The authors acknowledge the following reviewers:

Los Alamos National Laboratory

Shimshon Gottesfeld

Charles F. Keller

Steffen MØller-Holst

Antonio Redondo

Office of Advanced Automotive Technologies,

U.S. Department of Energy

JoAnn Milliken

LA-UR-99-3231

Los Alamos National Laboratory, an affirmative

action/equal opportunity employer, is operated

by the University of California for the US

Department of Energy under contract W-7405-

ENG-36. All company names, logos, and products

mentioned herein are trademarks of their

respective companies. Reference to any specific

company or product is not be construed as an

endorsement of said company or product by the

Regents of the University of California, the

United States Government, the US Department of

Energy, nor any of their employees. The Los

Alamos National Laboratory strongly supports

academic freedom and a researcher’s right to

publish; as an institution, however, the

Laboratory does not endorse the viewpoint of a

publication or guarantee its technical correctness.
1

 – Green Power

What’s Inside

2. A Brief History

4. The Very Basics

and More

5. Some

Comparisons

7. The Polymer Electrolyte

Membrane Fuel Cell

15. Other Types

of Fuel Cells

19. What About Fuel?

21. Applications

for Fuel Cells

24. Hydrogen as A Fuel

27. Getting To Cleaner

Transportation

28. Oil Reserves,

Transportation,

and Fuel Cells

29. Climate Change,

Greenhouse Gases,

and Fuel Cells:

What is the Link?

32. A Once-In-A-Lifetime

Opportunity

Fuel Cells

 – Green Power

was written by Sharon Thomas

and Marcia Zalbowitz at

Los Alamos National Laboratory

in Los Alamos, New Mexico

Designed by Jim Cruz

This publication has been funded by the

Office of Advanced Automotive Technologies

Office of Transportation Technologies

Energy Efficiency and Renewable Energy

U.S. Department of Energy

The 3M Foundation

 

For more information:

www.education.lanl.gov/resources/fuelcells
Lamps, burning coal

oil and coal gas, lit

the living rooms of

most homes of the

early 1900’s. But

when electric light

bulbs replaced those

smoky, smelly

sources of illumination, homes became

brighter, cleaner, and

safer. At first only

the wealthy could

afford electric lights.

But as the demand

went up and the cost

went down, more

and more of the

population were able

to afford electric

lighting even though

there was plenty

of coal to continue

lighting buildings in

the usual way. The

better technology

won.

D.S. Scott and W. Hafele.

“The Coming Hydrogen

Age: Preventing World

Climate Disruption.”

International Journal of

Hydrogen Energy. Vol.

15, No. 10, 1990.

A Brief History

Although fuel cells have been around since 1839, it took 120 years

until NASA demonstrated some of their potential applications in

providing power during space flight. As a result of these successes, in

the 1960s, industry began to recognize the commercial potential of

fuel cells, but encountered technical barriers and high investment costs

— fuel cells were not economically competitive with existing energy

technologies. Since 1984, the Office of Transportation Technologies at

the U.S. Department of Energy has been supporting research and

development of fuel cell technology, and as a result, hundreds of

companies around the world are now working towards making fuel

cell technology pay off. Just as in the commercialization of the electric

light bulb nearly one hundred years ago, today’s companies are

being driven by technical, economic, and social forces such as high

performance characteristics, reliability, durability, low cost, and

environmental benefits.

In 1839, William Grove, a British jurist and amateur physicist, first discovered the

principle of the fuel cell. Grove utilized four large cells, each containing hydrogen

and oxygen, to produce electric power which was then used to split the water in

the smaller upper cell into hydrogen and oxygen.

 “I cannot but regard the experiment

 as an important one...”

William Grove writing to Michael Faraday,

October 22, 1842
3

“The mission of our global fuel cell project

 center is nothing less than to make us the leader in

commercially viable fuel cell powered vehicles.”

Harry J. Pearce, Vice Chairman,

Board of Directors, General Motors.

May 1998

In March 1998, Chicago became the first

city in the world to put pollution-free,

hydrogen fuel cell powered buses in

their public transit system.

(Courtesy: Ballard Power Systems)

The FutureCar Challenge, sponsored by

the U.S. Department of Energy, presents

a unique assignment to students from

North America’s top engineering schools:

convert a conventional midsize sedan

into a super efficient vehicle without

sacrificing performance, utility, and

safety. In 1999, the Virginia Tech

team entered the competition with a

fuel cell vehicle.

The first fuel cell powered bicycle

to compete in the American Tour-de-Sol.

(Courtesy: H-Power)

The automobile, it is fair to say, changed the industrial and

social fabric of the United States and most

countries around the globe. Henry Ford epitomized “Yankee ingenuity”

and the Model T helped create the open road, new horizons, abundant and

inexpensive gasoline...and tailpipe exhaust. More people are driving more

cars today than ever before — more than 200 million vehicles are on the road

in the U.S. alone. But the car has contributed to our air and water pollution

and forced us to rely on imported oil from the Middle East, helping to create

a significant trade imbalance. Today many people think fuel cell technology

will play a pivotal role in a new technological renaissance — just as the

internal combustion engine vehicle revolutionized life at the beginning of

the 20th century. Such innovation would have a global environmental and

economic impact.

“In today’s world,

solving environmental problems

is an investment, not an expense.”

William Clay Ford, Jr.

Chairman and CEO, Ford Motor Company,

September 1998

Fuel cells are not just laboratory curiosities. While there is much work that

needs to be done to optimize the fuel cell system (remember, the gasoline

internal combustion engine is nearly 120 years old and still being improved),

hydrogen fuel cell vehicles are on the road — now. Commuters living in

Chicago and Vancouver ride on fuel cell buses. You can take a ride around

London in a fuel cell taxi and even compete in the American Tour de Sol

on a fuel cell bicycle. Every major automobile manufacturer in the world

 is developing fuel cell vehicles. To understand why fuel cells have received

such attention, we need to compare them to existing energy conversion

technologies.
Where the Action

in Fuel Cells is Today

Allied Signal

Volvo

Ballard

DaimlerChrysler

Detroit Edison

DuPont

Shell

Ford

General Motors

Honda

Mazda

Georgetown University

Case Western Reserve University

Los Alamos National Laboratory

Motorola

Penn State University

Princeton University

Rolls-Royce

Argonne National Laboratory

Sanyo

DAIS

Siemens

British Gas

Plug Power

University of Michigan

Texas A&M University

ARCO

Epyx

International Fuel Cells

H-Power

Energy Partners

Hydrogen Burner

W.L. Gore

A.D. Little

Institute of Gas Technology

Vairex

Electrochem

Giner

Jet Propulsion Laboratory

Toyota

University of California

Exxon

Westinghouse

Renault

3M

Nissan

BMW

PSA Peugeot Citroën

Texaco

University of Florida

Tokyo Electric Power

(This is just a partial list)

Carnot Cycle vs. Fuel Cells

T he theoretical thermodynamic derivation of Carnot Cycle shows

that even under ideal conditions, a heat engine cannot convert all

the heat energy supplied to it into mechanical energy; some of the

heat energy is rejected. In an internal combustion engine, the engine

accepts heat from a source at a high temperature (T1), converts part of

the energy into mechanical work and rejects the remainder to a heat

sink at a low temperature (T2). The greater the temperature difference

between source and sink, the greater the efficiency,

Maximum Efficiency = (T1 – T2) / T1

where the temperatures T1 and T2 are given in degrees Kelvin.

Because fuel cells convert chemical energy directly to electrical energy,

this process does not involve conversion of heat to mechanical energy.

Therefore, fuel cell efficiencies can exceed the Carnot limit even when

operating at relatively low temperatures, for example, 80°C.

The Very Basics

• A fuel cell is an electrochemical energy

conversion device. It is two to three

times more efficient than an internal

combustion engine in converting fuel

to power.

• A fuel cell produces electricity, water,

and heat using fuel and oxygen in the

air.

• Water is the only emission when

hydrogen is the fuel.

As hydrogen flows into the fuel cell on

the anode side, a platinum catalyst facilitates the separation of the hydrogen gas

into electrons and protons (hydrogen ions). The hydrogen ions pass

through the membrane (the center of the fuel cell) and, again with the

help of a platinum catalyst, combine with oxygen and electrons on the

cathode side, producing water. The electrons, which cannot pass

through the membrane, flow from the anode to the cathode through an

external circuit containing a motor or other electric load, which consumes the power generated by the cell.

The voltage from one single cell is about 0.7 volts – just about enough

for a light bulb – much less a car. When the cells are stacked in series,

the operating voltage increases to 0.7 volts multiplied by the number

of cells stacked.

Hydrogen Catalyst

Cathode (+)

Water

Oxygen

Anode (-)

Electrons

Protons

Membrane/

Electrolyte
5

W hat internal combustion

engines, batteries, and fuel

cells have in common is their

purpose: all are devices that convert

energy from one form to another.

As a starting point, let’s consider the

internal combustion engine — used

to power virtually all of the cars

driven on U.S. highways today.

These engines run on noisy, high

temperature explosions resulting

from the release of chemical energy

by burning fuel with oxygen from

the air. Internal combustion engines, as well as conventional utility

power plants, change chemical

energy of fuel to thermal energy to

generate mechanical and, in the case

of a power plant, electrical energy.

Fuel cells and batteries are electrochemical devices, and by their very

nature have a more efficient conversion process: chemical energy is

converted directly to electrical

energy. Internal combustion engines

are less efficient because they include

the conversion of thermal to mechanical energy, which is limited by

the Carnot Cycle.

If cars were powered by electricity

generated from direct hydrogen fuel

cells, there would be no combustion

involved. In an automotive fuel cell,

hydrogen and oxygen undergo a

relatively cool, electrochemical

reaction that directly produces

electrical energy. This electricity

would be used by motors, including

one or more connected to axles used

to power the wheels of the vehicle.

The direct hydrogen fuel cell vehicle

will have no emissions even during

idling — this is especially important

during city rush hours. There are

How do Fuel Cells Compare to

Internal Combustion Engines and Batteries?

some similarities to an internal

combustion engine, however. There

is still a need for a fuel tank and

oxygen is still supplied from the air.

Many people incorrectly assume that

all electric vehicles (EVs) are powered by batteries. Actually, an EV is

a vehicle with an electric drive train

powered by either an on-board

battery or fuel cell. Batteries and

fuel cells are similar in that they

both convert chemical energy into

electricity very efficiently and they

both require minimal maintenance

because neither has any moving

parts. However, unlike a fuel cell,

the reactants in a battery are stored

internally and, when used up, the

battery must be either recharged or

replaced. In a battery-powered EV,

rechargeable batteries are used.

With a fuel cell powered EV, the fuel

is stored externally in the vehicle’s

fuel tank and air is obtained from

the atmosphere. As long as the

vehicle’s tank contains fuel, the fuel

cell will produce energy in the form

of electricity and heat. The choice

of electrochemical device, battery or

fuel cell, depends upon use. For

larger scale applications, fuel cells

have several advantages over batteries including smaller size, lighter

weight, quick refueling, and longer

range.

