Proton Exchange Membrane Fuel Cells for Space Applications

1
Proton Exchange Membrane Fuel Cells for Space
Applications
2004 AIAA-Houston Annual Technical
Symposium Session 5 Power Systems New
Technology April 16, 2004 Karla F. Bradley
2
Background of Fuel Cells at NASA

• Alkaline Fuel Cells
• Selected for the Apollo Program
• Currently Over 100 Missions Flying on the Space
  Shuttle
• 3 Powerplants per Shuttle
• Each Produces 2-12 kW within 27.5 - 32.5 VDC
• Water Produced is Used for Life Support Cooling
• Reactant Gases H2 O2
• Historical Performance
• High Safety Reliability
• Power Section Has Limited Life Due to Corrosion
  Inherent to Alkaline Technology (Certified to
  2600 Hours on Existent Alkaline 5000 Hours on
  Long-Life Alkaline)

3
Proton Exchange Membrane Fuel Cell Development
Program

• Performance Goals of Proton Exchange Membrane
  (PEM) Fuel Cell Program
• Operating Life 10,000 hours
• Power Levels 3 - 25 kW, 7-10 kW nominal
• Voltage Applicable to 30V, 120V, 270V Systems
• Reactant Purity Capable of Operating on
  Propellant Grade Rather than High Purity
  Reactants
• Leverage off Stack Technology of Commercial
  Programs (Transportation Residential and
  Commercial Stationary Power)

4
Proton Exchange Membrane Fuel Cells for
Exploration

• Reduce Hazardous Materials/Fluids at KSC and
  Vendor
• No KOH
• No Asbestos
• Allows Greater Delta Pressure Across Solid
  Membrane than Across Asbestos Matrix
• Eliminates Hazard of KOH Elec. Contaminating
  Potable Water Supply
• Fuel Cell Flooding is Reversible with No Hardware
  Damage
• Potential for Greater Life would Support Longer
  Duration Missions
• Ability to Utilize Common Reactants with
  Propulsion Systems
• Propellant Grade Reactants (Instead of Ultra-High
  Purity O2)
• Reformed Hydrocarbons (Methane, Ethanol,
  Methanol)
• Possible Change from High Purity to Propellant
  Grade Reactants
• Potentially Reduces Number of Working Fluids for
  Ground Processing
• No FC-40 for Cooling
• Modernized Instrumentation Components Reduce
  Ground Mission Operations Support
• Single-Cell Monitoring

5
PEM Fuel Cell Development for Code T

• Previously Next Generation Launch Technology
  (NGLT)
• Multi-Center Program (JSC, GRC (lead), KSC, MSFC)
• JSC Helps Develop Requirements for Breadboard,
  Prototype and Flight PEM Fuel Cell
• 2 Vendors Design, Build, Test Breadboard PEMFC
  System
• 1 Vendor Designs, Builds Tests Prototype PEMFC
  System
• JSC Performs Testing
• 01 Build Test an Integrated System
• 03 Test Breadboard Systems from 2 Vendors
• 04 Perform Durability Testing on Selected
  Vendor Breadboard
• 05 Test Prototype System from 1 Vendor
• 06 PEMFC Ready for Flight Qualification

6
Top Issues for PEM Fuel Cell Development for Space

• Issues Driven by Pure O2 Environment
• Stack
• Durability of Constituents (Membranes, Separator
  Plates, etc.)
• Failure Modes
• Accessory Components Performance Life of
  Water/Oxygen Separation Recirculation Devices
  (Passive vs. Dynamic)
• System/Integration Issues Adequacy of Components
  Over Complete Range of Power Levels
• System Issues Driven by Space Environment
• Functionality of Components in Microgravity and
  Multi-G
• Functionality of Components Under Vibration
  Environments

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Summary of JSC PEM Fuel Cell Work Accomplished to
Date

• Fuel Cell Stack Tests
• Five Vendor-Supplied Cell Stack Tests have been
  Conducted to Help Establish Critical Performance
  Parameters
• PEM Durability in Pure Hydrogen/Oxygen (10,000
  Hour Goal)
• Humidity Control Design Features (Internal Versus
  External)
• Product Water Removal Schemes (Internal Versus
  External)
• Robustness and Durability of Graphite
• Over 11,000 hours Accumulated Test Time on One
  Vendors Stack
• Fuel Cell Accessory Section Component Tests
• Passive Water Separators
• Membrane Water Separator Testing Showed Gravity
  Dependence
• In-House Designed Built Water Separator
• KC-135 Flight Tested for 30-40 Parabolas with 25
  Seconds Zero-g Per Parabola
• Good Microgravity Performance but Needs
  Improvements for Gravity Operation
• System Modifications Needed for Further Testing
• Microchannel Water Separator
• Limited Ground Data Showed Good Performance in
  Various Orientations
• KC-135 Testing Scheduled for May 04

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PEM Fuel Cell Integrated Test System Schematic
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Summary of JSC PEM Fuel Cell Work Accomplished to
Date (continued)

• Use Ejectors for Reactant Recirculation (Passive)
• Procured and Tested Commercially Available
  Ejectors
• Design, Manufacture and Test Ejectors In-House
  Test Results Showed Ejectors can Successfully
  Achieve the Flow Rates and Pressures Needed for
  Reactant Recirculation in a PEMFC System
• Integrated Fuel Cell Testing
• System Including Stack, O2 and H2 Water
  Separators and JSC Ejectors was Operated
  Successfully
• Two Aerospace Vendors Prepared Conceptual Designs
  for Potential Shuttle Upgrades Fuel Cell Program
  in 97
• Performance Tested Two NGLT Breadboard PEMFC
  Systems
• One Stack Failed Due to Water Management Problems
• Other System Was Able to Successfully Demonstrate
  the NASA-Defined Performance Profile
• Fuel Cell-Powered Rover Demonstrations in FY03
  and FY04

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Fuel Cell Technology Roadmap

• Planetary Rovers
• PEM fuel cell power plant
• Steam reforming of fuel from planetary resources
• Methane (CH4), or
• Ethanol (C2H5OH)
• Methanol (CH3OH)
• Oxidant (O2) from planetary resources (e.g.,
  electrolysis)

• Fuel Cell Requirements
• Pure O2 oxidant stream
• Load following (e.g. 61 in 200 ms)

• Development toward improved
• Fluid commonality with propulsion,
• life support, thermal control, etc
• Mission reliability
• Life cycle cost
• Power/energy density

• Advanced Exploration
• Gravity independence
• Regenerative fuel cells
• Electrolysers
• H2O propulsion

• 1970s Space Shuttle
• Alkaline fuel cell power plant
• Gravity-independent water management
• (0-g, multi-g, vibration)
• Full mission reactant storage
• Reactant grade O2 (supercritical)
• Propulsion grade H2 (supercritical)

Next Generation Launch Technology

• Proton Exchange Membrane (PEM) fuel cell power
  plant
• Gravity-independent water management
• (0-g, multi-g, vibration)
• Full mission reactant storage
• Propulsion grade O2 (liquid)
• Propulsion grade H2 (supercritical)

• 1990s Shuttle Upgrades
• Long Life Alkaline Fuel Cell

• H2 reformed on-board (lt10 ppm CO) from C2H5OH
  fuel (common fuel with propulsion)