Online Health Monitoring of the Polymer Electrolyte Membrane Fuel Cell

The Polymer Electrolyte Membrane (PEM) Fuel Cell is a widely researched fuel cell, and a very promising candidate for alternate power generation. However, technical issues such as cell flooding and drying prevent its deployment in many applications. Electrochemical Impedance Spectroscopy (EIS) is a very powerful technique used to isolate flooding and drying in a fuel cell. However, the time required to obtain measurements in EIS can sometimes be too large to cause irreparable damage to the cell, rendering it a mere post-mortem technique. This is because EIS perturbs a fuel cell with multiple cycles of a large number of sinusoidal signals at different frequencies. A new technique is proposed that uses the concept of EIS, but excites the cell with a chirp signal, allowing scanning a large range of frequencies in a relatively short time. his technique which we call Fast EIS, is computationally much faster than traditional EIS. Processing of data obtained with Fast EIS is done using two methods - the traditional Fourier Transform division method, and a new Wavelet Coherence method. Simulation results of Fast EIS with PEMFC models taken from literature are shown with performance comparable with that of traditional EIS. The information extracted from Fast EIS is also used for implementing a preliminary control technique to maintain the health of the fuel cell.