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What is A Fuel Cell?
• A fuel cell is an electrochemical energy conversion device.
• It produces electricity from external supplies of fuel (anode side) and oxidant (cathode side).
• A fuel cell is similar to a battery in that an electrochemical reaction is used to create electric current.
• Fuel cells are different from batteries in that they consume reactant, which must be replenished, while batteries store electrical energy chemically in a closed system.
• (Recall that Solar cells are not electrochemical)
R. Chang: Fuel_Cell_technology_F07
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Fuel Cell Applications
• Fuel cells are very useful as power sources in remote locations, such as spacecraft, remote weather stations, large parks, rural locations, and in certain military applications.
• A fuel cell system running on hydrogen can be compact, lightweight and has no major moving parts.
• Because fuel cells have no moving parts, and do not involve combustion, in ideal conditions they can achieve up to 99.9999% reliability.
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Toyota FCHV PEM FC fuel cell vehicle
A hydrogen fuel cell public bus accelerating at traffic lights in Perth, Western Australia
The world's first certified Fuel Cell Boat (HYDRA), Karl-Heine Kanal in Leipzig, Germany
Micro-fuel cell developed by Fraunise ISE for use in applications such as cellular phones
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• Fuel cells have as reactants gases (hydrogen and oxygen) that are combined in a catalytic process.
• Since the gas reactants can be fed into the fuel cell and constantly replenished, the unit will never run down like a battery.
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A fuel cell consists of an anode, cathode, and electrolyte
A fuel cell consists of two electrodes (an anode and a cathode) that sandwich an electrolyte (a specialized material that allows ions to pass but blocks electrons).
CA
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Solid Oxide Fuel Cells ( SOFCs )
A solid oxide fuel cell is a device that converts gaseous fuels
(hydrogen, natural gas, gasified coal) via an Electrochemical
process directly into electricity.
Air is supplied to the cathode (air electrode)
At the cathode, the O2 molecules are ionized
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In SOFCs oxygen ions react with H2 from the
fuel The ionized oxygen diffuses across the electrolyte
At the anode, the O2- ions react with H (in the fuel).
H2 + O2- H2O + 2e-
The reaction produces electrons to do work and water.
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SOFC -- passing oxygen ions across a solid
electrolyte.1. SOFC has a ceramic cathode that ionizes
oxygen. The cathode needs to be porous to allow air in.
2. The oxygen ions diffuse across a solid, dense, ceramic electrolyte.
3. At the anode, the oxygen ions react with hydrogen to form water and electrons.
4. The electrons can not flow through the electrolyte so they leave through the load.
Cath.Anod.
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• A typical cell running at 0.7 V has an efficiency of about 50%.• Therefore 50% of the energy content of the hydrogen is converted into electrical energy;
• The remaining 50% will be converted into
heat.
Fuel Cell Efficiency
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Fuel Cell Lab Exercise
Charging
Discha
rging
Mod
e
motor
Fuel cell
H2 tank
O2 tank
plug
Power meter
Prop up the front wheels
Discharging Mode
Distilled Water Syrin
ge
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Q1. The major difference between fuel cells and batteries is:
A. Fuel cells generate hydrogen gas, whereas batteries consume stored solid or liquid
B. Fuel cells generate oxygen gas, whereas batteries consume electricity
C. Fuel cells consume hydrogen gas, whereas batteries consume stored solid or liquid
D. Fuel cells consume oxygen gas, whereas batteries consume stored solid or liquid
E. Fuel cells consume water, whereas batteries consume stored solid or liquid
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Q2. Which of the following is the by-product of
a fuel cell reaction? A. Water
B. Hydrogen
C. Oxygen
D. Electrolyte
E. All of the above
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Q3. Which of the following is not a reactant of a fuel cell?
A. Bio-diesel
B. Methane
C. Methanol
D. Air
E. Gasoline