Alkaline Fuel Cell(AFC)
First AFC, was a made for a bike by
Union Carbide's Karl Kordesch.
NASA building AFC for space.
http://fuelcells.si.edu/alk/alkmain.htm
How does it work?
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The electrolyte is potassium
hydroxide
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electrolyte flows through
the centre of the fuel cell plates
with porous membranes
between the electrolyte and the
hydrogen (anode) and oxygen
(cathode) gas supplies.
membranes contain the
catalysts (platinum & silver)
Produces Water and some
Carbon Dioxide
Works at –40 degrees C for
cooling and 70 degrees
regularly
http://www.fctec.com/fctec_types_afc.asp
Advantages of AFC
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Like PEM works at low
temperature and
“instant-starting”
Efficiency = 70% (One
of the Best)
Companies looking to
bring down cost (Astris)
http://www.h2fc.com/technology.html
http://fuelcells.si.edu/alk/alkmain.htm
Uses of AFC
NASA uses them for Space
Shuttles
 Commercially used in cars
 Used to generate electricity
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http://www.h2fc.com/technology.html
Phosphoric Fuel Cell - Application
golf cart powered by a
phosphoric acid fuel cell.
Georgetown University, and
the U.S. Department of
Energy adapted a 50 kw Fuji
Electric PAFC for transit
buses (photo at left), and
began running these buses in
1994.
New York, the Yonkers
Waste Treatment Plant has
been powered by a 200 kw
ONSI unit since 1997
http://fuelcells.si.edu/phos/pafcmain.htm#apps
Technology
http://voltaicpower.com/FuelCell/pafc.htm
Proton Exchange Membrane
Diagrams and picutres from Humboldt State University
PEM Chemical Reactions
Alkaline Fuel Cell
Molten Carbonate Fuel Cell
How Does It Work
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Molten Carbonate fuel cells (MCFC) use hightemperature compounds of salt (like sodium
or magnesium) carbonates (chemically, CO3)
as the electrolyte.
(http://fuelcells.si.edu/basics.htm)
The operation of a MCFC is based on the
shuttle action provided by carbonate ions.
The carbonate ions also serve as an acidic
electrolyte. The CO2 rich gas product gas of
the anode is fed to the cathode where CO2 is
transformed into carbonate ions during the
reduction of oxygen.
http://voltaicpower.com/FuelCell/mcfc.htm
Since it operates at high temperatures,
multiple fuel types can be used.
Reactions of Molten Carbonate
Advantages of Molten
Carbonate
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Efficiency ranges from 60 to 80 percent, and operating temperature is
about 650 degrees C (1,200 degrees F). Units with output up to 2
megawatts (MW) have been constructed, and designs exist for units up to
100 MW. (http://fuelcells.si.edu/basics.htm)
Molten carbonate fuel cells are not prone to carbon monoxide or carbon
dioxide "poisoning"—they can even use carbon oxides as fuel—making
them more attractive for fueling with gases made from coal.
(http://www.eere.energy.gov/hydrogenandfuelcells/fuelcells/types.html#m
cfc)
MCFCs don't require an external reformer to convert more energy-dense
fuels to hydrogen. Due to the high temperatures at which they operate,
these fuels are converted to hydrogen within the fuel cell itself by a
process called internal reforming, which also reduces cost.
(http://www.eere.energy.gov/hydrogenandfuelcells/fuelcells/types.html#m
cfc)
Uses of Molten Carbonate
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Renton, Washington, where a 1-megawatt power plant will be located at the
King County wastewater treatment facility and fueled by wastewater digester
gas. Scheduled to begin operations in the fall of 2002, the project is co-funded
by a grant from the U.S. Environmental Protection Agency.
http://www.fe.doe.gov/programs/powersystems/fuelcells/fuelcells_moltencarb.s
html
Los Angeles, California, where the city's Department of Water and Power has
ordered three 250-kilowatt plants, the first of which was shipped to the utility's
downtown headquarters in July, 2001.
http://www.fe.doe.gov/programs/powersystems/fuelcells/fuelcells_moltencarb.s
html
Cadiz, Ohio, where Northwest Fuel Development Inc., based on Lake Oswego,
Oregon, will operate a 250-kilowatt fuel cell on coal-mine methane gas from the
Harrison Mining Corporation and supply electricity back to the mining operation.
http://www.fe.doe.gov/programs/powersystems/fuelcells/fuelcells_moltencarb.s
html
Solid Oxide Fuel Cells
How Does It Work?
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First of all, the Solid Oxide Fuel Cell is very
different from the other forms of fuel cells. This
fuel cell is composed completely of materials in
a solid state, including the electroyte.
http://www.fe.doe.gov/programs/powersystems/fuelcells/fuelcell
s_solidoxide.shtml
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They operate at very high tempatures, ranging
from 600 to 1000 degrees Celsius
Initially, a gas consisting of hydrogen gas and
carbon monoxide is required for this fuel cell.
The anodes are porus allowing for the hydrogen
and oxygen molecules (after reacting with the
electrolyte) to permeate through to the other
side
The hydrogen molecules permeate through the
electrode where it will react and form water
The electrons resulting from this reaction will
consequently pass through an external electrical
load, creating an electrical flow
The excess oxygen will then react with the used
electrons forming oxygen gas and giving off as a
waste product
Advantages of Solid Oxide
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Normally, efficiency of this fuel cell is around
60%
However, if the waste heat is utililized in such
a manner is utilized in such a manner that
would incorporate it back into the fuel cell
stack, effciency can reach anywhere up to
85%
This occurs when the Solid Oxide Fuel Cell is
utilized in a tubular form – outputting 100kw
of electricity.
Uses of Solid Oxide Fuel Cells
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The high-temperature operation of a solid oxide
fuel cell and its capability to operate at elevated
pressures makes it an attractive candidate for
linking with a gas turbine in a "hybrid"
configuration. The hot, high pressure exhaust of
the fuel cell can be used to spin a gas turbine,
generating a second source of electricity.
The world's first solid oxide fuel cell/gas turbine
hybrid system is at Southern California Edison
for operation at the National Fuel Cell Research
Center in Irvine, California. The hybrid system
includes a pressurized solid oxide fuel cell
module integrated with a
microturbine/generator supplied by IngersollRand Energy Systems (formerly Northern
Research and Engineering Corp.). The system
has a total output of 220 kW, with 200 kW from
the fuel cell and 20 from the microturbine
generator. This proof of concept demonstration
is expected to demonstrate an electrical
efficiency of around 55%. Eventually, such
hybrids should be capable of electrical
efficiencies of 60-70%.
http://fossil.energy.gov/programs/powersystems/fuelcells/fuelcells_solidoxide.shtml