Fuel-cell generator for a private vehicle

We measure the polarization curve of a cell at 80°C, in different pressure conditions, and approximate this characteristic curve with the following equation (ignoring the effect of the concentration overvoltage term)  

V is the cell voltage (F) is the reversible potential at ambient temperature and atmospheric pressure, j is the surface density of current (A/cm ) is the surface density of exchange current (A/cm ) equal to 0.01 A/cm j represents the internal current density, equal to 1 ttiA/cm, . 4 is a constant linked to the influence of the partial pressure of hydrogen, equal to 0.05 V is a constant linked to the influence of the partial pressure of oxygen equal to 0.026 V C is the slope of the Tafel plot equal to -0.06 V r is the surface resistance to polarization, equal to 0.3 Qcm.  

The MEA technology used enables us to industrially make maximum surfaces of 250cm, for a nominal current density of 0.6 A/cm. We wish to make a 50 kW fuelcell generator to drive a small vehicle, hybridized with a battery. The anode is fed with pure hydrogen with an equivalent coeffident of overstoichiometry of 1.05. The cathode is fed with 100% humidified air, with a factor of overstoichiometry of 2. The gases enter into the cell at 80°C, at a pressure of 1.3 bar. The cells are considered to be isothermal at 80°C. 

The saturating vapor pressure at temperature T[K) can be approximated by the Clapeyron equation  

Calculation of the partial pressure of water equal to the saturating vapor 

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