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INDEX

Sr. no TITLE Page no.1 History and basics 42 Introduction 53 Construction 6

4 Fuel cell principle 75 Working 86 Types of fuel cell 97 Electrochemical reaction of fuel cell type 108 Fuel cell comparison 219 Problem with fuel cell 22

10 Fuel cell goals 2311 Technology compression 2412 Advantages 2513 Disadvantages 2614 Application 27

15 Research 2816 Conclusion 3017 reference 31

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LIST OF FIGURE

Sr. no. Title Page no1 Construction 62 Fuel cell 73 Working of fuel cell 84 Polymer electrolyte membrane fuel cell 105 Phosphoric acid fuel cell 116 Alkaline fuel cell 137 Molten carbonate fuel cell 148 Solid oxide fuel cell 189 Electro chemical reaction of fuel cell type 20

LIST OF TABLE

1 Compression of fuel cell 21

LIST OF GRAPH

1 Technology compression 24

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ABSTRACT

Fuel cell technology has in recent years undergone a period of rapid development.

This evolution has been driven by the requirements of developed countries to reduce the

emission of greenhouse gases, with particular emphasis placed on reducing CO2

emission. This article discussed the possibility of using fuel cell technology for rail

vehicle propulsion, with the United Kingdom chosen as a case study. A brief review of

fuel cell technology and its application with in the UK presented. It is conclude that,

although the technology for fuel cell power will be suitable with in the next few years, its

adoption by mainline Uk rail operators will be delayed considerably until exciting diesel

vehicles have reached the end of their useful life. By this time the technology of fuel cells

will be well proven within other transport markets and its transfer to rail markets will be

facilitated. This will be augmented at this time by increasing diesel fuel prices. However.

The adoption of fuel cell technology for light rail/tram system does offer advantage in

terms of infrastructure development and aesthetics which could make it a serious option

for new and upgraded light rail/tram schemes.

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HISTORY AND BASICS

The first demonstration of a fuel cell was by William grove in 1839. Real development in

fuel cells first happened for space application in the 1960es. Since the 80es and untilnow much development in the fuel cell has been focused on use for transportation,

combined heat and power production and power supply in portable products. Fuel cells

convert the chemical energy in a fuel, mostly hydrogen, into electricity and heat without

any noise and mechanical movement. The only emission of the reaction in the fuel cell is

pure water. A fuel cell is like a battery with the only difference that It will continue to

provide power as long a fuel is provided. Fuel cells are very scaleable and flexible in

design thus giving a vide range of possibilities of usage. A fuel cell can power a small

mobile cell phone, or a car, or even be used for large central power plants.

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INTRODUCTION

Fuel cells are often described as being continuously operation batteries, but this is anincomplete idea. Like batteries fuel cells produces power without combustion or

rotating machinery. Fuel Cell Produce electricity by utilizing an electrochemical

reaction to combine hydrogen ions with oxygen atoms. Hydrogen ions are obtained

from hydrogen-containing fuels. Fuel cells, unlike batteries, use an external and

continuous source of fuel and produce power continuously, as long as the fuel supply

is maintained.

Two electrodes, an anode and a cathode from an individual cell. They are sandwiched

around an electrolyte in the presence of a catalyst to accelerate and improve

electrochemical reaction. Fuel cell that uses fuel to create chemical reactions that

produce either hydrogen- or oxygen- bearing ions at one of the cells two electrodes.

These ions then pass through the electrolyte, such as phosphoric acid, and react with

oxygen atoms. The result is an electric current flowing between both electrodes plus

the generation of waste heat and water vapor. This current is proportional to the cross

sectional area of the electrodes. The voltage is limited electrochemically to about 1.23

volts electrode pair, or cell. These cells then can be stacked until the desired power

level is reached.

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CONSTRUCTION

Fig-1

The anode, the negative post of the fuel cell, has several jobs. It conducts the

electrons that are freed from the hydrogen molecules so that they can be used in

an external circuit. It has channels etched into it that disperse the hydrogen gas

equally over the surface of the catalyst.

The cathode, the positive post of the fuel cell, has channels etched into it that

distribute the oxygen to the surface of the catalyst. It also conducts the electrons

back from the external circuit to the catalyst, where they can recombine with the

hydrogen ions and oxygen to form water.

