Cedric Ball – Bulk Molding Compounds, Inc.
Bulk Molding Compound Use in Automotive Fuel Cell Applications
2011 Society of Plastics EngineersAutomotive Composites Conference & Exposition
Cedric Ball
Cedric Ball – Bulk Molding Compounds, Inc.
Abstract
Hydrogen fuel cell-driven electric cars continue on a slow, but steady, progression toward commercial viability. Dismissed by many as being too expensive, fuel cells are within range of the cost of other vehicle propulsion systems due to advancements in design and manufacturing that have taken place in recent years. Composites have been an integral part of the success of proton exchange membrane (PEM) fuel cells. Bipolar plates made from conductive bulk molding compound have proven to be effective, durable and low cost in comparison to other materials. This presentation documents properties, recent developments, and successful commercialization of thermoset bulk molding compound for transportation fuel cell applications.
Cedric Ball – Bulk Molding Compounds, Inc.
Outline
IntroductionNeed and Suitability of Fuel Cells for Automotive UseMaterial Options for Bipolar PlatesProperty and Cost ComparisonSuccessful CommercializationConclusion
Cedric Ball – Bulk Molding Compounds, Inc.
What Is a Fuel Cell?
A device that converts chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent.
Anode: H2 -> 2H+ + 2e-
Cathode: 2H+ ½ O2 + 2e- -> H2O
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Advantages of Fuel Cells
Direct conversion of chemical to electrical energyHigh conversion efficienciesSilent power, few or no moving partsNo pollution or toxic emissionsPlentiful fuel source: Hydrogen
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Outline
IntroductionNeed and Suitability of Fuel Cells for Automotive UseMaterial Options for Bipolar PlatesProperty and Cost ComparisonSuccessful CommercializationConclusion
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Automotive Requirements
Reduced CO2/GHG emissionsHigher fuel efficiencyExtended rangeLightweightSafe / Non-toxicLow Life Cycle ImpactCost Effective, Affordable
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System Cost Evolution
30% Reduction Since 2008
80% Reduction Since 2002
$51/KW vs. $30/KW Target
U.S. Dept. of Energy
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Types of Fuel Cells
Alkaline Fuel Cells (AFCs)Solid Oxide Fuel Cells (SOFCs)Molten-Carbonate Fuel Cells (MCFC)Proton Exchange Membrane (PEM)
Low TempDirect MethanolHigh Temp
PEM-Type fuel cell is focus for automotive use
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Fuel Cell – PEM Schematic
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Fuel Cell
(http://www.youtube.com/user/PoindexterSmith#p/u/0/WGproZrBQKk)
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Fuel Cell – PEM Construction
Gas Diffusion Layers (GDL)
(Porous Carbon Paper)
Flow Field Plate
(thermoset composite)
Flow Field Plate
(thermoset composite)
- Cathode Electrode+ Anode Electrode
Proton Exchange Membrane Electrode Assembly
O2H2
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Fuel Cell – PEM “Stack”
Photo: Plug Power, Inc.
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Bipolar Plate Assembly
Forms the anode side of one cell and the cathode side of the adjacent cellIts functions are:
Provide a rigid skeleton to support membranesConduct electricity from the anode to the cathodeDistribute gases evenly over electrode surfacesProvide cooling channels for the removal of heat
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Design Requirements
Electrical ConductivityChemical / Corrosion ResistanceTemperature StabilityMechanical, Impact StrengthGas PermeabilityProduction Repeatability Gravimetric Power Density
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Outline
IntroductionNeed and Suitability of Fuel Cells for Automotive UseMaterial Options for Bipolar PlatesProperty and Cost ComparisonSuccessful CommercializationConclusion
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Bi-Polar Plate Material Options
Expanded graphite / graphite foilsGraphite-thermoset compositesGraphite-thermoplastic compositesCoated metals / alloys
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Expanded Graphite / Foil
Example: GrafCell® Bipolar PlateGrafTech International Holdings Inc.
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Graphite-thermoset (BMC)
Example: BMC 940 Compression Molded Bipolar PlateBulk Molding Compounds, Inc.
