2.  First lets make a comparison to a battery:  Like the battery below, a Fuel Cell an allows conversion of chemical to electrical NRG  A half reaction at the anode produces free electrons  A half reaction at the cathode uses free electrons  Free electrons cannot pass through the electrolyte, so they are forced through the load by the potential difference the two half reactions generate and they can do work (light a bulb, turn a motor…) Fuel Cells: What are they & what do they do? http://www.odec.ca/projects/2006/glaz6j2/battery_encarta.JPG

3.  A Fuel Cell allows conversion of chemical to electrical NRG  Similar to a rechargeable battery in that respect but the reactants are stored outside device  Since a fuel cell only converts NRG forms, just as with a rechargeable battery, we still need a source of NRG Fuel Cells: What are they & what do they do? http://image.greenmanufacturer.net/a/sage-supplier-lowering-costs-of-lithium-ion- batteries-for-ev-power-trains-lithium-ion-battery-diagram.gif http://www.ultracell-llc.com/images/tech_fuel_dgrm.jpg & vice versa (electrolysis)

4. How does it work? A fuel cell separates the combination of H 2 and O 2 into half reactions so the flow of electrons can be allowed to do work

5. Hydrogen molecules flow over the anode PEM FUEL CELL: Step 1

6. A catalyst removes the electrons leaving H + ions PEM FUEL CELL: Step 2

7. Electrons flow through the wire PEM FUEL CELL: Step 3

8. H + ions flow through the electrolyte PEM FUEL CELL: Step 4

9. Oxygen molecules flow over the cathode PEM FUEL CELL: Step 5

10. Electrons combine with the O2 at the cathode PEM FUEL CELL: Step 6

11. Hydrogen ions react with the Oxygen to form… PEM FUEL CELL: Step 7

12. Water! PEM FUEL CELL: Step 8

13. PEM FUEL CELL: Step 9

14. PEM FUEL CELL: Reactions Anode:2H 2 → 4H + + 4e - Cathode:O 2 + 4H + + 4e - → 2H 2 O Net Reaction:O 2 + 2H 2 → 2H 2 O

15. How does this net reaction relate to electrolysis? Fuel Cell Net Reaction:O 2 + 2H 2 → 2H 2 O NRG Released Electrolysis Net Reaction: 2H 2 O → O 2 + 2H 2 NRG Required Electrical NRG can be used to run the Fuel Cell in reverse to electrolyze water and produce H 2 ! Hydrogen is then just a way of storing the NRG to be released when the Fuel Cell is run forwards

16. Where do you get the NRG to produce Hydrogen? ultimate source of NRG on earth is the Sun NRG sources fossil fuels (old solar NRG) "renewables" (new solar NRG)

17. US NRG SOURCES & CONSUMPTION-2005

18. US NRG SOURCES & CONSUMPTION-2008 http://www.eia.doe.gov/aer/

19. Energy Flow Chart Chem. NRG (Plants) Electromagnetic (sunlight) Nuclear (sun) Chem. NRG (Fossil Fuels) Where does the NRG come from? photosynthesis Milions of years worth are buried Chemical (Electrolytic Cell) Electrical (Fuel Cell) Electrical (Solar Cell) Electrical (Generator) Thermal (Furnace) Mechanical (Turbine) Power Plant Mechanical (Motor) Burining Biomas from last growing season Wind produced by ueven heating of earth by sun