The electrolyte is the proton exchange membrane . only conducts positively

charged ions. The membrane blocks electrons.

The catalyst i s a special material that facilitates the reaction of oxygen and

hydrogen. It is usually made of platinum powder very thinly coated onto carbon

paper or cloth. The catalyst is rough and porous so that the maximum surface area

of the platinum can be exposed to the hydrogen or oxygen. the platinum-coated

side of the catalyst faces the PEM

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FUEL CELL PRINCIPLES

The basic principle of a fuel cell is a chemical reaction between hydrogen and oxygen

that produces power and heat. The picture, next to, shows the principle. Hydrogen and

oxygen (air) is supplied on each side of a cell. When hydrogen is lead to the firstcatalyst layer, the anode, the hydrogen molecules are split into their basic elements, a

proton and an electron. The protons migrate through the electrolyte membrane to the

second catalyst layer, the cathode. Here they react with oxygen to form water. At the

same time the electrons are forced to travel around the membrane to the cathode side,

because they can not pass the membrane. This movement of electrons thus creates an

electrical current.

Fig-2

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WORKING

Fig-3

this Fig shows the process that goes on inside an individual fuel cell.

The red Hs represent hydrogen molecules (H2) from a hydrogen storage

tank. The orange H+ represents a hydrogen ion after its electron is

removed.

The yellow e- represents an electron moving through a circuit to do work

(like lighting a light bulb or powering a car). The green Os represent an

oxygen molecule (O2) from the air, and the blue drops at the end are for

pure water- the only byproduct of hydrogen power.

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Types of Fuel Cells

Fuel cells are classified primarily by the kind of electrolyte they employ. This

determine he kind of chemical reactions take place in the cell, the kind of

catalysts required, the temperature range in which the cell operates ,the fuel

required, and other factors. These characteristics, in turn, affect the applications

for which these cells are most suitable. There are several types of fuel cells

currently under development, each with its own advantages, limitations, and

potential application. A few of the most promising types include

Polymer Electrolyte Membrane (PEM) Phosphoric Acid

Direct Methanol

Alkaline

Molten Carbonate

Zinc air fuel cell

Protonic ceramic fuel cell

Solid Oxide

Regenerative (Reversible)

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The catalyst is a special material that facilitates the reaction of oxygen and

hydrogen. It is usually made of platinum nanoparticles very thinly coated onto

carbon paper or cloth. The catalyst is rough and porous so that the maximum

surface area of the platinum can be exposed to the hydrogen or oxygen. The

platinum-coated side of the catalyst faces the

PEM.

The pressurized hydrogen gas (H 2) entering the fuel

cell on the anode side. This gas is forced through the

catalyst by the pressure. When an H 2 molecule comes in

contact with the platinum on the catalyst, it splits into

two H + ions and two electrons (e -). The electrons are

conducted through the anode, where they make their way through the external circuit

(doing useful work such as turning a motor) and return to the cathode side of the fuel cell.

Meanwhile, on the cathode side of the fuel cell, oxygen gas (O 2) is being forced through

the catalyst, where it forms two oxygen atoms. Each of these atoms has a strong negative

charge. This negative charge attracts the two H + ions through the membrane, where they

combine with an oxygen atom and two of the electrons from the external circuit to form a

water molecule (H 2O).

This reaction in a single fuel cell produces only about 0.7 volts. To get this voltage up to

a reasonable level, many separate fuel cells must be combined to form a fuel-cell stack .

Bipolar plates are used to connect one fuel cell to another and are subjected to both

oxidizing and reducing conditions and potentials. A big issue with bipolar plates is

stability. Metallic bipolar plates can corrode, and the byproducts of corrosion (iron and

chromium ions) can decrease the effectiveness of fuel cell membranes and electrodes.

Low-temperature fuel cells use lightweight metals , graphite and carbon/thermoset

composites (thermoset is a kind of plastic that remains rigid even when subjected to high

temperatures) as bipolar plate material.

Chemistryof a Fuel Cell

Anode side:2H 2 => 4H + + 4e -

Cathode side:O 2 + 4H + + 4e - => 2H 2O

Net reaction:2H 2 + O 2 => 2H 2O

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Phosphoric Acid Fuel Cells (PAFC)

PhosphoricAcid Fuel

Cells

(PAFC)

were the

first fuel

cells to be

commercialized. Developed in the mid-1960s and field-

tested since the 1970s, they have improved significantly in

stability, performance, and cost. Such characteristics have

made the PAFC a good candidate for early stationary

application.

