110915 - final bulk molding compound use in automotive fuel … · 2011. 8. 30. · bulk molding...

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


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.


Outline

IntroductionNeed and Suitability of Fuel Cells for Automotive UseMaterial Options for Bipolar PlatesProperty and Cost ComparisonSuccessful CommercializationConclusion


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


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


Outline



Automotive Requirements

Reduced CO2/GHG emissionsHigher fuel efficiencyExtended rangeLightweightSafe / Non-toxicLow Life Cycle ImpactCost Effective, Affordable


System Cost Evolution

30% Reduction Since 2008

80% Reduction Since 2002

$51/KW vs. $30/KW Target

U.S. Dept. of Energy


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


Fuel Cell – PEM Schematic


Fuel Cell

(http://www.youtube.com/user/PoindexterSmith#p/u/0/WGproZrBQKk)


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


Fuel Cell – PEM “Stack”

Photo: Plug Power, Inc.


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


Design Requirements

Electrical ConductivityChemical / Corrosion ResistanceTemperature StabilityMechanical, Impact StrengthGas PermeabilityProduction Repeatability Gravimetric Power Density


Outline



Bi-Polar Plate Material Options

Expanded graphite / graphite foilsGraphite-thermoset compositesGraphite-thermoplastic compositesCoated metals / alloys


Expanded Graphite / Foil

Example: GrafCell® Bipolar PlateGrafTech International Holdings Inc.


Graphite-thermoset (BMC)

Example: BMC 940 Compression Molded Bipolar PlateBulk Molding Compounds, Inc.


Graphite-thermoplastic

Example: Vectra® LCP Injection Molded Bipolar PlateTicona / Celanese


Coated Metals / Alloys

Example: Borit Hydroformed Mettalic Bipolar PlateBorit NV


Outline



Stack Cost Breakdown

U.S. Dept. of Energy, 2011


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


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


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


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


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


Outline



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


Fuel Cell Fork Lift Providers

YaleCrown Raymond

Source: U.S. Department of Energy, EERE


GM Equinox Fuel Cell Program

Source: General Motors, Car Express News


2015 Passenger Car Launches

HondaToyotaDaimlerGeneral MotorsHyundai-Kia

Honda FCX Clarity

GM Equinox

Toyota Highlander

Mercedes-BenzB Class F-Cell

Hyundai Tuscon


Fuel Cell OutlookDeloitte Annual Technology Report

Fuel Cell Today

Automotive News

Fuel Cell


Outline



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


Acknowledgement

Special thanks toJohn Clulow

Fuel Cell and Technical Specialistand the team at BMC, Inc.


Thank You ! Obrigado !Gracias ! Danke ! Merci !


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


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)


Composite Bipolar Plates


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.

110915 - final bulk molding compound use in automotive fuel … · 2011. 8. 30. · bulk molding...

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