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Graphite-thermoplastic
Example: Vectra® LCP Injection Molded Bipolar PlateTicona / Celanese
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Coated Metals / Alloys
Example: Borit Hydroformed Mettalic Bipolar PlateBorit NV
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Outline
IntroductionNeed and Suitability of Fuel Cells for Automotive UseMaterial Options for Bipolar PlatesProperty and Cost ComparisonSuccessful CommercializationConclusion
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Stack Cost Breakdown
U.S. Dept. of Energy, 2011
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Qualitative Comparison*
*Actual properties and cost are determined by the cell design, specific composition and manufacturing process for each material
PropertyExpanded
Graphite FoilThermos et Compos ite
Thermoplas tic Compos ite
Metal
Corrosion Resistance Excellent Good Good Poor
Electrical Conductivity Good Fair Fair Excellent
Mechanical Strength Fair Fair Poor Excellent
Mechanical Flexibility Fair Fair Fair Excellent
Thermal Conductivity Excellent Fair Poor Fair
Temperature Stability Good Good Good Excellent
Formability Fair Good Fair Fair
Gas Permeability Poor Fair Fair Excellent
Specific Gravity Low Low Lowest High
Mass Production Difficult Capable Capable Capable
Material Cost High Low High Med. (Coated)
Cost per kW Medium Medium High High (Coated)
Material Type
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Properties Comparison
Sources: Manufacturers’ data sheets and available reports
Property Unit of MeasureExpanded
Graphite Foil
Thermoset Composite (BMC 940)
Thermoplastic Composite
(Graphite PVDF)
Metal (Coated Stainless Steel)
Corrosion Resistance mmpy 0.5 mM H2SO4 (pH3) @ 80ºC 0.000 0.002 0.020 0.193Electrical Conductivity S/cm (In Plane) 300 187 119 13,500Mechanical Strength Mpa (Tensile Strength) 39 30 25 1,000Mechanical Flexibility Mpa (Flexural Strength) 58 51 35 460Thermal Conductivity W / m°C 110 46 10 21Temperature Stability Tg / Melting Point °C 125 187 135 (200) 1,390
Formability
Minimum thickness 1.6 mm;
limited to mirror image flow design
Minimum thickness ~2.0
mm; unique flow design possible on
opposite sides
Minimum thickness ~1.0 mm; unique
flow design possible on
opposite sides
Minimum thickness < 1.0 mm; limited to
mirror image flow design; formability
Gas Permeability Hydrogen permeation rate, cc/min. 2.4 < 1.0 < 1.0 0Specific Gravity 1.6 1.82 1.33 7.45
Mass Production
Roller Embossing, Static Pressing or
High Speed Adiabatic Forming
Net shape compression
molding; gang press/robotic
feed
Net shape, injection molding or continuous lamination
Stamping press or hydroform; coating and/or sintering of
base metal required
Cost (Current) Est. $/kW @ <50K systems / yr $11 $13 $15 $15Cost (Projected) Est. $/kW @ 500K systems / yr $7 $8 $10 $10
Material Type
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Summary Pros / Cons
Poor corrosion resistance; contamination of cell if coating not perfectly appliedLimited formability
High power densityField demonstratedHigh volume process-capable
Coated metals
High material costField demonstrated (?)
Good corrosion resistanceInjection moldable
Graphite-thermoplastics
Lower power density than graphite or metal
Good corrosion resistanceLow material costField demonstrated
Graphite-thermosets
High material costHigh volume manufacturing method(s) not established
Excellent conductivity and corrosion resistanceField demonstrated
Flexible graphite
ConsProsMaterial
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Challenges for Thermoset BPP
Lower bulk electrical conductivityLower mechanical strength (flexural) for handling and durability in useMolding of thin plates, while maintaining required properties Hydrogen permeation at thinner web cross-sections (although not observed in stack)Perceived slow process speed, and therefore higher cost, when compared to metal stamping
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Bottom line …
Flexible graphiteExcellent electrical and corrosion performanceHigh volume production (will be) difficult
Graphite-thermoset compositesLow material cost; field provenNet shape molding, , < 1 min cure achieves high volume
Graphite-thermoplastic compositesHigh material costField demonstrated (?)
Coated metals / alloysVery thin cross sections possible > high power densityInherently susceptible to corrosionExpensive coating process must ensure perfection
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Outline
IntroductionNeed and Suitability of Fuel Cells for Automotive UseMaterial Options for Bipolar PlatesProperty and Cost ComparisonSuccessful CommercializationConclusion
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Where OEMs Are Placing Bets
Flexible graphiteBallard (for various OEMs)Daimler
Graphite-thermoset compositesBallard (for various OEMs)General Motors
Graphite-thermoplastic compositesExperimental
Coated metals / alloysGeneral MotorsHondaFord
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Fuel Cell Fork Lift Providers
YaleCrown Raymond
Source: U.S. Department of Energy, EERE
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GM Equinox Fuel Cell Program
Source: General Motors, Car Express News
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2015 Passenger Car Launches
HondaToyotaDaimlerGeneral MotorsHyundai-Kia
Honda FCX Clarity
GM Equinox
Toyota Highlander
Mercedes-BenzB Class F-Cell
Hyundai Tuscon
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Fuel Cell OutlookDeloitte Annual Technology Report
Fuel Cell Today
Automotive News
Fuel Cell
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Outline
IntroductionNeed and Suitability of Fuel Cells for Automotive UseMaterial Options for Bipolar PlatesProperty and Cost ComparisonSuccessful CommercializationConclusion
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Conclusion
Fuel cells well suited for automotive useClean, silent energyEfficientCosts reducing dramatically
Bipolar plates are key component made from thermoset (BMC) composites, other materialsComparison shows material and cost advantages/disadvantagesKey advantage for BMC bipolar plates is demonstrated field and commercial success
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Acknowledgement
Special thanks toJohn Clulow
Fuel Cell and Technical Specialistand the team at BMC, Inc.
