The Hydrogen Economy

1. The Hydrogen Economy By John Moore Physics 335 Spring 2004

2. Introduction • The Hydrogen Economy is the concept of using hydrogen as the energy carrier rather than fossil fuels. • There are numerous benefits from converting to a Hydrogen Economy. • However, the obstacles and the associated Physics are often not clearly understood.

3. Agenda • Why the United States needs an alternative to fossil fuels • The properties of hydrogen • The obstacles for the Hydrogen Economy • What a Fuel Cell is • How a Fuel Cell works • The future of the Hydrogen Economy

4. Currently, most the energy in the U.S. comes from fossil fuels However, there are problems with fossil fuels…

5. Main problems with fossil fuels • They will eventually be depleted. • They cause a variety of environmental problems. • They force the U.S. to be dependent on middle eastern countries.

6. Depletion • Millions of years ago, like today, plants used solar energy to power their growth • Plants decayed into oil, coal and natural gas • This left a giant warehouse of fossil fuels • This warehouse will eventually run low and the decay process will not repeat itself in the near to medium term future

7. Environmental Problems • Air pollution • Global warming • Effects on earth from mining or extracting the fuel • Effects on the earth when something goes wrong – Exxon Valdez

8. Dependence • United States may be forced to protect foreign sources of oil • Persian Gulf War • Current War with Iraq • Cost of War = Billions of dollars + American lives

9. The Properties of Hydrogen • Hydrogen is the smallest of all atoms • High energy content per weight - 3 times that of gasoline • Very low energy density per volume - Requires large storage tanks

10. Higher Heating Value of Different Fuel Options

11. The Obstacles to the Hydrogen Economy

12. Electricity Requirement • The electricity to produce Hydrogen would have to be derived from renewable sources rather than fossil fuels • All of the fossil fuel energy used for transportation now will have to convert to hydrogen which in turn will have to be produced by electricity • Electrical generating capacity of the U.S. will have to double

13. Production and Storage Questions that must be answered: • How will the Hydrogen be produced? • How will the produced Hydrogen be transported, distributed and stored?

14. How can Hydrogen be produced? Possible sources of production: • Electrolysis of water • Reforming fossil fuels

15. Electrolysis of Water • Dissociate water molecules into (H2) and (O2) • Can be done anywhere • One mole of water produces a mole of hydrogen gas and a half-mole of oxygen gas

16. Reforming Fossil Fuels • Oil and natural gas contain hydrocarbons • Split the hydrogen from the carbon using a fuel processor or a reformer • Discard leftover carbon as carbon dioxide

17. Does the reforming process really make sense? • Reforming fossil fuels does reduce air pollution. • However, it does not solve the: • Greenhouse gas problem • Depletion problem • Dependence problem • Therefore, it is only a transitional step and not the final solution.

18. Storage Options • Storing Hydrogen can be done in three ways: - Compressed form - Liquid form - Chemical bonding

19. Compressed Hydrogen • Similar to compressing natural gas but Hydrogen is less dense • Normally compressed between 200 and 250 bar for cylindrical tanks up to 50 liters • Currently, not practical for vehicles due to weight and size

20. Liquid Hydrogen • Does not liquefy until -253°C • 40% of energy can be lost • Liquid hydrogen has a high energy to mass ratio

21. Bonded Hydrogen • Certain metal and metal alloys can absorb Hydrogen • Metal hydride tank • Hydrogen released from metal when heat is applied

22. What is a Fuel Cell? • Creates electricity through electrochemical process • Emits heat and water only • Passenger vehicles • Most promising type - PEM

23. Parts of a PEMFC • There are four main parts: • Anode • Cathode • Catalyst • Proton Exchange Membrane

24. The Anode • The anode is the negative post of the fuel cell. • It conducts the electrons that are freed from the hydrogen molecules so that they can be used in an external circuit. • It has channels etched into it that disperse the hydrogen gas equally over the surface of the catalyst.

25. The Cathode • The cathode is the positive post of the fuel cell. • It has channels etched into it that distribute the oxygen to the surface of the catalyst. • It also conducts the electrons back from the external circuit to the catalyst, where they can recombine with the hydrogen ions and oxygen to form water.

26. The Catalyst • The catalyst is a special material that facilitates the reaction of oxygen and hydrogen. • It is usually made of platinum powder very thinly coated onto carbon paper or cloth. The catalyst is rough and porous so that the maximum surface area of the platinum can be exposed to the hydrogen or oxygen. • The platinum-coated side of the catalyst faces the PEM.

27. The Proton Exchange Membrane • The electrolyte is the proton exchange membrane. • This is a specially treated material that only conducts positively charged ions. • The membrane blocks electrons.

28. The Chemistry of a PEMFC • Pressurized hydrogen gas (H2), enters the fuel cell on the anode side • Oxygen gas (O2) is forced through the catalyst on the Cathode side • This reaction in a single fuel cell produces about 0.7 volts

29. In order to transition to a Hydrogen Economy… • Convert energy production to renewable sources • Build Hydrogen production, transportation, storage and distribution facilities • Large scale manufacture of fuel cells

30. Conclusion • In general, a transition to a pollution free, hydrogen economy is possible but the obstacles are significant. • The initiative has begun. President Bush has announced a $1.2 billion dollar initiative to reduce U.S. dependence on foreign oil by developing hydrogen-powered fuel cells. • Nevertheless, the complete transition is still a long way off. In the meantime, it is important to work to reduce fossil fuel dependence through efficiency and substitution.

31. Sources • "The Future of the Hydrogen Economy: Bright or Bleak?", Baldur Eliasson and Ulf Bossel, Proceedings, THE FUEL CELL WORLD, Lucerne /Switzerland, July 2002 • “How the Hydrogen Economy works” http://www.howstuffworks.com/hydrogen-economy.htm