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CoolStuff
Newsletter Article
Vol. 12, January 2004
Renewable
Energy:
Fuel Cell Technology |
Hydrogen: The Fuel of the Future
Global warming is a hot topic. Scientists tell
us that our hunger for energy may be heating up the planet, but we remain
unconvinced. We're loath to accept the fact that our desire for mobility,
is to a large extent, fueling the warming. Most of us are taken aback when
we learn that an average car produces six tons of the greenhouse gas
carbon dioxide annually. With over two hundred million vehicles on our
nation’s highways, the amount of CO2 pumped into our atmosphere
each year is
staggering. While
the automobile is certainly not the only source of man-made CO2,
it definitely is a major contributor. It’s no wonder that both
scientists and senators are anxious to find an emission-free vehicle.
Solutions to the problem are many and varied.
At the heart of many of the schemes are non-polluting, renewable
energy sources. Of all these sources, hydrogen is being touted as the fuel
of the future. Hydrogen is both the simplest and most plentiful element in
the universe. High in energy content, hydrogen produces virtually no
pollution when burned. In fact, when hydrogen is combined with oxygen,
only water and heat are produced. It is envisioned that hydrogen powered
devices called fuel cells will allow the pollution-free production of
electrical energy that may be used to power a car or even light your
home.
A fuel cell is an electrochemical device that
uses hydrogen and oxygen to create electricity. If pure hydrogen is used
as fuel, the fuel cell emits only water and heat as byproducts. Fuel cells
have the obvious advantages of not producing greenhouse gases that
contribute to global warming and none of the air pollutants that create
smog and health problems. Furthermore, fuel cells are significantly more
efficient than power producing technologies that rely on fossil fuels such
as oil, coal, and natural gas.
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Contributor Mark Sulek
Ford Motor
Company
Mark Sulek joined Ford
Motor Company in 1989 as a Research Scientist. In 1993 Mark moved to the
Alternative Power Source Technology Department where he supervised and
contributed to the installation of the first fuel cell test facility at
Ford Motor Company. The hydrogen fueling station was the first in North
America to fuel Hydrogen Fuel Cell vehicles with either liquid or
gaseous hydrogen. He played a major role in the design studies that
eventually lead to the development of the drivable P2000 fuel cell
vehicle and was awarded the Henry Ford Technical Achievement Award.
Mark’s current position involves bringing Ford’s fuel cell message to
the public through ride and drive events. Mark’s help in providing
detail, background, and student activities to this issue of CoolStuff
was tremendously valuable. Our thanks go to him and his associates who
actually worked out these student activities while also holding down
their regular duties at Ford.
Contact Mr. Sulek at:
msulek@ford.com Ford Motor Company
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The fuel cell’s operation is based on the
reversibility of an electrochemical process, first witnessed in 1839 by
British physicist William Grove. While performing electrolysis experiments, Grove observed that following the separation of water into
hydrogen and oxygen by electrolysis, a potential difference remained
across the platinum electrodes he was using even after the power supply
had been removed.
Despite its simplicity, abundance, and
cleanliness, hydrogen doesn't usually occur as a gas on Earth—it is most
often combined with other elements. However, hydrogen can be made by
separating it from chemical compounds by applying heat, a process known as
"reforming." Currently, most hydrogen is made this way from natural gas.
Through the process of electrolysis, an electrical current can also be
used to separate water into its components of oxygen and hydrogen.
But therein lies the rub. To produce the
energy needed for either reforming or electrolysis, conventional means of
power production must be used. But this negates the reason for switching
to fuel cells in the first place. The hope is that power from
environmentally friendly sources such as wind, hydro, tidal, geothermal,
or solar power may be used to produce hydrogen.
This is already happening in Iceland where
hydro and geothermal power is used to electrolyze water. There you can
find the world’s first hydrogen filling station sitting on the side of a
highway at Reykjavik city limits. In September, 2003 the first city buses
fueled up on hydrogen produced at the station through electrolysis.
Will
hydrogen be the fuel of the future? Only time will tell.
