Fuel Cell

Fuel cell Abstract

There are many types of fuel cells,

electricity

but

reaction with oxygen or another

they

all

consist

an anode (negative scist William Grove developed the first crude fuel cells in 1839. The first commercial use of fuel cells was in NASA space programs to generate power for probes, satellites and space capsules. Since then, fuel cells have been

used

in

many

other

applications. Fuel cells are used for primary and backup power for commercial,

industrial

and

residential buildings and in remote or inaccessible areas. They are used to power fuel cell vehicles, including automobiles,

buses,

forklifts,

airplanes, boats, motorcycles and submarines.

of side),

a cathode (positive

a

chemical

agent.[1]Hydrogen is

oxidizing

the

and

most common fuel, but hydrocarbons

an electrolyte that allows charges to

such as natural gas and alcohols

move between the two sides of the

like methanol are sometimes used.

fuel cell. Electrons are drawn from

Fuel

the anode to the cathode through an

from batteriesin that they require a

external

producing direct

constant source of fuel and oxygen to

As

main

run, but they can produce electricity

difference among fuel cell types is

continually for as long as these

the

inputs are supplied.

circuit,

current electricity.

electrolyte,

classified

side)

through

the

fuel

by

cells the

are

cells

are

different

type

of electrolyte they use. Fuel cells come in a variety of sizes. Individual fuel

cells

produce

very

small

amounts of electricity, about 0.7 volts, so cells are "stacked", or placed in series or parallel circuits, to increase the voltage and current output to meet an application’s power generation requirements. [2] In addition to electricity, fuel cells produce water, heat and, depending

Sketch of William Grove's 1839 fuel

on the fuel source, very small

cell

amounts other

of nitrogen emissions.

dioxide and The

energy

efficiency of a fuel cell is generally between 40-60%, or up to 85% efficient if waste heat is captured for use.

INTRODUCTION WHAT IS FUEL CELLS?

The principle of the fuel cell was discovered

by

scientist Christian

German Friedrich

Schönbein in 1838 and published in one of the scientific magazines of the time.[3]Based on this work, the first fuel cell was demonstrated by Welsh scientist and barrister Sir William Robert Grove in the February 1839

Demonstration model of a direct-

A fuel cell is a device that converts

methanol fuel cell.

the chemical energy from a fuel into

edition

of

the Philosophical

Magazine

and

Journal

of

commercial use of a fuel cell. In

United

Science and later sketched, in 1842,

1959,

Corporation's UTC Power subsidiary

in the same journal.[5] The fuel cell

Thomas

he made used similar materials to

developed a 5 kW stationary fuel

manufacture and commercialize a

today's phosphoric-acid fuel cell.

cell. In 1959, a team led by Harry

large, stationary fuel cell system for

Ihrig built a 15 kW fuel cell tractor

use as a co-generation power plant in

for

hospitals,

[4]

In 1955, W. Thomas Grubb, a chemist working for the General Electric

Company

(GE),

further

modified the original fuel cell design by using a sulphonated polystyrene ion-exchange

membrane

as

the

electrolyte. Three years later another GE

chemist,

Leonard

Niedrach,

devised a way of depositing platinum onto the membrane, which served as catalyst for the necessary hydrogen oxidation

and

oxygen

reduction

reactions. This became known as the 'Grubb-Niedrach fuel cell'. GE went on to develop this technology with NASA and McDonnell Aircraft, leading to its use during Project Gemini.

This

was

the

first

British

engineer Francis

Bacon

successfully

Allis-Chalmers

which

was

the

first

company

universities

fairs. This system used potassium

marketed their fuel cell, the PureCell

hydroxide

electrolyte

200, a 200 kW system, now replaced

hydrogen and

by a 400 kW version, the PureCell

oxygen as the reactants. Later in

Model 400.[7] UTC Power continues

1959, Bacon and his colleagues

to be the sole supplier of fuel cells to

demonstrated

NASA for use in space vehicles,

the

and compressed

a

practical

five-

kilowatt unit capable of powering a

having

supplied

UTC

large

office

as

buildings.

and

to

demonstrated across the US at state

fuel

Power

cells

for

[8]

welding machine. In the 1960s, Pratt

theApollo missions, and the Space

and Whitney licensed Bacon's U.S.

