reading

Cover
Title Page
Brief Biographies
Preface
Acknowledgments
Acronyms and Initialisms
Symbols and Units
1 Introducing Fuel Cells
1. 1.1 Historical Perspective
2. 1.2 Fuel‐Cell Basics
3. 1.3 Electrode Reaction Rates
4. 1.4 Stack Design
5. 1.5 Gas Supply and Cooling
6. 1.6 Principal Technologies
7. 1.7 Mechanically Rechargeable Batteries and Other Fuel Cells
8. 1.8 Balance‐of‐Plant Components
9. 1.9 Fuel‐Cell Systems: Key Parameters
10. 1.10 Advantages and Applications
11. Further Reading
2 Efficiency and Open‐Circuit Voltage
1. 2.1 Open‐Circuit Voltage: Hydrogen Fuel Cell
2. 2.2 Open‐Circuit Voltage: Other Fuel Cells and Batteries
3. 2.3 Efficiency and Its Limits
4. 2.4 Efficiency and Voltage
5. 2.5 Influence of Pressure and Gas Concentration
6. 2.6 Summary
7. Further Reading
3 Operational Fuel‐Cell Voltages
1. 3.1 Fundamental Voltage: Current Behaviour
2. 3.2 Terminology
3. 3.3 Fuel‐Cell Irreversibilities
4. 3.4 Activation Losses
5. 3.5 Internal Currents and Fuel Crossover
6. 3.6 Ohmic Losses
7. 3.7 Mass‐Transport Losses
8. 3.8 Combining the Irreversibilities
9. 3.9 The Electrical Double‐Layer
10. 3.10 Techniques for Distinguishing Irreversibilities
11. Further Reading
4 Proton‐Exchange Membrane Fuel Cells
1. 4.1 Overview
2. 4.2 Polymer Electrolyte: Principles of Operation
3. 4.3 Electrodes and Electrode Structure
4. 4.4 Water Management
5. 4.5 Cooling and Air Supply
6. 4.6 Stack Construction Methods
7. 4.7 Operating Pressure
8. 4.8 Fuel Types
9. 4.9 Practical and Commercial Systems
10. 4.10 System Design, Stack Lifetime and Related Issues
11. 4.11 Unitized Regenerative Fuel Cells
12. Further Reading
5 Alkaline Fuel Cells
1. 5.1 Principles of Operation
2. 5.2 System Designs
3. 5.3 Electrodes
4. 5.4 Stack Designs
5. 5.5 Operating Pressure and Temperature
6. 5.6 Opportunities and Challenges
7. Further Reading
6 Direct Liquid Fuel Cells
1. 6.1 Direct Methanol Fuel Cells
2. 6.2 Direct Ethanol Fuel Cells
3. 6.3 Direct Propanol Fuel Cells
4. 6.4 Direct Ethylene Glycol Fuel Cells
5. 6.5 Formic Acid Fuel Cells
6. 6.6 Borohydride Fuel Cells
7. 6.7 Application of Direct Liquid Fuel Cells
8. Further Reading
7 Phosphoric Acid Fuel Cells
1. 7.1 High‐Temperature Fuel‐Cell Systems
2. 7.2 System Design
3. 7.3 Principles of Operation
4. 7.4 Performance
5. 7.5 Technological Developments
6. Further Reading
8 Molten Carbonate Fuel Cells
1. 8.1 Principles of Operation
2. 8.2 Cell Components
3. 8.3 Stack Configuration and Sealing
4. 8.4 Performance
5. 8.5 Practical Systems
6. 8.6 Future Research and Development
7. 8.7 Hydrogen Production and Carbon Dioxide Separation
8. 8.8 Direct Carbon Fuel Cell
9. Further Reading
9 Solid Oxide Fuel Cells
1. 9.1 Principles of Operation
2. 9.2 Components
3. 9.3 Practical Design and Stacking Arrangements
4. 9.4 Performance
5. 9.5 Developmental and Commercial Systems
6. 9.6 Combined‐Cycle and Other Systems
7. Further Reading
10 Fuels for Fuel Cells
1. 10.1 Introduction
2. 10.2 Fossil Fuels
3. 10.3 Biofuels
4. 10.4 Basics of Fuel Processing
5. 10.5 Membrane Developments for Gas Separation
6. 10.6 Practical Fuel Processing: Stationary Applications
7. 10.7 Practical Fuel Processing: Mobile Applications
8. 10.8 Electrolysers
9. 10.9 Thermochemical Hydrogen Production and Chemical Looping
10. 10.10 Biological Production of Hydrogen
11. Further Reading
11 Hydrogen Storage
1. 11.1 Strategic Considerations
2. 11.2 Safety
3. 11.3 Compressed Hydrogen
4. 11.4 Liquid Hydrogen
5. 11.5 Reversible Metal Hydrides
6. 11.6 Simple Hydrogen‐Bearing Chemicals
7. 11.7 Complex Chemical Hydrides
8. 11.8 Nanostructured Materials
9. 11.9 Evaluation of Hydrogen Storage Methods
10. Further Reading
12 The Complete System and Its Future
1. 12.1 Mechanical Balance‐of‐Plant Components
2. 12.2 Power Electronics
3. 12.3 Hybrid Fuel‐Cell + Battery Systems
4. 12.4 Analysis of Fuel‐Cell Systems
5. 12.5 Commercial Reality
6. 12.6 Future Prospects: The Crystal Ball Remains Cloudy
7. Further Reading
Appendix 1: Calculations of the Change in Molar Gibbs Free Energy
1. A1.1 Hydrogen Fuel Cell
2. A1.2 Carbon Monoxide Fuel Cell
Appendix 2: Useful Fuel‐Cell Equations
1. A2.1 Introduction
2. A2.2 Oxygen and Air Usage
3. A2.3 Exit Air Flow Rate
4. A2.4 Hydrogen Usage
5. A2.5 Rate of Water Production
6. A2.6 Heat Production
Appendix 3: Calculation of Power Required by Air Compressor and Power Recoverable by Turbine in Fuel‐Cell Exhaust
1. A3.1 Power Required by Air Compressor
2. A3.2 Power Recoverable from Fuel‐Cell Exhaust with a Turbine
Glossary of Terms
Index
End User License Agreement

List of Tables

