Bulk Molding Compound Use in Automotive Fuel Cell Applications

Transcription

1 Bulk Molding Compound Use in Automotive Fuel Cell Applications 2011 Society of Plastics Engineers Automotive Composites Conference & Exposition Cedric Ball

2 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.

3 Outline Introduction Need and Suitability of Fuel Cells for Automotive Use Material Options for Bipolar Plates Property and Cost Comparison Successful Commercialization Conclusion

4 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: H 2 -> 2H + + 2e - Cathode: 2H + ½O 2 + 2e - -> H 2 O

5 Advantages of Fuel Cells Direct conversion of chemical to electrical energy High conversion efficiencies Silent power, few or no moving parts No pollution or toxic emissions Plentiful fuel source: Hydrogen

6 Outline Introduction Need and Suitability of Fuel Cells for Automotive Use Material Options for Bipolar Plates Property and Cost Comparison Successful Commercialization Conclusion

7 Automotive Requirements Reduced CO2/GHG emissions Higher fuel efficiency Extended range Lightweight Safe / Non-toxic Low Life Cycle Impact Cost Effective, Affordable

8 System Cost Evolution 30% Reduction Since % Reduction Since 2002 $51/KW vs. $30/KW Target U.S. Dept. of Energy

9 Types of Fuel Cells Alkaline Fuel Cells (AFCs) Solid Oxide Fuel Cells (SOFCs) Molten-Carbonate Fuel Cells (MCFC) Proton Exchange Membrane (PEM) Low Temp Direct Methanol High Temp PEM-Type fuel cell is focus for automotive use

10 Fuel Cell PEM Schematic Cedric Ball Bulk Molding Compounds, Inc.

11 Fuel Cell (

12 Fuel Cell PEM Construction Proton Exchange Membrane Electrode Assembly + Anode Electrode H 2 - Cathode Electrode O 2 Flow Field Plate (thermoset composite) Flow Field Plate (thermoset composite) Gas Diffusion Layers (GDL) (Porous Carbon Paper)

13 Fuel Cell PEM Stack Photo: Plug Power, Inc.

14 Bipolar Plate Assembly Forms the anode side of one cell and the cathode side of the adjacent cell Its functions are: Provide a rigid skeleton to support membranes Conduct electricity from the anode to the cathode Distribute gases evenly over electrode surfaces Provide cooling channels for the removal of heat

15 Design Requirements Electrical Conductivity Chemical / Corrosion Resistance Temperature Stability Mechanical, Impact Strength Gas Permeability Production Repeatability Gravimetric Power Density

16 Outline Introduction Need and Suitability of Fuel Cells for Automotive Use Material Options for Bipolar Plates Property and Cost Comparison Successful Commercialization Conclusion

17 Bi-Polar Plate Material Options Expanded graphite / graphite foils Graphite-thermoset composites Graphite-thermoplastic composites Coated metals / alloys

18 Expanded Graphite / Foil Example: GrafCell Bipolar Plate GrafTech International Holdings Inc.

19 Graphite-thermoset (BMC) Example: BMC 940 Compression Molded Bipolar Plate Bulk Molding Compounds, Inc.

20 Graphite-thermoplastic Example: Vectra LCP Injection Molded Bipolar Plate Ticona / Celanese

21 Coated Metals / Alloys Example: Borit Hydroformed Mettalic Bipolar Plate Borit NV

22 Outline Introduction Need and Suitability of Fuel Cells for Automotive Use Material Options for Bipolar Plates Property and Cost Comparison Successful Commercialization Conclusion

23 Stack Cost Breakdown U.S. Dept. of Energy, 2011

24 Qualitative Comparison* Material Type Property Expanded Graphite Foil Thermos et Composite Thermoplas tic Composite 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) *Actual properties and cost are determined by the cell design, specific composition and manufacturing process for each material

25 Properties Comparison Material Type Property Unit of Measure Expanded Graphite Foil Thermoset Composite (BMC 940) Thermoplastic Composite (Graphite PVDF) Metal (Coated Stainless Steel) Corrosion Resistance mmpy 0.5 mm H2SO4 80ºC Electrical Conductivity S/cm (In Plane) ,500 Mechanical Strength Mpa (Tensile Strength) ,000 Mechanical Flexibility Mpa (Flexural Strength) Thermal Conductivity W / m C Temperature Stability Tg / Melting Point C (200) 1,390 Minimum thickness 1.6 mm; limited to mirror image flow design Minimum thickness ~2.0 mm; unique flow design possible on opposite sides Sources: Manufacturers data sheets and available reports Minimum thickness ~1.0 mm; unique Minimum thickness flow design < 1.0 mm; limited to possible on mirror image flow opposite sides design; formability Formability Gas Permeability Hydrogen permeation rate, cc/min. 2.4 < 1.0 < Specific Gravity 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 Mass Production Cost (Current) Est. <50K systems / yr $11 $13 $15 $15 Cost (Projected) Est. 500K systems / yr $7 $8 $10 $10

26 Summary Pros / Cons Material Flexible graphite Pros Excellent conductivity and corrosion resistance Field demonstrated Cons High material cost High volume manufacturing method(s) not established Graphitethermoplastics Graphitethermosets High power density Field demonstrated High volume processcapable Coated metals Good corrosion resistance Low material cost Field demonstrated Good corrosion resistance Injection moldable Lower power density than graphite or metal High material cost Field demonstrated (?) Poor corrosion resistance; contamination of cell if coating not perfectly applied Limited formability