The
following experiments will help you understand how sunlight may be used to
split water into hydrogen and oxygen and how a fuel cell produces
electrical energy through the recombination of these gases. Although all
the experiments relate to the operation of a fuel cell car, they may be
used as stand alone experiments and demonstrations. We hope you and your
students enjoy this interactive introduction to hydrogen power.
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Student Activities |
1.
Solar Energy
Key Concept
Radiant energy may be transformed into other forms.
Example 1: The Radiometer
Teacher's Notes:
A radiometer is a device that converts radiant energy into rotational
kinetic energy. It consists of four vanes, silvered on one side and
blackened on the other. When light falls on the vanes they rotate.
Contrary to popular belief, this motion is not produced by radiation
pressure. So what does produce the rotation? (Hint: Which ways do the
vanes rotate?)
The vanes are mounted in a glass bulb that is evacuated to a low pressure.
The black surfaces absorb more radiant energy, and hence are warmer than
the silvered surfaces. Molecules colliding with the black surfaces gain
more energy than those rebounding from the silvered surfaces. The more
energetic molecules transfer more momentum to the vanes than do the
molecules bouncing off the silvered sides. The overall effect: a net push
in the direction of the silver side of the vanes.
Student Instructions:
Place a radiometer in sunlight or light from a lamp. What do you observe?
Which way are the vanes rotating? Can you get the vanes to move in the
opposite direction?
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Get Radiometer details here:
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Example 2: The Photocell
Teacher's Notes:
Photocells (solar cells) transform light energy into electrical energy.
They are most effective in bright light that shines directly onto the
cell. Students will experiment with different intensities and angles of
incidence, and observe how these different arrangements affect the reading on
a galvanometer and the motion of a motor.
Student Instructions:
Connect the photocell’s two leads to an electrical meter such as a
galvanometer or milliammeter. Hold the front side of the photocell toward
the sun or light from a bright light bulb. What do you observe? (If
nothing happens, reverse the leads on the meter). If you are using a light
bulb as a light source, vary the distance between the light bulb and the
photocell. What happens as the distance between the photocell and the
light bulb increases? Decreases? For a given distance from the photocell,
how does tilting the photocell affect the meter reading? How do you
explain this?
Remove the photocell’s leads from the meter and connect them to a small
motor. Describe what happens when the photocell is illuminated by a light
bulb. If the motor shaft doesn’t begin to spin what might you do to remedy
the situation? Once you have the motor operating, move the photocell
closer, then farther away from the light bulb. What effect does distance
between light source and photocell have on the motor speed? Now tilt the
photocell so that it doesn’t point directly at the light source. Describe
how this affects the operation of the motor.
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2.
Electrical
Current
Key Concept
An electrical current consists of moving charges.
Teacher's Notes:
When charged particles such as electrons move, they create a magnetic field.
This field can be detected with a magnetic compass. Students will arrange
a current-carrying wire near a compass to show that when the circuit is
complete, a magnetic field results and shows evidence of moving charges.
This concept is important in understanding the importance of removing
electrons from the hydrogen atoms to create an electric current. Note:
This is a short circuit, and the wire will become hot after only a short
time. Remind students to disconnect the wire from the battery after they
make their observations.
Student Instructions:
Place a length of insulated wire over the needle of a compass making
certain that the wire is touching the cover of the compass and that it is
aligned parallel to the needle. Watch the needle carefully as you attach
the ends of the wire to the positive and negative terminals of a standard
1.5 v cell. What do you observe?
Repeat the procedure, but this time reverse the leads to the battery. What
happens this time? What hypothesis can you formulate to explain your
observations? Cite evidence that something is moving in the wire in a
particular direction.
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3.
Electrolysis
Key Concept
Electrolysis is the process of decomposing a substance, e.g. water, into
positive and negative ions using electricity.
Teacher's Notes:
It’s
a simple matter to use electrolysis to produce hydrogen gas. The following
activities guide students through the basic electrolysis of water,
yielding gaseous hydrogen and chlorine. The primary reaction of interest
is:
2H2O(l)
+ 2Cl-(aq) ® Cl2(g)
+ H2(g) + 2OH-(aq)
Sodium
ions and hydroxide ions combine in solution to form sodium hydroxide.
