Electrochemical Impedance Parameter Extraction for Online Control of Reformed Methanol High Temperature PEM Fuel Cells

This work focuses towards online control strategy for detecting fuel and oxidant starvation and predicting an optimal stoichiometry for operation under different fuel compositions using the electrochemical impedance spectroscopy (EIS) parameter extraction method. The tests involve three fuel compositions, namely dry hydrogen, dry reformate (Open image in new window, Open image in new window, Open image in new window and Open image in new window) and wet reformate (Open image in new window, Open image in new window, Open image in new window and Open image in new window). The characterization of anode and cathode stoichiometry (both low and high) is carried out with each fuel composition by measuring electrochemical impedance spectroscopy (EIS) and current–voltage (IV ) curves. The results suggest positive effects of humidified gas on the fuel cell stack performance. The changes in the mass transport resistance due to excess gas or gas starvation both on the anode and cathode could only be deduced using the EIS method. Online EIS measurement seems useful in deducing the optimal stoichiometry as the IV curves are unable to show the changes in the mass transport. Thus, to operate the fuel cell stack under an optimal fuel and oxidant utilization, an online EIS with parameter extraction algorithm can be helpful. This would ensure a better fuel and oxidant utilization and improve the system efficiency.