Chapter 01
1. Table 1.1 Principal types of fuel cell.
Chapter 02
1. Table 2.1 for the reaction at various temperatures.
2. Table 2.2 , maximum open‐circuit voltage and thermodynamic efficiency limit (HHV) for hydrogen fuel cells.
Chapter 03
1. Table 3.1 Values of i_o for the hydrogen electrode for various metals in an acid electrolyte.
2. Table 3.2 PEMFC voltages at low current densities.
3. Table 3.3 Example values of parameters for equation (3.22).
Chapter 04
1. Table 4.1 Structure of Nafion and characteristics of other PFSAs.
2. Table 4.2 Saturated vapour pressure of water at selected temperatures.
3. Table 4.3 Theoretical exit air relative humidities at selected temperatures and stoichiometries. The inlet air is assumed to be at 20 °C and 70% relative humidity; the exit air pressure is assumed to be at 100 kPa. The blanks in the Table are where the relative humidity is too high or too low.
4. Table 4.4 Parameters for the examples given in Figure 4.30.
Chapter 05
1. Table 5.1 Operating parameters for certain AFCs. The pressure data are approximate as there are usually small differences between each reactant gas.
Chapter 06
1. Table 6.1 Thermodynamic characteristics of PEMFC and some DLFCs at 25°C and 101.325 kPa.
2. Table 6.2 Comparison of specific energy (LHV) for common energy storage materials and the most important hydrogen storage technologies.
Chapter 08
1. Table 8.1 Values of and for hydrogen and carbon monoxide fuel cells at 650°C.
2. Table 8.2 Evolution of cell component technology for molten carbonate fuel cells.
3. Table 8.3 Equilibrium constant (K_c) and equilibrium gas compositions for fuel gas and reversible cell voltage (V_r) calculated using the Nernst equation for an initial anode gas composition of 77.5 vol.% H₂, 19.4 vol.% CO₂ and 3.1 vol.% H₂O at 0.1 MPa and a cathode composition of 30 vol.% O₂, 60 vol. % CO₂ and 10 vol.% N₂.
Chapter 09
1. Table 9.1 Summary of output powers for the hybrid system shown in Figure 9.17.
Chapter 10
1. Table 10.1 Some properties of hydrogen and other candidate fuels for fuel‐cell systems.
2. Table 10.2 Typical coal gas compositions (mole per cent basis).
3. Table 10.3 Typical compositions of natural gases from different geographic regions.
4. Table 10.4 Example compositions of biogases.
5. Table 10.5 Fuel quality for principal types of fuel cell.
6. Table 10.6 Typical heats of reaction in naphtha reforming at different temperatures, pressure and steam‐to‐carbon ratios.
7. Table 10.7 Thermochemical cycles currently under consideration.
Chapter 11
1. Table 11.1 Applications that employ hydrogen storage.
2. Table 11.2 Possible materials for hydrogen storage.
3. Table 11.3 Properties relevant to safety for hydrogen and two other commonly used gaseous fuels.
4. Table 11.4 Comparative data for two cylinders used to store hydrogen at high pressure.
5. Table 11.5 Details of a cryogenic hydrogen container for BMW cars.
6. Table 11.6 Details of Horizon Hydrostik hydrogen container for portable electronics equipment.
7. Table 11.7 Approximate comparison of mass and volume of gasoline and stored forms of hydrogen for equivalent energy content (1.4 GJ).
Chapter 12
1. Table 12.1 Key data for the main types of electronic switch used in power electronics.
Appendix 01
1. Table A1.1 Values of are in J mol⁻¹ and those for in J mol⁻¹ K⁻¹, both at 298.15 K, for the hydrogen fuel‐cell reaction (A1.1).
