Improving hydrogen sensors for diagnostics in heavy duty fuel cell applications

Ballard Power Systems is a leading company in the field of hydrogen fuel cell research and manufacture. Monitoring membrane deterioration through excessive crossover requires accurate hydrogen leak sensors within the vehicle safety systems. Hydrogen sensors are typically used to detect fuel crossover and external leaks in fuel cells. They are expensive and have typically exhibited short lifetimes. Two methods of lengthening the sensor life have been examined in this thesis. The first is physical filtering of poisoning agents. These components, particularly the siloxane compounds that are off-gassed from the silicone tubing, coalesce on the surface of the hydrogen sensor as silicates, reducing the sensor sensitivity. With these compounds mostly removed by the filters, the sensor life has been extended. While preventing degradation of the cathode exhaust sensor is the best approach, it was not wholly effective. Significant effort went into recalibrating the hydrogen sensor in situ, the second method. This methodology uses anode and cathode mass flow sensors in the fuel cell to automatically calibrate the hydrogen sensor as it degrades. The results from this approach were found to be promising, and we showed that the auto-calibration algorithm was robust enough to accept disturbances in system inputs.