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Performance assessment of proton exchange membrane fuel cell (PEMFC) stack by means of semi-empirical model
The charge transfer coefficient estimated around 0.4In this study, the performance of a 10 kW peak power proton exchange membrane fuel cell stack under different operating conditions was investigated experimentally by its i-V polarization curve. The stack has been fed with pure hydrogen and air and PEM fuel cell stack has active area 200 cm2 and is composed of 75 single cells. The stack was tested for different reactant inlet temperatures as from 50 °C to 65 °C with 5 °C intervals keeping constant other conditions and for different relative humidities as 75%, 85% and 95% again keeping constant other operation conditions. Then the analytical nonlinear model adapted to describe the polarization curve has been discussed. Model parameters have been simultaneously estimated by fitting data into model by using LABFIT nonlinear regression program. These parameters are the cathode exchange current density, charge transfer coefficient and polymer electrolyte membrane internal resistance. The polarization curve of the fuel cell stack showed the stack performance improved from 50 °C to 65 °C temperature with the decrease of voltage losses. However the decrease of relative humidity from 95% to 75% did not show any explicit effect onto stack performance. Data fitting was obtained with reasonable model parameters in accordance with literature and with high coefficient of determination (R2) values. The effect of temperature on model parameters was also investigated. The cathode exchange current density value increased from 2.247X10-6 A/cm2 at T=50 °C to 5.643X10-6 A/cm2 at T=65 °C. The charge transfer coefficient estimated around 0.4 coherently with literature. The membrane internal resistance value followed the slightly decreasing tendency with increasing temperature as the value around 0.1 cm2.