Electric equivalent circuit model of an alkaline fuel cell

The Centre of Economic Renewable Power Delivery (CERPD) at the University of Strathclyde has developed various fuel cell (FC) systems for stationary and vehicular applications. The aim of the research is to design and build reliable and cost efficient FC systems, which could replace existing conventional technology in the near future. To size each component of the system efficiently the behaviour of the alkaline fuel cell (AFC) stack has been modelled. The electric equivalent circuit model developed allows easy characterization of the fuel cell stack by electric parameters, such as internal resistance and stack capacitance. The model is used to forecasts the behaviour of the fuel cell stack under various operating conditions. A mathematical analysis of the suggested equivalent circuit is presented in the paper. The so-called Nernst potential, which describes the open circuit voltage of the stack, is calculated using thermodynamic theory. Electrochemistry theory has been used to explain the causes of the different losses within the FC, such as activation, ohmic and concentration losses. In the model these losses are expressed using electric circuit elements. The circuit elements are derived from experimental tests, which are described in detail in the paper.