2. Table A1.2 Sample values for Δ and Δ in J mol⁻¹, and Δ in J mol⁻¹ K⁻¹, for the reaction (A1.2).
3. Table A1.3 Values of in J mol⁻¹ and in J mol⁻¹ K⁻¹, both at 298.15 K, for the carbon monoxide fuel‐cell reaction (A1.12).
4. Table A1.4 Sample values for Δ and Δin J mol⁻¹, and Δin J mol⁻¹ K⁻¹, for the carbon monoxide fuel‐cell reaction (A1.12).
Appendix 02
1. Table A2.1 Energy content of hydrogen fuel expressed in different forms.

List of Illustrations

Chapter 01
1. Figure 1.1 Terminology employed in operation of (a) electrolysis cells and (b) fuel cells.
2. Figure 1.2 (a) William Robert Grove (1811–1896) and (b) Grove’s sketch of four cells of his gaseous voltaic battery’ (1842).
3. Figure 1.3 Electrode reactions and charge flow for fuel cell with an acid electrolyte. Note that although the negative electrons flow from the anode to cathode, the ‘conventional positive current’ flows from cathode to anode.
4. Figure 1.4 Electrode reactions and charge flow for a fuel cell with an alkaline electrolyte. Electrons flow from negative anode to positive cathode, but ‘conventional positive current’ flows from cathode to anode.
5. Figure 1.5 Classical energy diagram for a simple exothermic chemical reaction.
6. Figure 1.6 Transmission electron microscope image of a fuel‐cell catalyst. The black spots are the catalyst particles that are finely divided over a carbon support. The structure clearly has a large surface area.
7. Figure 1.7 Simple edge connection of three‐planar fuel cells in series. When the electrolyte is a membrane, the cathode–electrolyte–anode unit is generally known as a membrane–electrode assembly (MEA).
8. Figure 1.8 Single cell with end‐plates for collecting current from the whole face of the adjacent electrode and applying gases to each electrode.
9. Figure 1.9 A three‐cell stack showing how bipolar plates connect the anode of one cell to the cathode of its neighbour.
10. Figure 1.10 The construction of cathode–electrolyte–anode units with edge seals that prevent the gases leaking in or out through the edges of the porous electrodes.
11. Figure 1.11 Three‐cell stack, with external manifolds. Unlike the stack shown Figure 1.9, the electrodes now have edge seals.
12. Figure 1.12 Internal manifolding. A more complex bipolar plate allows reactant gases to be fed to electrodes through internal tubes.
13. Figure 1.13 A 96‐cell, water‐cooled PEMFC stack that produces up to 8.4 kW and weighs 1.4 kg.
14. Figure 1.14 Phosphoric acid fuel cell for stationary power‐plant applications
15. Figure 1.15 Operating principle of the vanadium redox battery.
16. Figure 1.16 Redox zinc–bromine battery.
17. Figure 1.17 Hyundai fuel‐cell system located under the car hood.
Chapter 02
1. Figure 2.1 Inputs and outputs of a fuel cell.
2. Figure 2.2 Simple reversible process.
3. Figure 2.3 Maximum efficiency (HHV) of the hydrogen fuel cell at standard pressure. By way of comparison, the Carnot limit is shown for a 50°C exhaust temperature.
Chapter 03
1. Figure 3.1 Voltage versus current density performance of a typical fuel cell operating at low temperature and air pressure.
2. Figure 3.2 Voltage versus current density performance of a typical fuel cell operating at about 800°C and air pressure.
3. Figure 3.3 Tafel plots for slow and fast electrochemical reactions.
4. Figure 3.4 Cell voltage versus current density, assuming losses due only to the activation overpotential at one electrode, for exchange‐current density i_o values of 0.01, 1.0 and 100 mA cm^–2.
5. Figure 3.5 Fuel‐cell voltage modelled using activation and fuel crossover/internal current losses only.
6. Figure 3.6 Charge double layer at the cathode surface of a fuel cell.
7. Figure 3.7 Simple equivalent circuit model of a fuel cell.
8. Figure 3.8 Simple 3‐electrode setup for cyclic voltammetry.
9. Figure 3.9 (a) Nyquist plot of a practical SOFC anode in 97% CH₄ and 3% H₂O, at 932°C. Inset: Zoom at frequencies higher than 1 Hz. (b) Corresponding Bode plots.
10. Figure 3.10 (a) Effect of overpotential on impedance plots for Nafion 117. Applied DC potential: (ο) 0.775 V, (▲) 0.75 V, (∙) 0.725 V and (•) 0.70 V. Temperature 303 K and oxygen pressure 207 kPa. Solid lines represent fits of the equivalent circuits. (b) Typical equivalent circuit of PEMFC for ORR at Pt/Nafion interface.
