Electricity and Magnetism > EMF and Current DCS# 5E40.60
HYDROGEN FUEL CELL

APPARATUS
hydrogen fuel cell stack
 202-19-D
electrolyzer
 202-19-D
AC adapter/power supply
 202-19-D6
DC/DC converter
 202-19-D6
fan
 202-19-E2
two multimeters
 214-02-C6
distilled water
 202-01-A
video camera
 202-09-D

DESCRIPTION
There are eight PEM (proton exchange membrane) fuel cells arranged in back-to-back pairs, with hydrogen supplied to the inner faces and oxygen from the air supplied to the outer faces.  The two cells in each pair are electrically connected in series.  The first pair is used in reverse as an electrolyzer to produce the hydrogen to be consumed by the other three.  Those three are connected in series and produce about 3 W of power at 3 V.  A DC/DC converter is available for output voltages up to 14 V.

With the hose clamp between the electrolyzer and storage tank open and the other two clamps closed, plug in the electrolyzer power supply.  Oxygen will bubble out through the water tank and hydrogen will be collected in the 80 ml storage tank at a rate of about 50 ml/minute.  Fifty ml is enough to run the small fan for about half an hour.  Unplug the power supply and close the hose clamp.

Open the clamp between the hydrogen tank and the fuel cell stack and the fan should run.  If the fan doesn't start, there may be air inside the cells - open the hydrogen outlet clamp briefly to vent hydrogen through the system.

Top off the electrolyzer water tank with distilled water if the level drops below the "minimum" mark. 
 

NOTES
Setup:
Fill the electrolyzer water tank with distilled water to the A level.   Fill the hydrogen storage tank with distilled water to the top and secure the compensation tank on top of it.

Flush distilled water through the fuel cell stack (or not - see troubleshooting tips below).  Then vent some hydrogen through the system to remove any air.  If you don't measure ~0.8 V across each cell, there may be air trapped inside.  Try holding the cells upside down to dislodge any air bubbles while venting hydrogen through them.

Connect the positive and negative terminals to a load - the fan works well - and use the multimeters to measure voltage and current.

Apply no more than 4 V DC to the electrolyzer.
Troubleshooting:
Poor performance can be caused by water adhering to the inner surfaces of the cells after they are flushed with distilled water.  The cells should be tested initially just by flushing with hydrogen and not water to see if they work.  If not, they should be flushed with distilled water and then hydrogen to see if they work.  If not, check for water adhering to the inner membranes – if so blow it out with lungs and then purge with hydrogen.  If the cells still aren’t working, let them sit overnight with some hydrogen, but with both the inflow and outflow tubes closed (to prevent water being drawn in).  This gives the water droplets time to evaporate so that the PEM is moist, but not covered by a thick film of water.
Storage:
Empty the water from the electrolyzer tank.

Leave a little water in the tubing and cap the hydrogen inlet and valve off the outlet on the fuel cell stack to keep the cells from drying out.
Additional info:

Using the AC adapter provided, the electrolyzer consumes 3.26 A at 3.68 V or 12.0 W and produces hydrogen gas at a rate of 50 ml/min.  This is 14 kJ/L of H2 gas.

The energy density of hydrogen gas at atmospheric pressure is 10.8 x 103 J/L.

The fan consumes about 1.4 ml/min at 0.09 W.  This suggests an efficiency of about 35%.

PEM fuel cells typically have efficiencies of 50-60%.


REFERENCES
instruction manuals: electrolyzer, fuel cells

PEM fuel cells instructional materials