Temperature and Pressure Effects Analysis on Fuel Cell System Voltage using a Generic Circuit Model

This paper presents a mathematical study which explains the temperature and reactants pressures effects on the internal voltage dynamics in fuel cell systems operating with hydrogen and oxygen gases, using a generic circuit model. This study focuses on studying the nonlinear dynamic voltage as a mathematical function that changes with temperature reaction, current intensity, hydrogen and oxygen gas pressure. From analyzing the complex system equations algebraically and graphically, the representations describe the behavior of the internal voltage under specific assumptions and conditions of system parameters, and various scenarios within both the experimental and theoretical ranges of variables. The results analysis shows that the temperature effect on the internal voltage is always directly proportional within the operating range, unless the output current exceeds the critical current threshold. The oxygen gas pressure controls directly how the hydrogen pressure affects the internal voltage of the fuel cell system. The results demonstrated that equalizing the pressures of both gases represents the best operating condition for the hydrogen fuel cell system, in that case, the effect of hydrogen pressure is always directly proportional to the internal voltage within the operating range, once the operating pressure threshold is exceeded. Moreover, the dynamics of the internal voltage exhibit a faster and more stable response.