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Introduction to Fuel Cell Systems

Introduction to Fuel Cell Systems. Conventional Current. e -. e -. e -. Anode (-) for fuel cell Electrons flow FROM anode H 2 is OXIDIZED. Cathode (+) for fuel cell Electrons flow TO cathode O 2 is REDUCED. H 2. 1/2O 2. 2H +. 3-phase region Reactant (O 2 ) Electrode (e - )

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Introduction to Fuel Cell Systems

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  1. Introduction to Fuel Cell Systems

  2. Conventional Current e- e- e- Anode (-) for fuel cell Electrons flow FROM anode H2 is OXIDIZED Cathode (+) for fuel cell Electrons flow TO cathode O2 is REDUCED H2 1/2O2 2H+ 3-phase region Reactant (O2) Electrode (e-) Electrolyte (H+) Electrolyte Conducts ions Impermeable to reactants Does not conduct e- H2O Fuel Cell Basics

  3. Electrical load e- Fuel in Oxidant in + Ions Anode gas channel Cathode gas channel Porous anode Porous cathode - Ions Electrolyte Depleted fuel out Product gas out (MCFC, SOFC) Fuel Cell Types Depleted oxidant out Product gas out (PEMFC, PAFC) Fuel cell typeElectrolyte (Mobile Ion) Proton exchange membrane fuel cell (PEMFC) Sulfonated polymer (H+) Direct methanol fuel cell (DMFC) Sulfonated polymer (H+) Phosphoric acid fuel cell (PAFC) Phosphoric acid (H+) Molten carbonate fuel cell (MCFC) Molten carbonate (CO32-) Solid oxide fuel cell (SOFC) Solid YSZ (O2-)

  4. Proton Exchange Membrane Fuel Cells (PEMFC) • Low temperature 60-80C (140–180F) • High power density • Potential for low cost • Attractive for transportation and small-scale CHP • 5 – 250 kWe Polymer membrane H2 - Rich Fuel Humid Air Anode: Pt supported on carbon Gas diffusion layers - porous carbon paper Flow channels cut in collector plate Cathode: Pt supported on carbon Cathode collector plate Anode collector plate Unused Fuel Depleted Air and Product Water (Vapor and Liquid)

  5. Direct Methanol Fuel Cells (DMFC) • Low temperature 20-90C (70–190F) • Low power density • High energy density (when fuel is considered) • Simplified fuel requirements • Attractive as an alternative to Li-ion batteries in portable electronics • Size: ~ Watts Polymer membrane CH3OH+H2O Humid Air Anode: Pt /Ru supported on carbon Backing layers - porous carbon paper Flow channels cut in collector plate Cathode: Pt supported on carbon Cathode collector plate Anode collector plate Unused Fuel, H2O & CO2 Depleted Air and Product Water (Vapor and Liquid)

  6. Phosphoric Acid Fuel Cells (PAFC) Phosphoric acid in Porous matrix • Op. temperature 200 C (390 F) • Commercially available • 200 kWe @ 40% electrical efficiency • Hundreds of demo stacks installed • Current cost is $5000/kWe H2 - Rich Fuel Air Anode: Pt supported on carbon Gas diffusion layers - porous carbon paper Flow channels cut in collector plate Cathode: Pt supported on carbon Cathode collector plate Anode collector plate Unused Fuel Depleted Air and Product Water (Vapor and Liquid)

  7. Molten Carbonate Fuel Cells (MCFC) Molten carbonate in porous matrix • High temperature 650 C (1200 F) • No precious metal catalysts • Inexpensive materials • Internal reforming of simple fuels • Compatible with bottoming cycles • Size range: 250–2000 kWe Humid Air and CO2 H2 - Rich Fuel Anode – Ni alloy Cathode - NiO Corrugated stainless steel collector plates Depleted Air Unused Fuel, Water, and CO2

  8. Solid Oxide Fuel Cells (SOFC) • High temperature 1000 C (1800 F) • No precious metal catalysts • Internal reforming of simple fuels • Compatible with bottoming cycles • 5 – 2000 kWe Materials of construction Air electrode (cathode): Lanthanum manganite Electrolyte: YSZ Fuel electrode (anode): Cermet – Nickel/YSZ

  9. Summary of Fuel Cell Characteristics

  10. Fuel cell stack

  11. Fuel Cell Systems Source Fuel Fuel Processor Fuel in Electrical Power Out FUEL CELL STACK Power Conditioner Exh Water Water Mgmt Heat Air Heat Out Thermal Mgmt Air Mgmt Exhaust Out

