A. Testing Precautions

To ensure the safety of the testers and the product, precautions must be taken when testing a fuel cell stack. With regard to the test syste, this includes ensuring that the hydrogen gas is properly vented from the area.

To avoid damaging the stack during testing, there are several other precautions that should be taken. The first is to avoid operating the stack at very low voltage. Do not ever short circuit the fuel cell stack. Do not allow the stack to operate at a level such that the average operating voltage of the individual cells is less than 0.2V for a hydrogen fueled stack. A second precaution that should be taken to ensure proper stack operation is to introduce only humidified (preferably saturated) gases to the stack. If localized dry out of the MEA occurs, small holes could develop in the membrane material due to local hot spots. These hols would allow hydrogen and air to mix, resulting in a dangerous situation.

Caution: Confirm that MEAs are in good condition prior to exposure to hydrogen. Conduct a leak check to prevent mixing of hydrogen and ambient air.

III. Proton Exchange Membrane Fuel Cells Reference Information

This section seeks to provide a general introduction to basic concepts related to basic operation of fuel cells and how to quantify the performance of a fuel cell. For more detailed information, please refer to more in-depth fuel cell references, such as Fuel Cell Systems Explained and The Fuel Cell Handbook.

On a fundamental level, a PEM fuel cell is a device that converts hydrogen and oxygen into water and electricity. As shown in the schematic below, hydrogen molecules flow to the anode of the MEA. HEre, they are split into electrons and positive ions. The positive ions migrate through the membrane material; the electrons cannot pass through the membrane, so they are forced to pass through the load (e.g., a light bulb) before the electrons reah the cathode of the MEA. At the cathode, the electrons combine with the positive ions (positive hydrogen ions or protons) that have passed through the membrane and oxygen molecules from the air to form water. This completes the electrical circuit, resulting in electrical power from the stack. A fuel cell’s performance is primarily defined by the amount of fuel and air required to produce a certain amount of power. More specifically, the amount of reactants necessary to yield a specific cell or stack voltage at a specific current density defines a fuel cell’s performance.