The polymer electrolyte membrane

(PEM) fuel cell is one in a family of

five distinct types of fuel cells. The

PEM fuel cell, under consideration

by vehicle manufacturers around the

world as an alternative to the

internal combustion engine, will be

used to illustrate the science and

technology of fuel cells.

The P2000, from Ford Motor Company, is a zero-emission vehicle that utilizes a direct

hydrogen polymer electrolyte fuel cell. (Courtesy of Ford Motor Co.)

Hydrogen Fuel Cell Car

Chemical Energy

(gaseous flow) Electrical Energy

Fuel

Cells Hydrogen

Tank

Mechanical Energy

Traction

Inverter

Module

Turbocompressor

Hydrogen is

supplied to the Fuel Cells

Air is supplied to

the fuel cells by

turbocompressor

The traction inverter module

converts the electricity for

use by the electric motor/

transaxles

The electric motor/

transaxle converts the

electric energy into the

mechanical energy

which turns the wheels 

Oxygen from the air and

hydrogen combine in the

fuel cells to generate electricity

that is sent to the traction

inverter module

Electric

Motor/

Transaxle
References:

Bill McKibben, “A Special Moment in

History.” The Atlantic Monthly,

May, 1998.

James J. MacKenzie, “Oil as a Finite

Resource: When is Global

Production Likely to Peak?”

World Resources Institute, March

1996.

Colin Campbell and Jean H. Laherre`re

“The End of Cheap Oil .” Scientific

American, March 1998.

“Busting Through with Ballard.”

Financial Times Energy

World. Number Five, Winter

1998.

Jacques Leslie. “The Dawn of the

Hydrogen Age.” Wired. October,

1997.

McGraw-Hill Dictionary of Scientific

and Technical Terms. 1994.

Motor Vehicle Facts and Figures.

American Automobile

Manufacturers Association. 1998.

Resources:

World Resources Institute

http://www.wri.org

International Fuel Cells

http://www.hamiltonstandard.com/ifc-onsi

United Nations Framework Convention

on Climate Change

http://www.unfccc.de/

Linkages http://www.iisd.ca/

linkages/

Environmental Protection Agency,

Alternative Fuels

http:// www.epa.gov/omswww

U.S. Fuel Cell Council

http://www.usfcc.com

Fuel Cells 2000

http://fuelcells.org

Future Opportunities

Polymer electrolyte membrane fuel cells are

limited by the temperature range over which

water is a liquid. The membrane must contain

water so that the hydrogen ions can carry the

charge within the membrane. Operating polymer electrolyte membrane fuel cells at

temperatures exceeding 100 ̊C is possible

under pressurized conditions, required to keep

the water in a liquid state, but shortens the

life of the cell. Currently, polymer electrolyte

membranes cost about $100/square foot.

Costs are expected to decrease significantly

as the consumer demand for polymer electrolyte membrane fuel cells increases.

Remaining Challenges:

• producing membranes not limited by the

temperature range of liquid water,

possibly based on another mechanism for

protonic conduction

• reducing membrane cost by developing

different membrane chemistries

Structure of Polymer Electrolyte Membranes

T he polymer electrolyte membrane is a solid, organic polymer,

usually poly[perfluorosulfonic] acid. A typical membrane material,

such as NafionTM, consists of three regions:

(1) the Teflon-like, fluorocarbon backbone, hundreds of repeating

– CF2 – CF – CF2 – units in length,

(2) the side chains, –O– CF2 – CF – O– CF2 – CF2 –, which connect the

molecular backbone to the third region,

(3) the ion clusters consisting of sulfonic acid ions, SO3

-

 H+.

The negative ions, SO3

-

, are permanently attached to the side chain

and cannot move. However, when the membrane becomes hydrated

by absorbing water, the hydrogen ions become mobile. Ion movement

occurs by protons, bonded to water molecules, hopping from SO3

-

 site

to SO3

-

 site within the membrane. Because of this mechanism, the

solid hydrated electrolyte is an excellent conductor of hydrogen ions.

– CF2 – CF – CF2 –

 l

O

 l

CF2

 l

CF – CF3

 l

O

 l

CF2

 l

CF2

 l

SO3

-

 H+

Chemical structure

of membrane

material;

NafionTM by DuPont

Definitions:

Electrochemical reaction: A reaction

involving the transfer of

electrons from one chemical

substance to another.

Fuel cell: An electrochemical device

that continuously converts the

chemical energy of externally

supplied fuel and oxidant directly

to electrical energy.

Oxidant: A chemical, such as oxygen,

that consumes electrons in an

electrochemical reaction.

Electrolyte: A substance composed of

positive and negative ions,

Ion: An atom that has acquired an

electrical charge by the loss or gain

of electrons.

1 micron = 10-6 m, 10-4 cm, 10-3 or

0.001 mm = 1 m

 Polymer: A substance made of giant

molecules formed by the union of

simple molecules (monomers).

Thermal: Pertaining to heat
7

A s little as 10 years ago, vehicles powered by

fuel cells seemed more science fiction than fact.

Today, development of fuel cell technology for transportation is made possible due to the polymer electrolyte

membrane fuel cell. This type of fuel cell is also known

as the proton exchange membrane fuel cell, the solid

polymer electrolyte (SPETM) fuel cell and simply, polymer electrolyte fuel cell. It is often referred to simply as

the “PEM” fuel cell. The center of the fuel cell is the

polymer electrolyte membrane. For all five families of

fuel cells, it is the electrolyte that defines the type of fuel

cell, so the discussion of the polymer electrolyte membrane fuel cell should logically begin with its electrolyte,

the membrane.

The Polymer Electrolyte Membrane

An ordinary electrolyte is a substance that dissociates

into positively charged and negatively charged ions in

the presence of water, thereby making the water solution electrically conducting. The electrolyte in a

polymer electrolyte membrane fuel cell is a type of

plastic, a polymer, and is usually referred to as a membrane. The appearance of the electrolyte varies

depending upon the manufacturer, but the most prevalent membrane, Nafion TM produced by DuPont,

resembles the plastic wrap used for sealing foods. Typically, the membrane material is more substantial than

common plastic wrap, varying in thickness from 50 to

175 microns. To put this in perspective, consider that a

piece of normal writing paper has a thickness of about 25

microns. Thus polymer electrolyte membranes have

thicknesses comparable to that of 2 to 7 pieces of paper.

In an operating fuel cell, the membrane is well humidified so that the electrolyte looks like a moist piece of

thick plastic wrap.

Polymer electrolyte membranes are somewhat unusual

electrolytes in that, in the presence of water, which the

membrane readily absorbs, the negative ions are rigidly

held within their structure. Only the positive ions

contained within the membrane are mobile and are free

to carry positive charge through the membrane. In

polymer electrolyte membrane fuel cells these positive

ions are hydrogen ions, or protons, hence the term –

proton exchange membrane. Movement of the hydrogen ions through the membrane, in one direction only,

from anode to cathode, is essential to fuel cell operation.

Without this movement of ionic charge within the fuel

cell, the circuit defined by cell, wires, and load remains

open, and no current would flow.

Because their structure is based on a TeflonTM backbone,

polymer electrolyte membranes are relatively strong,

stable substances. Although thin, a polymer electrolyte

membrane is an effective gas separator. It can keep the

hydrogen fuel separate from the oxidant air, a feature

essential to the efficient operation of a fuel cell. Although ionic conductors, polymer electrolyte

membranes do not conduct electrons. The organic

nature of the polymer electrolyte membrane structure

makes them electronic insulators, another feature

essential to fuel cell operation. As electrons cannot

move through the membrane, the electrons produced at

one side of the cell must travel, through an external

wire, to the other side of the cell to complete the circuit.

It is in their route through the circuitry external to the

fuel cell that the electrons provide electrical power to

run a car or a power plant.

The Polymer Electrolyte Membrane Fuel Cell
 The Electrodes

All electrochemical reactions consist of two separate reactions: an oxidation half-reaction occurring at the anode and

a reduction half-reaction occurring at the cathode. The anode and the cathode are separated from each other by the

electrolyte, the membrane.

In the oxidation half-reaction, gaseous hydrogen produces hydrogen ions, which travel through the ionically conducting membrane to the cathode, and electrons which travel through an external circuit to the cathode. In the

reduction half-reaction, oxygen, supplied from air flowing past the cathode, combines with these hydrogen ions and

electrons to form water and excess heat. These two half-reactions would normally occur very slowly at the low

operating temperature, typically 80 ̊C, of the polymer electrolyte membrane fuel cell. Thus, catalysts are used on

both the anode and cathode to increase the rates of each half-reaction. The catalyst that works the best on each

electrode is platinum, a very expensive material.

The final products of the overall cell reaction are electric power, water, and excess heat. Cooling is required, in fact,

to maintain the temperature of a fuel cell stack at about 80 ̊C. At this temperature, the product water produced at

the cathode is both liquid and vapor. This product water is carried out of the fuel cell by the air flow.

Electrochemistry of Fuel Cells

Oxidation half reaction 2H2 ➔ 4H+ + 4eReduction half reaction O2 + 4H+

 + 4e- ➔ 2H2O

Cell reaction 2H2 + O2 ➔2H2O

T he physical and electrochemical processes that occur at each

electrode are quite complex. At the anode, hydrogen gas (H2)

must diffuse through tortuous pathways until a platinum (Pt) particle

is encountered. The Pt catalyzes the dissociation of the H2 molecule

into two hydrogen atoms (H) bonded to two neighboring Pt atoms.

Only then can each H atom release an electron to form a hydrogen ion

(H+). Current flows in the circuit as these H+ ions are conducted

through the membrane to the cathode while the electrons pass from

the anode to the outer circuit and then to the cathode.

The reaction of one oxygen (O2) molecule at the cathode is a 4

electron reduction process (see above equation) which occurs in a

multi-step sequence. Expensive Pt based catalysts seem to be the

only catalysts capable of generating high rates of O2 reduction at the

relatively low temperatures (~ 80 ̊C) at which polymer electrolyte

membrane fuel cells operate. There is still uncertainty regarding the

mechanism of this complex process. The performance of the polymer

electrolyte membrane fuel cells is limited primarily by the slow rate of

the O2 reduction half reaction which is more than 100 times slower

than the H2 oxidation half reaction.

Definitions:

Catalyst: A substance that

participates in a reaction,

increasing its rate, but is not

consumed in the reaction.

Current: The flow of electric charge

through a circuit.

Electrode: An electronic conductor

through which electrons are

exchanged with the chemical

reactants in an electrochemical cell.

Electron: An elementary particle

having a negative charge.

1 nanometer: = 10-9 m = 10-7 cm

= 10-6 mm = 10-3 μm = 1 nm

Oxidation half reaction: A process in

which a chemical species changes to

another species with a more

positive charge due to the release

of one or more electrons. It can

occur only when combined with a

reduction half reaction.

Reduction half reaction: A process in

which a chemical species changes

to another species with a less

positive charge due to the

addition of one or more electrons.

