Maximum efficiency points of a proton-exchange membrane fuel cell system: Theory and experiments

In this paper, a theoretical expression for the efficiency of a fuel cell system is derived. The studied system consists of a proton-exchange membrane fuel cell stack coupled at its output to a DC/DC boost converter. A fuel cell stack Larminie and Dicks model along with an efficiency curve for our boost converter are fitted using experimental data. One maximum efficiency point for the fuel cell stack coupled to the DC/DC power converter is shown and lies in the safe zone of the fuel cell stack. Experimental results on the fuel cell efficiency, DC/DC efficiency and their association on a test bench indicate a good agreement between the theoretical estimations and the experimentally obtained results at different values of the DC/DC converter output voltage. The results provide strong theoretical and experimental evidence for a unique maximum efficiency point for the fuel cell system and form a basis for developing maximum efficiency point tracking algorithms.