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Thank You ! Obrigado !Gracias ! Danke ! Merci !
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Fuel Cell Comparison to Other Power Sources
Strengths• Direct conversion of chemical to electrical
energy• High conversion efficiencies (up to 80%)• Silent power, few or no moving parts• No pollution or toxic emissions• Plentiful fuel source: hydrogen vs. fossil fuels
Weaknesses• High system cost• Lack of Hydrogen Infrastructure• Limited demonstration of durability and reliability
especially at operating extremes• System size and weight compared to other
energy sources e.g. ICE• Air, Thermal and Water Management
Opportunities• Significant cost reductions still possible• Very high growth prospects• Complementary technology to ICE, battery,
solar, wind• Significant government incentives/regulations
and venture capital funding
Threats• Relatively low cost of existing energy sources• Lack of continuing investment• High uncertainty about market demand• Energy price fluctuations• Competing technologies with potentially shorter
development cycle
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Metal CompositeStrengthsThin and capable of high ratio of power to stack volume (power density)High inherent electrical conductivityExcellent resistance to hydrogen permeation even in very thin cross sectionCheap flow field fabrication via stampingExcellent physical durability
WeaknessesCorrosion leading to increased contact resistance and membrane foulingRequires conductive protective coating such as gold increasing costRestricted flow field options – design on one side dictates design on otherOn-going development of lower cost protective coatingModerate thermal conductivity (stainless steel ~ 16 W/m°C)
StrengthsMoldable net shape < 1 minute cyclesEasily machined during development of channel geometryDesign flexibility - independent flow channel geometry on each sideLower plate / bipolar assembly costExcellent corrosion resistance and durability, especially in low-temp PEMBetter thermal conductivity (40 W/m°C in-plane, 20 through-plane)Capable of < 2 mm thick bonded two-plate assemblies with cooling channelsProven success in both stationary power and transportation applications.
WeaknessesWeb thickness limited to around 0.5 mmHigher hydrogen permeation at thinner cross-sectionsFragile, requiring careful handling in post-mold operationsRequires special compression press and tooling capabilities to moldLower ratio of power to stack volume versus metal plates (power density)
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Composite Bipolar Plates
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References2007 U.S. Department of Energy Program Review: Next Generation Bipolar Plates for Automotive PEM Fuel Cells, Adrianowicz, 16 May 2007.Innovative Concepts for Bipolar Plates, CLEFS CEA No. 50/51. http://www.clefscea.fr/, Winter 2004-2005.PEMFC Metallic Bipolar Plates- Effect of Manufacturing Method on Corrosion Resistance, ECS Transactions, 25 (1) 1773-1782 10.1149/1.3210733 © The Electrochemical Society, Koç, S. Mahabunphachaia, and F. Dundar, 2009.Development of Low-Cost, Clad Metal Bipolar Plates for PEM Fuel Cells, Pacific Northwest National Laboratory and Battelle, M. Hardy and S. Chang, 2005.Low-Cost Composite Materials for Polymer Electrolyte Fuel Cells Bipolar Plates, Los Alamos National Laboratory, 1998 Fuel Cell Seminar, Palm Springs, CA November 1998.A Study of the Impact of Bipolar Plate Material Choices on Portable Fuel Cell Performance and Economy, Ramsey, Rowley et al., Los Alamos National Laboratory, 2004.Injection Moulded Low Cost Bipolar Plates for PEM Fuel Cells, Heinzel, Mahlendorf et al., Zentrum fur BrennstoffzellenTechnik GmbH (ZBT), 2000 – 2002.Technical Cost Analysis for PEM Fuel Cells, Bar-On, Kirchain and Roth, Massachusetts Institute of Technology, 2002.A Review of PEM Fuel Cell Durability: Degradation Mechanisms and Mitigation Strategies, J. Wu, X. Yuan et al., Institute for Fuel Cell Innovation, National Research Council of Canada, 2008.Metallic Bipolar Plate Technology for Automotive Fuel Cell Stack, Hirano, Kumar, Ricketts, Wilkosz, Saloka, Research and Innovation Center Ford Motor Company, 2010.A Novel Composite Plate for PEM Fuel Cell, Abd Elhamid et. Al., General Motors Research Laboratories, 2002.Corrosion Resistance Characteristics of Stamped and Hydroformed Proton Exchange Membrane Fuel Cell Metallic Bipolar Plates, Dundar et. Al, Virginia Commonwealth University, Journal of Power Sources, 2010.Metal Bipolar Plates for PEM Fuel Cell - A Review, Tawfika, Hunga, Mahajan, Journal of Power Sources, 2007.Conductive Thermoplastic Composite Blends for Flow Field Plates for Use in Polymer Electrolyte Membrane Fuel Cells (PEMFC), Yuhua Wang, University of Waterloo Canada, 2006.