  12. Fuel Cell System Performance

  13. Fuel Processing Exhaust Compressed Air Spent Fuel From Anode LTS Water Natural Gas Feed (CH4) PROX Fuel to Anode (H2,CO2,H2O) HTS REF MS Desulfurizer Reformer CH4 + H2O + HEAT  3H2 + CO Shift Converters CO + H2O  H2 + CO2 + HEAT

  14. Fuel Cell Systems for Buildings

  15. Combined Heat & Power (CHP)For Building Applications Simultaneous production of heat and power for useful purposes 0.67 0.33 1 Conventional Electric Power Generation 0.2 0.4 1 0.4 Combined Heat and Power

  16. Fuel Cell Systems for CHP Applications in Buildings • Wide size range • Excellent full and part load performance • Minimal environmental impact • Simple maintenance • Site friendly

  17. FC System Integration for Buildings Typical 200kWe/200kWt PAFC System Exhaust 18% Thermal Energy 40 – 80 C (100 – 175 F) 40% Heat Recovery 40% 42% 100% 85% Fuel Cell Stack Air & Thermal Management Fuel Processor Power Conditioning Fuel Power 2% Heat

  18. 5 kWe/9kWt Residential PEMFC System

  19. Commercially Available 200 kWe PAFC System

  20. Prototype 100 kWe SOFC System

  21. Fuel Cell CHP System Economics • Cost of electricity ($/kWh) Maint 0.01-0.03 Net cost 0.05–0.17 Capital 0.01–0.08 = Fuel 0.06 + + HR Credit 0 – 0.03 - Basis: CC = $500 – $3000/kW r = 10% LF = 0.5 FC = $8/MCF E= 45% T= 40% A= 80%

  22. FCCHP Economics: Commercial Bldgs Basis: LF = 0. 5 F1 = 0.3 r = 12% N = 20years E=0.4 T=0.4 A=0.8 MC = $0.01/kWh

  23. Economic/Energy/EnvironmentalPerformance of FCCHP • 2,500 ft2 residence • Atlanta, GA • Alternatives: • Elec AC/Elec Ht (EAC-EH) • Elec AC/Gas Ht (EAC-GH) • Fuel cell CHP (FCCHP) WH HT FC HP AC ELEC

  24. Potential Driving Factors forFuel Cells in Buildings • REDUCED FIRST COST • Increased energy costs • Increased valuation of environmental benefits • Enhanced concern for power quality (e.g. Hospitals, data processing, security) • Integration with hydrogen infrastructure

  25. Fuel Cell Systems for Transportation

  26. Comparison of Fuel Cell Vehicles and Conventional IC Engine Vehicles • Primary energy use • Gasoline ICEV: 5 MJ/mile • FCV using cH2 – onsite NG SR: 2.3 MJ/mile • Emissions (GHG,regulated) • Gasoline ICEV: 410 g-CO2/mile • FCV using cH2 – onsite NG SR: 250 g-CO2/mile • Alternative/Renewable/Domestic fuels

  27. Efficiency of Conventional and Alternative Engines

  28. Automotive Fuel Cell System Water Vapor Condenser Air Humidifier Fuel Fuel System Air Air System De-ionized Water Thermal System From Hydrogen Storage Tanks H2 Humidifier Dome-Loaded Pressure Regulator Air In Water Injection Pump Air Compressor Humidification Water Reservoir Fuel Cell Stack H2 Inlet Air in Air out Thermostat Bypass Main Thermal Pump Radiator Reservoir

  29. Fuel Cell Engine

  30. On-Board versus Off-Board Reforming 1. On-Board Reforming Fuel Cell Fuel Tank Gasoline Methanol Other Hydrocarbon Fuel Processor 2. Direct Hydrogen: (Reforming off the Vehicle) Fuel Processing Station (reforming + purification + storage) Fuel Cell Hydrogen Tank Natural Gas Other Hydrocarbon Hydrogen Ref: SAE 2000-01-0001

  31. Fuel Selection Challenges

  32. Well to Wheel Energy Use for Conventional and Alternative Systems

  33. Well-to-wheels GHG Emissions

  34. Keys to FCV Commercialization • Affordability, plus people must want them (conventional vehicles are very good, and improving) • Hydrogen fuel storage and range (or on-board fuel processing?) • Infrastructure for hydrogen energy carrier; feedstock diversity to get to renewables

  35. Future H2 Energy System Configurations Hydrogen Storage and Dispensing Hydrogen Vehicle Electricity Heat Natural Gas Hydrogen Fuel processor Electrolyzer

  36. Possible Cost “Timeline” for Fuel Cells

  37. Questions???

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