(Fig.2)
While
gas is evolving at the two aluminum electrodes, submerge a test tube in
the tray of water (see Fig.2). After completely filling the test tube with
water, carefully pull the closed end of the test tube out of the water
while keeping the opening of the test tube submerged. Move the
upwards-pointing test tube over the cathode. The cathode is the electrode
connected to the power supply’s negative terminal. Try to catch all the
bubbles rising from the cathode in the test tube. Wait until the test tube
is filled about one-third with gas. Lift the test tube out of the water
while keeping the opening pointed downwards. Now quickly and carefully
move the test tube towards a lighted candle and hold it over the flame.
What do you observe? (The hydrogen will explode, producing a "pop.")
Safety notes: the test for hydrogen should be done by an adult. Chlorine
gas is dangerous if inhaled. Perform electrolysis in a well-ventilated
area.
Students will then power their electrolysis apparatus with a photocell, as
might be done in a solar powered fuel cell car or at a solar powered
hydrogen fuel station.
Student Instructions:
Electrolysis using a battery or power supply. (Fig.1)
First dissolve a teaspoon of salt in a tank or tray of water. Attach two
1cm x 6cm strips of aluminum foil to the ends of two connecting
wires. (Fig.1) Now place the two aluminum electrodes in the saltwater solution.
Make certain that the two strips are not touching. Connect the other ends
of wires to a 3-v to 6-v DC power supply. (This may be accomplished with
either two to four 1.5 v batteries connected in series or a DC power
supply.) Watch the two electrodes closely once the connections to the
power source have been made. What do you observe? What is the source of
the gases that are forming on the electrodes? Do you know what these gases
are? Are the gases produced at the same rate at each electrode?
Electrolysis using a photocell (fig.3)
Remove the two connecting wires from the power source. Connect the two
leads from the photocell to the two connecting wires. Illuminate the
photocell with light from the sun or a lamp. What do you observe? How does
the use of the photocell affect the rate of gas production? How does the
intensity of the light striking the photocell affect the rate of gas
production?
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Fig.1
Fig.2
Fig. 3 |
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4.
Constructing a Simple Fuel Cell
Key Concept
A reverse electrolysis reaction may be used to produce a potential
difference.
Teacher's Notes:
By introducing a few new materials, you
can build a simple fuel cell. The process begins with electrolysis, as
before. Hydrogen gas collects on the electrodes and the voltage source is
removed. The platinum serves as a catalyst allowing the recombination of
hydrogen and chlorine into hydrochloric acid. The process, known as
heterogeneous catalysis, is the basis of this type of fuel cell. The
resulting potential difference (voltage) can deflect a voltmeter or
light an LED for a few seconds.
Student Instructions
A form of fuel cell, referred to as a gas battery, may be easily
constructed using two nickel electrodes or two platinum electrodes, salt
water, a beaker or glass, a DC 4.5 to 6 volt power supply, a voltmeter,
and some connecting wires with alligator clips.
First set up the electrochemical cell as shown in the schematic below:
The voltmeter should be set to the 0 – 20 DC range before completing the
circuit. When the circuit is closed, electrolysis will begin and the
voltmeter will read between 4 and 6 v. Shortly after completing the
circuit, you should observe the production of gas at the electrodes.
Hydrogen gas will collect at one electrode, chlorine gas at the other. In
fact, you may be able to smell the chlorine when you are close to the
beaker.
After gas covers both electrodes, carefully remove the battery from the
circuit. The goal is to retain as many bubbles on the electrodes as
possible. When the circuit is once again closed, the voltmeter will still
indicate a reading of between 1 and 1.5-v. With the battery removed from
the circuit, a reaction now occurs at the surfaces of the platinum
electrodes that produces a potential difference. How long does a
measurable potential difference exist?
Repeat the experiment using other types of electrodes. Compare the
magnitude and duration of the potential difference produced by the
different metals.
