B. Test Preparation/Set-up

As discussed above, there are several ways that reactant streams may be supplied to the fuel cell stack. Here, the test prep procedure is described for each of those flow scenarios.

If the hydrogen outlet is to be closed off so that the stack is “dead-ended,” then hydrogen flow will be controlled by a pressure regulator. Begin by connecting the hydrogen supply to the stack via pressure regulators. If a flow controller is in the fuel line, set it to full flow. Turn the pressure regulator(s) down to fully open (no pressure). Cap off the fuel outlet of the stack with the included plug. Turn on the hydrogen source--either by opening the pressurized cylinder or by activating the hydrogen generator. Slowly increase the pressure on the regulator closest to the hydrogen supply. If only one regulator is used, set the pressure seen by the stack (i.e. downstream from the regulator and upstream of the stack) to between 0.3 and 2 psi. Record the fuel pressure.

Warning: Hydrogen pressure should never exceed 3 psi. Immediately turn off hydrogen supply and relieve hydrogen pressure in a WELL VENTILATED area if a pressure spike occurs.

If a series of regulators is used to supply fuel to the stack at an appropriate level, then set the pressure in each regulator sequentially, beginning with the regulator closest to the fuel supply. Make sure that each regulator receives an input pressure within its operating range. Increase the pressure at each regulator from 0 very slowly. If the pressure exceeds the recommended range for a regulator or the stack itself, carefully vent the hydrogen and lower the pressure setting on the regulator to 0. Turn the hydrogen supply back on and slowly increase the pressure until it is in the appropriate range. Note: If the fuel supply is humidified and the stack is dead-ended, then it will be necessary to purge the fuel side of the stack by opening the fuel outlet and allowing water to be drained. This should be done approximately every 30 minutes.

Setup for Continuous Flow Testing

Connect the fuel supply to pressure regulators such that the supply pressure is no more than 2 psi. Install a flow controller or flow meter and proportional valve downstream of the last regulator. Close the controller or valve so that there is no flow. Ensure that the hydrogen outlet is open. Slowly open the controller or valve to increase the hydrogen flow rate to an appropriate level based upon the tests to be conducted. Assuming that the hydrogen is Ultra-High Purity (UHP) or chemically pure, then no filtration is required. Otherwise, be sure to use a 10 micron (or finer) filter to eliminate impurities. Downstream of the flow controller, the hydrogen should be hydrated as descrived above.

Air Flow Setup

If the stack is air-breathing, no setup is required. As an option, a small fan (see accessories) can be connected to a power supply to increase the air flow through the fuel cell stack. If the stack requires a pressurized air supply, set up the air supply in a similar fashion to how the hydrogen supply is set up for continuous flow testing, using pressure regulators and a flow controller. If a shop air supply is used, it is important that the gas be dried and be sure to use a 10 micron (or finer) filter to eliminate impurities. After the air has passed through the flow controller, it shoud be humidified using an appropriately sized humidifier or bubbler.

Electrical Setup

In order to measure the electrical performance of the fuel cell stack, the stack cathode (air electrode) should be connected to the positive terminal fo teh electronic load and the anode should be connected to the negative terminal of the load. If using a four point measurement system, the positive voltage sense lead should be connected to the cathode and the negative sense lead should be connected to the anode. Once fuel flow is initiated, the load can be turned on. Ensure that the current load is off (set to 0 A).