It can occur only when combined

with an oxidation half reaction.
9

Polymer electrolyte membrane with porous electrodes that

are composed of platinum particles uniformly supported

on carbon particles.

Why a Fuel Cell Goes “Platinum”

T he half reactions occurring at each electrode can only occur at a

high rate at the surface of the Pt catalyst. Platinum is unique

because it is sufficiently reactive in bonding H and O intermediates as

required to facilitate the electrode processes, and also capable of

effectively releasing the intermediate to form the final product. For

example, the anode process requires Pt sites to bond H atoms when

the H2 molecule reacts, and these Pt sites next release the H atoms,

as H+ + eH2 + 2Pt ➔ 2 Pt-H

2 Pt – H ➔ 2 Pt + 2 H+ + 2eThis requires optimized bonding to H atoms — not too weak and not

too strong — and this is the unique feature of a good catalyst. Realizing that the best catalyst for the polymer electrolyte membrane fuel

cell is expensive, lowering Pt catalyst levels is an on-going effort.

One of the best ways to accomplish this is to construct the catalyst

layer with the highest possible surface area. Each electrode consists

of porous carbon (C) to which very small Pt particles are bonded. The

electrode is somewhat porous so that the gases can diffuse through

each electrode to reach the catalyst. Both Pt and C conduct electrons

well, so electrons are able to move freely through the electrode. The

small size of the Pt particles, about 2 nanometers in diameter, results

in an enormously large total surface area of Pt that is accessible to

gas molecules. The total surface presented by this huge number of

small particles is very large even when the total mass of Pt used is

small. This large Pt surface area allows the electrode reactions to

proceed at many Pt surface sites simultaneously. This high dispersion

of the catalyst is one key to generating significant electron flow, i.e.

current, in a fuel cell.

Water and Fuel Cell Performance

“W ater management” is key to effective operation of a

polymer electrolyte membrane fuel cell. Although water

is a product of the fuel cell reaction, and is carried out of the cell

during its operation, it is interesting that both the fuel and air

entering the fuel cell must still be humidified. This additional water

keeps the polymer electrolyte membrane hydrated. The humidity

of the gases must be carefully controlled. Too little water prevents

the membrane from conducting the H+ ions well and the cell

current drops.

If the air flow past the cathode is too slow, the air can’t carry all

the water produced at the cathode out of the fuel cell, and the

cathode “floods.” Cell performance is hurt because not enough

oxygen is able to penetrate the excess liquid water to reach the

cathode catalyst sites.

Future Opportunities

• Impurities often present in the H2 fuel

feed stream bind to the Pt catalyst

surface in the anode, preventing H2

oxidation by blocking Pt catalyst sites.

Alternative catalysts which can oxidize

H2 while remaining unaffected by

impurities are needed to improve cell

performance.

• The rate of the oxygen reduction

process at the air electrode is quite low

even at the best Pt catalysts developed

to date, resulting in significant

performance loss. Alternative catalysts

that promote a high rate of oxygen

reduction are needed to further enhance

fuel cell performance.

• Future alternative catalysts must be less

expensive than Pt to lower the cost of

the cell.

9

Polymer

Electrolyte

Membrane Pathway(s) allowing

conduction of electrons

Pathway(s) allowing

conduction of hydrogen ions

Pathway(s) allowing

access of gas to

catalyst surface

Carbon

Platinum
The

Membrane/Electrode

Assembly

T he combination of anode/membrane/cathode is

referred to as the membrane/electrode assembly.

The evolution of membrane/electrode assemblies in

polymer electrolyte membrane fuel cells has passed

through several generations. The original membrane/

electrode assemblies were constructed in the 1960s for

the Gemini space program and used 4 milligrams of

platinum per square centimeter of membrane area

(4 mg/cm2

). Current technology varies with the manufacturer, but total platinum loading has decreased from

the original 4 mg/cm2

 to about 0.5 mg/cm2. Laboratory

research now uses platinum loadings of 0.15mg/cm2 .

This corresponds to an improvement in fuel cell performance since the Gemini program, as measured by

amperes of current produced, from about 0.5 amperes

per milligram of platinum to 15 amperes per milligram

of platinum.

The thickness of the membrane in a membrane/electrode assembly can vary with the type of membrane.

The thickness of the catalyst layers depends upon how

much platinum is used in each electrode. For catalyst

layers containing about 0.15 mg Pt/cm2

, the thickness of

the catalyst layer is close to 10 microns, less than half the

thickness of a sheet of paper. It is amazing that this

membrane/electrode assembly, with a

total thickness of about 200 microns or 0.2

millimeters, can generate more than half

an ampere of current for every square

centimeter of membrane/electrode assembly at a voltage between the cathode and

anode of 0.7 volts, but only when encased

in well engineered components — backing

layers, flow fields, and current collectors.

Membrane/electrode assembly

Future Opportunities

Optimization of membrane/electrode

assembly (MEA) construction is on-going.

Fundamental research into the catalyst layer/

membrane interface is needed to further

understand the processes involved in current

generation. New MEA designs which

will increase fuel cell performance

are needed. As always, the science and

technology of MEAs are interconnected;

whether improved understanding will lead

to better MEA design or a different design

will lead to improved understanding remains

to be seen.

Making a Membrane/Electrode Assembly

M embrane/electrode assembly construction varies greatly,

but the following procedure is one of several used at Los

Alamos National Laboratory where fuel cell research is actively

pursued. The catalyst material is first prepared in liquid “ink”

form by thoroughly mixing together appropriate amounts of

catalyst (a powder of Pt dispersed on carbon) and a solution of

the membrane material dissolved in alcohols. Once the ink is

prepared, it is applied to the surface of the solid membrane in

a number of different ways. The simplest method involves

painting the catalyst “ink” directly onto a dry, solid piece of

membrane. The wet catalyst layer and the membrane are

heated until the catalyst layer is dry. The membrane is then

turned over and the procedure is repeated on the other side.

Catalyst layers are now on both sides of the membrane. The

dry membrane/electrode assembly is next rehydrated by

immersing in lightly boiling dilute acid solution to also ensure

that the membrane is in the H+ form needed for fuel cell operation. The final step is a thorough rinsing in distilled water. The

membrane/electrode assembly is now ready for insertion into

the fuel cell hardware.

0.2

mm

Anode

Cathode

Polymer electrolyte membrane
11

The

Backing Layers

T he hardware of the fuel cell, backing layers,

flow fields and current collectors, is designed to

maximize the current that can be obtained from a

membrane/electrode assembly. The so-called backing

layers, one next to the anode, the other next to the

cathode, are usually made of a porous carbon paper or

carbon cloth, typically 100 to 300 microns thick (4 to 12

sheets of paper). The backing layers have to be made of

a material, such as carbon, that can conduct the electrons

exiting the anode and entering the cathode.

The porous nature of the backing material ensures

effective diffusion of each reactant gas to the catalyst on

the membrane/electrode assembly. In this context,

diffusion refers to the flow of gas molecules from a

region of high concentration, the outer side of the

backing layer where the gas is flowing by in the flow

fields, to a region of low concentration, the inner side of

the backing layer next to the catalyst layer where the gas

is consumed by the reaction. The porous structure of

the backing layers allows the gas to spread out as it

diffuses so that when it penetrates the backing, the gas

will be in contact with the entire surface area of the

catalyzed membrane.

Enlarged cross-section of a membrane/electrode assembly showing structural details.

The backing layers also assist in water

management during the operation of

the fuel cell; too little or too much

water can cause the cell to cease operation. The correct backing material

allows the right amount of water vapor

to reach the membrane/electrode

assembly to keep the membrane

humidified. The backing material also

allows the liquid water produced at the

cathode to leave the cell so it doesn’t

“flood”. The backing layers are often

wet-proofed with TeflonTM to ensure

that at least some, and hopefully most,

of the pores in the carbon cloth (or

carbon paper) don’t become clogged

with water, which would prevent rapid

gas diffusion necessary for a good rate

of reaction to occur at the electrodes.

Electrode

Pathways for

gas access

to electrode

Backing layer Membrane/electrode assembly Backing layer

Cathode

backing

Anode

backing

Polymer

Electrolyte

Membrane

Membrane/electrode assembly with backing layers.
P ressed against the outer surface of each backing

layer is a piece of hardware, called a plate, which

often serves the dual role of flow field and current

collector. In a single fuel cell, these two plates are the

last of the components making up the cell. The plates

are made of a light-weight, strong, gas-impermeable,

electron-conducting material; graphite or metals are

commonly used although composite plates are now

being developed.

The first task served by each plate is to provide a gas

“flow field.” The side of the plate next to the backing

layer contains channels machined into the plate. The

channels are used to carry the reactant gas from the

point at which it enters the fuel cell to the point at

which the gas exits. The pattern of the flow field in the

plate as well as the width and depth of the channels have

a large impact on the effectiveness of the distribution of

the reactant gases evenly across the active area of the

membrane/electrode assembly. Flow field design also

affects water supply to the membrane and water removal

from the cathode.

The second purpose served by each plate is that of

current collector. Electrons produced by the oxidation

of hydrogen must be conducted through the anode,

through the backing layer and through the plate before

they can exit the cell, travel through an external circuit

and re-enter the cell at the cathode plate.

With the addition of the flow fields and current collectors, the polymer electrolyte membrane fuel cell is now

complete. Only a load-containing external circuit, such

as an electric motor, is required for electric current to

flow, the power having been generated by passing

hydrogen and air on either side of what looks like a

piece of food wrap painted black.

The Flow

Fields / Current

Collectors

Photographs of stainless steel

flow fields/current collectors

Micrograph of a milled carbon-fiber

composite flow-field. Height, width

and spacing of channels = 0.8mm

(0.032 inch)

A single polymer electrolyte membrane fuel cell.

Hydrogen

flow field Air (oxygen)

flow field

Hydrogen

outlet

Water and air

e- eAnode

backing MEA

Cathode

backing

Cathode

current

collector

Anode

current

collector
13

Efficiency, Power and Energy of Polymer Electrolyte Membrane Fuel Cell

Energy conversion of a fuel cell can be summarized in the following equation:

Chemical energy of fuel = Electric energy + Heat energy

A single, ideal H2/air fuel cell should provide 1.16 volts at zero current (“open

circuit” conditions), 80°C and 1 atm gas pressure. A good measure of energy

conversion efficiency for a fuel cell is the ratio of the actual cell voltage to the theoretical maximum voltage for the H2/air reaction. Thus a fuel cell operating at 0.7 V is

generating about 60% of the maximum useful energy available from the fuel in the

form of electric power. If the same fuel cell is operated at 0.9 V, about 77.5% of the

maximum useful energy is being delivered as electricity. The remaining

energy (40% or 22.5%) will appear as heat. The characteristic performance curve

for a fuel cell represents the DC voltage delivered at the cell terminals as a function of

the current density, total current divided by area of membrane, being drawn from the

fuel cell by the load in the external circuit

The power (P), expressed in units of watts, delivered by a cell is the product of the current (I) drawn and the terminal voltage (V) at that current (P = IV). Power is also the rate at which energy (E) is made available (P = E/t) or conversely, energy, expressed in units of watt-hours, is

the power available over a time period (t) (E = Pt). As the mass and volume of a fuel cell system are so important, additional terms are also

used. Specific power is the ratio of the power produced by a cell to the mass of the cell; power density is the ratio of the power produced by a

cell to the volume of the cell. High specific power and power density are important for transportation applications, to minimize the weight and

volume of the fuel cell as well as to minimize cost.