Shuttle program, and is developing

patents for use in the U.S. space

fuel cells for automobiles, buses, and

program to supply electricity and

cell phone towers. The company has

drinking

and

demonstrated the first fuel cell

oxygen being readily available from

capable of starting under freezing

the spacecraft tanks). In 1991, the

conditions with its proton exchange

first hydrogen fuel cell automobile

membrane.

water

(hydrogen

was developed by Roger Billings. [6]

History

was

Technologies

How do fuel cells work?

The chemical reactions that produce

The purpose of a fuel cell is to produce an electrical current that can be directed outside the cell to do work, such as powering an electric motor or illuminating a light bulb or a city. Because of the way electricity behaves, this current returns to the fuel cell, completing an electrical circuit.

(To

learn

more

about

electricity and electric power, visit “Throw

The

Switch”

on

the

Smithsonian website Powering a Generation of Change.)

this current are the key to how a fuel cell works. There are several kinds of fuel cells, and each operates a bit differently. But in general terms, hydrogen atoms enter a fuel cell at the anode where a chemical reaction strips them of their electrons. The hydrogen atoms are now “ionized,” and carry a positive electrical charge. The negatively charged electrons provide the current through wires to do work. If alternating current (AC) is needed, the DC output of the fuel

cell must be routed through a

the electrolyte to the anode, where it

supplied with hydrogen and oxygen,

conversion device called an inverter.

combines with hydrogen ions.

it will generate electricity.

The electrolyte plays a key role. It

Even better, since fuel cells create

must permit only the appropriate

electricity chemically, rather than by

ions to pass between the anode and

combustion, they are not subject to

cathode. If free electrons or other

the thermodynamic laws that limit a

substances could travel through the

conventional

electrolyte, they would disrupt the

“Carnot Limit” in the glossary).

chemical reaction.

Therefore,

Graphic by Marc Marshall, Schatz Energy

Research

CenterOxygen

enters the fuel cell at the cathode and, in some cell types (like the one illustrated above), it there combines with electrons returning from the electrical circuit and hydrogen ions that

have

traveled

through

the

electrolyte from the anode. In other cell types the oxygen picks up electrons and then travels through

Whether they combine at anode or cathode,

together

hydrogen

and

oxygen form water, which drains from the cell. As long as a fuel cell is

power

fuel

cells

plant

are

(see

more

efficient in extracting energy from a fuel. Waste heat from some cells can also be harnessed, boosting system efficiency still further.

Types of fuel cells; design Different types of fuel cells.

Drawing of an alkali cell.

Efficiency is about 70 percent, and

filled with liquid, they can leak.

operating temperature is 150 to 200 degrees C, (about 300 to 400 degrees F). Cell output ranges from 300 watts (W) to 5 kilowatts (kW). Alkali cells were used in Apollo spacecraft to provide both electricity and drinking water. They require pure hydrogen fuel, however, and their platinum electrode catalysts are expensive. And like any container

Alkali

fuel

cells

operate

on

Drawing of a molten carbonate cell

compressed hydrogen and oxygen.

Molten Carbonate fuel cells

They generally use a solution of

(MCFC)

potassium hydroxide (chemically,

compounds of salt (like sodium or

KOH) in water as their electrolyte.

use

high-temperature

magnesium) carbonates (chemically,

sulfur must be removed. Platinum

compound of metal (like calcium or

CO3) as the electrolyte. Efficiency

electrode-catalysts are needed, and

zirconium) oxides (chemically, O2)

ranges from 60 to 80 percent, and

internal parts must be able to

as electrolyte. Efficiency is about 60

operating temperature is about 650

withstand the corrosive acid.

percent, and operating

degrees C (1,200 degrees F). Units with output up to 2 megawatts (MW)

Drawing of how both phosphoric acid and PEM fuel cells operate.

have been constructed, and designs exist for units up to 100 MW. The high temperature limits damage from carbon monoxide "poisoning" of the cell and waste heat can be recycled to make additional electricity. Their nickel

electrode-catalysts

inexpensive

compared

to

are the

platinum used in other cells. But the high temperature also limits the Drawing

materials and safe uses of MCFCs—

of

a

solid

oxide

celltemperatures are about 1,000

they would probably be too hot for

Proton Exchange Membrane (PEM)

home use. Also, carbonate ions from

fuel cells work with a polymer

the electrolyte are used up in the

electrolyte in the form of a thin,

reactions, making it necessary to

permeable sheet. Efficiency is about

inject carbon dioxide to compensate.

