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Fuel Cell Basic
How Fuel Cells work
Applications of Fuel Cell Experiment Setup
Fuel CellFuel Cell
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work with a PEM (proton exchange
membrane) electrolyzer and a PEM fuel cell
to study the electrochemistry of water
electrolysis
how much power it takes to generate a
meaningful quantity of hydrogen (10 cm^3)
how efficient the electrolyzer is
measure the breakdown voltage of water
Power output from the fuel cell
Laboratory Objectives
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What is a Fuel Cell
A Fuel Cell is an electrochemical device that
combines hydrogen (and oxygen) to produce
electricity, with water and heat as its by-product.
Fuel (H2) + O2 / Catalyst (H2)O + Heat
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How a Fuel Cell work
A Fuel Cell consists of two catalyst coated electrodes
surrounding an electrolyte
One electrode is an anode and the other is a cathode
The process begins when Hydrogen molecules enter the
anode
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How a Fuel Cell work
The catalyst coating separates hydrogens negatively charged
electrons (e-) from the positively charged protons (H+)
The electrolyte allows the protons to pass through to the
cathode, but not the electrons
Instead the electrons are directed through an external circuit
which creates electrical current
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How a Fuel Cell work
While the electrons pass through the external circuit,
oxygen molecules pass through the cathode on the
other side of the fuel cell
There the oxygen and the protons combine with the
electrons after they have passed through the external
circuit
When the oxygen and the protons combine with the
electrons it produces water and release heat
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Fuel Cells Concept
Individual fuel cells can then be placed in a series
to form a fuel cell stack
The stack can be used in a system to power a
vehicle or to provide stationary power to a
building
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Fuel Cells Concept
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Hydrogen Generation and applications
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Types of Fuel Cells
Type Efficiency(%) Operating Temp
Solid Oxide 45-65 800-1000
Molten Carbonate 50 650
Phosphoric Acid 40 200
Alkaline 50-60 80
Direct Methanol 40 80
Polymer (PEM) 40 50
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Benefits
Low / Zero Emissions
Based on measured data, a fuel cell power plant may
create less than one ounce ofpollution per1,000
kilowatt-hours of electricity (25 pounds for Conventional
systems) -- Clean Energy
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Benefits
High Efficiency (for power output) 2nd law ?
Quiet
Fuel Flexible (Next slide)
Combine with wind power and solar power
Lightweight battery alternative
Wide Range of Applications
High Quality, Reliable Power
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Applications
Transportation All major automakers are working to commercialize a fuel cell car
Automakers and experts speculate that a fuel cell vehicle will becommercialized by 2012, others later
50 fuel cell buses are currently in use in North and South America,Europe, Asia and Australia
Trains, planes, boats, scooters, forklifts and even bicycles areutilizing fuel cell technology as well
Ford Hyundai Toyota
HondaGM
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Applications Honda
TOYOTA FCHV-adv
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Hyundai's zero-emissions ix35 Fuel Cell is
similar in performance to the petrol version
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Applications
Stationary Power Stations
Over 2,500 fuel cell systems have been installedall over the world in hospitals, nursing homes,hotels, office buildings, schools and utility power
plants
Most of these systems are eitherconnected tothe electric grid to provide supplemental powerand backup assurance or as a grid-independentgenerator for locations that are inaccessible bypower lines
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Applications
Telecommunications Due to computers, the Internet and sophisticated
communication networks there is a need for an
incredibly reliable power source
Fuel Cells have been proven to be 99.999% reliable
Micro Power Consumer electronics could gain drastically longer
battery power with Fuel Cell technology Cell phones can be powered for 30 days without
recharging
Laptops can be powered for 20 hours without recharging
2020
Thermodynamics analysis
Gibbs function (g) : property defined in
terms of properties
U: internal energy
H: Enthalpy
T: Absolute temperature
S: Final entropy
P: Absolute pressure
V: Final volume
TsPVU
Tshg
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The change in Gibbs free energy, G, in a
reaction can be thought of as the maximum
amount of work obtainable from a reaction.
For example, in the oxidation of glucose, the
change in Gibbs free energy is G = 686 kcal =
2870 kJ.
(n=number of electrons released at the anode
F=Faraday constant, = electric potential) nFG
STHG
Thermodynamics
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Electrolysis of Water
The amount power must be supplied by the
battery is actually the change in the Gibbs
function G = H - TSElectrical Energy input
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Electrolysis of Water
Electrolysis of WaterH20 H2+1/2O2 (T=298K, P=1 atm)
H=285.83 kJ
TS = 48.7 kJ (S = 130.68+ 0.5 x 205.14 - 69.91, T=298 K)
G = H - TS =285.83 kJ-48.7 kJ=237.1kJ
Theoretical Electrical Energy input for Electrolysis of Water :
G =237.1kJ
H2O H2 0.5 O2 Change
Enthalpy -285.83 kJ H = 285.83 kJ
Entropy 69.91 J/K 130.68 J/K 0.5 x 205.14 J/K TS = 48.7 kJ
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Hydrogen Fuel Cell
The theoretical efficiency of a fuel cell is
The overall system efficiency
( : the reform efficiency (hydrocarbon),
: the DC/AC convert efficiency)
fcH
G
max
CRfc
R
C
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Example Hydrogen and oxygen are combined in a fuel cell to produce
electrical energy in a fuel cell. This process is presumed to be
at 298K and one atmosphere pressure. For the ideal case,
determine the efficiency of fuel energy converted to electrical
energy.
G =
H - T
S = -285.83 kJ + 48.7 kJ = -237.1 kJ H = 285.83 kJ
83%x100%8237.1/285.max
fcH
G
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work with a PEM electrolyzer and a PEM fuel
cell to study the electrochemistry of water
electrolysis how much power/time it takes to generate a
meaningful quantity of hydrogen (10 cm^3)
measure the breakdown voltage of water
Voltage and Power output from the fuel cell
Laboratory Objectives
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