Obtain a red Light Emitting Diode (LED) and repeat the electrolysis with
new salt solution and, if needed, new electrodes. After gas covers both
electrodes, remove the power supply from the circuit and replace it with a
red LED. Does the LED light? If so, for how long? Try lighting LEDs of
different colors. You have
to connect two or more fuel cells in series to light the LED. (
A note from Mark: To do this
activity you'll need to hook up two or more fuel cells in series to
light the LED. After your students do the first activity, have them get
together in groups to make the series circuit.
)
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5.
Gas Laws
From Conceptual Chemistry: Prof. John Suchocki shows the physical
change of a balloon submerged in liquid nitrogen.
Watch the
video
Key Concept
If the pressure is kept constant, the volume
of a gas increases, or decreases, in direct proportion to the increase, or
decrease, in absolute temperature. This basic law of gases is known as
Charles’ Law.
Teacher
Demonstration: Decreasing the volume of a gas
with liquid nitrogen
Caution:
Liquid nitrogen should only be used by an adult and with proper safety
precautions (heavy gloves, goggles).
Place an inflated balloon in a
container of liquid nitrogen. A
decrease in molecular kinetic energy causes the pressure exerted by the
air in the balloon to decrease dramatically. As a result, the balloon
shrivels up into what resembles a wrinkled pancake. Try placing additional
balloons into the container. You’ll be amazed at the number of
super-cooled balloons you can fit into a small volume.
Using forceps, remove a balloon
from the liquid nitrogen. If the balloon is translucent, hold it up to a
bright light source. You will see your condensed breath sloshing around at
the bottom of the balloon. You must make this observation immediately
after removing the balloon from the liquid nitrogen, for the liquid air
quickly evaporates.
Once again, use forceps to remove the balloons one at a time from the
liquid nitrogen and place them on the table. Heat transferred from the
table to the air in the balloon causes the pressure inside the balloon to
increase. Watching the balloons return to their original shape and size is great fun. Uneven thawing of the rubber will sometimes
produce a tear, so be prepared for an occasional pop!
The decrease in volume with temperature will allow the storage of a great
deal of air in a small volume. This principle is used to store and
transport a variety of gases, including hydrogen
for use in fuel cells.
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5.
Efficiency
Key Concept
Efficiency is the ratio of energy output to
energy input, stated as a percentage.
The efficiency of a machine is always less than 100% because of
friction and other factors.
Teacher's Notes:
This is a
simple experiment for measuring efficiencies of a mechanical system and a
simple electrical system. Students can analyze the energy losses in these
systems and predict what factors might affect the efficiency of a fuel
cell.
Student Instructions:
Example 1: The efficiency of a simple machine
Set up an inclined
plane by placing one end of a board on a stack of books (see figure above).
Slowly pull a dynamics cart up the incline using a Newton spring scale.
Observe and record the reading on the scale
as well as the length of inclined
plane. Calculate the work done in pulling the cart up the incline by
finding the product of the force and distance. This will yield the energy
input.
To find the energy output, weigh the cart by suspending it from the scale.
Also measure the height of the upper end of the incline. The work done
lifting the cart directly to the top of the incline is found by
multiplying the weight of the cart by the height of the incline. This
equals the useful energy output.
The efficiency of the incline plane is found
by dividing the useful energy output by the energy input and multiplying
by 100%:
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Example 2: The efficiency of the Genecon
generator.
Connect the leads of two Genecon generators together. As you turn the
handle of one of the Genecons, the handle of the second Genecon
will also turn. In this arrangement, the first Genecon is
functioning as a generator, the second Genecon, a motor.
Disconnect the wires and line up
the handles on the two Genecons. For example, they both could point
straight up. After reconnecting the wires, turn the handle of one Genecon
10 times while a second person simultaneously counts the number of times
the second handle turns. The ratio of the number of turns of the “motor”
to the number of turns of the “generator” times 100% equals the efficiency
of the two-Genecon system.
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6.
Catalysts
Key Concept
A catalyst is a substance that increases the rate of a chemical reaction
without being used up or changed itself. Catalysts are used in a wide
range of chemical processes. These include metallurgy, petroleum cracking,
and organic synthesis. The catalytic converter, perhaps the best known
example of a catalytic device, has greatly reduced the harmful emissions
associated with the combustion of gasoline. In the fuel cell, catalysts
aid in the combination of hydrogen and oxygen.