. The PAFC uses an electrolyte that is phosphoric acid (H 3PO 4) that can approach 100%

concentration. The ionic conductivity of phosphoric acid is low at low temperatures, so

PAFCs are operated at the upper end of the range 150C220C.

The charge carrier in this type of fuel cell is the hydrogen ion (H+, proton). This is

similar to the PEFC where the hydrogen introduced at the anode is split into its protons

and electrons. The protons migrate through the electrolyte and combine with the oxygen,

usually from air, at the cathode to form water. The electrons are routed through an

external circuit where they can perform useful work. This set of reactions in the fuel cell produces electricity and by-product heat.

Anode Reaction: 2 H 2 => 4 H + + 4 e-

Cathode Reaction: O 2(g) + 4 H + + 4 e- => 2 H 2O

Overall Cell Reaction: 2 H 2 + O2 => 2 H 2O

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The PAFC operates at greater than 40% efficiency in generating electricity. When

operating in cogeneration applications, the overall efficiency is approximately 85%.

Furthermore, at the operating temperature of PAFCs, the waste heat is capable of heating

hot water or generating steam at atmospheric pressure.

The high efficiency of the PAFC when operated in cogeneration mode is one advantageof this fuel cell type. In addition, CO 2 does not affect the electrolyte or cell performance

and can therefore be easily operated with reformed fossil fuel. Simple construction, low

electrolyte volatility and long-term stability are additional advantages.

Approximately 75 MW of PAFC generating capacity has been installed and is operating.

Typical installations include buildings, hotels, hospitals, and electric utilities in Japan,

Europe and the United States. One particular program sponsored by CERL was to

demonstrate 30 PAFCs generating 200 kW apiece at military installations. The objective

of this program was to gain experience with PAFC operation for maintenance, reliability

and performance.

DIRECT METHANOL

Most fuel cells are powered by hydrogen, which can be fed to the fuel cell system

directly or can be generated within the fuel cell system by reforming hydrogen-rich fuels

such as methanol, ethanol, and hydrocarbon fuels. Direct methanol fuel cells (DMFCs),

however, are powered by pure methanol, which is mixed with steam and fed directly to

the fuel cell anode.

Direct methanol fuel cells do not have many of the fuel storage problems typical of some

fuel cells since methanol has a higher energy density than hydrogenthough less than

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gasoline or diesel fuel. Methanol is also easier to transport and supply to the public using

our current infrastructure since it is a liquid, like gasoline.

Direct methanol fuel cell technology is relatively new compared to that of fuel cells

powered by pure hydrogen, and DMFC research and development are roughly 3-4 years

behind that for other fuel cell types.

Alkaline Fuel Cells

Fig-6

Alkaline fuel cells (AFCs) were one of the first fuel cell technologies developed, and they

were the first type widely used in the U.S. space program to produce electrical energy and

water onboard spacecraft. These fuel cells use a solution of potassium hydroxide in water

as the electrolyte and can use a variety of non-precious metals as a catalyst at the anode

and cathode. High-temperature AFCs operate at temperatures between 100C and 250C(212F and 482F). However, newer AFC designs operate at lower temperatures of

roughly 23C to 70C (74F to 158F)

AFCs' high performance is due to the rate at which chemical reactions take place in the

cell. They have also demonstrated efficiencies near 60 percent in space applications.

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The disadvantage of this fuel cell type is that it is easily poisoned by carbon dioxide (CO 2

). In fact, even the small amount of CO 2 in the air can affect this cell's operation, making

it necessary to purify both the hydrogen and oxygen used in the cell. This purification

process is costly. Susceptibility to poisoning also affects the cell's lifetime (the amount of

time before it must be replaced), further adding to cost.

Cost is less of a factor for remote locations such as space or under the sea. However, to

effectively compete in most mainstream commercial markets, these fuel cells will have to

become more cost-effective. AFC stacks have been shown to maintain sufficiently stable

operation for more than 8,000 operating hours. To be economically viable in large-scale

utility applications, these fuel cells need to reach operating times exceeding 40,000 hours,

something that has not yet been achieved due to material durability issues. This is

possibly the most significant obstacle in commercializing this fuel cell technology.