Derivation of Ideal Fuel Cell Voltage

Prediction of the maximum available voltage from a fuel cell process involves evaluation of energy differences between the initial state of reactants in the process (H2 +1/2 O2) and the final state (H2O). Such evaluation relies on thermodynamic functions of state in a chemical process,

primarily the Gibbs free energy. The maximum cell voltage ( E) for the hydrogen/air fuel cell reaction ( H2 + 1/2 O2 ➔ H2O) at a specific temperature and pressure is calculated [ E = - G/nF], where G is the Gibbs free energy change for the reaction, n is the number of moles of

electrons involved in the reaction per mole of H2, and F is Faraday’s constant, 96, 487 coulombs (joules/volt), the charge transferred per mole

of electrons.

At a constant pressure of 1 atmosphere, the Gibbs free energy change in the fuel cell process (per mole of H2) is calculated from the reaction

temperature (T), and from changes in the reaction enthalpy ( H) and entropy ( S)

G = H - T S

= - 285,800 J – (298 K)(-163.2 J/K)

= - 237,200 J

For the hydrogen/air fuel cell at 1 atmosphere pressure and 25 ̊C (298 K), the cell voltage is 1.23 V.

E = - G/nF

= - (-237,200 J/2 x 96,487 J/V)

= 1.23 V

As temperature rises from room temperature to that of an operating fuel cell (80 ̊C or 353 K), the values of H and S change only slightly,

but T changes by 55 ̊. Thus the absolute value of G decreases. For a good estimation, assuming no change in the values of H and S

G = - 285,800 J/mol – (353 K)(-163.2 J/mol K)

= - 228,200 J/mol

Thus, the maximum cell voltage decreases as well (for the standard case of 1 atm), from 1.23 V at 25 ̊C to 1.18 V at 80 ̊C

E = - (-228,200 J/2 x 96,487 J/V)

= 1.18 V

An additional correction for air, instead of pure oxygen, and using humidified air and hydrogen, instead of dry gases, further reduces the

maximum voltage obtainable from the hydrogen/air fuel cell to 1.16 V at 80 ̊C and 1 atmosphere pressure.

13

0

Current Density (mA/cm2)

Cell Voltage (mV)

1200

800

600

200

0

200 600 800 1000 1400 1600

400

400 1200

1000

l

l l

Graph of voltage vs. current density of a hydrogen/air

polymer electrolyte membrane fuel cell.
Rate of Heat Generation in an Operating Fuel Cell

Assume a 100 cm2

 fuel cell is operating, under typical conditions

of 1 atmosphere pressure and 80 ̊C, at 0.7 V and generating

0.6 A/cm2 of current, for a total current of 60 A. The excess

heat generated by this cell can be estimated as follows:

Power due to heat = Total power generated – Electrical power

Pheat = Ptotal – Pelectrical

= (Videal x Icell) – (Vcell x Icell)

= (Videal – Vcell) x Icell

= (1.16 V – 0.7 V) x 60 A

= 0.46 V x 60 coulombs/sec. x 60 seconds/min.

= 1650 J/min

This cell is generating about 1.7 kJ of excess heat every minute

it operates, while generating about 2.5 kJ of electric energy

per minute.

S ince fuel cells operate at less than 100% efficiency,

the voltage output of one cell is less than 1.16 volt.

As most applications require much higher voltages than

this, (for example, effective commercial electric motors

typically operate at 200 – 300 volts), the required voltage

is obtained by connecting individual fuel cells in series to

form a fuel cell “stack.” If fuel cells were simply lined-up

next to each other, the anode and cathode current

collectors would be side by side. To decrease the overall

volume and weight of the stack, instead of two current

collectors, only one plate is used with a flow field cut

into each side of the plate. This type of plate, called a

“bipolar plate,” separates one cell from the next, with

this single plate serving to carry hydrogen gas on one

side and air on the other. It is important that the bipolar

plate is made of gas-impermeable material. Otherwise

the two gases would intermix, leading to direct oxidation

of fuel. Without separation of the gases, electrons pass

directly from the hydrogen to the oxygen and these

electrons are essentially “wasted” as they cannot be

routed through an external circuit to do useful electrical

work. The bipolar plate must also be electronically

conductive because the electrons produced at the anode

on one side of the bipolar plate are conducted through

the plate where they enter the cathode on the other side

of the bipolar plate. Two end-plates, one at each end of

the complete stack of cells, are connected via the external

circuit.

In the near term, different manufacturers will provide a

variety of sizes of fuel cell stacks for diverse applications.

The area of a single fuel cell can vary from a few square

centimeters to a thousand square centimeters. A stack

can consist of a few cells to a hundred or more cells

connected in series using bipolar plates. For applications

that require large amounts of power, many stacks can be

used in series or parallel combinations.

A 3 cell fuel cell stack with two bipolar plates and two end plates.

The Polymer

Electrolyte Membrane

Fuel Cell Stack

Polymer electrolyte membrane fuel cell stack.

(Courtesy: Energy Partners)

End-plate Bipolar plates End-plate

Hydrogen

flow fields

Air

flow fields

e- e-
15

T here are several other types of polymer electrolyte

membrane fuel cells for transportation applications,

although none have reached the same stage of development and simplicity as the hydrogen/air.

Reformate/Air Fuel Cell

In addition to the direct hydrogen fuel cell, research is

currently underway to develop a fuel cell system that

can operate on various types of hydrocarbon fuels —

including gasoline, and alternative fuels such as methanol, natural gas, and ethanol. Initially, this fuel-flexible

fuel strategy will enable reformate/air fuel cell systems

to use the exisiting fuels infrastructure. A hydrogen/air

polymer electrolyte membrane fuel cell would be fueled

from an onboard reformer that can convert these fuels

into hydrogen-rich gas mixtures. Processing hydrocarbon fuels to generate hydrogen is a technical challenge

and a relatively demanding operation.

Hydrocarbon fuels require processing temperatures of

700 ̊C - 1000 ̊C. Sulfur, found in all carbon-based fuels,

and carbon monoxide generated in the fuel processor,

must be removed to avoid poisoning the fuel cell

catalyst. Although the reformate/air fuel cell lacks the

zero emission characteristic of the direct hydrogen fuel

cell, it has the potential of lowering emissions significantly vs. the gasoline internal combustion engine. The

near-term introduction of reformate/air fuel cells is

expected to increase market acceptance of fuel cell

technology and help pave the way for the widespread

use of direct hydrogen systems in the future.

Other Types of Polymer

 Electrolyte Membrane

Fuel Cell Systems

Computer model of 50kW fuel cell stack with reformer.

(Courtesy: International Fuel Cells)

Processing Hydrocarbon Fuels into Hydrogen

As long as hydrogen is difficult to store on a vehicle, on-board

fuel processors will be needed to convert a hydrocarbon fuel,

such as methanol or gasoline, to a H2 rich gas for use in the fuel

cell stack. Currently, steam reforming of methanol to H2 is the

conventional technology, although partial oxidation of gasoline to

H2 is attractive because of the gasoline infrastructure already in

place in most countries. Both types of fuel processors are complex

systems.

The steam reforming of methanol involves the reaction of steam

and pre-vaporized methanol at 200 ̊C (gasoline requires temperatures over 800 ̊C) to produce a mixture of H2, carbon dioxide

(CO2), carbon monoxide (CO), and excess steam. This mixture

passes through another reactor, called a shift reactor, which uses

catalysts and water to convert nearly all of the CO to CO2 as well

as additional H2. There can be a third stage in which air is injected into the mixture in a third type of reactor, the preferential

oxidation reactor. Oxygen in the air reacts with the remaining CO

over a Pt-containing catalyst to convert CO to CO2. The final gas

mixture contains about 70% H2 , 24% CO2, 6% nitrogen (N2)

and traces of CO.

With the partial oxidation reformer system, liquid fuel is first

vaporized into a gas. The gas is then ignited in a partial oxidation

reactor which limits the amount of air so that primarily H2 , CO

and CO2 are produced from the combustion. This mixture is

passed through a shift reactor to convert the CO to CO2 and then

through a preferential oxidation reactor to convert any remaining

CO to CO2. Conventional partial oxidation takes place at

~1000 ̊C and catalytic partial oxidation takes place at ~700 ̊C.

The final reformate composition is about 42% N2, 38% H2,

18% CO2 , less than 2% CH4 and traces of CO.
Diagram of reformate/air fuel cell “engine” utilizing liquid methanol as fuel.

Hydrogen (H2) CO2

and H2

Cooling pump

Fresh Air

Cooling

air out

Cooling

air in

Water produced

by fuel cells

Fuel Cells

Compressor/

expander

Cooler

Reformer

and

catalytic

burner

Gas 

purification

Vaporizer

Methanol

tank

Water

tank

The Fuel Cell Engine

F uel cell stacks need to be integrated into a complete fuel cell

engine. A fuel cell engine must be of appropriate weight and

volume to fit into the space typically available for car engines. Importantly, the operation of the entire engine must maintain the near zero

emissions and high efficiency of fuel cells. Finally, all these requirements must be met with components that are both inexpensive and

designed for low cost, high volume manufacturing.

References:

Fuel Cell Handbook on CD

(4th Edition), U.S. Department of

Energy, Office of Fossil Energy,

Federal Energy Technology

Center. November 1998.

C.E. (Sandy) Thomas, et.al.

Integrated Analysis of Hydrogen

Passenger Vehicle

Transportation Pathways.

National Renewable Energy

Laboratory, March, 1998.

Shimshon Gottesfeld. Polymer

Electrolyte Fuel Cells. Advances

in Electrochemical Science and

Engineering, Vol.5, Wiley-VCH,

1997.

Fritz R. Kalhammer, et. al. Status

and Prospects of Fuel Cells as

Automotive Engines. Prepared

for the State of California Air

Resources Board, July, 1998.

Regenerative Fuel Cell System

Testbed Program for Government

and Commercial Applications.

http://www.lerc.nasa.gov/

www/RT1995/5000/

5420p.htm

Solar-Powered Plane Flies to New

Record Height — One Step

Closer to a Commercial Satellite

Substitute. http://

www.aerovironment.com

Resources:

A.J. Appleby and F.R. Foulkes. Fuel

Cell Handbook. Van Norstand

Reinhold, New York: 1989.

S.R. Narayanan, G. Halpert, et.al.

The Status of Direct Methanol

Fuel Cells at the Jet Propulsion

Laboratory. Proceedings of the

37th Annual Power Source

Symposium, Cherry Hill, N.J.,

June 17, 1996.

