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Fuel cells, myths and facts

Fuel cells, myths and facts. PhD candidate Ole-Erich Haas. Outline. Fuel cell, history and general principle Fuel cell types and chemical systems PEM fuel cells for transport sector Polymer membranes Electrodes and catalysts Myths. Fuel cell history, new or old?. SOFC. Westinghouse.

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Fuel cells, myths and facts

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  1. Fuel cells, myths and facts PhD candidate Ole-Erich Haas

  2. Outline • Fuel cell, history and general principle • Fuel cell types and chemical systems • PEM fuel cells for transport sector • Polymer membranes • Electrodes and catalysts • Myths

  3. Fuel cell history, new or old? SOFC Westinghouse MCFC Mond & Langer [coined Fuel Cell] Broes & Ketelaar PAFC William Grove AFC PEMFC Bacon DMFC GE’s Membrane FC 1800 1839 1900’s 1930’s 1950’s 1970’s Now

  4. Fuel cells general principle • Fuel cells convert chemical energy to electric energy and heat • Combination of internal combustion engine and battery • More efficient than combustion, due to higher energy grade >

  5. Fuel cells general principle e- e- Unused Fuel Out Oxidant In Electron consumption Electron production Cathode Anode Fuel In Unused Oxidant Out Electrolyte

  6. Fuel cell types and chemical systems UTC, 12 kW stack

  7. Fuel cell types and chemical systems 200 kW UTC PureCell 200, installed power stations, PAFC

  8. Fuel cell types and chemical systems 430 kW hybrid, MCFC

  9. Fuel cell types and chemical systems 220 kW hybrid, SOFC

  10. Fuel cell types and chemical systems 100 kW (134 hp) Honda FCX Clarity

  11. PEM Fuel cell for transport sector • Reduce dependence of fossil fuels • Use PEM fuel cell to open for H2

  12. Hydrogen economy Where does H2 come from? • H2 from natural gas • Shift to electrolysis • Fossil fuels 85% of current world energy, IEA • Must invest in renewable energy sources geo wind hydro

  13. PEM Fuel cell for transport sector • Fuel cell system closest to our everyday life • Introduced in transport sector to reduce dependence on fossil fuel

  14. PEM Fuel Cell for transport sector How conversion of chemicals happen • Transport in the electrodes • Transport in the catalyst layer, membrane • Water management

  15. PEM Fuel Cell for transport sector Important improvements: • Membranes with better stability, conductivity, water, temperature • Catalyst, higher surface area, activity, stability • Support materials, conductivity, stability, water transport • Meet targets for lifetime, 40000 stationary, 5000 transport

  16. Status of PEM technology Polymer membranes, mechanical strength • Lifetime under cyclic conditions, about 2000 h • Degrade by swelling and chemical degrading • Support materials, chemically stabilized • Micromoulds, Nafion 112 • Swelling/drying cycles • 3 times less degradation

  17. Status of PEM technology Polymer membranes, mechanical strength • Fluorine release used as measure of degradation • 3 membranes in the same test, Nafion as the reference • Improvements in stability from different approaches

  18. Status of PEM technology Electrodes and catalyst, Pt on Carbon • Lifetime of the catalyst layer mainly related to the growth of Pt particles and carbon corrosion • Pt stable under 0.7 V • Startup/shutdown, above 0.7 V • Pt dissolves • Migrates to membrane • Redeposit on larger Pt particles

  19. Status of PEM technology Catalysts, Progress • New alloys increase stability of catalyst, Co, Au, Ni, Cr, Ir Improved catalyst stability

  20. Status of PEM technology Electrodes and catalyst, Pt on Carbon • Lifetime of the catalyst layer mainly related to the growth of Pt particles and carbon corrosion • C stable under 0.7 V • Startup/shutdown, above 0.7 V • C corrodes, CO2 • Reduced conductivity • Catalyst layer and electrode

  21. Status of PEM technology Electrode material, Progress • Support stability increase • New materials • Pretreatments Improved support stability

  22. Status of PEM technology Overall issues of PEM fuel cells • More expensive than competing technologies • Actual price depends on production numbers • Lifetime lower than competing technology • Need research on lifetime issues, performance is good - P. Mock, Journal of Power Sources, 190, (2009), 133-140

  23. Status of PEM technology Why keep on trying? • Research improves technology each year • Prototypes are closing in on targets • New technology chosen when its better • Also climate crisis and energy crisis urges progress/change

  24. Let’s go mythbusting!!

  25. Myth #1, not enough Platinum? World Platinum resources • The lucky few • 47000 metric tones Pt • How many fuel cell • cars can we make?