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Molten Carbonate Fuel Cells

Fig-7

Molten carbonate fuel cells (MCFCs) are currently being developed for natural gas and

coal-based power plants for electrical utility, industrial, and military applications. MCFCs

are high-temperature fuel cells that use an electrolyte composed of a molten carbonate

salt mixture suspended in a porous, chemically inert ceramic lithium aluminum oxide

(LiAlO 2) matrix. Since they operate at extremely high temperatures of 650C (roughly

1,200F) and above, non-precious metals can be used as catalysts at the anode and

cathode, reducing costs.

Improved efficiency is another reason MCFCs offer significant cost reductions over

phosphoric acid fuel cells (PAFCs). Molten carbonate fuel cells can reach efficiencies

approaching 60 percent, considerably higher than the 37-42 percent efficiencies of a

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phosphoric acid fuel cell plant. When the waste heat is captured and used, overall fuel

efficiencies can be as high as 85 percent.

Unlike alkaline, phosphoric acid, and polymer electrolyte membrane fuel cells, MCFCs

don't require an external reformer to convert more energy-dense fuels to hydrogen. Due

to the high temperatures at which MCFCs operate, these fuels are converted to hydrogenwithin the fuel cell itself by a process called internal reforming, which also reduces cost.

Molten carbonate fuel cells are not prone to carbon monoxide or carbon dioxide

"poisoning" they can even use carbon oxides as fuelmaking them more attractive for

fueling with gases made from coal. Because they are more resistant to impurities than

other fuel cell types, scientists believe that they could even be capable of internal

reforming of coal, such as sulfur and particulates.

ZINC AIR FUEL CELL

In a typical zinc / air fuel cell, there is a gas diffusion electrode (GDE) a

permeable membrane that allows atmospheric oxygen to pass through , a zinc

anode separated by electrolyte, and some form of mechanical separators. After theoxygen has converted into the hydroxyl ions and water, the hydroxyl ions will

travel through the electrolyte, and reaches the zinc anode. Here, it reacts with the

zinc, and forms zinc oxide. This process creates an electric current.

High energy

Material costs are low.

Refuelling is a complex process

PROTONIC CERAMIC FUEL CELL

This is similar to the solid oxide fuel cell, but would operate at slightly lower temperature

(500-700C). The electrolyte allows the passage of protons (Hydrogen ions, H+).

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Similar to Solid Oxide Fuel Cells.

Not very developed, still in research stage.

Solid Oxide Fuel Cells

Fig-8

Solid oxide fuel cells (SOFCs) use a hard, non-porous ceramic compound as the

electrolyte. Since the electrolyte is a solid, the cells do not have to be constructed in the

plate-like configuration typical of other fuel cell types. SOFCs are expected to be around

50-60 percent efficient at converting fuel to electricity. In applications designed to

capture and utilize the system's waste heat (co-generation), overall fuel use efficiencies

could top 80-85 percent.

Solid oxide fuel cells operate at very high temperaturesaround 1,000C (1,830F).High temperature operation removes the need for precious-metal catalyst, thereby

reducing cost. It also allows SOFCs to reform fuels internally, which enables the use of a

variety of fuels and reduces the cost associated with adding a reformer to the system.

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SOFCs are also the most sulfur-resistant fuel cell type; they can tolerate several orders of

magnitude more sulfur than other cell types. In addition, they are not poisoned by carbon

monoxide (CO), which can even be used as fuel. This allows SOFCs to use gases made

from coal.

High-temperature operation has disadvantages. It results in a slow startup and requiressignificant thermal shielding to retain heat and protect personnel, which may be

acceptable for utility applications but not for transportation and small portable

applications. The high operating temperatures also place stringent durability requirements

on materials. The development of low-cost materials with high durability at cell operating

temperatures is the key technical challenge facing this technology.

Scientists are currently exploring the potential for developing lower-temperature SOFCs

operating at or below 800C that have fewer durability problems and cost less. Lower-

temperature SOFCs produce less electrical power, however, and stack materials that will

function in this lower temperature range have not been identified.

Regenerative Fuel Cells

Regenerative fuel cells produce electricity from hydrogen and oxygen and generate heat

and water as byproducts, just like other fuel cells. However, regenerative fuel cell

systems can also use electricity from solar power or some other source to divide the

excess water into oxygen and hydrogen fuelthis process is called "electrolysis." This is

a comparatively young fuel cell technology being developed by NASA and others.

