Transcript What is A Fuel Cell?

Renewable Energy Sources
.
Fuel Cells
SJSU-E10
S-2008
John Athanasiou
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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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http://www.greenjobs.com/Public/images/fuel-cell.jpg
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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
Micro-fuel cell developed by Fraunise ISE for
use in applications such as cellular phones
The world's first certified Fuel Cell Boat (HYDRA),
Karl-Heine Kanal in Leipzig, Germany
A hydrogen fuel cell public bus accelerating5 at
traffic lights in Perth, Western Australia
• 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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How does a fuel cell
work?
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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).
A
C
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Solid Oxide Fuel Cells ( SOFCs )
Air is supplied to the cathode
(air electrode)
At the cathode, the O2
molecules are ionized
A solid oxide fuel cell is a device that converts gaseous fuels
(hydrogen, natural gas, gasified coal) via an Electrochemical
process directly into electricity.
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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 + 2eThe 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.
Anod.
Cath.
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Fuel Cell Efficiency
• 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.
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Voltage Vs Current
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Voltage (mV)
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Series1
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Current (mA)
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Power Vs Voltage
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Power (mW)
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Series1
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Voltage (mV)
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Fuel Cell Lab Exercise
plug
Charging
H2 tank
Fuel
cell
O2 tank
plug
hose
water
reservoir
Distilled Water
motor
Power meter
H2 tank
Fuel
cell
O2 tank
plug
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Prop up the front wheels
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.
B.
C.
D.
E.
Water
Hydrogen
Oxygen
Electrolyte
All of the above
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Q3.
A.
B.
C.
D.
E.
Which of the following is
not a reactant of a fuel cell?
Bio-diesel
Methane
Methanol
Air
Gasoline
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Q4. Which of the following describes the
function of a fuel cell in a discharge mode?
A. Air is supplied to the cathode side.
B. Air is supplied to the anode side.
C. Water is supplied to the cathode
side.
D. Water is supplied to the anode side.
E. Hydrogen gas is supplied to the
cathode side.
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