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)70-90Space  Phosphoric Acid 150-210 Commercially available (PAFC)  Solid Polymer70-90Automotive application (PEMFC)  Moltan Carbonate 550-650 Power generation (MCFC)  Solid Oxide 1000-1100Power generation (SOFC)  Direct Methanol70-90Under 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.