Hydrogen Economy

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					The Hydrogen Economy:
      Fuel Cells

PGCC Honors Academy Project
         Presented by
        Queenet Ibekweh

       7 December 2007

         Supervised by
      Prof. William A. Boyle
        What Is A Fuel Cell?
A fuel cell, also known as a flow battery, is
  an electrochemical device that combines a
  fuel and an oxidizer such hydrogen and
  oxygen to produce electricity.
       Purpose of a Fuel Cell
 It is used to produce electrical current that
  can be directed outside the cell to perform
  work, such as powering an electric motor
  or illuminating a light bulb or a city.
 Due to the way electricity behaves, this
  current returns to the fuel cell, completing
  an electric circuit.
        How the Fuel Cell Works
   Hydrogen molecules enter the fuel cell at the anode and
    are stripped of their electrons.
   Hydrogen atoms become “ionized” and carry positive
    charges.
   Negative charged electrons provide current through the
    electrical circuit to perform work.
   Oxygen enters at the cathode and combines with the
    electrons returning from the electric circuit and the
    hydrogen ions that have traveled through the electrolyte
    to the anode.
           Types of Fuel Cells
 Proton  exchange membrane fuel
  cell (PEMFC)
 Solid oxide fuel cell (SOFC)
 Alkali fuel cell (AFC)
 Molten-carbonate fuel cell (MCFC)
 Phosphoric-acid fuel cell (PAFC)
 Direct-methanol fuel cell (DMFC)
                          Alkali Fuel Cell
   Reactants: Pure hydrogen and oxygen (compressed)
   Electrolyte: Potassium hydroxide (KOH) in water.
    Its operating temperature is 150 to 200 degrees C.
    Alkali cells were used in the Apollo spacecraft to provide both electricity and
    drinking water. It has an efficiency of about 70%. It is very susceptible to
    contamination, so it requires very pure hydrogen and oxygen. It is also very
    expensive, so this type of fuel cell is unlikely to be commercialized.
                 Solid Oxide Fuel Cell




These fuel cells are best suited for large-scale
stationary power generators that could provide
electricity for factories or towns. They operate at a
temperature of about 700-1000 degrees C. The high
temperature also has an advantage: the steam
produced by the fuel cell can be channeled into
Drawing of a solid oxide cell




turbines to generate more electricity.
                            Molten Carbonate Fuel Cells




Drawing of a molten carbonate cell




        This type of fuel cells use high temperature compounds of
          salts such as sodium or magnesium carbonate. Its
          efficiency ranges from 60-80% and it operates at a
          temperature of about 650 degrees C.
                  PEM Fuel Cells
    The Proton Exchange Membrane Fuel Cell (PEMFC) is
    the most likely candidate for transportation applications
    due to its high power density and low operating
    temperature which ranges from 60-80 degrees Celsius.
    With its low operating temperature, it does not take a
    long time for the fuel cell to warm up and start generating
    energy. The solid, flexible electrolyte will not leak or
    crack, and these cells operate at a low enough
    temperature to make them suitable for homes and cars.
Hydrogen Fuel Cell
       Purpose of Electrolyte
 Electrolyte permits the appropriate ions to
  pass between the anode and the cathode.
 It acts as the proton exchange membrane
  which only conducts positively charged
  ions and blocks the electrons.
         Fuel Cell Problems

 Cost


 Durability


 Infrastructure
             Why Use Fuel Cells?
The efficiency of a gasoline-powered car is surprisingly low
  and all the heat that comes out in the exhaust or goes
  into the radiator is wasted energy. The overall efficiency
  of a gas engine is around 20% which refers to the
  thermal-energy content of the gasoline converted into
  mechanical work.
 Fuel-cell vehicles are potentially as efficient as a battery-
  powered car that relies on a non-fuel-burning power
  plant, therefore, decreasing our dependency on oil and
  atmospheric deterioration (“pollution”) due to the
  combustion of fossil fuels.
Gas prices from 1990-2004
                          Literature Cited
CBC News, Technology and Science. Research boosts potential of
   hydrogen fuel.
http://www.cbc.ca/technology/story/2007/11/13/hydrogen.html#skip300x250

The Lugar Energy Initiative.
http://lugar.senate.gov/.../fuel/electricity.htm

The Time to Care.
http://thetimetocare.blogspot.com/

How Stuff Works. It’s good to know.
http://auto.howstuffworks.com/fuel-cell2.htm

Fuell Cells: Fuel Cell Basics
http://americanhistory.si.edu/fuelcells/basics.htm

				
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