Activity 1.3.1 Fuel Cell User Guide

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

© 2012 Project Lead The Way, Inc. Principles of Engineering Fuel Cell User Guide – Page 1 to produce electricity. Note: In fuel cell mode, the fuel cell will only generate electricity when a load is connected. . To view an animation of a fuel cell in operation and for additional technical detail, please visit: http://www.heliocentris.com/en/academia- offering/information/technology-guide/fuel-cell.html

The Parts of the Heliocentris Reversible Fuel Cell

1. Water reservoir – Hydrogen side 2. Storage cylinder – Hydrogen side 3. Hydrogen side stopper 4. Storage cylinder – Oxygen side (hidden) 5. Banana jack – negative terminal 6. Protective diode 7. Banana jack – positive terminal 8. 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.

© 2012 Project Lead The Way, Inc. Principles of Engineering Fuel Cell User Guide – Page 3 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.

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.

© 2012 Project Lead The Way, Inc. Principles of Engineering Fuel Cell User Guide – Page 4 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.

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.

• 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).

Solar Panel

Characteristics Value Operating Temperature 10–65 °C (50–149 °F) 52 mm × 70 mm × 130 mm Length / width / height (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 2 V * 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 70 mm × 90 mm × 80 mm Length / width / height (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