11. Figure 3.11 Simple circuit for performing a current‐interrupt test.
12. Figure 3.12 Schematic of voltage against time for a fuel cell after a current‐interrupt test.
13. Figure 3.13 Current‐interrupt test for a low‐temperature, ambient pressure, hydrogen fuel cell. Ohmic and activation overpotentials are similar. (Time scale 0.2 s per division; i = 100 mA cm⁻².)
14. Figure 3.14 Current‐interrupt test for a direct methanol fuel cell. There are large activation losses at both electrodes so that, by comparison, the ohmic losses are barely discernable. (Time scale 2 s per division; i = 10 mA cm^–2.)
15. Figure 3.15 Current‐interrupt test for a small SOFC working at about 700°C. The large immediate rise in voltage shows that ohmic losses are responsible for most of the voltage drop. (Time scale 0.02 s per division; i = 100 mA cm^–2.)
Chapter 04
1. Figure 4.1 Four PEMFC stacks that illustrate development by Ballard Power Systems through the 1990s. The left‐hand stack, the 1989 model, has a power density of 100 W L⁻¹. The right‐hand, 1996 model delivers 1.1 kW L⁻¹
2. Figure 4.2 Honda FC stack and Gearbox (exhibited at the Tokyo Motor Show 2007).
3. Figure 4.3 Chemical structure of polyethylene.
4. Figure 4.4 Chemical structure of PTFE.
5. Figure 4.5 Chemical structure of a sulfonated fluoroethylene, also called ‘perfluorosulfonic acid PFTE copolymer’.
6. Figure 4.6 Structure of PFSA‐type membrane materials: long‐chain molecules containing hydrated regions around the sulfonated side‐chains.
7. Figure 4.7 Chemical structure of polybenzimidazole (PBI).
8. Figure 4.8 Serenegy liquid‐cooled high‐temperature PEMFC: (a) stack and (b) system.
9. Figure 4.9 Basic structure of a low‐temperature PEMFC with a simple configuration of bipolar plate.
10. Figure 4.10 Structure, idealized, of a carbon‐supported platinum catalyst.
11. Figure 4.11 Cyclic voltammograms for thin‐film platinum electrodes (curves 1–5) and bulk platinum (curve 6) in (a) argon‐saturated 0.1 M HClO₄ and (b) 0.05 M H₂SO₄. Film thickness: (1) 0.25, (2) 0.5, (3) 1, (4) 2 and (5) 10 nm. Sweep rate: 100 mV s⁻¹. Note the negative peak at 0.40–0.45 V is caused by the ORR.
12. Figure 4.12 Molecular structures of macrocyclic organic frameworks used for ORR catalysts: tetraazaanulene (TAA), tetraphenylporphyrin (TPP), tetramethoxyphenyl‐porphyrin (TMPP).
13. Figure 4.13 Molecular structure of 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine (TPTZ).
14. Figure 4.14 Simplified structure of a PEMFC electrode.
15. Figure 4.15 Enlargement of part of Figure 4.14 to show that the electrolyte reaches out to the catalyst particles.
16. Figure 4.16 Example of a membrane electrode assembly (MEA). The membrane is a little larger than the electrodes that are attached. The 10 cm² membrane is typically 0.05–0.1 mm thick, the electrodes are about 0.03 mm thick, and the GDL is between 0.2 and 0.5 mm thick.
17. Figure 4.17 Schematic illustration of the different water movements to, within and from the electrolyte of a PEMFC.
18. Figure 4.18 A graph of relative humidity versus temperature for the exit air of a PEMFC with an air stoichiometry of 2 and 4. The entry air is assumed to be dry, and the total pressure is 100 kPa.
19. Figure 4.19 Contra‐flow of reactant gases to even the humidification throughout a cell.
20. Figure 4.20 Diagrams to show the principle of humidification using interdigitated flow‐fields.
21. Figure 4.21 Three‐cell PEMFC stack with bipolar plates with separate reactant and cooling air channels.
22. Figure 4.22 Example of a commercial air‐cooled stack manufactured by Horizon Fuel Cells.
23. Figure 4.23 Diagram showing bipolar plate construction from metal foam.
24. Figure 4.24 Main flow‐field patterns used in PEMFC bipolar plates: (a) pin or grid type, (b) parallel channels, (c) interdigitated, (d) single serpentine channel (e–h) oxygen concentration in the cathode GDL for each of the flow‐field patterns (schematic). Red, high oxygen concentration; blue, low oxygen concentration.
25. Figure 4.25 Method of connecting fuel cells in series to simplify reactant gas supply.
26. Figure 4.26 Examples of MEMS‐based air‐breathing PEMFCs. (a) Six cells sealed with epoxy resin (Si and glass wafers, 1.2 cm × 1.2 cm single‐cell active area, ~4 cm³, >140 mW cm⁻² peak power with H₂)²³. (b) PCB‐based air‐breathing PEMFC with other integrated components²⁴.
