Operating strategy for successful start-up in self-humidified polymer electrolyte membrane fuel-cell system

A parametric study on the current distribution of a polymer electrolyte membrane fuel cell in dry conditions was conducted to suggest an optimal start-up strategy to achieve stable and successful operation. We used a segmented cell to measure the current distribution on the fuel cell depending on operating parameters. First, we examined the effect of the operating parameters on the current distribution. When the mass flow rate was high, the flow could easily remove flooding at the exit; however, it easily dehydrated the membrane at the inlet. Therefore, the maximum value of the local current was 1.2 A and 1.15 A for low and high flow rate, respectively. When the pressure was high, the current was distributed uniformly. The difference between the maximum and minimum current values was 0.55 A for 1 bar and 0.45 A for 3 bar. This is because the membrane was easily hydrated when the partial pressure of the vapor was high. Moreover, when high-temperature gas entered the fuel cell, the membrane was dehydrated; therefore, only a small amount of current was generated. According to this analysis, we suggested an optimal dry start-up process. The proposed procedure ensures successful start-up and reduces the start-up time.