Fuel Cell Fundamentals

Fuel Cell Fundamentals provides a thorough introduction to the principles and practicalities behind fuel cell technology. Beginning with the underlying concepts, the discussion explores fuel cell thermodynamics, kinetics, transport, and modeling before moving into the application side with guidance on system types and design, performance, costs, and environmental impact. This new third edition has been updated with the latest technological advances and relevant calculations, and enhanced chapters on advanced fuel cell design and electrochemical and hydrogen energy systems. Worked problems, illustrations, and application examples throughout lend a real-world perspective, and end-of chapter review questions and mathematical problems reinforce the material learned.

Fuel cells produce more electricity than batteries or combustion engines, with far fewer emissions. This book is the essential introduction to the technology that makes this possible, and the physical processes behind this cost-saving and environmentally friendly energy source.

• Understand the basic principles of fuel cell physics
• Compare the applications, performance, and costs of different systems
• Master the calculations associated with the latest fuel cell technology
• Learn the considerations involved in system selection and design

As more and more nations turn to fuel cell commercialization amidst advancing technology and dropping deployment costs, global stationary fuel cell revenue is expected to grow from $1.4 billion to $40.0 billion by 2022. The sector is forecasted to explode, and there will be a tremendous demand for high-level qualified workers with advanced skills and knowledge of fuel cell technology. Fuel Cell Fundamentals is the essential first step toward joining the new energy revolution.

RYAN O'HAYRE, PhD, is a Professor of Metallurgical and Materials Engineering at the Colorado School of Mines where his Advanced Energy Materials Laboratory develops new materials and devices to enable alternative energy technologies.

SUK-WON CHA, PhD, is a Professor in the School of Mechanical and Aerospace Engineering at Seoul National University, Seoul, South Korea.

WHITNEY G. COLELLA, PhD, is Faculty with the G.W.C. Whiting School of Engineering at The Johns Hopkins University in Baltimore, Maryland and Principal Research Engineer with Gaia Energy Research Institute.

FRITZ B. PRINZ, PhD, is the Finmeccanica Professor in the School of Engineering, Professor of Mechanical Engineering and Professor of Materials Science and Engineering at Stanford University.

