121
Figure 3.27 - Five activation curves for MEA1-B1 (Batch 1) ................................................... 124
Figure 3.28 - Activation curves for MEA3-B2 (Batch 2) ............................................................ 125
Figure 3.29 - Activation curves for MEA4-B2 ................................................................................ 126
Figure 3.30 - A selection of activation polarisation curves for MEA6-B2 ........................... 127
Figure 3.31 - Breakdown of MEA layers - convective and diffusive mass transfer ......... 130
Figure 3.32 - Damage to MEA’s from batches one and two post hot pressing .................. 131
Figure 3.33 - Bolting sequence for the structural fuel cell ........................................................ 132
Figure 3.34 - Polarisation curve for MEA T1 .................................................................................. 134
Figure 3.35 - Polarisation curves for the 25cm2 Pragma and Structural fuel cells.......... 135
Figure 3.36 - Actuator control - static and dynamic bending loads ...................................... 140
Figure 3.37 - Peak power against deflection .................................................................................. 142
Figure 3.38 - Static bending from 6mm back to zero deflection. ............................................ 143
Figure 3.39 - Peak power against deflection and peak power against bending load ..... 144
Figure 3.40 - Polarisation curves for static bending -1mm to -7mm deflection .............. 145
Figure 3.41 - Peak power against deflection .................................................................................. 146
Figure 3.42 - Peak power against deflection .................................................................................. 146
Figure 3.43 - Polarisation curves for static torsion 0° to 5° ..................................................... 148
Figure 3.44 - Peak power against torsion ........................................................................................ 149
Figure 3.45 - Cell performance after multiple rounds of torsional loading ....................... 150

7
Figure 3.46 - Peak power 0 to 100 cycles ........................................................................................ 151
Figure 3.47 - Polarisation curves for 500 to 1000 cycles .......................................................... 152
Figure 3.48 - Peak power performance from 250 to 1000 cycles .......................................... 152
Figure 3.49 - Polarisation curves for 1100 to 2000 cycles ....................................................... 154
Figure 3.50 - Peak power performance from 1100 to 2000 cycles ....................................... 155
Figure 3.51 - Peak power performance from 125 to 400 cycles ............................................ 156
Figure 3.52 - Polarisation curves for 500 to 1000 cycles .......................................................... 157
Figure 3.53 - Peak power performance from 500 to 1000 cycles .......................................... 158
Figure 3.54 - Polarisation curves for 1100 to 1500 cycles ....................................................... 159
Figure 3.55 - Polarisation curves for 1600 to 2000 cycles ....................................................... 159
Figure 3.56 - Peak power performance from 1100 to 2000 cycles ....................................... 160
Figure 3.57 - Polarisation curves for 125 to 200 cycles ............................................................. 161
Figure 3.58 - Peak power performance from 125 to 500 cycles ............................................ 162
Figure 3.59 - Polarisation curves for 500 to 1000 cycles .......................................................... 163
Figure 3.60 - Peak power performance from 250 to 1000 cycles .......................................... 164
Figure 3.61 - Polarisation curves for 1100 to 2000 cycles ....................................................... 166
Figure 3.62 - Peak power performance from 1100 to 2000 cycles ....................................... 167
Figure 3.63 - Polarisation curves for 500 to 1000 cycles .......................................................... 168
Figure 3.64 - Peak power performance from 250 to 1000 cycles .......................................... 169
Figure 3.65 - Polarisation curves for 1600 to 2000 cycles ....................................................... 170
Figure 3.66 - Peak power performance from 1100 to 2000 cycles ....................................... 171
Figure 3.67 - Polarisation curves for 50 to 100 cycles ............................................................... 172
Figure 3.68 - Polarisation curves for 500 to 1000 cycles .......................................................... 173
Figure 3.69 - Peak power performance from 250 to 1000 cycles .......................................... 174
Figure 3.70 - Polarisation curves for 1100 to 2000 cycles ....................................................... 175
Figure 3.71 - Peak power performance from 1100 to 2000 cycles ....................................... 176
Figure 3.72 - Peak power performance between each group of bending cycles .............. 177
Figure 3.73 - Peak power percentage losses from zero cycles to 2000 cycles .................. 178
Figure 3.74 - Peak power change from zero cycles to 2000 cycles ....................................... 179
Figure 3.75 - Peak power performance between each group of torsional cycles. ........... 180
Figure 3.76 - Peak power change from zero cycles to 2000 cycles ....................................... 181
Figure 3.77 - Peak power percentage losses from zero cycles to 2000 cycles .................. 182
Figure 3.78 - Demonstration of recovery behaviour of the MEA ........................................... 184
Figure 3.79 - MEA’s after 2000 torsional load cycles at 3.4 and 5° ....................................... 185
Figure 3.80 - Damage to MEA7-B3 after 2000 bending cycle at 5mm deflection ............ 187
Figure 3.81 - Damage to MEA6-B3 after 2000 bending cycle at 7mm deflection ............ 187
Figure 4.1 - Unknown deposits on MEA and bipolar plate surfaces. .................................... 189
Figure 4.2 - Anode, Cathode, and MEA samples in SEM/EDS machine ................................ 191
Figure 4.3 - SEM and EDS analysis of anode surface ................................................................... 192
Figure 4.4 - SEM and EDS analysis of cathode surface ............................................................... 193
Figure 4.5 - SEM and EDS analysis of MEA surface ...................................................................... 194
Figure 4.6 - Post application of Gold protective coating system ............................................ 199
Figure 4.7 - Second polarisation curve produced approximately 24hrs after the first. 200

8