Experimental Characterization of Fuel Cells, Supercapacitors, and Their Passive Connection

This paper investigates a passive hybrid configuration consisting of a fuel cell stack and a supercapacitor bank. In this configuration, the fuel cell and the supercapacitor are directly connected in parallel without the use of any DC/DC converters. Extensive experiments are performed on the fuel cell stack, the supercapacitor bank, and their passive hybrid connection. The internal impedance of the supercapacitor bank is 10 times lower than that of the fuel cell stack. The hybrid system shows a capacitive behavior in the selected frequency range, as given by the electrochemical impedance spectroscopy results. For the fuel cell stack, its voltage response to the step load current shows an inductive behavior, which can be represented by an RL circuit. On the other hand, the dynamics of the supercapacitor bank can be represented by two RC branches. When a step load current is applied, the supercapacitor provides the transient current while the fuel cell provides the steady current.