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May 16, 2010 [THE CLEAN ENERGY]
1 Khalil Raza Bhatti
www.postomotors.tk
The ROLE OF
FUEL CELL AS
CLEAN ENERGY
Khalil Raza Bhatti,
Department of Mechanical Engineering,
QuaideAwam University of Engineering,
Science & Technology, Pakistan.
www.postomotors.tk
ABSTRACT
The purpose of this paper is to give basic
information about technology, applications
and perspectives of fuel cell.
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CONTENTS
1. What is a Fuel Cell?
2. Fuel Cells Technology & Applications
2.1. Alkali Fuel Cells
2.2. Molten Carbonate Fuel Cells
2.3. Phosphoric Acid Fuel Cells
2.4 PEM Fuel Cells
2.5 Solid Oxide Fuel Cells
3. Future Fuel Cell Technology &
Applications
4. Fuel Cell Challenges
What is fuel cell technology?
Clean and efficient electrochemical
devices that convert fuel into
electricity without combustion.
A fuel cell combines hydrogen
fuel (obtained from: natural gas,
methanol, gasoline, propane, etc.), with
oxygen (from air), to electrochemically
produce electricity, heat, and water.
Fuel Processor
Power Section
Power Conditioner
Types of Fuel Cells:
Alkali Fuel Cells
Molten Carbonate Fuel Cells
Phosphoric Acid Fuel Cells
PEM Fuel Cells
Solid Oxide Fuel Cells
Use compressed hydrogen and oxygen
The electrolyte is usually a solution of
potassium hydroxide in water
Operating temperatures are around 150 to
200 degrees C
Selected for the Space Shuttle fleet and for
the Apollo program:
Power generating efficiencies approach 70
percent. (And also providing drinking water)
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The cells are too expensive for commercial
applications -- but several companies are
examining ways to reduce costs.
Most of alkali fuel cells are being designed
for transport applications
In a molten carbonate fuel cell (MCFC),
carbonate salts are the electrolyte. Heated to
650 degrees C, the salts melt and conduct
carbonate ions (CO3--) from the cathode to
the anode.
At the anode, hydrogen reacts with the ions
to produce water, carbon dioxide, and
electrons.
At the cathode oxygen from air and carbondioxide recycled from the anode react with
the electrons to form CO3 ions that replenish
the electrolyte and transfer current through
the fuel cell.
Molten carbonate fuel cells demand high
operating temperatures and the applications
are limited to large, stationary power plants.
Fuel cell waste heat makes steam for space
heating, industrial processing, or in a steam
turbine to generate more electricity
(cogeneration ).
Phosphoric acid fuel cells (PAFC) operate at
temperatures around 150° to 200° C and use
platinum catalyst at the electrodes.
PAFCs use phosphoric acid as the electrolyte.
Positively charged hydrogen ions migrate
through the electrolyte from the anode to the
cathode.
At the cathode the electrons, hydrogen ions
and oxygen form water.
PHOSPHORIC ACID F.C.
PHOSPHORIC ACID FUEL CELL APPLICATIONS
TRANSPORTATION:
50-100 kw PAFC for transit buses
PAFCs currently require an extended warm-up
period, however, so their usefulness in
private cars remains l imited.
PHOSPHORIC ACID FUEL CELL APPLICATIONS
STATIONARY POWER AND MILITARY
APPLICATIONS:
Stationary power for building (<200 kw).
Uses sewage methane as a fuel, and the
stacks have an estimated life of 5 to 6 years(they cost about $100,000 to replace).
Plant for military uses
Proton exchange membrane (PEM) fuel cells
work with a polymer electrolyte in the form of
a thin, permeable sheet.
This membrane is small and light, and it works
at low temperatures (about 80 degrees C).
PEM FUEL CELL
Since the mid-1980s, PEM development has
included stationary power applications (5-250
kw hydrogen and air PEM stack).
One of the more publicized demonstrations
has been Plug Power's PEM unit in Albany,
New York, which began powering a home in
June 1998.
Automotive research has taken on new
urgency as air quality regulations grow
steadily stricter
In 1995, Ballard Systems tested PEM cells in
buses in Vancouver and Chicago and later in
experimental vehicles made by
DaimlerChrysler.
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two 20 kw fuel cell stacks have been used by
Virginia Tech and Texas Tech universities to
evaluate performance in hybrid electric cars.
Major automakers like Ford and Volkswagen
are also testing PEM vehicles.
PEM cells have also supplied power to
unmanned blimps called aerostats and to
sonobuoys, which are nautical buoys that
generate and receive sonar signals.
Early in 2000, AeroVironment selected PEM
technology to provide night time power for its
solar-powered Helios long-duration aircraft.
The goal is to make the unpiloted aircraft fly
continuously for up to six months.
Photovoltaic panels during the day will run electric motors and electrolyze water. At
night, the fuel cell will run the motors by
converting the hydrogen and oxygen back into
water. Test flights were planned for 2003.
A solid oxide fuel cell (SOFC) uses a ceramic
electrolyte (zirconium oxide and calcium
oxide) and operates at temperatures up to
1,000 degrees C
Oxygen ions migrate through the crystallattice. When a fuel gas containing hydrogen
is passed over the anode, a flow of negatively
charged oxygen ions moves across the
electrolyte to oxidize the fuel.
The oxygen is supplied, usually from air, at the
cathode. Generating efficiencies can range up
to about 60 percent (<100 kw).
a reformer is not required to produce
hydrogen from the fuel.
SOLID OXIDE FC:
SOLID OXIDE F.C. APPLICATIONS:
Their most common application is in large,
stationary power plants with the opportunity
for "cogeneration"–using waste heat to
generate steam for space heating, industrial
processing, or in a steam turbine to make
more electricity.
They can be manufactured in relatively small,modular units.
The compact size and cleanliness of SOFCs
make them especially attractive for urban
settings like Tokyo, where 25 kw units are
already on line.
SOLID OXIDE F.C. APPLICATIONS
COGENERATION :
• In April 2000, the U.S. Department of
Energy announced that a SOFC-
microturbine cogeneration unit will
be evaluated by the National Fuel Cell
Research Center and Southern
California Edison.
• In a year of actual operating
conditions, the 220 kw SOFC will run
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CHALLENGES:
STORAGE:
Automotive researchers are looking for ways
to make hydrogen tanks as space-efficient as
gasoline tanks and as easy to refill. They are
studying several different hydrogen storage
systems: compressed, liquid and carbon
nanostructure storage, and metal hydride.
COST:
While the cost of fuel cell stacks has
decreased tenfold in just three years, the
price is still too high to gain commercial
support for use in vehicles, homes and
businesses.
Fuel cells require precious metals for catalysts
and expensive polymer membranes.
Engineers continue to look for solutions in
alternative applications, such as smaller
amounts of catalysts and less costly polymer
membranes.
By far the largest challenge to fuel cell
commercialisation is infrastructure.
Creation of a hydrogen infrastructure is an
important prerequisite of fuel cell
commercialisation.
While automotive companies are developing
fuel cell vehicles, they cannot develop the
necessary supporting infrastructure on their
own.
Incentives for refuelling stations, the
development of uniform standards, funding
and education are all key aspects that must be
addressed.
Mercedes Benz Fuel Cell
BMW FUEL CELL VEHICLE