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Electrochemical reactions of the Fuel Cell types

Fig-9

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Fuel Cell Comparisons

Table-1

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PROBLEMS WITH FUEL CELL

Cost

Chief among the problems associated with fuel cells is how expensive they are. Many of

the component pieces of a fuel cell are costly. For PEMFC systems, proton exchange

membranes, precious metal catalysts (usually platinum), gas diffusion layers, and bipolar

plates make up 70 percent of a system's cost [Source: Basic Research Needs for a

Hydrogen Economy ]. In order to be competitively priced (compared to gasoline-powered

vehicles), fuel cell systems must cost $35 per kilowatt. Currently, the projected high-

volume production price is $110 per kilowatt [Source: Testimony of David Garman ]. In

particular, researchers must either decrease the amount of platinum needed to act as a

catalyst or find an alternative.

Durability

Researchers must develop PEMFC membranes that are durable and can operate at

temperatures greater than 100 degrees Celsius and still function at sub-zero ambient

temperatures. A 100 degrees Celsius temperature target is required in order for a fuel cell

to have a higher tolerance to impurities in fuel. Because you start and stop a car relatively

frequently, it is important for the membrane to remain stable under cycling conditions.

Currently membranes tend to degrade while fuel cells cycle on and off, particularly as

operating temperatures rise.

Hydration

Because PEMFC membranes must by hydrated in order to transfer hydrogen protons,

researches must find a way to develop fuel cell systems that can continue to operate in

sub-zero temperatures, low humidity environments and high operating temperatures. At

around 80 degrees Celsius, hydration is lost without a high-pressure hydration system.

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Delivery

The Department of Energys Technical Plan for Fuel Cells states that the air compressor

technologies currently available are not suitable for vehicle use, which makes designing a

hydrogen fuel delivery system problematic.

FUEL CELL GOALS

Pollution reduction is one of the primary goals of the fuel cell. By comparing a fuel cell-

powered car to a gasoline-engine-powered car and a battery-powered car, you can see

how fuel cells might improve the efficiency of cars today.

Since all three types of the cars have many of the same components (tires, transmission

etc.) we will ignore that part of the car and compare efficiency up to point where

mechanical power is generated. Lets start with the fuel cell car. (All of these efficiencies

are approximation, but they should be close enough to make a rough comparison.)

If the fuel cell is powered with pure hydrogen, it has the potential to be up to 80%

efficient. That is, it converts 80% of the energy content of the hydrogen into electrical

energy. But, as we learned in the previous section, hydrogen in difficult to store in a car.

When we add a reformer to convert methanol to hydrogen, the overall efficiency drops to

about 30 to 40 %.

We still need to convert the electrical energy into mechanical work. This is accomplished

by the electric motor and inverter. A reasonable number for the efficiency of the

motor/inverter is about 80%. So we have 30 to 40 % efficiency at converting methanol to

electricity, and 80% efficiency converting electricity to mechanical power. That give an

overall efficiency of about 24 to 32%.

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Technology comparison

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Fig-10

ADVANTAGES

Zero Emissions : a fuel cell vehicle only emits water vapor if fueled with pure

hydrogen, while if it has an on board reformer for the hydrogen production we

have to take into account its emission. The vehicle is a really no-noise vehicle,

except for the noise of the auxiliaries (pumps, fan etc.)

High efficiency : since fuel cell does not use combustion, their efficiency is not

linked to their maximum operation temperature. As a result, the efficiency of the

power conversion step( the actual electrochemical reaction as opposed to the

actual combustion reaction) can be significantly higher that that of thermal

engines. In addition fuel cell also exhibit higher part load efficiency and do not

display a sharp drop in efficiency as the power plant size decrease.

Rapid load-following : fuel cell exhibit good load following characteristics. Fuel

cell systems, however, are comprised of predominately mechanical device each of

which has it own response time to changes in load demand.

Low temperatures : fuel cell systems suitable for automotive application operate

at low temperature. This is an advantages in the fuel cells require little warm up

time ,high temperature hazards are reduce, and the thermodynamic efficiency of the electro-chemical reaction is inherently better.