ACKNOWLEDGMENTS xiii

NOMENCLATURE xvii

I FUEL CELL PRINCIPLES

1 Introduction 3

1.1 What Is a Fuel Cell? / 3

1.2 A Simple Fuel Cell / 6

1.3 Fuel Cell Advantages / 8

1.4 Fuel Cell Disadvantages / 11

1.5 Fuel Cell Types / 12

1.6 Basic Fuel Cell Operation / 14

1.7 Fuel Cell Performance / 18

1.8 Characterization and Modeling / 20

1.9 Fuel Cell Technology / 21

1.10 Fuel Cells and the Environment / 21

1.11 Chapter Summary / 22

Chapter Exercises / 23

2 Fuel Cell Thermodynamics 25

2.1 Thermodynamics Review / 25

2.2 Heat Potential of a Fuel: Enthalpy of Reaction / 34

2.3 Work Potential of a Fuel: Gibbs Free Energy / 37

2.4 Predicting Reversible Voltage of a Fuel Cell under Non-Standard-State Conditions / 47

2.5 Fuel Cell Efficiency / 60

2.6 Thermal and Mass Balances in Fuel Cells / 65

2.7 Thermodynamics of Reversible Fuel Cells / 67

2.8 Chapter Summary / 71

Chapter Exercises / 72

3 Fuel Cell Reaction Kinetics 77

3.1 Introduction to Electrode Kinetics / 77

3.2 Why Charge Transfer Reactions Have an Activation Energy / 82

3.3 Activation Energy Determines Reaction Rate / 84

3.4 Calculating Net Rate of a Reaction / 85

3.5 Rate of Reaction at Equilibrium: Exchange Current Density / 86

3.6 Potential of a Reaction at Equilibrium: Galvani Potential / 87

3.7 Potential and Rate: Butler–Volmer Equation / 89

3.8 Exchange Currents and Electrocatalysis: How to Improve Kinetic Performance / 94

3.9 Simplified Activation Kinetics: Tafel Equation / 97

3.10 Different Fuel Cell Reactions Produce Different Kinetics / 100

3.11 Catalyst–Electrode Design / 103

3.12 Quantum Mechanics: Framework for Understanding Catalysis in Fuel Cells / 104

3.13 The Sabatier Principle for Catalyst Selection / 107

3.14 Connecting the Butler–Volmer and Nernst Equations (Optional) / 108

3.15 Chapter Summary / 112

Chapter Exercises / 113

4 Fuel Cell Charge Transport 117

4.1 Charges Move in Response to Forces / 117

4.2 Charge Transport Results in a Voltage Loss / 121

4.3 Characteristics of Fuel Cell Charge Transport Resistance / 124

4.4 Physical Meaning of Conductivity / 128

4.5 Review of Fuel Cell Electrolyte Classes / 132

4.6 More on Diffusivity and Conductivity (Optional) / 153

4.7 Why Electrical Driving Forces Dominate Charge Transport (Optional) / 160

4.8 Quantum Mechanics–Based Simulation of Ion Conduction in Oxide Electrolytes (Optional) / 161

4.9 Chapter Summary / 163

Chapter Exercises / 164

5 Fuel Cell Mass Transport 167

5.1 Transport in Electrode versus Flow Structure / 168

5.2 Transport in Electrode: Diffusive Transport / 170

5.3 Transport in Flow Structures: Convective Transport / 183

5.4 Chapter Summary / 199

Chapter Exercises / 200

6 Fuel Cell Modeling 203

6.1 Putting It All Together: A Basic Fuel Cell Model / 203

6.2 A 1D Fuel Cell Model / 206

6.3 Fuel Cell Models Based on Computational Fluid Dynamics (Optional) / 227

6.4 Chapter Summary / 230

Chapter Exercises / 231

7 Fuel Cell Characterization 237

7.1 What Do We Want to Characterize? / 238

7.2 Overview of Characterization Techniques / 239

7.3 In Situ Electrochemical Characterization Techniques / 240

7.4 Ex Situ Characterization Techniques / 265

7.5 Chapter Summary / 268

Chapter Exercises / 269

II FUEL CELL TECHNOLOGY

8 Overview of Fuel Cell Types 273

8.1 Introduction / 273

8.2 Phosphoric Acid Fuel Cell / 274

8.3 Polymer Electrolyte Membrane Fuel Cell / 275

8.4 Alkaline Fuel Cell / 278

8.5 Molten Carbonate Fuel Cell / 280

8.6 Solid-Oxide Fuel Cell / 282

8.7 Other Fuel Cells / 284

8.8 Summary Comparison / 298

8.9 Chapter Summary / 299

Chapter Exercises / 301

9 PEMFC and SOFC Materials 303

9.1 PEMFC Electrolyte Materials / 304

9.2 PEMFC Electrode/Catalyst Materials / 308

9.3 SOFC Electrolyte Materials / 317

9.4 SOFC Electrode/Catalyst Materials / 326

9.5 Material Stability, Durability, and Lifetime / 336

9.6 Chapter Summary / 340

Chapter Exercises / 342

10 Overview of Fuel Cell Systems 347

10.1 Fuel Cell Subsystem / 348

10.2 Thermal Management Subsystem / 353

10.3 Fuel Delivery/Processing Subsystem / 357

10.4 Power Electronics Subsystem / 364

10.5 Case Study of Fuel Cell System Design: Stationary Combined Heat and Power Systems / 369

10.6 Case Study of Fuel Cell System Design: Sizing a Portable Fuel Cell / 383

10.7 Chapter Summary / 387

Chapter Exercises / 389

11 Fuel Processing Subsystem Design 393

11.1 Fuel Reforming Overview / 394

11.2 Water Gas Shift Reactors / 409

11.3 Carbon Monoxide Clean-Up / 411

11.4 Reformer and Processor Efficiency Losses / 414

11.5 Reactor Design for Fuel Reformers and Processors / 416

11.6 Chapter Summary / 417

Chapter Exercises / 419

12 Thermal Management Subsystem Design 423

12.1 Overview of Pinch Point Analysis Steps / 424

12.2 Chapter Summary / 440

Chapter Exercises / 441

13 Fuel Cell System Design 447

13.1 Fuel Cell Design Via Computational Fluid Dynamics / 447

13.2 Fuel Cell System Design: A Case Study / 462

13.3 Chapter Summary / 476

Chapter Exercises / 477

14 Environmental Impact of Fuel Cells 481

14.1 Life Cycle Assessment / 481

14.2 Important Emissions for LCA / 490

14.3 Emissions Related to Global Warming / 490

14.4 Emissions Related to Air Pollution / 502

14.5 Analyzing Entire Scenarios with LCA / 507

14.6 Chapter Summary / 510

Chapter Exercises / 511

A Constants and Conversions 517

B Thermodynamic Data 519

C Standard Electrode Potentials at 25∘C 529

D Quantum Mechanics 531

D.1 Atomic Orbitals / 533

D.2 Postulates of Quantum Mechanics / 534

D.3 One-Dimensional Electron Gas / 536

D.4 Analogy to Column Buckling / 537

D.5 Hydrogen Atom / 538

D.6 Multielectron Systems / 540

D.7 Density Functional Theory / 540

E Periodic Table of the Elements 543

F Suggested Further Reading 545

G Important Equations 547

H Answers to Selected Chapter Exercises 551

BIBLIOGRAPHY 555

INDEX 565

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