Department of Defense Fuel Cell

Demonstration Program

http://dodfuelcells.com/

Energy Efficiency/Renewable Energy

Network http://

www.eren.doe.gov

Hydrogen & Fuel Cell Letter

http://mhv.net/~hfcletter

Hydrogen and the Materials of a

Sustainable Energy Future

http://education.lanl.gov/

RESOURCES/h2

Karl Kordesh and Gunter Sinander.

Fuel Cells and Their Applications.

VCH Publishers, New York, 1996.

DOE Office of Transportation

Technologies http://

www.ott.doe.gov

United States Council For Automotive

Research http://www.uscar.org/

Arthur D. Little

http://www.arthurdlittle.com
17

Electrochemistry of a Direct Methanol Fuel Cell

T he electrochemical reactions occurring

in a direct methanol fuel cell are:

Anode CH3OH + H2O ➔ CO2 + 6H+ + 6eCathode 3/2 O2 + 6H+

 + 6e- ➔ 3H2O

Cell reaction CH3OH + 3/2 O2 ➔ CO2 + 2H2O

Mixing Tank

MeOH + H2O

Air exhaust

Air

Air outlet

CO2 vented

Fan Condenser

Methanol Tank

DMFC stack

Emissions from Fuel Cell Engines

The potential of fuel cells to provide zero or near zero

emissions has been a significant force in the development

of the technology over the past 30 years. Direct hydrogen/air systems (utilizing on-board hydrogen storage)

are the only fuel cells having zero emissions from the

tailpipe. On-board processing of gasoline, methanol and

other carbon-based fuels into hydrogen rich gas can be

done with minute amounts of tailpipe emissions and

water and CO2

 as the major by-products. Over the next

few years, near-zero emissions and performance will

continue to improve.

Schematic of direct methanol fuel cell system.

(Courtesy: Los Alamos National Laboratory)

The Opel Zafira, by General Motors, reforms methanol to operate

a polymer electrolyte membrane fuel cell. This vehicle has nearly

zero emissions of sulfur dioxide and nitrogen oxides and the carbon

dioxide output is expected to be 50% less than a comparable

internal combustion engine vehicle. (Courtesy: General Motors)

Direct Methanol Fuel Cell

As its name implies, methanol fuel is directly used in this fuel cell. In the

direct methanol fuel cell, as in the hydrogen/air fuel cell, oxygen from the

surrounding air is the oxidant, however, there is no oxidation of hydrogen.

Liquid methanol is the fuel being oxidized directly at the anode.

Direct methanol fuel cell technology, unique as a low

temperature fuel cell system not utilizing hydrogen, is

still relatively new compared to hydrogen/air polymer

electrolyte fuel cell technology, with several challenges

remaining. Recent advances in direct methanol fuel cell

research and development have been substantial, with

the direct methanol fuel cell achieving a significant

fraction of the performance of direct hydrogen/air fuel

cells. However, there are critical obstacles to be overcome. To achieve high current, the necessary amount of

expensive platinum catalyst is still much greater than the

amount used in hydrogen/air polymer electrolyte fuel

cells. Methanol fuel crosses through the membrane from

the anode to the cathode; this undesired methanol

“crossover” decreases the performance of the air cathode

and wastes fuel.

The advantages of supplying methanol directly to the

fuel cell are significant — with consumer acceptance of a

liquid fuel being high on the list. While a new or

modified infrastructure would be required to supply

large quantities of methanol, there are some methanol

pumps already available. Importantly, a direct methanol

fuel cell system does not require a bulky and heavy

hydrogen storage system or a reforming subsystem.

This advantage, in terms of simplicity and cost, means

the direct methanol fuel cell system presents an attractive alternative to hydrogen or reformate-fed systems. In

addition, a direct methanol fuel cell is considered a zero

emission vehicle.
Renewable regenerative fuel cell utilizing the energy source of the sun

to produce power (Courtesy: Aerovironment)

In the near term, fuel

availability could be

an important reason

for operating fuel cell

vehicles on gasoline.

Today, oil refiners in

the U.S. are spending

over $10 billion

to comply with

reformulated gasoline

regulations to help

lower tailpipe

emissions. Fuel cell

vehicles operating on

alternative fuels

will require new and

expensive fueling

infrastructures.

However,

alternative fuels will

provide superior

environmental

performance. In the

long term, incremental

investments in a new

domestic fuel

infrastructure will be

necessary for the

21st century.

RFG :

Reformulated

Gasoline

M 100 :

Methanol

E 100 :

Ethanol

H2 :

Hydrogen

CNG :

Compressed

Natural Gas

Regenerative Fuel Cell

A regenerative fuel cell, currently being developed for utility applications, uses hydrogen and

oxygen or air to produce electricity, water, and waste heat as a conventional fuel cell does.

However, the regenerative fuel cell also performs the reverse of the fuel cell reaction, using

electricity and water to form hydrogen and oxygen. In the reverse mode of the regenerative

fuel cell, known as electrolysis, electricity is applied to the electrodes of the cell to force the

dissociation of water into its components.

The “closed” system of a regenerative fuel cell could have a significant advantage because it

could enable the operation of a fuel cell power system without requiring a new hydrogen

infrastructure. There are two concerns to be addressed in the development of regenerative

fuel cells. The first is the extra cost that would be incurred in making the fuel cell reversible.

Unmanned solar plane powered by a renewable regenerative

fuel cell (Courtesy: Aerovironment)

The second drawback to the

operation of the regenerative

fuel cell is the use of grid

electricity to produce the

hydrogen. In the United States,

most electricity comes from

burning fossil fuels. The fossil

fuel ➔ electricity ➔ hydrogen

energy route generates significantly more greenhouse gases

than simply burning gasoline in

an internal combustion engine.

Although the concept of a

regenerative fuel cell is attractive, until renewable electricity,

e.g. electricity from solar or

wind sources, is readily

available, this technology

will not reduce greenhouse

gas emissions.
19

Characteristics of Potential Fuel Cell Fuels

Production

RFG

M 100

E 100

H2

CNG

Storage

Cost est./

gal. eq Safety

Distribution

Infrastructure

Environmental

Attributes

Large existing 

production operation

Uses imported 

feedstock

No energy security or 

trade balance 

benefits

Conventional 

storage tanks

Low flashpoint

Narrow flammability 

limits

Potentially 

carcinogenic when 

inhaled

Existing 

infrastructure 

and distribution 

system

Reduction in 

greenhouse gases

Much lower reactive 

hydrocarbon and 

sulfur oxide 

emissions than 

gasoline

Abundant 

domestic/imported 

natural gas feedstock

Can be manufactured 

renewably from 

domestic biomass - 

not currently being 

done

Requires special 

storage because fuel 

can be corrosive to 

rubber, plastic and 

some metals

Toxic and can be 

absorbed through the 

skin

No visible flame

Adequate training 

required to operate 

safely

Infrastructure 

needs to be 

expanded

High greenhouse 

gas emissions 

when manufactured 

from coal

Zero emissions 

when made 

renewably

Made from domestic 

renewable resources: 

corn, wood, rice, straw, 

waste, switchgrass. 

Many technologies 

still experimental

Production from 

feedstocks are energy 

intensive

Requires special 

storage because 

fuel can be 

corrosive to rubber, 

plastic and some 

metals

Wide flammability 

limit

Adequate training 

required to operate 

safely

Less toxic than 

methanol and 

gasoline

Nearly no 

infrastructure 

currently 

available

Food/fuel 

competition at 

high productions 

levels

Zero carbon dioxide 

emissions as a fuel

Significant emissions 

in production

Domestic 

manufacturing:

Steam reforming of 

coal, natural gas or 

methane

Renewable solar

Compressed gas 

cylinders

Cryogenic fuel tanks

Metal hydrides

Carbon nanofibers

Currently storage 

systems are heavy 

and bulky

Low flammability limit

Disperses quickly when 

released

Nearly invisible flame

Odorless and colorless

Non-toxic

Adequate training 

required to operate safely

Needs new 

infrastructure

High emissions 

when manufactured 

from electrolysis

Lower emissions 

from natural gas

Zero emissions 

when manufactured 

renewably

$.05-.15 

more 

than 

gasoline

$1.10-

$1.15

$.79-

$1.91

Abundant 

domestic/imported 

feedstock

Can be made from 

coal

CNG needs to be 

compressed during 

refueling and requires 

special nozzles to 

avoid evaporative 

emissions

Stored in compressed 

gas cylinders

Low flashpoint

Non-carcinogenic

Dissipates into the air in 

open areas

High thermal efficiency

Adequate training 

required to operate safely

Limited

infrastructure

Non-renewable

Possible increase 

in nitrogen oxide 

emissions

$.85

 $.90

U.S. Congress, Office of Technology Assessment, “Replacing Gasoline-Alternative Fuels for Light-Duty Vehicles” OTA-E-364, September, 1990.

Union of Concerned Scientists, Summary of Alternative Fuels, 1991.

U.S. Department of Energy, Taking an Alternative Route, 1994.

National Alternative Fuel and Clean Cities Hotline: http://www.afdc.doe.gov

Jason Mark. “Environmental and Infrastructure Trade-Offs of Fuel Choices for Fuel Cell Vehicles.” Future Transportation Technology Conference,

 San Diego, CA. August 6-8, 1997. SAE Technical Paper 972693.

19
A laptop computer using a fuel cell power source can operate for up to 20 hours

on a single charge of fuel. (Courtesy: Ballard Power Systems)

References:

Natural Gas Fuel Cells, Federal

Technology Alert, Federal Energy

Management Program. U.S.

Department of Energy,

November 1995.

J.L. Preston, J.C. Trocciola, and R.J.

Spiegel. “Utilization and Control of

Landfill Methane by Fuel Cells”

presented at U.S. EPA Greenhouse

Gas Emissions & Mitigation

Research Symposium, June 27-29,

1995, Washington, D.C.

G.D. Rambach and J.D. Snyder. An

Examination of the Criteria

Necessary for Successful Worldwide

Deployment of Isolated, Renewable

Hydrogen Stationary Power

Systems. XII World Hydrogen

Energy Conference, Buenos Aires,

June, 1998.

Keith Kozloff, “Power to Choose.”

Frontiers of Sustainability. World

Resources Institute, Island Press,

1997.

Resources:

Federal Energy Technology Center

http://www.fetc.doe.gov/

World Fuel Cell Council

http://members.aol.com/fuelcells/

Michael Corbett. Opportunities in

Advanced Fuel Cell Technologies:

Volume One, Stationary Power

Generation 1998 – 2009, Kline &

Co., Inc. Fairfield, N.J. August,

1998.