40 to 50 percent, and operating

Phosphoric Acid fuel cells

temperature is about 80 degrees C

(PAFC) use phosphoric acid as the

(about 175 degrees F). Cell outputs

electrolyte. Efficiency ranges from

generally range from 50 to 250 kW.

40 to 80 percent, and operating

The solid, flexible electrolyte will

temperature is between 150 to 200

not leak or crack, and these cells

degrees C (about 300 to 400 degrees

operate at a low enough temperature

F). Existing phosphoric acid cells

to make them suitable for homes and

have outputs up to 200 kW, and 11

cars. But their fuels must be purified,

More detailed information about

MW units have been tested. PAFCs

and a platinum catalyst is used on

each

tolerate

both sides of the membrane, raising

histories and current applications,

concentration of about 1.5 percent,

costs.

can be found on their specific parts

which broadens the choice of fuels

Solid

they can use. If gasoline is used, the

(SOFC)

a

carbon

monoxide

Oxide

fuel

cells

use a hard, ceramic

degrees C (about 1,800 degrees F). Cells output is up to 100 kW. At such high temperatures a reformer is not required to extract hydrogen from the fuel, and waste heat can be recycled electricity.

to

make

However,

additional the

high

temperature limits applications of SOFC units and they tend to be rather large. While solid electrolytes cannot leak, they can crack.

fuel

cell

type,

including

of this site. We have also provided a glossary of technical terms–a link is

provided

at

the

top

of

each

technology page.

Application 85%.[22] This is significantly more efficient than

Power

traditional coal power plants,

Stationary fuel cells are used for commercial, industrial and residential primary and backup power generation. Fuel cells are very useful as power sources in remote locations, such as spacecraft, remote weather stations, large parks, communications centers, rural locations including research

stations,

and

in

certain

military

applications. A fuel cell system running on

(type of submarin with fuel cell)

hydrogen can be compact and lightweight, and have

which are only about one third energy efficient.

no major moving parts. Because fuel cells have no

[48]

moving parts and do not involve combustion, in

save 20-40% on energy costs when used in

ideal conditions they can achieve up to 99.9999%

cogeneration systems.[49] Fuel cells are also much

reliability.[45] This equates to less than one minute

cleaner than traditional power generation; a fuel

of downtime in a six year period.[46]

cell power plant using natural gas as a hydrogen

Since fuel cellelectrolyzer systems do not store fuel in themselves, but rather rely on external storage units, they can be successfully applied in largescale energy storage, rural areas being one example.[47] There are many different types of stationary fuel cells so efficiencies vary, but most are between 40% and 60% energy efficient. [22]

However, when the fuel cell’s

Assuming production at scale, fuel cells could

source would create less than one ounce of pollution (other than CO2) for every 1,000 kW produced, compared to 25 pounds of pollutants generated by conventional combustion systems. [50]

Fuel Cells also produce 97% less nitrogen oxide

emissions then conventional coal-fired power plants. Coca-Cola, Google, Walmart, Sysco, FedEx, UPS, Ikea, Staples, Whole Foods, Gills Onions, Nestle Waters, Pepperidge Farm, Sierra Nevada Brewery,

waste heat is used to heat a building in a cogeneration system this efficiency can increase to

Super

Store

Industries,

Brigestone-Firestone,

Nissan North America, Kimberly-Clark, Michelin and more have installed fuel cells to help meet their

power needs.[51][52] One such pilot program is

and at the same time produces hot air and water

operating on Stuart Island in Washington State.

from thewaste heat. MicroCHP is usually less than

There the Stuart Island Energy Initiative [53] has built

5 kWe for a home fuel cell or small business.

a complete, closed-loop system: Solar panels power

The waste heat from fuel cells can be diverted

an electrolyzer which makes hydrogen. The

during the summer directly into the ground

hydrogen is stored in a 500 US gallons (1,900 L) at

providing further cooling while the waste heat

200 pounds per square inch (1,400 kPa), and runs a

during winter can be pumped directly into the

ReliOn fuel cell to provide full electric back-up to

building. The University of Minnesota owns the

the off-the-grid residence. Another closed system

patent rights to this type of system

loop was unveiled in late 2011 in Hempstead, NY. Co-generation systems can reach 85% efficiency

[54]

(40-60%

Cogeneration

electric

+

remainder

as

thermal).