27. Figure 4.27 Structure PEMFC demonstrated by Intelligent Energy.
28. Figure 4.28 Schematic representation of a simple PEMFC system, as employed in Hydrogenics fuel‐cell modules.
29. Figure 4.29 Effect of increasing pressure on the voltage versus current relationship for a typical fuel cell.
30. Figure 4.30 Net voltage change that results from operating at higher pressure — for two different PEMFC designs.
31. Figure 4.31 Horizon Fuel Cell products: (a) 12‐W ‘H‐Series’, (b) 1‐kW ‘H‐Series’ and (c) ‘Mini‐Pak’ phone charger.
32. Figure 4.32 Mobile phone charger from Intelligent Energy (the ‘UPP’).
33. Figure 4.33 Hydrogenics, rack‐mounted, ‘HYPM’ module, covers removed to show the stack and balance‐of‐plant items.
34. Figure 4.34 Sankey diagram of energy flows in a Hydrogenics fuel‐cell power module.
35. Figure 4.35 Mercedes‐Benz Citaro FuelCELL‐Hybrid bus.
36. Figure 4.36 Roof compartment of the Mercedes‐Benz Citaro FuelCELL‐Hybrid bus (showing seven storage tanks and lithium batteries behind them).
37. Figure 4.37 Roof compartment of the Mercedes‐Benz Citaro FuelCELL‐hybrid bus (showing the fuel cell stacks and associated BOP).
38. Figure 4.38 Intelligent Energy 100‐kW fuel‐cell system for vehicles: (a) water‐cooled stack and (b) packaged system.
Chapter 05
1. Figure 5.1 Alkaline fuel‐cell system (1.5 kW) employing 32 circular fuel cells (200 mm diameter) as used in the Apollo spacecraft. The cells were in the lower container that was purged with nitrogen to remove waste heat. The stack area of 465 cm² gave 0.86 V at 470 mA cm⁻² (4.0 kW m⁻²). Three of these units were connected in parallel to provide redundancy, each weighed 109 kg. The fuel cells provided the electrical power, as well as much of the potable water, for the craft that took mankind to the moon.
2. Figure 5.2 Diagram of an alkaline fuel cell with circulating electrolyte solution, which also serves as a coolant for the fuel cell.
3. Figure 5.3 Alkaline fuel cells: (a) Schematic of Zetek Mk2 stack and (b) Intensys–Vito 6‐kW system.
4. Figure 5.4 Alkaline fuel cell with static electrolyte solution held in a matrix. The system uses pure hydrogen and oxygen, e.g., as employed in spacecraft.
5. Figure 5.5 Alkaline fuel‐cell module used in Space Shuttle Orbiter.
6. Figure 5.6 Schematic representation of a dissolved fuel AFC, arguably the simplest of all types, it has a selective catalyst on the cathode that does not react with the fuel. An alternative design has a membrane within the electrolyte solution that isolates the fuel from the air cathode, but adds to cost and complexity.
7. Figure 5.7 Chemical reaction steps to convert a polysulfone into an anion‐exchange membrane polymer.
8. Figure 5.8 The structure of a rolled AFC electrode. The catalyst is mixed with a PTFE binder and rolled onto nickel mesh. The thin layer of PTFE on the gas side is shown partially rolled back.
9. Figure 5.9 AFC stack configurations: (a) monopolar and (b) bipolar.
10. Figure 5.10 Change in vapour pressure with temperature for different concentrations of KOH solution.
Chapter 06
1. Figure 6.1 Voltage versus current density performance of a 2010 state‐of‐the‐art DMFC and a typical PEMFC when operating under ambient conditions.
2. Figure 6.2 Stepwise reaction paths for oxidation of methanol at a DMFC anode.
3. Figure 6.3 The main components of an ‘active’ DMFC system. Not all the components will always be present. Larger systems may have additional components, such as heat‐exchangers in the fuel system for cooling, air pumps and methanol condensers in the CO₂ outlet pipe. Note that the electrode connections are shown at the edge for simplicity; normally, the current will be taken off the whole face of the electrode, as in Figure 1.8, Chapter 1.
4. Figure 6.4 Graph showing how the crossover of methanol to the cathode changes with fuel concentration at the anode and with load current.
5. Figure 6.5 Mechanism of ethanol electro‐oxidation at platinum surface in acid medium. (RHE = reversible hydrogen electrode.)
6. Figure 6.6 Stepwise reaction scheme for the oxidation of ethylene glycol.
7. Figure 6.7 Cyclic voltammogram for a smooth Pt bead electrode (diameter = 0.15 mm) at 25°C in 0.5 M H₂SO₄ containing 0.1 M HCOOH. Scan rate = 140 mV s⁻¹. (–) continuous reading and (‐‐‐) after 5 min at open circuit.
8. Figure 6.8 Principles of operation of a DBFC with (a) a cation‐conducting membrane and (b) an anion‐conducting membrane. Drawn to emphasize the chemical balance of the reactions at the electrodes.