Definitions:

Quad: A unit of heat energy, equal to

1015 British thermal units.

The world's first prototype polymer electrolyte membrane fuel cell (on the

right) used to provide all residential power needs for a home in Latham,

 New York. This 7kW unit is attached to a power conditioner/storage unit

 that stores excess electricity. (Courtesy: Plug Power)
21

4 Times Square in New York City is one of the

first office buildings in the U.S. to be powered

by a 200 kW phosphoric acid fuel cell system

(Courtesy: International Fuel Cells)

Fuel cells are becoming an

alternative choice for rural

energy needs

• In places where there are no

existing power grids

• Where power supply is often

unreliable

• In remote locations that are

not accessible to power lines

F uel cells were developed for and have long been used in the space program

to provide electricity and drinking water for the astronauts. Terrestrial

applications can be classified into categories of transportation, stationary or

portable power uses.

Polymer electrolyte membrane fuel cells are well suited to transportation

applications because they provide a continuous electrical energy supply from

fuel at high levels of efficiency and power density. They also offer the

advantage of minimal maintenance because there are no moving parts in the

power generating stacks of the fuel cell system.

The utility sector is expected to be an early arena where fuel cells will be

widely commercialized. Today, only about one-third of the energy consumed reaches the actual user because of the low energy conversion

efficiencies of power plants. In fact, fossil and nuclear plants in the U.S vent

21 quads of heat into the atmosphere — more heat than all the homes and

commercial buildings in the country use in one year! Using fuel cells for

utility applications can improve energy efficiency by as much as 60% while

reducing environmental emissions. Phosphoric acid fuel cells have been

generally used in the initial commercialization of stationary fuel cell systems.

These environmentally friendly systems are simple, reliable, and quiet. They

require minimal servicing and attention. Natural gas is the primary fuel,

however, other fuels can be used — including gas from local landfills, propane, or fuels with high methane content. All such fuels are reformed to

hydrogen-rich gas mixtures before feeding to the fuel cell stack. Over 200

(phosphoric acid fuel cells) units, 200 kilowatts each, are currently in operation around the world. Fuel cell manufacturers are now developing small

scale polymer electrolyte fuel cell technology for individual home utility and

heating applications at the power level of 2-5 kilowatts because the potential

for lower materials and manufacturing costs could make these systems

commercially viable. Like the larger fuel cell utility plants, smaller systems

will also be connected directly to natural gas pipe lines — not the utility grid.

In addition to these small scale uses, polymer electrolyte fuel cell technology

is also being developed for large scale building applications.

“Distributed power” is a new approach utility companies are beginning to

implement — locating small, energy-saving power generators closer to where

the need is. Because fuel cells are modular in design and highly efficient,

these small units can be placed on-site. Installation is less of a financial risk

for utility planners and modules can be added as demand increases. Utility

systems are currently being designed to use regenerative fuel cell technology

and renewable sources of electricity.

Potential

Applications

for Fuel Cells
Comparison of Five Fuel Cell Technologies

T he electrolyte defines the key properties, particularly operating temperature, of the fuel cell. For this reason, fuel cell technologies are named by

their electrolyte. Four other distinct types of fuel cells have been developed

in addition to the polymer electrolyte membrane fuel cell:

• alkaline fuel cells

• phosphoric acid fuel cells

• molten carbonate fuel cells

• solid oxide fuel cells

These fuel cells operate at different temperatures and each is best suited to

particular applications. The main features of the five types of fuel cells are

summarized in chart form.

Other Fuel Cell Technologies

Fuel Cell

Polymer Electrolyte/

Membrane (PEM)

Alkaline (AFC)

Phosphoric Acid (PAFC)

Molten Carbonate (MCFC)

Solid Oxide (SOFC)

Electrolyte

Solid organic

polymer

poly-perfluorosulfonic

acid

Aqueous solution of

potassium hydroxide

soaked in a matrix

Liquid phosphoric

acid soaked in a

matrix

Liquid solution of

lithium, sodium and/

or potassium carbonates, soaked in a

matrix

Solid zirconium oxide

to which a small

amount of ytrria is

added

Operating

Temperature (°C)

60 - 100

90 - 100

175 - 200

600 - 1000

600 - 1000

Electrochemical

Reactions

Anode: H2 ➔ 2H+

 + 2eCathode: 1/2 O2

 + 2H+ + 2e- ➔ H2O

Cell: H2 + 1/2 O2 ➔ H2O

Anode: H2 + 2(OH)- ➔ 2H2O + 2eCathode: 1/2 O2

 + H2O + 2e- ➔ 2(OH)-

Cell: H2 + 1/2 O2 ➔ H2O

Anode: H2 ➔ 2H+ + 2eCathode: 1/2 O2

 + 2H+ + 2e- ➔ H2O

Cell: H2 + 1/2 O2 ➔ H2O

Anode: H2 + CO3

2- ➔ H2

O + CO2 + 2eCathode: 1/2 O2

 + CO2 + 2e- ➔ CO3

2-

Cell: H2 + 1/2 O2 + CO2 ➔ H2O + CO2

(CO2 is consumed at cathode and produced at anode)

Anode: H2 + O2- ➔ H2O + 2eCathode: 1/2 O2

 + 2e- ➔ O2 -

Cell: H2 + 1/2 O2 ➔ H2O
23

 Applications

electric utility

portable power

transportation

military

space

electric utility

transportation

electric utility

electric utility

 Advantages

• Solid electrolyte reduces

corrosion & management problems

• Low temperature

• Quick start-up

• Cathode reaction faster in alkaline

electrolyte — so high performance

• Up to 85 % efficiency

 in co-generation of electricity

and heat

• Impure H2 as fuel

• High temperature advantages*

• High temperature advantages*

• Solid electrolyte advantages

(see PEM)

 Disadvantages

• Low temperature requires

expensive catalysts

• High sensitivity to fuel impurities

• Expensive removal of CO2 from fuel

and air streams required

• Pt catalyst

• Low current and power

• Large size/weight

• High temperature enhances

corrosion and breakdown of cell

components

• High temperature enhances

breakdown of cell components

*High temperature advantages include higher efficiency, and the flexibility to use more types of fuels and inexpensive catalysts as the

reactions involving breaking of carbon to carbon bonds in larger hydrocarbon fuels occur much faster as the temperature is increased.

23
C=Carbon H=Hydrogen

Trends in energy use: Hydrogen-to-Carbon

ratio increases as we become less dependent

on carbon-based fuels.

(Courtesy: “Wired” 10/97)

H ydrogen is the most attractive fuel for fuel cells — having excellent

electrochemical reactivity, providing adequate levels of power density

in a hydrogen /air system for automobile propulsion, as well as having zero

emissions characteristics.

Historically, the trend in energy use indicates a slow transition from fuels

with high carbon content, beginning with wood, to fuels with more hydrogen. Fossil fuels release varying quantities of carbon dioxide into the

atmosphere — coal having the highest carbon content, then petroleum, and

finally natural gas — the lowest carbon dioxide emitter per thermal unit.

Hydrogen obviously releases no carbon dioxide emissions when burned.

Hydrogen (H2

) is the most abundant element in the universe, although

practically all of it is found in combination with other elements, for example, water (H2

O), or fossil fuels such as natural gas (CH4). Therefore,

hydrogen must be manufactured from either fossil fuels or water before it

can be used as a fuel. Today, approximately 95% of all hydrogen is produced

by “steam reforming” of natural gas, the most energy-efficient, large-scale

method of production. Carbon dioxide (CO2

) is a by-product of this

reaction.

CH4 + 2H2O ➔ 4H2 + CO2

Hydrogen can also be produced by gasification of carbon containing materials such as coal — although this method also produces large amounts of

carbon dioxide as a by-product. Electrolysis of water generates hydrogen

and oxygen.

H2O ➔ H2 + 1/2O2

The electricity required to electrolyze the water could be generated from

either fossil fuel combustion or from renewable sources such as hydropower, solar energy or wind energy. In the longer term, hydrogen

generation could be based on photobiological or photochemical methods.

While there is an existing manufacturing, distribution, and storage infrastructure of hydrogen, it is limited. An expanded system would be required if

hydrogen fuel were to be used for automotive and utility applications.

In 1809, an amateur inventor

submitted a patent for this hydrogen car.

Wood Coal Oil Hydrogen As a Fuel Natural

Gas Hydrogen

C

H
25

While a single hydrogen production/distribution/

storage system may not be appropriate for the diverse

applications of fuel cells, it is certainly possible that a

combination of technologies could be employed to meet

future needs. All of the system components are currently available — but cost effective delivery and

dispensing of hydrogen fuel is essential. If hydrogen

were to become available and affordable, this would

reduce the complexity and cost of fuel cell vehicles —

enhancing the success of the technology.

“Hydrogen Economy” is an energy system based upon

hydrogen for energy storage, distribution, and utilization. The term, coined at General Motors in 1970,

caught the imagination of the popular press. During the

oil crisis in the early 70’s, the price of crude oil sharply

increased, concern over stability of petroleum reserves

and the potential lack of a secure energy source grew,

and government and industry together developed plans

and implementation strategies for the introduction of

hydrogen into a world energy system. However, the

lessening of tensions in the Middle East led to a lowering

of crude oil prices and the resumption of business as

usual. Petroleum has continued to be the fuel of choice

for the transportation sector worldwide.

Hydrogen fuel has the reputation of being unsafe.

However, all fuels are inherently dangerous — how

much thought do you give to the potential dangers of

gasoline when you drive your car? Proper engineering,

education, and common sense reduce the risk in any

potentially explosive situation. A hydrogen vehicle and

supporting infrastructure can be engineered to be as safe

as existing gasoline systems. Dealing with the perception

and reality of safety will be critical to the successful wide

introduction of hydrogen into our energy economy.

References:

Peter Hoffmann. “The Forever Fuel:

The Story of Hydrogen. Boulder:

Westview Press,” 1981.

James Cannon. “Harnessing

Hydrogen: The Key to

Sustainable Transportation.”

New York: Inform, 1995.

”Strategic Planning for the Hydrogen

Economy: The Hydrogen

Commercialization Plan.”

National Hydrogen Association.

November, 1996.

U.S. Department of Energy.

Hydrogen Program Plan,

FY 1993 - FY 1997.

Richard G. Van Treuren. “Odorless,

Colorless, Blameless.”

Air & Space, May, 1997.

National Hydrogen Association

http://www.ttcorp.com/nha/

advocate/ad22zepp.htm

Resources:

HyWeb http://www.HyWeb.de

Hydrogen InfoNet

http://www.eren.doe.gov/

hydrogen/infonet.html

The New Sunshine Program

http://www.aist.go.jp/nss/

text/wenet.htm

C.E. Thomas. Hydrogen Vehicle

Safety Report. National

Technical Information Service.

U.S. Department of Commerce.

Springfield, Virginia. July, 1997.

“Shell has established a Hydrogen Economy team dedicated

to investigate opportunities in hydrogen manufacturing and

new fuel cell technologies...”