[22]

Phosphoric-acid fuel cells (PAFC) comprise the

Combined heat and power (CHP) fuel cell systems,

largest

including Micro

and

worldwide and can provide combined efficiencies

power(MicroCHP) systems are used to generate

close to 90%.] Molten Carbonate (MCFC) and

both electricity and heat for homes (see home fuel

Solid Oxide Fuel Cells (SOFC) are also used for

cell), office building and factories. The system

combined heat and power generation and have

generates constant electric power (selling excess

electrical energy effciences around 60%.

combined

heat

segment

of

existing

CHP

products

power back to the grid when it is not consumed),

Automobiles

produced with "a driving range of

Although there are currently no Fuel cell

vehicles

available

for

commercial sale, over 20 FCEVs prototypes and demonstration cars have been released since 2009. Demonstration the Honda

models

FCX

include

Clarity, Toyota

FCHV-adv, and Mercedes-Benz FCell.[60] As

of

June

2011

demonstration FCEVs had driven

Fuel Cell Electric Vehicles (FCEVs)

more

than

(3,000,000 mi), 27,000 fuel

4,800,000 with

more

km than

refuelings. Demonstration cell

vehicles

have

been

more than 400 km (250 mi) between refueling" They can be refueled in less

than

5

minutes. The

U.S.

Department of Energy's Fuel Cell Technology Program claims that, as of 2011, fuel cells achieved 53–59% efficiency at ¼ power and 42–53% vehicle efficiency at full power, [64]

and a durability of over 120,000

km (75,000 mi) with less than 10% degradation, double that achieved in 2006.[62] In

a

Well-to-Wheels

simulation analysis, that "did not address the economics and market constraints", General Motors and its

partners estimated that per mile

infrastructure in the U.S. as an

would

traveled, a fuel cell electric vehicle

ongoing challenge to Fuel Cell

production date of their fuel cell car

running on

gaseous

Electric Vehicle commercialization.

from 2015 up to 2014, asserting that

hydrogen produced from natural gas

In 2006, a study for the IEEE

"The product is ready for the market

could use about 40% less energy and

showed that for hydrogen produced

technically.

compressed

emit 45% less greenhouse gasses

via electrolysis of water: "Only about

than an internal combustion vehicle.

25% of the power generated from

[65]

the

wind, water, or sun is converted to

Department of Energy whose team is

practical use." The study further

testing fuel cell cars said in 2011 that

noted that "Electricity obtained from

the potential appeal is that "these are

hydrogen fuel cells appears to be

full-function

four times as expensive as electricity

A

lead

engineer

from

vehicles

with

no

limitations on range or refueling rate

drawn

from

the

so they are a direct replacement for

transmission grid. ... Because of the

any vehicle. For instance, if you

high

drive a full sized SUV and pull a

cannot

energy

losses

electrical

[hydrogen]

compete

with

electricity." Furthermore, the study

do that with this technology and you

found: "Natural gas reforming is not

can't

battery-only

a sustainable solution".[72] "The large

vehicles, which are more geared

amount of energy required to isolate

toward city driving."[66]

hydrogen from natural compounds

current

Some experts believe that fuel cell cars will never become economically competitive

with

technologies decades

[67][68]

for

other

or that it will take

them

to

become

profitable.[69][70] In July 2011, the Chairman

and

CEO

ofGeneral

(water,

too expensive and probably won't be practical until the 2020-plus period, I don't know."[71] Analyses cite the lack

of

an

extensive hydrogen

gas,

biomass),

or liquefaction, transfer the energy carrier to the user, plus the energy lost when it is converted to useful electricity with fuel cells, leaves around 25% for practical use." [16][38]

Motors, Daniel Akerson, stated that

cars is decreasing: "The car is still

natural

package the light gas by compression

[73]

while the cost of hydrogen fuel cell

the

...

infrastructure."

scheduled

The

issue

is

[75]

In 2003 US President George W. Bush proposed the Hydrogen Fuel Initiative (HFI). This aimed at further developing hydrogen fuel cells and infrastructure technologies with

the

goal

of

producing

commercial fuel cell vehicles. By 2008, the U.S. had contributed 1 billion [76]

dollars

The Obama

to

this

project.

