Introduction to Fuel Cell Systems

1
Introduction to Fuel Cell Systems
2
Fuel Cell Basics
3
Fuel Cell Types
Depleted oxidant out Product gas out (PEMFC,
PAFC)
Fuel cell type Electrolyte (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)
Polymer membrane

• Low temperature 60-80C (140180F)
• High power density
• Potential for low cost
• Attractive for transportation and small-scale CHP
• 5 250 kWe

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)
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Direct Methanol Fuel Cells (DMFC)
Polymer membrane

• Low temperature 20-90C (70190F)
• 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

CH3OHH2O
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)
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Phosphoric Acid Fuel Cells (PAFC)
Phosphoric acid in Porous matrix

• Op. temperature 200 C (390 F)
• Commercially available
• 200 kWe _at_ 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)
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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 2502000 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
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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
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Summary of Fuel Cell Characteristics
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Fuel cell stack
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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
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Fuel Cell System Performance
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Fuel Processing
Compressed Air
Exhaust
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
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Fuel Cell Systems for Buildings
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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
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Fuel Cell Systems for CHP Applications in
Buildings

• Wide size range
• Excellent full and part load performance
• Minimal environmental impact
• Simple maintenance
• Site friendly

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FC System Integration for Buildings
Typical 200kWe/200kWt PAFC System
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Exhaust
Thermal Energy 40 80 C (100 175 F)
40
Heat Recovery
85
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40
100
Fuel Cell Stack Air Thermal Management
Fuel Processor
Power Conditioning
Fuel
Power
2
Heat
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5 kWe/9kWt Residential PEMFC System
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Commercially Available 200 kWe PAFC System
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Prototype 100 kWe SOFC System
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Fuel Cell CHP System Economics

• Cost of electricity (/kWh)

Maint 0.01-0.03
Capital 0.010.08
Fuel 0.06
HR Credit 0 0.03
Net cost 0.050.17


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Basis CC 500 3000/kW r 10 LF
0.5 FC 8/MCF ?E 45 ?T 40 ?A 80
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FCCHP Economics Commercial Bldgs
Basis LF 0. 5 F1 0.3 r 12 N
20 years ?E0.4 ?T0.4 ?A0.8
MC 0.01/kWh
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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
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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

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Fuel Cell Systems for Transportation
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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

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Efficiency of Conventional and Alternative Engines
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Automotive Fuel Cell 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
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Fuel Cell Engine
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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
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Fuel Selection Challenges
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Well to Wheel Energy Use for Conventional and
Alternative Systems
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Well-to-wheels GHG Emissions
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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

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Future H2 Energy System Configurations
Hydrogen Storage and Dispensing
Hydrogen Vehicle
Electricity
Heat
Natural Gas
Hydrogen
Fuel processor
Electrolyzer
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Possible Cost Timeline for Fuel Cells
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Questions???