9. Figure 6.9 (a) EFOY Comfort fuel cell installed in a mobile home with a container of methanol on the left and (b) range of EFOY Pro series (800–2400 W).
10. Figure 6.10 5‐kW DMFC stack developed within the framework of the European ‘Dreamcar’ project.
Chapter 07
1. Figure 7.1 (a) Current density distribution and (b) electrochemical impedance spectroscopy Nyquist plot at selected cell segments for a PEMFC at 200°C; cathode stoichiometry of λ = 3.
2. Figure 7.2 Open‐circuit voltage of a hydrogen fuel cell under different conditions. The two curves for the voltage at the exit show how the voltage depends on fuel utilization and temperature. In both cases, the oxygen utilization is 50%.
3. Figure 7.3 Common symbol for a heat‐exchanger. The fluid to be heated passes through the zigzag element.
4. Figure 7.4 Hot and cold heating plots for a conceptual 3.25‐MW MCFC system with high‐pressure steam generation. ss, steam superheat; Bfw, boiler feed water.
5. Figure 7.5 Composite curves derived from data presented in Figure 7.4.
6. Figure 7.6 Cell arrangement using ribbed substrates (bipolar plates): a, anode; e, electrolyte; and c, cathode layers.
7. Figure 7.7 Schematic basic design of water‐cooled PAFC stacks produced by International Fuel Cells (IFC). The figure shows a cross section through two cells of the stack.
8. Figure 7.8 Effect of temperature on PAFC cell voltage for different fuels: H₂, H₂ + 20 ppm H₂S, H₂ + CO and simulated coal gas (SCG).
Chapter 08
1. Figure 8.1 Anode and cathode reactions for a MCFC using hydrogen fuel. Note that the product water is at the anode and that both carbon dioxide and oxygen have to be supplied to the cathode.
2. Figure 8.2 Adding carbon dioxide to the cathode gas stream does not add complexity.
3. Figure 8.3 Anode and cathode reactions for an MCFC using carbon monoxide fuel.
4. Figure 8.4 Schematic cross‐section of an MCFC: cell components exposed to high‐temperature hot corrosion environment showing the location of the wet seals on the anode and cathode sides of the electrolyte support matrix.
5. Figure 8.5 Examples of practical separator‐plate designs with internal manifolding: (a) IMHEX design of ECN, (b) multiple‐cell stack of Hitachi and (c) cross‐section of wet‐seal area in an internally manifolded MCFC stack.
6. Figure 8.6 Combination of IIR and DIR achieves very high electrical conversion efficiency and high conversion of fuel.
7. Figure 8.7 Alkali transport mechanisms in the DIR‐MCFC.
8. Figure 8.8 Influence of oxidant gas composition on cathode overpotential in a MCFC at 650°C.
9. Figure 8.9 Fuel‐cell stack manufactured by Fuel Cell Energy.
10. Figure 8.10 A 300‐kW DFC‐300® system.
11. Figure 8.11 DFC1500® 1.4‐MW system showing the different process units.
12. Figure 8.12 DFC3000® 2.8‐MW system.
13. Figure 8.13 Example of MCFC system assembly. MTU ‘Hot Module’ cogeneration system showing (a) stack construction, (b) simplified flow diagram and (c) early demonstration units under construction.
14. Figure 8.14 World’s largest operating MCFC power plant (59 MW) located in Hwaseong, South Korea, comprises 21 DFC‐3000® systems and is owned by Gyeonggi Green Energy.
15. Figure 8.15 Stack networking can simplify system design and increase overall performance.
16. Figure 8.16 Electricity production and carbon separation.
17. Figure 8.17 Illustration of the Jacques and Briggs carbon battery: (a) 100 cells sitting on top of a coal‐fired furnace. (b) Details of an individual cell: a carbon, C, is plunged into a solution of caustic soda, E; a pump, A, forces air into a perforated nozzle, R, which distributes the air uniformly in the electrolyte. The positive pole is fixed upon an iron receiver, I, that contains the solution, and the negative pole, B, upon the carbon that is supported and insulated from the receiver by a collar, S. Two tubes, o and i, serve for the admission and discharge of the electrolyte solution.
Chapter 09
1. Figure 9.1 Anode and cathode reactions for the SOFC, when using hydrogen and carbon monoxide fuel.
2. Figure 9.2 Structure of yttria‐stabilized zirconia.
3. Figure 9.3 Two representations of the cubic perovskite structure of LaGaO₃; (a) La‐centred unit cell; (b) corner‐shared GaO₆ octahedra (Ga in the centre surrounded by 6 atoms) with La centred on 12 coordinate sites. Large red spheres = O²⁻ ions; light green spheres = La³⁺ ions; small blue spheres = Ga³⁺.
