Modeling the steady-state and dynamic V-I characteristics of PEM fuel cell

The performance of a fuel cell can be expressed by the polarization curve, which describes the cell voltage–load current (V–I) characteristics of the fuel cell. Optimization of fuel cell operating points, design of the power conditioning units, design of simulators for fuel cell stack systems, depend on such characteristics. Therefore, modeling V–I characteristics of fuel cells is important. A number of publications reported various attempts to model V–I characteristics of fuel cells. In this paper, two mathematical models are developed to simulate both the steady-state and transient phenomena in a PEMFC system. At the first, the electrochemical model has been developed. Mass transport properties are considered steady-state via Stefan-Maxwell equation. Thermodynamic equilibrium potentials are defined using the modified Nernst equation. Activation, ohmic and concentration overpotentials are defined via the special equations. By addition of these terms to the thermodynamic potentials, the V-I characteristics can be predicted. Then, the dynamic electrochemical model is developed which incorporates the effects of charge double layer capacitance and can predict the transient response of the cell voltage. These proposed models are implemented in MATLAB environment. Additionally, these models were tested for the SR-12Modular PEM Generator, the Ballard Mark V and FC, the BCS 500-W stack and various experimental data in open literature. By simulating these models, it can be seen that various operating coditions such as different feed gas stoichiometry, operating temperature, feed gas humidity, air pressure and fuel cell size, can affect both the steady-state and dynamic response of the fuel cell.

کلیدواژه ها:

PEM fuel cell ، modeling ، V-I characteristics ، transient response