FUEL CELL AS CLEAN ENERGY

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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



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FUEL CELL AS CLEAN ENERGY