Reversible Fuel Cell User Guide
Introduction
The information in this document provides instruction on the proper way to setup, and
use the Heliocentris Reversible Fuel Cells. It is recommended that this document be
read carefully and completely before attempting to use the fuel cells. Following the
proper directions will ensure that the fuel cell
membrane is not damaged during use in the
classroom.
What is a Reversible Fuel Cell?
The Heliocentris Reversible Fuel Cell is a
unique type of a fuel cell because it can be
used as an electrolyzer to split water into
hydrogen and oxygen and as a fuel cell to
generate electricity from the electrochemical
reaction between hydrogen and oxygen.
Electrolyzer Mode:

The unit is supplied with an electrical current, which is used to split the water
(H2O) contained in the cylinders into
hydrogen and oxygen. The hydrogen
and oxygen gas are stored in the bottom
of the cylinder, while the remaining water
is displaced to and stored in the top part
of the cylinder.
Fuel Cell Mode:

Once the unit has hydrogen and oxygen stored in its cylinders it is ready for use
in fuel cell mode. When a load (motor) is attached to the unit, the stored
hydrogen and oxygen are consumed - an electrochemical reaction takes place
between the protons and electrons of the hydrogen and the ions from the oxygen
to produce electricity. Note: In fuel cell mode, the fuel cell will only generate
electricity when a load is connected.
© 2012 Project Lead The Way, Inc.
Principles of Engineering Fuel Cell User Guide – Page 1

