Experimental analysis of the dynamic performance of PEM fuel cell under various load changes

The dynamic performance is one of the most important specifications for Fuel Cell system (FCs). In this paper, practical experimental investigation of dynamic performance and transient responses of Proton Exchange Membrane (PEM) FC under various load conditions are presented using Ballard Nexa (1.2kW) PEMFC system. In order to test different characteristics of FCs, the practical tests have been separated into four different categories: for instance start-up, shut-down, step-up load, and irregular load variation. It is observed that the external load changes the current output proportionally and reverses stack voltage consequently. The purge operation benefits performance recovery and improvement during a constant load and its time constant completely depends on the current working point. Overshoot and undershoot behaviours were observed throughout start up and transience. Magnitudes of overshoot/undershoot voltage show a discrepancy under different current intensities conditions. The operating temperature of the system reacted quickly to current load without observation of overshoot or undershoot event. At the same time the air flow rate is directly affected by the dynamics load demand. Whereas, the increased amount of air flow rate during different step-changes is not identical, but depends on the requirement of internal reaction and flooding intensity. The results presented in this paper can be extended for validation of dynamic behaviour for different FC models.