27 Challenges for Thermoset BPP Lower bulk electrical conductivity Lower mechanical strength (flexural) for handling and durability in use Molding of thin plates, while maintaining required properties Hydrogen permeation at thinner web crosssections (although not observed in stack) Perceived slow process speed, and therefore higher cost, when compared to metal stamping

28 Bottom line Flexible graphite Excellent electrical and corrosion performance High volume production (will be) difficult Graphite-thermoset composites Low material cost; field proven Net shape molding,, < 1 min cure achieves high volume Graphite-thermoplastic composites High material cost Field demonstrated (?) Coated metals / alloys Very thin cross sections possible > high power density Inherently susceptible to corrosion Expensive coating process must ensure perfection

29 Outline Introduction Need and Suitability of Fuel Cells for Automotive Use Material Options for Bipolar Plates Property and Cost Comparison Successful Commercialization Conclusion

30 Where OEMs Are Placing Bets Flexible graphite Ballard (for various OEMs) Daimler Graphite-thermoset composites Ballard (for various OEMs) General Motors Graphite-thermoplastic composites Experimental Coated metals / alloys General Motors Honda Ford

31 Fuel Cell Fork Lift Providers Yale Crown Raymond Source: U.S. Department of Energy, EERE

32 GM Equinox Fuel Cell Program Source: General Motors, Car Express News

33 2015 Passenger Car Launches Honda Toyota Daimler General Motors Hyundai-Kia Honda FCX Clarity Toyota Highlander Mercedes-Benz B Class F-Cell Hyundai Tuscon GM Equinox

34 Fuel Cell Fuel Cell Outlook Deloitte Annual Technology Report Automotive News Fuel Cell Today

35 Outline Introduction Need and Suitability of Fuel Cells for Automotive Use Material Options for Bipolar Plates Property and Cost Comparison Successful Commercialization Conclusion

36 Conclusion Fuel cells well suited for automotive use Clean, silent energy Efficient Costs reducing dramatically Bipolar plates are key component made from thermoset (BMC) composites, other materials Comparison shows material and cost advantages/disadvantages Key advantage for BMC bipolar plates is demonstrated field and commercial success

37 Acknowledgement Special thanks to John Clulow Fuel Cell and Technical Specialist and the team at BMC, Inc.

38 Thank You! Obrigado! Gracias! Danke! Merci!

39 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

40 Metal Composite Strengths Thin and capable of high ratio of power to stack volume (power density) High inherent electrical conductivity Excellent resistance to hydrogen permeation even in very thin cross section Cheap flow field fabrication via stamping Excellent physical durability Weaknesses Corrosion leading to increased contact resistance and membrane fouling Requires conductive protective coating such as gold increasing cost Restricted flow field options design on one side dictates design on other On-going development of lower cost protective coating Moderate thermal conductivity (stainless steel ~ 16 W/m C) Strengths Moldable net shape < 1 minute cycles Easily machined during development of channel geometry Design flexibility - independent flow channel geometry on each side Lower plate / bipolar assembly cost Excellent corrosion resistance and durability, especially in low-temp PEM Better thermal conductivity (40 W/m C in-plane, 20 through-plane) Capable of < 2 mm thick bonded twoplate assemblies with cooling channels Proven success in both stationary power and transportation applications. Weaknesses Web thickness limited to around 0.5 mm Higher hydrogen permeation at thinner cross-sections Fragile, requiring careful handling in post-mold operations Requires special compression press and tooling capabilities to mold Lower ratio of power to stack volume versus metal plates (power density)

41 Composite Bipolar Plates Cedric Ball Bulk Molding Compounds, Inc.

42 References 2007 U.S. Department of Energy Program Review: Next Generation Bipolar Plates for Automotive PEM Fuel Cells, Adrianowicz, 16 May Innovative Concepts for Bipolar Plates, CLEFS CEA No. 50/51. Winter PEMFC Metallic Bipolar Plates- Effect of Manufacturing Method on Corrosion Resistance, ECS Transactions, 25 (1) / The Electrochemical Society, Koç, S. Mahabunphachaia, and F. Dundar, Development of Low-Cost, Clad Metal Bipolar Plates for PEM Fuel Cells, Pacific Northwest National Laboratory and Battelle, M. Hardy and S. Chang, Low-Cost Composite Materials for Polymer Electrolyte Fuel Cells Bipolar Plates, Los Alamos National Laboratory, 1998 Fuel Cell Seminar, Palm Springs, CA November 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, Injection Moulded Low Cost Bipolar Plates for PEM Fuel Cells, Heinzel, Mahlendorf et al., Zentrum fur BrennstoffzellenTechnik GmbH (ZBT), Technical Cost Analysis for PEM Fuel Cells, Bar-On, Kirchain and Roth, Massachusetts Institute of Technology, 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, Metallic Bipolar Plate Technology for Automotive Fuel Cell Stack, Hirano, Kumar, Ricketts, Wilkosz, Saloka, Research and Innovation Center Ford Motor Company, A Novel Composite Plate for PEM Fuel Cell, Abd Elhamid et. Al., General Motors Research Laboratories, 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, Metal Bipolar Plates for PEM Fuel Cell - A Review, Tawfika, Hunga, Mahajan, Journal of Power Sources, Conductive Thermoplastic Composite Blends for Flow Field Plates for Use in Polymer Electrolyte Membrane Fuel Cells (PEMFC), Yuhua Wang, University of Waterloo Canada, 2006.