TEMPERATURE AND FUEL DEPENDENCE OF AN EQUIVALENT CIRCUIT MODEL OF DMFC DYNAMIC RESPONSE

Kshitiz Singh, Bill Diong, Diego Estrada, and Bao Q. Nguyen

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Keywords

Fuel cells, methanol, dynamic response, equivalent circuit model,parameter estimation

Abstract

Fuel cells are increasingly important sources of electrical power as they can reduce the world’s use of fossil fuels, leading to benefits such as decreased greenhouse gas emissions and cleaner air. However, their dynamic responses are slower than that of typical electrical and electronic systems drawing power from them. Hence, it is important to properly characterize an equivalent circuit model of the fuel cell’s dynamic behaviour, for performing accurate analysis and optimal design of the power systems based on such sources. This paper describes a method of estimating the parameters of a second-order equivalent circuit model, a first-order model being less accurate, for the direct methanol fuel cell from measurements of its responses to step-changes in load at various temperatures, fuel flow rates and fuel concentrations. Analysis of these parameter values, which provided excellent fits of the test data, indicated that they are quite sensitive to temperature but relatively insensitive to fuel flow rates – more so for load-off than for load-on responses – for the same fuel concentration. Furthermore, different fuel concentrations resulted in greater variability of the parameter values during the load-on responses as compared to the load-off ones.

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