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Fuel cells

Fuel cells. Fuel cell history. First demonstrated in principle by British Scientist Sir Willliam Robert Grove in 1839. Grove’s invention was based on idea of reverse electrolysis. What is a fuel cell. Creates electricity through electrochemical process Operates like a battery

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Fuel cells

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  1. Fuel cells

  2. Fuel cell history • First demonstrated in principle by British Scientist Sir Willliam Robert Grove in 1839. • Grove’s invention was based on idea of reverse electrolysis.

  3. What is a fuel cell • Creates electricity through electrochemical process • Operates like a battery • Emits heat and water only

  4. Parts of fuel cells • There are 4 main parts • Anode • Cathode • Catalyst • Proton exchange membrane

  5. Fuel cell theory • A fuel cell consists of two electrodes - Anode and Cathode. • Hydrogen and Oxygen are fed into the cell. • Catalyst at Anode causes hydrogen atoms to give up electrons leaving positively charged protons. • Oxygen ions at Cathode side attract the hydrogen protons.

  6. Cont….. • Protons pass through electrolyte membrane. • Electrons are redirected to Cathode through external circuit. • Thus producing the current - power

  7. Fuel cell working

  8. Types of fuel cells Temp.°CApplication • Alkaline (AFC) 70-90 Space • Phosphoric Acid 150-210 Commercially available (PAFC) • Solid Polymer 70-90 Automotive application (PEMFC) • Moltan Carbonate 550-650 Power generation (MCFC) • Solid Oxide 1000-1100 Power generation (SOFC) • Direct Methanol 70-90 Under development (DMFC)

  9. Alkaline Fuel Cell • Used in spacecraft to provide drinking water and electricity • Electrolyte: Aqueous solution of alkaline potassium Hydroxide • Output of 300w -5KW • Power generation efficiency of about 70% • Too expensive for commercial applications

  10. Phosphoric Acid Fuel cell • Used in hospitals, nursing homes and for all commercial purposes • Electrolyte: Liquid Phosphoric acid • Catalyst: platinum • Electrical efficiency of 40% • Advantages :using impure hydrogen as fuel and 85% of the steam can be used for cogeneration

  11. Contd … • Disadvantages: uses expensive platinum as catalyst • Large size and weight • Low power and current • Existing PAFC’s have outputs of 200kw and 1Mw are being tested

  12. Proton Exchange Membrane Cells • Also called as Solid Polymers and used for quick startup in automobiles, light duty vehicles and potentially to replace rechargeable batteries • Electrolyte :Solid organic polymer poly-perflourosulfonic acid. • Catalyst: Metals (usually platinum) coated on both sides of membrane act as catalyst • Advantages: Use of solid electrolyte reduces corrosion and management problems

  13. Contd.. • Disadvantages: Sensitive to fuel impurities • Cell outputs generally range from 50 to 250 kW.

  14. Molten Carbonate Fuel cell • Majorly used for electric utility applications • Electrolyte: Liquid solution of lithium, sodium and/or potassium carbonates. • Catalyst: Inexpensive metals can be used as catalyst other than Platinum • Advantages: High operating temperature allow for inexpensive catalysts

  15. Contd.. • Higher efficiency and flexibility to use more type of fuels like carbon monoxide, propane, marine gas due to high temperatures • Disadvantage: Higher temperature enhances corrosion and breakage of cell components • High fuel to electricity generation of about 60% or 85% with cogeneration. • 10 kw’s -1 mw’s MCFCS have been tested

  16. Solid Oxide Fuel Cell • Highly promising fuel cell • Used in big, high-power applications including industrial and large-scale central electricity generating stations • Some developers also see SOFC use in motor vehicles • Power generating efficiencies could reach 60% and 85%

  17. Cont.. • Two Variations • One type of SOFC uses an array of meter-long tubes, and other variations include a compressed disc that resembles the top of a soup can • Closer to commercialization • Demonstrations of tubular SOFC technology have produced as much as 220 kW

  18. Direct Methanol Fuel Cells • Similar to the PEM cells in that they both use a polymer membrane as the electrolyte • The anode catalyst itself draws the hydrogen from the liquid methanol, eliminating the need for a fuel reformer. • Efficiency of about 40% • typically operate at a temperature between 120-190 degrees F

  19. Cont.. • Relatively low range • Attractive for tiny to mid-sized applications, to power cellular phones and laptops • Higher efficiencies are achieved at higher temperatures • Major problem: Fuel crossing over from the anode to the cathode without producing electricity.

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