Chris Fay, Chief Executive, Shell UK

25
Front page of The New York Times, May 7, 1937, the day after the explosion

of the Hindenberg. (Enhanced color photograph courtesy: National Hydrogen Association)

“Don’t paint your ship with rocket fuel”

At 7:30, on the evening of May 6, 1937, the Hindenburg dirigible was destroyed by fire and explosions as it was about to land in

Lakehurst, New Jersey. 62 passengers survived and 35 lost their lives. The Hindenburg was nearing its landing site during an

electric storm. According to observers on the ground, the dirigible began to drift past its landing position, and after a brief delay,

the ship started to valve hydrogen into what was highly charged outside air. This combination of factors could prompt severe

corona activity on any airship. In fact, an eyewitness reported seeing a blue glow of electrical activity atop the ill-fated Hindenburg

before the fire started, which is indicative of the extremely high temperatures typical of a corona discharge. As the crew

attempted to bring it back on course, the ship lost its balance, the tail touched the ground, and the stern burst into flames. Passengers who were afraid the ship might explode, jumped to their deaths. The burns and other injuries were a result of the diesel fuel

fire, not from hydrogen. Most of the

passengers, who waited for the airship to

land, walked safely away from the accident.

Until recently, this tragedy was thought

to be caused by hydrogen, the highly

flammable gas used to inflate the skin of

the ship. However, historical photographs show red-hot flames, and

hydrogen burns invisibly. Also, no one

smelled garlic, the scent which had been

added to the hydrogen to help detect a

leak. The mystery of the Hindenburg

was solved by Addison Bain, a former

manager of the hydrogen programs for

NASA. Using infrared spectrographs and

a scanning electron microscope, Bain,

working with other NASA scientists, was

able to discover the chemical makeup of

the organic compounds and elements

present in the fabric of the dirigible’s

skin. The Hindenburg was covered with a

cotton fabric that had been treated with a

doping compound to protect and

strengthen it — however, this compound

contained a cellulose acetate or nitrate

(gunpowder). Aluminum powder (which

is used in rocket fuel) was also identified.

The outside structure was wooden and

the inside skeleton was duralumin coated

with lacquer. The combination was flammable and deadly.
27

T he success story of the past three decades in the transportation sector has

been the dramatic reduction of air-polluting emissions from new vehicles. Emission rates of gasoline vehicles have fallen by 70 – 90%, and the

costs for cleaner cars have also fallen. Under real driving conditions, actual

reductions are about 70% for nitrogen oxides and 90% for hydrocarbon and

carbon monoxide emissions. With a near zero emission gasoline car on the

horizon, and legislation in California and the Northeast states mandating

10% of the new vehicle market to be zero emission vehicles by 2003, even

greater reductions in emissions are imminent. These are important improvements in the U.S. — but still, one in four Americans breathes unhealthy air.

It’s worse in the rest of the world. Cities such as Mexico City, Athens, and

Shanghai don’t have the same stringent emissions standards found at home —

and transportation remains the largest contributor to urban pollution.

Worldwide, over one billion people living in urban areas are suffering from

severe air pollution, and according to the World Bank, over 700,000 deaths

result each year.

Estimates from the EPA indicate

that motor vehicles in the U.S. still account for

• 78% of all Carbon Monoxide emissions

• 45% of Nitrogen Oxide emissions

• 37% of Volatile Organic Compounds

The impact of lower emission gasoline vehicles is being offset by the growth

in the number and size of vehicles on the road as well as an increase in the

number of miles each vehicle travels. Americans pay around $.36 per gallon

in fuel tax as opposed to our European counterparts who spend an average of

$2.50 per gallon in taxes. Low gasoline prices don’t encourage fuel efficiency

or conservation. Rather, the sport utility vehicle market share continues to

rise, now surpassing passenger vehicles. Even as these larger vehicles have

cleaner tailpipe emissions, energy use and carbon dioxide emissions will

continue to increase. If recent growth trends continue, Americans will be

driving twice as many miles in 2015 as we do today. Along with continuing

research on cleaner transportation options, it will be critical to develop

policies that decrease the number of cars on the road, minimize congestion,

encourage public transportation as well as telecommuting.

The remarkable developments

of fuel-cell engines will help

California in its war on smog as

well as provide new consumers

choices for transportation.

California Air Resources Board, August, 1998

The Evolution of

the Zero Emission

Vehicle (in the 1990’s)

The 1990 Clean Air Act Amendments along with

the National Energy Policy Act of 1992 paved

the way for less polluting gasoline vehicles and

the introduction of alternative fuel vehicles on

the roads in the U.S. Also in 1990, the California Air Resources Board recognized that even

the cleanest gasoline powered vehicles wouldn’t

reduce pollution enough to satisfy the state’s

goals for healthful air. Meeting state and federal air standards in seriously polluted areas

such as Los Angeles would require either restrictions on driving or a large-scale switch to

vehicles that don’t pollute. California adopted

the Low Emission Vehicle Act that mandated the

seven largest auto manufacturers begin immediately to reduce all tailpipe emissions and to

introduce zero emission vehicles (ZEVs) by

1998.

In March 1996, the California Air Resources

Board modified their zero emission vehicle program to encourage a market based introduction

in the near-term and to promote future advances in electric vehicle (including fuel cells)

technology. Beginning in 2003, 10% of the

new vehicles will be required to be zero emission vehicles or nearly zero emission vehicles

— also knows as equivalent ZEVs.

Because of the legislative initiative taken by

California and subsequent similar regulations

imposed by a number of states in the Northeast, every major automobile manufacturer has

made significant progress toward the development of ultra-low and zero emission vehicles.

Getting To Cleaner

Transportation
1930 ’40 ’50 ’60 ’70 ’80 ’90 2000 ’10 ’20 ’30 ’40 ’50

Annual oil production (billions of barrels)

0

5

10

15

20

25

30

World

World projected

World outside Persian Gulf

World outside projected

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

1950 ’60 ’70 ’80 ’90 2000

Billions of barrels/year

Lower 48

Projected

Year

Year

N o one can predict what will

happen to world wide oil prices

or global oil demand. The world’s

production of oil reached a record

level of 65 million barrels a day in

1997, and global demand is rising

more than 2% a year. Americans

spend roughly $100,000 per minute

to purchase foreign oil, and the U.S.

transportation sector uses over 10%

of the world’s oil. Consumption of

oil by passenger vehicles, which

include automobiles and light duty

trucks, exceeds all of the United

States’ domestic production. Reserves of fossil fuels are large but

finite, and there is growing evidence

to suggest that world production of

crude oil will peak early in the 21st

century. The Energy Information

Agency forecasts that worldwide

demand for oil will increase 60% by

2020. By 2010, Middle East OPEC

states (Organization of Petroleum

Exporting Countries), considered to

U.S. oil production in the lower 48 states (upper right) peaked in 1970 as

predicted by a bell shaped curve. World oil production is expected to follow suit.

(Courtesy: Science, vol. 281, Aug. 21,1998, p.1128; C. Campbell & J. Laherre`re)

Oil Reserves,

Transportation,

and Fuel Cells

be unpredictable and often unstable,

will have over 50% of the world oil

business, and the switch from

growth to decline in oil production

could cause economic and political

tension. As excess oil production

capacity begins to decline over the

coming decades, oil prices can be

expected to rise, and the transportation sector is likely to be most

heavily affected by these fluctuations. World wide, transportation

relies almost totally on oil, and there

are few viable short-term fuel

options.

Every gallon of gasoline

manufactured, distributed, and

then consumed in a vehicle

releases roughly 25 pounds

of carbon dioxide.

About 25% of all human-generated

greenhouse gases come from transportation — more than half of that

from light-duty vehicles. Unlike air

pollutants (carbon monoxide,

nitrogen oxides, hydrocarbons, and

particulates — soot, smoke, etc.),

greenhouse gas emissions (primarily

carbon dioxide, methane, nitrous

oxide, water vapor, etc.) from

vehicles cannot be easily or inexpensively reduced by using add-on

control devices such as a catalytic

converter. In addition, unlike air

pollutants, greenhouse gas emissions

are not regulated by the Environmental Protection Agency. The

relationship between gasoline

consumption and carbon dioxide

emissions is fixed. Today, increasing

fuel economy, reducing vehicle miles

traveled, and switching to lower or

non-carbon fuels will begin to

decrease carbon dioxide emissions.

The introduction of fuel cells into

the transportation sector will

increase fuel efficiency, decrease

foreign oil dependency, and become

an important strategy/technology to

mitigate climate change. As fuel cell

vehicles begin to operate on fuels

from natural gas or gasoline, greenhouse gas emissions will be reduced

by 50%. In the future, the combination of high efficiency fuel cells and

fuels from renewable energy sources

would nearly eliminate greenhouse

gas emissions. The early transition to

lower carbon-based fuels will begin

to create cleaner air and a stronger

national energy security.

Since 1985, energy use is up

• 40% in Latin America

• 40% In Africa

• 50% in Asia
29

T here is a growing scientific consensus that increasing

levels of greenhouse gas emissions are changing the

earth’s climate. The natural greenhouse gases include

carbon dioxide (CO2

), water vapor (H2O), nitrous oxide

(N2

O), methane (CH4) and ozone (O3), and are essential

if the Earth is to support life. With the exception of

water vapor, carbon dioxide is the most plentiful. Since

the beginning of the Industrial Revolution in 1765,

burning fossil fuels and the increased energy needs of a

growing world population have added man-made, or

anthropogenic, greenhouse gas emissions into the

environment. Carbon dioxide constitutes a tiny fraction

of the earth’s atmosphere — about one molecule in three

thousand — but is the single largest waste product of

modern industrial society. The concentration of carbon

dioxide in the atmosphere has risen from about 280 parts

per million by volume to the current level of over 360

parts per million by volume and anthropogenically

caused atmospheric concentration of methane has

doubled. In the past 100 years, levels of nitrous oxide

have risen about 15%. Increasing concentrations of

greenhouse gases trap more terrestrial radiation in the

lower atmosphere (troposphere), artificially enhancing

the natural greenhouse effect. The average temperature

of the Earth has warmed about 1°C since the mid-19th

century when measurements began, and fragmentary

records suggest the Earth is warmer than it has been in

nearly 2,000 years.

“The balance of evidence suggests that there

is a discernible human influence on global

climate.”

United Nations Intergovernmental Panel on Climate Change, 1995

Under the most optimistic scenarios proposed by the

United Nations Intergovernmental Panel on Climate

Change, carbon dioxide is expected to rise to approximately 600 parts per million by volume during the next

century — more than double the level held for 10,000

years since the end of the last ice age.

Climate Change,

Greenhouse Gases, and Fuel

Cells: What is the Link?

The CO2 level has increased sharply since the beginning of the

Industrial Era and is already outside the bounds of natural variability

seen in the climate record of the last 160,000 years. Continuation of

current levels of emissions are predicted to raise concentrations to

over 600 ppm by 2100. (Courtesy: Office of Science and Technology

Policy)
Based on these scenarios, the Intergovernmental Panel on Climate Change

has concluded that the increase in greenhouse gases may be expected to

cause a rise in the global average temperature of between 1°C and 3.5°C in

the 21st century.

In 1997, global carbon emissions amounted to more than six billion

tons — more than a ton for every human being on the planet.

