Fuel Cell Handbook (Seventh Edition) By EG&G Technical Services, Inc. Under Contract No. DE-AM26-99FT40575 U.S. Department of Energy Office of Fossil Energy National Energy Technology Laboratory P.O. Box 880 Morgantown, West Virginia 26507-0880 November 2004 DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or respon- sibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manu- facturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Govern- ment or any agency thereof. Available to DOE and DOE contractors from the Office of Scientific and Technical Information, P.O. Box 62, 175 Oak Ridge Turnpike, Oak Ridge, TN 37831; prices available at (423) 576-8401, fax: (423) 576-5725, E-mail: [email protected] Available to the public from the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Road, Springfield, VA 22161; phone orders accepted at (703) 487-4650. TABLE OF CONTENTS Section Title Page 1. TECHNOLOGY OVERVIEW ................................................................................................. 1-1 1.1 INTRODUCTION ................................................................................................................ 1-1 1.2 UNIT CELLS ..................................................................................................................... 1-2 1.2.1 Basic Structure ................................................................................................... 1-2 1.2.2 Critical Functions of Cell Components.............................................................. 1-3 1.3 FUEL CELL STACKING ..................................................................................................... 1-4 1.3.1 Planar-Bipolar Stacking ..................................................................................... 1-4 1.3.2 Stacks with Tubular Cells .................................................................................. 1-5 1.4 FUEL CELL SYSTEMS....................................................................................................... 1-5 1.5 FUEL CELL TYPES............................................................................................................ 1-7 1.5.1 Polymer Electrolyte Fuel Cell (PEFC)............................................................... 1-9 1.5.2 Alkaline Fuel Cell (AFC)................................................................................. 1-10 1.5.3 Phosphoric Acid Fuel Cell (PAFC).................................................................. 1-10 1.5.4 Molten Carbonate Fuel Cell (MCFC) .............................................................. 1-11 1.5.5 Solid Oxide Fuel Cell (SOFC) ......................................................................... 1-12 1.6 CHARACTERISTICS......................................................................................................... 1-12 1.7 ADVANTAGES/DISADVANTAGES................................................................................... 1-14 1.8 APPLICATIONS, DEMONSTRATIONS, AND STATUS ........................................................ 1-15 1.8.1 Stationary Electric Power................................................................................. 1-15 1.8.2 Distributed Generation ..................................................................................... 1-20 1.8.3 Vehicle Motive Power...................................................................................... 1-22 1.8.4 Space and Other Closed Environment Power .................................................. 1-23 1.8.5 Auxiliary Power Systems................................................................................. 1-23 1.8.6 Derivative Applications.................................................................................... 1-32 1.9 REFERENCES.................................................................................................................. 1-32 2. FUEL CELL PERFORMANCE............................................................................................... 2-1 2.1 THE ROLE OF GIBBS FREE ENERGY AND NERNST POTENTIAL........................................ 2-1 2.2 IDEAL PERFORMANCE ..................................................................................................... 2-4 2.3 CELL ENERGY BALANCE ................................................................................................. 2-7 2.4 CELL EFFICIENCY ............................................................................................................ 2-7 2.5 ACTUAL PERFORMANCE................................................................................................ 2-10 2.6 FUEL CELL PERFORMANCE VARIABLES........................................................................ 2-18 2.7 MATHEMATICAL MODELS............................................................................................. 2-24 2.7.1 Value-in-Use Models ....................................................................................... 2-26 2.7.2 Application Models.......................................................................................... 2-27 2.7.3 Thermodynamic System Models...................................................................... 2-27 2.7.4 3-D Cell / Stack Models................................................................................... 2-29 2.7.5 1-D Cell Models............................................................................................... 2-31 2.7.6 Electrode Models.............................................................................................. 2-32 2.8 REFERENCES.................................................................................................................. 2-33 3. POLYMER ELECTROLYTE FUEL CELLS ........................................................................ 3-1 3.1 CELL COMPONENTS......................................................................................................... 3-1 3.1.1 State-of-the-Art Components ............................................................................. 3-2 3.1.2 Component Development................................................................................. 3-11 3.2 PERFORMANCE .............................................................................................................. 3-14 iii 3.3 PEFC SYSTEMS.............................................................................................................. 3-16 3.3.1 Direct Hydrogen PEFC Systems ...................................................................... 3-16 3.3.2 Reformer-Based PEFC Systems....................................................................... 3-17 3.3.3 Direct Methanol Fuel Cell Systems ................................................................. 3-19 3.4 PEFC APPLICATIONS..................................................................................................... 3-21 3.4.1 Transportation Applications............................................................................. 3-21 3.4.2 Stationary Applications.................................................................................... 3-22 3.5 REFERENCES.................................................................................................................. 3-22 4. ALKALINE FUEL CELL ......................................................................................................... 4-1 4.1 CELL COMPONENTS......................................................................................................... 4-5 4.1.1 State-of-the-Art Components ............................................................................. 4-5 4.1.2 Development Components ................................................................................. 4-6 4.2 PERFORMANCE ................................................................................................................ 4-7 4.2.1 Effect of Pressure ............................................................................................... 4-8 4.2.2 Effect of Temperature ........................................................................................ 4-9 4.2.3 Effect of Impurities .......................................................................................... 4-11 4.2.4 Effects of Current Density................................................................................ 4-12 4.2.5 Effects of Cell Life........................................................................................... 4-14 4.3 SUMMARY OF EQUATIONS FOR AFC............................................................................. 4-14 4.4 REFERENCES.................................................................................................................. 4-16 5. PHOSPHORIC ACID FUEL CELL .......................................................................................