Teacher's Notes:
Examples of the use of catalysts to speed up chemical reactions abound.
The two demonstrations that follow were selected for their simplicity.
Example 1:
Place a sugar cube in a clothespin or lab forceps. Insert the sugar cube
in a candle flame. Observe that the sugar cube browns and melts, but does
not catch fire. Now rub a tiny bit of wood ash on the sugar and once again
hold the sugar cube in the flame. It will immediately flame up and
continue to burn.
The ash serves as a catalyst. An analysis of the post-combustion remains
would indicate that the ash remains unchanged. The ash is needed to
initiate combustion, but does not take part in the reaction.
Example 2:
Hydrogen peroxide is an unstable chemical compound that readily breaks
down into water and oxygen. The reaction is accelerated by exposure to
light. For that reason, hydrogen peroxide is stored in opaque bottles.
The break down of hydrogen peroxide can be greatly accelerated by using
manganese dioxide as a catalyst. Have students watch a sample of hydrogen
peroxide as the catalyst is added to the liquid. The increase in oxygen
production will be dramatic. Also have students note that the manganese
dioxide does not appear to change. This of course is the defining
characteristic of a catalyst.
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How the Fuel Cell transfers energy
PEM fuel cell diagram and explaination
Hydrogen
Hydrogen flows through channels in flow field plates to the anode where
the platinum catalyst promotes its separation into protons and electrons.
Hydrogen can be supplied to a fuel cell directly or may be obtained from
natural gas, methanol or petroleum using a fuel processor, which converts
the hydrocarbons into hydrogen and carbon dioxide through a catalytic
chemical reaction.
Membrane Electrode Assembly
Each membrane electrode assembly consists of two electrodes (the anode and
the cathode) with a very thin layer of catalyst, bonded to either side of
a proton exchange membrane.
Air
Air flows through the channels in flow field plates to the cathode. The
hydrogen protons that migrate through the proton exchange membrane combine
with oxygen in air and electrons returning from the external circuit to
form pure water and heat. The air stream also removes the water created as
a by-product of the electrochemical process.
Flow Field Plates
Gases (hydrogen and air) are supplied to the electrodes of the membrane
electrode assembly through channels formed in flow field plates.
Fuel Cell Stack
To obtain the desired amount of electrical power, individual fuel cells
are combined to form a fuel cell stack. Increasing the number of cells in
a stack increases the voltage, while increasing the surface area of the
cells increases the current.
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Get information on a complete Fuel Cell Car kit and curriculum here.
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Hydrogen Fuel Cell Car and Experiment Kit
Students
can experiment with all of these concepts and more with the Hydrogen
Fuel Cell Car and Experiment Kit. More than 30 experiments and
demonstrations help users learn about solar power, electricity, electric
motors, electrolysis, efficiency, fuel cells, and more. The kit
includes everything you need to build a working solar powered fuel cell
car, including the fuel cell itself! For more information, click on the
yellow button.
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Interesting Links
Try out the
New
Archives Search for past articles from CoolStuff
Arbor
Scientific online conversion calculators
Fuel Cell Technology information from Ford Motor
Cool New Fuel Cell Product!
Indoor Fuel Cell
Powered Generator AirGen™
Great Fuel Cell
Graphics and Video on "How Fuel Cells Work"
Great Student link for information on Hydrogen
as a fuel from the Environmental Media Northwest Group
http://4hydrogen.com/
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In the next issue of CoolStuff…
We live in an age of electricity and electrical devices. Every facet of
our lives - communication, transportation, medicine, manufacturing,
entertainment, the storage and processing of information, and even
agriculture - is somehow connected to electrically powered machines,
instruments, or gadgets. A basic knowledge of electricity, and its
companion phenomenon magnetism, is essential if we, and our students, are
to understand much of the technological world in which we live.
For this reason, the next two issues of CoolStuff will focus on hands-on
activities designed to demystify electromagnetic phenomena. Who knows,
after performing these experiments your students may find science
electrifying!
Regards,
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