1998 was the warmest year on record, and no one is absolutely certain what

these temperature increases will do — changes in precipitation, extreme

weather, and sea level rise are all possible. The climate modeling and

resulting scientific conclusions are not universally accepted because climate

codes have difficulties simulating such events. The picture is far from clear,

but it appears that climate is driven by a variety of forcing mechanisms —

and anthropogenic forcing must be placed within the total context that

includes the long-term variations of the earth’s orbit, solar variability, and

the natural cycles of nature. However, as all of these data are taken into

account, evidence is increasing that the climate model predictions cannot be

too far wrong and that we are warming the Earth. Compelling societal

implications place even more significance on prudent policy directions.

References:

Jason Mark. “Zeroing out Pollution:

The Promise of Fuel Cells.”

Union of Concerned Scientists,

1996.

Daniel Sperling . “A New Agenda,”

ACCESS, Number 11, University

of California Transportation

Center, Fall 1997.

Reinhold Wurster. “PEM Fuel Cells

in Stationary and Mobile Applications.” Electric and Lighting

Industry Biennial, Buenos Aries,

September, 1997.

W. Wayt Gibbs. “Transportation’s

Perennial Problems.” Scientific

American. Oct. 1977.

Toward a Sustainable Future:

“Addressing the Long-Term

Effects of Motor Vehicle

Transportation on Climate and

Ecology.” Transportation

Research Board: National

Research Council, National

Academy Press, 1997.

James J. MacKenzie. “Driving the

Road to Sustainable Ground

Transportation.” World

Resources Institute. “Frontiers

of Sustainability:

Environmentally Sound

Agriculture, Forestry,

Transportation, and Power

Production.” Island Press,

1997.

“Cars and Trucks and Global

Warming.” Union of Concerned

Scientists, N.D.

M. Kerr. “The Next Oil Crisis Looms

Large — and Perhaps Close.”

Science. August 21, 1998.

Resources:

President’s Council on Sustainable

Development http://

www.whitehouse.gov/PCSD/

Rocky Mountain Institute http://

www.rmi.org

California Air Resources Board

http://www.arb.ca.gov/

homepage.htm

Instrumental

Temperature Record

from 1860 – 1999

indicates a global

warming over the

past century, with

many peaks and valleys suggesting the

natural year-to-year

variability of climate.

(Courtesy: Hadley

Centre for Climate

Prediction

& Research)

The Science of Global Climate Change

T he regulating factor for global climate change depends on a fundamental principle, the

First Law of Thermodynamics, also known as the Law of Conservation of Energy.

Mathematically this can be represented as follows:

dQ = dU – dW

where dQ = heat added to the system, dU = change in the internal energy of the system, and

dW = work extracted. Energy cannot be gained or lost in a stable system; it can only change

forms. Such a system is said to follow an “Energy Balance Model.” To maintain stability,

the Earth-ocean-atmosphere system absorbs energy from the Sun, radiates it in the form of

infrared (heat) energy, and transports it in the form of both latent heat and sensible heat

flux. Several natural events (volcanic eruptions, forest fires, fluctuating intensity of solar

radiation, varying cloud cover, and others) and human activities (fuel combustion, aerosol

production, and industrial and land use practices that release or remove heat-trapping

greenhouse gases, and others) can affect the balance between absorption and emission

of radiation.

1840

1.00

0.90

0.80

0.70

0.60

0.50

0.40

0.30

0.20

0.10

0.00

-0.10

-0.20

-0.30

1860 1880 1900 1920 1940 1960 1980 2000

Global surface temperatures, 1860 - 1999

Change in temperature (degrees C)
31

While the link between climate

and ecology remains uncertain,

decisions made during the

next ten years could affect

generations to come.

The Climate Change Debate

The Road to Kyoto: How the Global Climate Treaty Fosters Economic Impoverishment and Endangers U.S. Security. Angela Antonelli, et.al.

The Heritage Foundation, Roe Backgrounder No.1143, October 6, 1997.

The Forgiving Air – Understanding Environmental Change. Richard C.J. Sommerville. University of California Press, 1996.

Global Warming: The High Cost of the Kyoto Protocol – National and State Implications. WEFA, Inc. 1998.

Kyoto Protocol: A Useless Appendage to an Irrelevant Treaty. Testimony of Patrick Michaels, Cato Institute, Committee on Small Business,

U.S. House of Representatives, July 29, 1998.

CLIMATE: Making Sense and Making Money. Amory B. Lovins and L.Hunter Lovins, Rocky Mountain Institute, November 13, 1997.

The Costs of Climate Protection: A Guide for the Perplexed. Robert Repetto and Duncan Austin, World Resources Institute, 1997.

The Greenhouse Effect: Essentially, all energy that enters the Earth’s atmosphere

comes from the sun. The incoming radiation is partly absorbed, partly scattered, and partly

reflected back into space by the various gases of the atmosphere, clouds, and aerosols — tiny

particles suspended in the atmosphere. The sun emits solar radiation mainly in the form of visible and ultraviolet radiation. As this radiation travels toward Earth, approximately 25% of it

is absorbed by the atmosphere and 25% is reflected by the clouds back into space. The remaining radiation travels to the Earth and heats its surface. Because the Earth is much cooler

than the sun, energy reflected from the Earth’s surface is lower in intensity than that emitted

from the sun, i.e. in the form of invisible infrared radiation. About 90% of the infrared radiation reflected by the earth’s surface is absorbed by atmospheric trace gases, also known as

“greenhouse gases,” before it can escape to space. These gases, as well as clouds, re-emit

this radiation — sending it back toward ground. The atmosphere acts like the glass in a greenhouse, allowing short-wavelength radiation to travel through, but trapping some of the long

wavelength infrared radiation which is trying to escape. This process makes the temperature

of the atmosphere rise just as it does in the greenhouse. This is the Earth’s natural greenhouse

effect and keeps our planet about 60oF warmer than it might otherwise be.

(Courtesy: National Oceanic and Atmospheric Administration)

While the link between climate and

ecology remains uncertain, decisions

made during the next ten years could

affect generations to come. Given

the current levels of uncertainty, the

complexity of our environment, and

the potential for “surprises” or

unanticipated events, prudent action

appears to win out over a “business

as usual” scenario. Given the long

time lags between cause and effect,

and between effect and remedy, we

are challenged to use technology

wisely to enhance our investment in

the future. The world’s governments

have signed a climate convention and

are negotiating implementation

strategies. It is not unreasonable to

suggest that the introduction of fuel

cells into the transportation and

energy sectors will have global

implications. Energy efficiency,

reducing world use of petroleum, the

transition to renewable fuels, and

continued support for research are

important and responsible steps.
S ustainable development is one of those often used,

but seldom defined, phrases. According to the

United Nations, it is “meeting the needs of the present

without compromising the ability of future generations

to meet their own needs.” Attaining sustainable development doesn’t mean that growth must stop; it does

mean that environmental limits do exist because of the

limited ability of the biosphere to deal with the wastes

from human activities. This is one of the greatest

challenges we face today — a challenge that can only be

met by responsibly developing and using technologies

that will protect our environment for everyone.

Today’s innovations in fuel cell technology are addressing local, national, and global environmental needs. The

decision to become involved with bringing these innovations into our daily lives is a strategic career opportunity

and a smart thing to do. The winners will be those

people who are ahead of the crowd.

Innovative solutions can be an important competitive

plus. Over half of the threat to our climate disappears if

we use energy in ways that save money. In general, it’s

far cheaper to be efficient and save fuel than burn fuel.

Fuel cells offer an opportunity for innovation. Helping

to make fuel cells be a part of the solution might be a

challenge that’s too exciting to ignore.

“Developing countries face a fundamental choice. They can mimic the industrial

countries, and go through a development phase that is dirty and wasteful and creates an

enormous legacy of pollution. Or they can leapfrog over some of the steps followed by

industrial countries and incorporate modern efficient technologies.”

“The Human Development Report.” The United Nations.

Oxford University Press, September, 1998.

A Once-In-A-Lifetime

Opportunity

References:

“Report to the Nation: On Our

Changing Planet.” National

Oceanic and Atmospheric

Administration. Fall, 1997.

C.K. Keller. “Global Warming: An

Update.” http://

www.igpp.lanl.gov/

“Climate Change: State of

Knowledge. ” Office of Science

and Technology Policy. 1997.

Michael MacCracken and Tom Karl.

“Is the Climate Changing?

Indeed It Is” http://

www.usgcrp.gov/usgcrp/

mmbralmanac.html

Global Climate Change Information

Programme. http://

www.doc.mmu.ac.uk/aric/

gcc/gcciphm.html

Michael B. McElroy. A Warming

World. Harvard Magazine,

November - December 1997.

JD Mahlman. Uncertainties in

Projections of Human-Caused

Climate Warming. Science,

278, 1997.

Michael Porter. “Towards a New

Conception of the EnvironmentCompetitiveness Relationship.”

Environmental Protection

Agency Clean Air Marketplace,

Washington, D.C. September,

1993.

Environmental Sciences Division:

Carbon Dioxide Division. Oak

Ridge National Laboratory

http://cdiac.esd.ornl.gov

Intergovernmental Panel on

Climate Change http://

www.usgcrp.gov/usgcrp/

IPCCINFO.html
T he U.S. Department of Energy through its Office of Transportation

Technologies is pursuing critical technological advances that can help to

create new and improved national transportation systems. The Office of

Transportation Technologies supports research that is often too financially

risky for private industry to develop on its own. Partnerships are developed

with industry, working with national laboratories, as a way to strengthen

resources.

The mission of the Office of Transportation Technologies

is to reduce U.S. dependence on petroleum.

Within the Office of Transportation Technologies, the Office of Advanced

Automotive Technologies focuses its efforts on developing cleaner and more

energy-efficient technologies for automobiles of the future. The Transportation Fuel Cell Program is just one of many exciting research activities.

The Partnership for a New Generation of Vehicles (PNGV) Program is a

partnership between 11 government agencies and the United States

Council for Automotive Research, a cooperative research effort among

DaimlerChrysler Corporation, Ford Motor Company, and General Motors

Corporation, to develop commercially-viable vehicle technology that, over

the long-term, can preserve personal mobility, reduce the impact of cars and

light trucks on the environment and reduce U.S. dependency on foreign oil.

The Alternative Fuels Research and Development Program has been

developing alternative fuels technologies in partnership with industry for

more than 20 years.

The CARAT Program (Cooperative Automotive Research for Advanced

Technology) supports universities and small businesses to accelerate the

development and production of innovative technologies that address barriers

to producing ultra-efficient vehicles including the design and development of

advanced, energy-efficient automotive components and systems.

The Graduate Automotive Technology Education Program (GATE) is a

multidisciplinary automotive engineering program for graduate students that

focuses on technologies critical to the development and production of future

automobiles.

Benefits of Office of Transportation Technologies Program

• Reducing dependence upon foreign oil

• Increasing energy savings

• Improving air quality by reducing destructive air pollution and

greenhouse gases

To learn more about the Office of Transportation Technologies:

www.ott.doe.gov