Discussion of critical measurement issues of impedance spectroscopy on PEM fuel cells

This paper aims at discussing some critical measurement issues in the electrochemical impedance spectroscopy technique, widely employed to identify fuel cell dynamic models. The evaluation of the model uncertainty and the definition of the model validity limits are not easy tasks because they depend on several aspects. Among these, the measurement repeatability is a critical issue because of the difficulty to control the cell internal conditions (gas pressure, membrane temperature and humidity). Besides, the validity of the linear-model approximation should be discussed, both in the model identification process and in the model applications.