Inside a Fuel Cell

1
Inside a Fuel Cell
The red Hs represent hydrogen molecules (H2) from
a hydrogen storage tank. The orange H
represents a hydrogen ion after its electron is
removed. The yellow e- represents an electron
moving through a circuit to do work (like
lighting a light bulb or powering a car). The
green Os represent an oxygen molecule (O2) from
the air. The blue drops at the end are for pure
water--the only byproduct of hydrogen power.
2
Types of Fuel Cells-Alkaline-

• Operate on compressed hydrogen and oxygen.
• Uses an alkaline electrolyte such as potassium
  hydroxide.
• Efficiency is about 70 percent, cell output being
  300 watts-5 kW
• Originally used by NASA on space missions,
  specifically in Apollo to provide electricity and
  drinking water.
• It is now finding applications in
  hydrogen-powered vehicles.

3
Molten Carbonate

• The molten carbonate fuel cell uses a molten
  carbonate salt as the electrolyte. It has the
  potential to be fueled with coal-derived fuel
  gases or natural gas.
• Efficiency ranges from 60-80 percent with an
  output of 2 MW.
• They operate at around 1,200 degrees Fahrenheit,
  making them too hot for home use.

4
Phosphoric Acid

• A phosphoric acid fuel cell (PAFC) consists of an
  anode and a cathode made of a finely dispersed
  platinum catalyst on carbon paper, and a silicon
  carbide matrix that holds the phosphoric acid
  electrolyte.
• This is the most commercially developed type of
  fuel cell and is being used in hotels, hospitals,
  and office buildings. The phosphoric acid fuel
  cell can also be used in large vehicles, such as
  buses.
• Efficiency is 40-80 percent with outputs of 200kW

5
Proton Exchange Membrane

• The proton-exchange membrane (PEM) fuel cell uses
  a fluorocarbon ion exchange with a polymeric
  membrane as the electrolyte.
• The PEM cell appears to be more adaptable to
  automobile use than the PAFC type of cell. These
  cells operate at relatively low temperatures and
  can vary their output to meet shifting power
  demands.
• Efficiency is about 40 to 50 percent with outputs
  generally ranging from 50 to 250 kW

6
Solid Oxide

• Solid oxide fuel cells (SOFC) currently under
  development use a thin layer of zirconium oxide
  as a solid ceramic electrolyte, and include a
  lanthanum manganate cathode and a nickel-zirconia
  anode.
• This is a promising option for high-powered
  applications, such as industrial uses or central
  electricity generating stations.
• Efficiency is about 60 percent with outputs of
  100kW

7

• What do you get when you cross a fuel cell, an
  ear of a corn and a fuel injector from a stray
  jalopy?

8
Ethanol as a Fuel Source

• Ethanol is produced by converting biomass like
  cornstarch, sugarcane, sugar beets, and some
  trees and grasses to sugar, then fermenting it.
• In the United States each year, approximately 2
  billion gallons are added to gasoline to increase
  octane and improve the emissions quality of
  gasoline
• It's not cheaper than natural gas or coal... but
  it's cleaner, and renewable
• -Lanny Schmidt

9
Ethanol and Fuel Cells

• Though hydrogen is the most abundant element on
  Earth, most of it is locked up with other
  elements in forms such as hydrocarbons and water.
  It takes a lot of energy to get significant
  quantities of hydrogen from water alone, so the
  most practical sources from which to liberate
  hydrogen are fossil fuels such as natural gas,
  diesel fuel or gasoline. But using fossil fuels
  as a hydrogen source removes some of the green
  appeal of fuel cells.
• University of Minnesotas Lanny Schmidt was able
  to produce hydrogen from ethanol after two simple
  adjustments to a process already used to get
  hydrogen from methane, natural gas and gasoline.

• Ethanol is fairly flammable, and the process of
  extracting hydrogen from ethanol destroys
• the catalyst traditionally used to extract
  hydrogen from hydrocarbons like oil.
• The first step was to use an automotive fuel
  injector to vaporize an ethanol-water mix.
• The second required altering the composition of
  the reactors ceramic catalyst material,
• a combination of the elements rhodium and cerium,
  for the vaporized ethanol to pass
• through and be converted

10
Why Ethanol is better

• Conversion of biomass materials such as ethanol
  into hydrogen is a more cost-efficient method to
  power fuel cells.
• Ethanol in car engines is burned at 20
  efficiency because you have to remove the water
  first. But if you use ethanol to produce
  hydrogen, the efficiency is 50 to 60 because you
  dont need to remove the water. Hydrogen comes
  from the ethanol and the water.
• Ethanol is relatively easy to make, transport and
  store, and it's renewable.
• Ethanol reduces our dependence on foreign oil
  because it can be produced domestically.
• Ethanol is low in reactivity and high in oxygen
  content, making it an effective tool in reducing
  ozone pollution.

11
Why it hasnt happened yet

• Were not going to be switching tomorrow,
  because theres not enough corn out there. If you
  took it all, you could replace maybe 40 percent
  of our petroleum needs."
• The energy that goes into raising corn and making
  ethanol makes it less attractive than natural gas
  as a source for hydrogen. (It's only if you make
  the ethanol from a cellulosic material with not
  much energy going into it that it becomes even
  plausible as an option for hydrogen)
• The potential for the new reactor, in its current
  form, is also restricted by an existing
  fossil-fuel dependent infrastructure.