Administration has

[72]

boat up into the mountains, you can

with

move

Despite this, several major car

manufacturers have announced plans to introduce a production model of a fuel cell car in 2015. Toyota has stated that it plans to introduce such a

vehicle

at

a

price

of

around US$50,000.[74] In June 2011, Mercedes-Benz announced that they

sought to reduce funding for the development of fuel cell vehicles, concluding

that

other

vehicle

technologies will lead to quicker reduction in emissions in a shorter time.[77] Steven

Chu,

the US

Secretary of Energy, stated that hydrogen vehicles "will not be practical over the next 10 to 20 years".[78]He told MIT's Technology Review that he is skeptical about hydrogen's

use

in transportation

because of four problems: "the way we get hydrogen primarily is from reforming [natural] gas. ... You're giving away some of the energy content of natural gas. ... [For] transportation, we don't have a good storage mechanism yet. ... The fuel

cells aren't there yet, and the

by UTC Power, Toyota, Ballard,

distribution infrastructure isn't there

Hydrogenics, and Proton Motor.

(Mercedes-Benz (Daimler AG) Citaro fuel cell bus on Aldwych, London.)

yet. ... In order to get significant

UTC

(600,000 mi) of driving. [81] Fuel cell

deployment,

accumulated over 970,000 km

you

significant breakthroughs. Mary

need

four

Buses

have

already

buses have a 30-141% higher fuel

technological [79]

Nichols,

Critics

economy than diesel buses and

disagree.

Chairwoman

natural gas buses.[82] Fuel cell buses

of

have been deployed around the

California's Air Resources Board,

world including in Whistler Canada,

said: "Secretary Chu has firmly set

San

his mind against hydrogen as a

Germany, Shanghai China, London

passenger-car

England, São Paulo Brazil as well as

fuel.

Frankly,

his

explanations don’t make sense to me.

Francisco

USA,

Hamburg

several others

They are not based on the facts as we know them."[80]

Buses In total there are over 100 fuel cell buses deployed around the world today. Most buses are produced

refilling:

all

that

enters

is

electricity

and

water. Royal Dutch Shell is also a partner in the project. The station has no roof, in order to allow

Fueling stations

any leaked hydrogen to escape to the atmosphere. There are already over 85 hydrogen refueling stations in the U.S.[110] The National Research Council estimated that creating the infrastructure to supply fuel for 10 million FCVs through 2025 would cost the government US$8 billion over 16 years.[]The first public hydrogen refueling station was opened inReykjavík, Iceland in April 2003.

As part of the California Hydrogen Highway

This

built

initiative California has the most extensive

by DaimlerChrysler that are in service in the public

hydrogen refueling infrastructure in the U.S.A. As

transport net of Reykjavík. The station produces the

of June 2011 California had 22 hydrogen refueling

hydrogen it needs by itself, with an electrolyzing

stations in operation.[110] Honda announced plans in

unit (produced by Norsk Hydro), and does not need

March 2011 to open the first station that would

station

serves

three

buses

generate

hydrogen

through

solar-powered

electrolysis. [citation

renewable

needed]

South

Carolina also has two hydrogen fueling stations, in Aiken and Columbia, SC. According to the South Carolina Hydrogen & Fuel Cell Alliance, the Columbia station has a current capacity of 120 kg a day, with future plans to develop on-site hydrogen production from electrolysis and reformation. The Aiken station has a current capacity of 80 kg. The University of South Carolina, a founding member of the South Carolina Hydrogen & Fuel Cell Alliance, received 12.5 million dollars from the United States Department of Energy for its Future Fuels Program.[112] Japan also has a hydrogen highway, as part of the Japan

hydrogen

fuel

cell

project.

Twelve hydrogen fueling stations have been built in

Reference: 1: http://www.fuelcells.org 2:www.google.co.in 3: Book fuel cell by B.VISWANATHAN 4: protium.us/files/course_outline.doc 5: en.wikipedia.org/wiki/Fuel_cell

11

cities

Japan. Canada, Sweden and Norway also have

in