  26. Myth #1, not enough Platinum? World Platinum resources • The lucky few • 47000 metric tones Pt • How many fuel cell • cars can we make? Given, 90 kW with 45 g Pt, 1 billion cars or 1.7 times today's number

  27. Myth #1, not enough Platinum? World Platinum resources • The lucky few • 47000 metric tones Pt Given, 90 kW with 45 g Pt, 1 billion cars or 1.7 times today's number • Some remarks • Pt in car catalyzers all ready • What about Pt production • Few countries have reserves • Should research alternatives

  28. Myth #1, not enough Platinum? World Platinum resources • The lucky few Given, 90 kW with 45 g Pt, 1.037 billion cars or 1.73 times today's number

  29. Myth #2, batteries are better! Batteries or Li-ion, do not H2 • Easy transport of electrons compared to H2 • Less energy lost to surroundings

  30. Myth #2, batteries are better! Yes, but what about… • Carries oxidizer, heavy • Low energy density, long charging time • Low lifetime, 5 years, Tesla Motors • High cost, 200 – 300 $/kW • Lithium found in few countries, limited reserves? 5kWh pack in 1 billion cars use 25%

  31. Myth #2, batteries are better! Yes, but no.. • In price and performance PEMFC is leading • Both technologies needs further research • Similar problems regarding Pt and Li reserves • Combination seems best, Hybrids So, the myth that Batteries are better!

  32. Myth #3, not limited by the Carnot cycle Statement found in many text books • Fuel cells above the law? • Maximum efficiency of a heat engine TH QH W QL TL

  33. Myth #3, not limited by the Carnot cycle Statement found in many text books • What does it mean? • Maximum efficiency of a heat engine TH 1st law 2nd law QH W QL TL

  34. Myth #3, not limited by the Carnot cycle Statement found in many text books • What does it mean? • Maximum efficiency of a heat engine H2+1/2O2 QH 1st law 2nd law TH H2O QH W If we consider a Thermal Energy Reservoir 1st law 2nd law QL TL

  35. Myth #3, not limited by the Carnot cycle 1st law 2nd law (1) (2) H2+1/2O2 QH If we consider a Thermal Energy Reservoir 1st law 2nd law TH H2O (3) (4) QH W Now we can express the efficiency And from (2) and (4): (5) QL (6) TL (7)

  36. Myth #3, not limited by the Carnot cycle 1st law 2nd law (1) (2) H2+1/2O2 If we consider a Thermal Energy Reservoir QH 1st law 2nd law (3) TH (4) H2O Now we can express the efficiency QH W (5) (6) (7) Inserting (7) in to (6): QL (8) TL

  37. Myth #3, not limited by the Carnot cycle Now we can express the efficiency (5) H2+1/2O2 (6) (7) QH Inserting (7) in to (6): TH H2O (8) QH W Inserting (8) in to (5): (9) If this is ideal processes: QL TL

  38. Myth #3, not limited by the Carnot cycle Inserting (7) in to (6): (8) H2+1/2O2 Inserting (8) in to (5): QH (9) TH H2O If this is ideal processes: QH W And we get: Since: QL TL Which is the same expression we have for PEMFC’s

  39. Myth #3, not limited by the Carnot cycle Heat engine and PEMFC thermodynamic efficiencies H2+1/2O2 QH TH H2O QH W QL TL

  40. Myth #3, not limited by the Carnot cycle Heat engine and PEMFC thermodynamic efficiencies H2+1/2O2 QH TH H2O QH W QL TL

  41. Fuel cells, summary • Fuel cells have the possibility to reduce CO2 emmisions • Fuel cells need more research to improve • Main focus should be on lifetime issues • There is much to be done…..

  42. Fuel cells, summary Thank you for your attention!

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