A simple fuel cell model fitting and parameter estimation apriori to the experimental domain of AC impedance techniques.

Fuel cell behavior is characterized by important electric and kinetic parameters such as charge transfer coefficient, exchange current density and ohmic resistance. The quantitative estimate of these parameters by a semi-empirical approach without resorting to the sophisticated and costly methods like AC Impedance spectroscopy is presented in this paper. A fuel cell model that describes voltage-current density behavior is utilized to acquire the fuel cell parameters by using two different kinds of fitting procedures. A set of equations suitable for fitting various regions of voltage-current density variation are proposed and the criteria used to assess the quality of fit is uniformly applied to all the fitting procedures. The importance of leakage current as a parameter is also discussed by presenting improved form of fuel cell model. The model is fitted on the DC Impedance (Polarization) curve experimental data obtained for liquid feed passive Direct Methanol Fuel Cell (DMFC) at different methanol feed concentration and the operating torque. After establishing the applicability of the model and the proposed fitting procedure, a detailed sensitivity analysis is conducted to demonstrate the reliability of the model. The sensitivity analysis, along with an independent parameter sensitivity method is used to study the impact of individual model parameters on fitting criteria. The results showed higher sensitivity ratio (SR) for the model equation as compared to the sensitivity analysis for a given assumed value of charge transfer coefficient. Also, the fitted curve on experimental data shows nearly same Sum of Squared Residue (SSR) for two kinds of fitting procedures. The 95% confidence intervals for all the fuel cell parameters were presented and analyzed. The ohmic resistance and exchange current density obtained by improved form of model equation were validated by the experimental data in the literature. The deviation and dispersion behavior of important parameters of charge transfer coefficient and ohmic resistance are thoroughly studied for various kinds of variation types, percentage of points and the type of method. Finally, the trends of the sensitivity factor based on the value of model parameter were analyzed. The importance of the present model in obtaining valuable information regarding the fuel cell behavior under different operating conditions is presented. [Display omitted] • A simple semi-empirical method for estimation of kinetic and electric parameters of the fuel cell is developed. • Normal equations and well-defined objective function have been used for fitting. • Experimental I–V curve is used for fitting and EIS-ohmic resistance is utilized for validation. • Sensitivity analysis accompanied with parameter sensitivity method are used to establish the validity of the model and fitting procedure. • Estimation of important fuel cell parameters without resort to sophisticated AC Impedance techniques is a novel feature. [ABSTRACT FROM AUTHOR]