4. Figure 9.4 Specific conductivity versus reciprocal temperature for selected solid oxide electrolytes.
5. Figure 9.5 Typical single‐cell performance of LSGM electrolyte (500 µm thick) over a range of temperatures.
6. Figure 9.6 Total conductivities of several well‐known oxide‐ion conductors as a function of reciprocal temperature: CGO, Ce_0.8Gd_0.2O_1.9; Ge‐apatite, La₁₀(GeO₄)₆O₃; LAMOX, La₂Mo₂O₉; LSGM, La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85; Si‐apatite, La₁₀(SiO₄)₆O₃ and YSZ, (ZrO₂)_0.92(Y₂O₃)_0.08.
7. Figure 9.7 (a) Illustration of the three‐phase boundary regions of different SOFC anode materials. (b) Extension of the boundary is obtained with mixed conducting cathode materials.
8. Figure 9.8 End view of tubular SOFC produced by Siemens Westinghouse. Both electrolyte and anode are built onto the air cathode.
9. Figure 9.9 Small stack of 24 tubular SOFCs. Each tube has a diameter of 22 mm and is about 150 cm long.
10. Figure 9.10 Diagram showing how the tubular‐type SOFC can be constructed with (almost) no seals.
11. Figure 9.11 Influence of temperature on the performance of Siemens Westinghouse tubular fuel cells.
12. Figure 9.12 Stack with four 10 × 10 cm² SOFCs in one layer (window‐frame design FY520).
13. Figure 9.13 Acumentrics tubular SOFC bundle as used in the RP1500, 1.5‐kW system.
14. Figure 9.14 (a) Kyocera–Osaka gas power‐generation unit (left) and heating unit that uses SOFC exhaust heat (right) and (b) Kyocera flat tubular cells.
15. Figure 9.15 Rolls‐Royce Integrated Planar SOFC concept.
16. Figure 9.16 System concept for an SOFC–GT combined cycle.
17. Figure 9.17 SOFC–PEMFC hybrid system (see also Table 9.1).
Chapter 10
1. Figure 10.1 The many different pathways by which hydrogen can be supplied to fuel cells.
2. Figure 10.2 Distillation products of crude petroleum.
3. Figure 10.3 Equilibrium concentrations of products and reactants for steam reforming of methane at 100 kPa as a function of temperature.
4. Figure 10.4 Pre‐reformer system devised for a Siemens 50‐kW SOFC demonstration.
5. Figure 10.5 Schematic representation of direct and indirect internal reforming.
6. Figure 10.6 Three main designs of solar furnace: (a) parabolic dish, (b) central receiver and (c) parabolic trough.
7. Figure 10.7 Schematic of a membrane reactor.
8. Figure 10.8 Diagram of a fuel‐processing system for a phosphoric acid fuel cell. The numbers indicate approximate temperatures (°C).
9. Figure 10.9 Haldor Topsøe heat‐exchange reformer.
10. Figure 10.10 Plate or microchannel reformer concept. Catalyst is coated as thin film onto one or both sides of a heat‐exchange material.
11. Figure 10.11 Experimental compact reformer reactors. (a) and (b) Pacific Northwest National Laboratory liquid fuel reformer (courtesy of Pacific Northwest National Laboratory). (c) Proof‐of‐concept Advantica natural gas reformer, a diffusion‐bonded multichannel reactor block (3 × 3 × 10 cm).
12. Figure 10.12 Concept of membrane reformer system under development by Tokyo Gas.
13. Figure 10.13 Johnson Matthey HotSpot^™ reactor. These were made in different forms for methanol, methane or gasoline processing.
14. Figure 10.14 ITM Power HGas electrolyser stacks, each operating at 8 MPa pressure.
15. Figure 10.15 Hydrogen filling stations using (a) ITM Power PEM electrolysers coupled with wind turbine at the Advanced Manufacturing Park, South Yorkshire, United Kingdom. (b) Hydrogenics HySTAT alkaline electrolysers 130 kg day⁻¹ dispensing 70 MPa H₂, Stuttgart, Germany.
16. Figure 10.16 ITM Power HGas rapid‐response electrolyser: (a) installed in a P2G system in Frankfurt, Germany and (b) stack of PEM cells.
17. Figure 10.17 Operating principles of a tandem cell for enhanced hydrogen production.
Chapter 11
1. Figure 11.1 Tube trailer for delivery of compressed hydrogen gas — 30 tubes and 1225 m³ (105 kg) capacity.
2. Figure 11.2 Composite hydrogen storage tanks on the Honda FCX fuel‐cell car chassis.
3. Figure 11.3 Examples of cryogenic LH₂ tanks: (a) NASA bulk storage for space missions. (b) installation for AC Transit fuelling station at Emeryville, California. (c) Tank in the rear of BMW series 7 car. (d) Proposed bulk ocean transport from Australia to Japan by Kawasaki Heavy Industries.
4. Figure 11.4 Refilling with H₂.
5. Figure 11.5 PCT curve for hydrogen absorption and desorption with a LaNi₅ alloy. Note that absorption and desorption have different pressures (P_a, P_d) in the almost horizontal portion of the relationship; pressure is given in P_a.
