Cell voltage and two-phase flow in a unitized regenerative fuel cell operating in alternate fuel cell and electrolytic cell modes

Abstract

ABSTRACT Mode switching between fuel cell and electrolytic mode is inevitable for actual applications. During the mode switching, complicated electrical response and gas-liquid phase change occur due to the different operation conditions in these two modes. To explore the effect of water removal method on electrical performance before fuel cell mode startup in mode switching process and get better overall cell performance. In this paper, the continuous mode switching within three cycles is explored by experimental works. It is found that the voltage decreases slightly with the cycle running, and the two-phase flow in the corresponding mode of each cycle is similar through analyzing the two-phase flow phenomenon of the two modes during mode switching. It is also found that bubbles are generated during electrolytic cell, the water is consumed and there is only water mist at the transparent end plate during electrolytic cell mode without water. A handful of liquid water gathers at the bottom of the flow channel during fuel cell mode. Experiments of the cycle test process are also conducted. It is shown that with the cell mode switching periodically, the cell voltages of the electrolytic cell and fuel cell both decrease periodically. The fuel cell performance changes more, especially under high current density.