Reduced number of energy transformations . Fuel cell system do not require

recharging. Rather, fuel cell systems must be re-fueled, which is faster than

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charging a battery and can provide greater range depend-in on the size of the

storage tank.

DISADVANTAGES

Hydrogen : ironically, hydrogen which is of such benefit environmentally when

used in a fuel cell, is also its greatest liability in that it is difficult to manufacture

and store. Current manufacturing process are expensive and energy in-tensive and

also often drive ultimately from fossil fuels.

High-cost catalyst : fuel cell suitable for automotive application typically requires

the use of a platinum catalyst to promote the power generation reaction. Platinum

is a rare metal and is very expensive.

New technology : fuel cells are an emerging technology. As with my new

technology, reactions in cost, weight and size concurrent with increase in

reliability and lifetime remain pri-Mary engineering goals.

Lack of infrastructures : an effective hydrogen infrastructure has yet to be

established.

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FUEL CELL APPLICATIONS

Fuel cells have many applications today, and the list is growing fast. There are three basic

market segments that fuel cells satisfy: portable/battery substitution, transportation and

distribute power.

Applications for Portable and Battery Substitution

Portable appliances and power tools

Small personal vehicles

Consumer electronics(laptops, cell phone)

Backup power

Applications for Transportation

Automotive

Public transportation

Commercial transportation (truck, tractor)

Marine

military

Applications for Distributed Power

Homes ands small businesses

Commercial and industrial sites

Remote, off-grid location ( telecom tower, weather station)

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SOME COMPANIES INVOLVED IN RESEARCH

Ballard power, Canadapredominately working on PEFC for transpiration and electric

power plants. Most of the PEFC technology was developed in house and they own over

200 patents. They are working loosely with Daimler Chrysler and ford. According to

Merrill lynch, the PEFC fuel cell cars powered by Ballard will not commence mass

production until 2004. In Aug 1999 however they announced purchase of a world wide,

non-exclusive license to DMFC intellectual property from the California. Institute of

technology(Caltech) and the university of southern California (USC) through DTI

energy., inc. which holds exclusive licensing rights to the intellectual property.

CSIRO , Australia... Large scientific research agency, working on planner SOFC, claim to

be making good progress.

Energy ventures Inc , Canada is developed DMFC, AFC and lithium ion batteries for

portable power. Dec 1999 the company claimed its new DMFC technology has resolved

the historic problem of methanol cross-over and would result in an initial 30-40%

improvement in output. Wayne Hartford, president of EVI stated that we feel that the

marketplace has hugely underestimated and difficulty in developing a broadly based

consumer friendly fuelling infrastructure for hydrogen. With out that, there is a need to

reform any other fuel into hydrogen on board a vehicle and this equipment is costly, takesup space and requires a significant percentage of the power out put to operate.

Fuel cell energy, USA working on MCFC of 300kw, 1.5 MW and 3 Mw for electric

generation, this technology cannot be scaled down below 300 KW because of their need

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for significant amounts of auxiliary equipment such as pumps. They target jan2001 as

their date of market entry.

JPL, USA.. a division of NASA, they have been working on DMFC extensively since

1992. many of the increase in efficiency and power density are as a result or their efforts.

Nissan & Suzuki, JapanNissans announced on feb1998 that they would developed a

PEFC automobile based on the Ballard technology, one year later however they have

announced they will be joining Suzuki to develop their own DMFC automobile

Sulzer , Germanyworking on a 3 KW SOFC for CHP

Toyota , Japanhas their own PEFC technology they are working on.

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CONCLUSIONS

Fuel cells are still a few years away from commercialization on a large scale. It is

very difficult to tell which fuel and which technology will be predominant in the

future. There are some problems to be solved in the SOFC and the DAFC. If these

can be solved then these will become the predominant fuel cells being developed

in the future.

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References:

www.howstuffworks.comwww.fuelcellworks.comwww.minihydrogen.comMicro-vettFuel Cell SystemsSecond EditionBy: James LarminieControl of Fuel Cell Power Systems: Principles, Modeling, Analysis, andFeedback DesignJay T. PukrushpanAnna G. StephanopoulosHuei Peng

http://www.howstuffworks.com/http://www.fuelcellworks.com/http://www.minihydrogen.com/http://www.howstuffworks.com/http://www.fuelcellworks.com/http://www.minihydrogen.com/