6. Figure 11.6 Dissociation pressures of various metal hydrides. Note that Mm in MmNi₅H₆ denotes mischmetal, which is a mixture of alkali earth elements.
7. Figure 11.7 Hydrostik hydrogen canister (left) that accompanies the Horizon ‘MiniPak’ fuel‐cell USB charger (right), employed to power portable electronic equipment such as smartphones.
8. Figure 11.8 Schematic representations of (a) buckminsterfullerene, (b) carbon nanofibres, (c) single‐ and multiwalled carbon nanotubes and (d) metal oxide framework.
9. Figure 11.9 Schematic representation of the relative volumes of two hydrides, liquid hydrogen and compressed gas (20 MPa pressure) to contain 4 kg of hydrogen for a vehicle driving range of 400 km.
10. Figure 11.10 Small metal hydride hydrogen store for fuel cells used with small portable electronic equipment.
Chapter 12
1. Figure 12.1 Some different types of compressor: (a) Roots positive‐displacement pump, (b) twin‐screw Lysholm, (c) centrifugal (radial) design and (d) axial flow design.
2. Figure 12.2 (a) Typical centrifugal air‐compressor rotor and (b) twin‐screw compressor.
3. Figure 12.3 Symbols for (a) a compressor and (b) a turbine.
4. Figure 12.4 Performance chart for a typical twin‐screw compressor. A mass flow factor of 5 corresponds to the air needs of a fuel cell with an output of about 250 kW.
5. Figure 12.5 Performance chart for a typical centrifugal compressor.
6. Figure 12.6 Eaton supercharger. The unit is about 25 cm long and will boost pressure to between 36 and 70 kPa.
7. Figure 12.7 Lysholm compressor (Model 1200 AX). Air enters a hole (not visible) on the left and exits via the six holes on the visible face. The pulley on the right drives the screws.
8. Figure 12.8 Performance chart for a typical small radial turbine.
9. Figure 12.9 Diagram of a simple ejector circulation pump.
10. Figure 12.10 Diagram of a diaphragm pump — a device with the advantages of low‐cost, quiet operation and long‐term reliability.
11. Figure 12.11 Data from a 250‐kW fuel‐cell system designed to power a bus.
12. Figure 12.12 Symbol used for an electronically operated switch.
13. Figure 12.13 Circuit diagrams showing the operation of a switch‐mode, step‐down, voltage regulator: (a) current path when switch is on and (b) current path when switch is off.
14. Figure 12.14 Currents in the switch‐mode, step‐down, regulator circuit.
15. Figure 12.15 Circuit diagram to show the operation of a switch‐mode, step‐up, voltage regulator: (a) current path when switch is on and (b) current path when switch is off.
16. Figure 12.16 H‐bridge inverter circuit for producing single‐phase alternating current.
17. Figure 12.17 Current versus time graph for a square‐wave, switched mode, single‐phase inverter.
18. Figure 12.18 Pulse‐width modulation switching sequence for producing an approximately sinusoidal alternating current from the circuit of Figure 12.17.
19. Figure 12.19 Typical voltage versus time waveforms from a pulse‐modulated inverter.
20. Figure 12.20 Graph summarizing some data from a real 250‐kW fuel‐cell system used to power a bus: (a) narrow tolerance band and (b) wide tolerance band.
21. Figure 12.21 (a) Circuit diagram of a simple three‐phase DC–AC inverter and (b) current versus time graph for the inverter assuming a purely resistive load. One complete cycle for each phase is shown. Current flowing out from the common point is taken as positive.
22. Figure 12.22 ‘Universal’ three‐phase inverter.
23. Figure 12.23 Voltage and current out of phase. The reactive power can be generated locally by distribution systems such as fuel cells.
24. Figure 12.24 Relationship between true power, apparent power and reactive power.
25. Figure 12.25 Diagram of a simple fuel‐cell–battery hybrid system.
26. Figure 12.26 Power versus time graphs for systems suitable for a soft hybrid electric vehicle: (a) without and (b) with regenerative braking.
27. Figure 12.27 Diagram of a hybrid fuel‐cell–battery system for a vehicle with regenerative braking. Bold arrows indicate energy flows. A current‐sensing resistor in series with the battery measures the input and output of charge.
28. Figure 12.28 Diagrams of (a) parallel and (b) series versions of hybrid fuel‐cell vehicle.
29. Figure 12.29 The 75 different pathways investigated in the North American well‐to‐wheels study conducted in 2001 by GM, ANL, BP, Exxon/Mobil and Shell.
30. Figure 12.30 Process flowsheet for a 100 kW PEMFC system operating in a stationary power application of about 100 kW output. Note that, for clarity, some stream numbers have been omitted from the table. HX, heat‐exchanger; HTS, high‐temperature shift; LTS, low‐temperature shift.
31. Figure 12.31 The Alstom Coradia iLint zero‐emission fuel‐cell train.