To view an animation of a fuel cell in operation and for additional technical detail,
please visit: http://www.heliocentris.com/en/academiaoffering/information/technology-guide/fuel-cell.html
The Parts of the Heliocentris Reversible Fuel Cell
1.
2.
3.
4.
5.
6.
7.
8.
Water reservoir – Hydrogen side
Storage cylinder – Hydrogen side
Hydrogen side stopper
Storage cylinder – Oxygen side
(hidden)
Banana jack – negative terminal
Protective diode
Banana jack – positive terminal
Water reservoir – oxygen side
Preparing the Reversible Fuel Cell for Use
1. Place the fuel cell upside down on a flat surface. In this orientation the numbers
will be upside down and the negative (black) terminal will be on top.
2. Remove the stoppers from both the oxygen and hydrogen storage cylinders.
3. With distilled water, fill both storage cylinders to the top of the small tubes in the
center.
Note: The use of any liquid other than distilled water will result in
permanent damage to the proton exchange membrane (PEM)
© 2012 Project Lead The Way, Inc.
Principles of Engineering Fuel Cell User Guide – Page 2
4. Tap the fuel cell lightly. This causes water to flow into the area surrounding the
proton exchange membrane (PEM).
5. Be sure to have towels nearby, because water will spill on the table during this
step. Add more water until it starts to overflow into the small tubes in the center.
6. Put the stoppers back onto the cylinders. Make sure no air bubbles larger than
0.5mL are trapped inside.
7. If the membrane has not been used in a while and is dried out, allow it to soak for
a minimum of 30 minutes before attempting to use the fuel cell.
8. Turn the fuel cell right side up.
Electrolyzer Mode
In this mode, the reversible fuel cell is supplied with electricity to split water into
hydrogen and oxygen. The oxygen and hydrogen are stored in separate cylinders for
later use in fuel cell mode.
Solar Panel as a Power Source
1. When powering the fuel cell, a solar panel in combination with a light source
can be used as the power source.
•
Light Recommendations:
o Halogen: A PAR 30 or PAR 38 Halogen Spot
 Color temperature close to 2700k
 75 – 100 W
o Incandescent: 120 W PAR 38 Spot
 Color temperature close to 3000k
 These bulbs will get hot so use caution
 Do not leave unattended or too close to the solar panel.
They have the potential to melt the solar panel.
o Using the sun as a power source is only recommended on a very
sunny day. It may take significantly longer to produce enough
hydrogen and oxygen to power the fuel cell using the sun than one
of the recommended light sources listed above.
•
Warning: Failure to follow guidelines regarding the light source could
result in malfunction or permanent damage to the solar cells.
o Use light sources with a maximum power of 120W.
o Keep the light source at least 8 inches away from the solar panel.
o Do not concentrate the light with a reflector.
© 2012 Project Lead The Way, Inc.
Principles of Engineering Fuel Cell User Guide – Page 3
2. Connect the solar panel and the fuel cell as shown. The diagram below
illustrates the necessary setup for separating hydrogen and oxygen in the fuel
cell.
•
The positive terminals on both the solar panel (1) and fuel cell (3) are
connected by a conducting wire.
•
The negative terminals on both the solar panel (2) and fuel cell (4) are
connected by a conducting wire.
•
NOTE: Always remember to maintain the minimum distance between the
light and the solar panel so you do not melt the solar panel. You will need
to experiment with the distance angle to achieve acceptable performance.
3. The formation of gas should begin immediately in both storage cylinders.
4. The reversible fuel cell completes electrolysis when the water in the hydrogen
storage cylinder completely pushes into the reservoir on top. The bottom part
of the cylinder contains no water, only gas.
5. When the hydrogen has filled the storage cylinder, disconnect the energy
source by unplugging the banana jacks.
 It is not necessary to completely fill the H2 cylinder with hydrogen. It
simply means less hydrogen is available. Less hydrogen means that
the unit will not produce power for a shorter time when in fuel cell
mode.
6. The reversible fuel cell is now ready to be used in fuel cell mode.
© 2012 Project Lead The Way, Inc.
Principles of Engineering Fuel Cell User Guide – Page 4
Fuel Cell Mode
In this mode, the reversible fuel cell is used to generate electricity when a load (motor)
is attached to the unit.
1. Attach your load (motor) to the fuel cell using the red and black cables.
• The red (positive) banana plug should connect to the red terminal on
the fuel cell
• The black (negative) banana plug should connect to the black terminal
on the fuel cell
2. Electricity will be produce immediately upon connecting both cables from the
load to the reversible fuel cell.
•
Once the load is connected the reversible fuel cell is operating in fuel
cell mode – producing electricity from an electrochemical reaction
between the hydrogen and oxygen supplied from the storage cylinders.
3. To stop electricity production, disconnect the motor cables from the fuel cell.
As long as the storage containers contain both hydrogen and oxygen,
the unit will can produce electricity when a load is applied.
Warnings Regarding Operation
•
Avoid a short circuit with the fuel cell by including a 10 Ω resistor in the
circuit. A short circuit connected to the fuel cell will result in irreversible
deterioration of the PEM.
Alternative Power Sources
Other power sources can be used to power the fuel cell, but this should be done
with caution. Failure to power the fuel cell according to the following guidelines
will result in permanent damage to the PEM. Over time, the fuel cell may lose its
functionality.
•
Do not allow currents more than 500 mA to flow through the fuel cell.
•
Electrical connections are the same as when using a solar panel. Connect
the positive terminal of the power source to the positive terminal of the fuel
cell with a conducting wire. Connect the negative terminal of the power
source to the negative terminal of the fuel cell with a conducting wire.
© 2012 Project Lead The Way, Inc.
Principles of Engineering Fuel Cell User Guide – Page 5
Examples of Alternative Power Sources
•
A current limiting DC power supply set to a maximum current below 500
mA and maximum voltage of 2 V. (Note: Do not use a battery power DC
supply.)
1. Prior to connecting the fuel cell to the power supply, set the voltage
limit to 2 V and the current limit to 0 A.
2. Connect the positive terminal of the power supply to the positive
terminal of the fuel cell. Connect the negative terminal of the power
supply to the negative terminal of the fuel cell.
3. Gradually increase the current limit until it reaches 0.4-0.45 A, which is
safely below the 0.5A threshold. Gas should be produced immediately.
•
A different solar panel with the same current / voltage limits.
•
Two solar panels connected in parallel, as long as the 500 mA current limit
is not exceeded.
•
Hand-crank generator, as long as the 500 mA current limit is not
exceeded.
Fuel Cell Storage
1. Remove stoppers and pour out all remaining water. Storing the fuel cell with
water in it will result in deterioration of the fuel cell.
2. Allow the fuel cell to dry completely.
3. To ensure that the PEM is allowed to dry fully, do not replace the stoppers prior
to storage.
4. Store the components at temperatures between 10–35 °C (50–95 °F).
© 2012 Project Lead The Way, Inc.
Principles of Engineering Fuel Cell User Guide – Page 6
Specifications
Solar Panel
Characteristics
Value
Operating Temperature
10–65 °C (50–149 °F)
Length / width / height
52 mm × 70 mm × 130 mm
(2.04" × 2.8" × 5.11“)
Weight
60 g
Incident power of 1000 W/m2 at 25 °C (77°F):
Open circuit voltage
2.5 V *
Short circuit current
250 mA *
Operating current
180 mA (with 10 Ω load)
Operating voltage
2V*
Output
0.36 W *
* Typical value produced with a 120 watt PAR lamp from Heliocentris at a distance of 20 cm.
Reversible Fuel Cell
Characteristics
Value
Length / width / height
70 mm × 90 mm × 80 mm
(2.75" × 3.54" × 3.14“)
Weight (unfilled)
140 g (2.1 oz)
Operating temperature
10–40 °C (50–104 °F)
Storage temperature
5–40 °C (41–104 °F)
Gas storage
2 × 15 mL
Electrolyzer operation
Working voltage
1.4 – 1.8 V
Operating Current
0–500 mA
Rate of hydrogen production, maximum
3.5 mL / min
Fuel cell operation
Operating voltage
0.5–0.9 V
Operating current
500 mA
Operating power
250 mW
© 2012 Project Lead The Way, Inc.
Principles of Engineering Fuel Cell User Guide – Page 7