Equivalent circuit modeling and performance evaluation of proton exchange membrane fuel cells

This thesis provides an analysis of, and contrasts, published dynamic and static equivalent circuit models of fuel cells. The six models included in the analysis are significantly different from one another. They were derived from electrochemical impedance spectrometry, current interrupt techniques, the fuel cell's I-V (polarization) curve, the physical assembly of the fuel cell or the losses inherent to fuel cells. Passive models are inferred from these models and are compared to 25 W proton exchange membrane (PEM) fuel cell stack experimental results using PSpice and MATLAB simulations. This thesis also proposes a passive equivalent circuit model of a PEM fuel cell stack and a test methodology for monitoring the individual cells in the stack. The model is derived from a simple fuel cell circuit model, electric circuit theory, and the experimental response of 25 W PEM fuel cell stacks. This model response closely resembles the stack response to various stimuli. Finally, this research provides a performance evaluation of two 25 W PEM fuel cell stacks based on a series of tests performed on these stacks in both passive and active mode. The fuel cell stacks exhibited some expected, as well as some unexpected, characteristics.