Operating Conditions of PEMFC

Modern polymer electrolyte membrane fuel cell stacks are basically intended for high energy densities at the electrodes (up to 0.6 W/cm ). For this reason, and also because of the compact design, the maximum values of the stacks specific power per unit volume and weight are higher for them, than for all other batteries of conventional type. Often, polymer electrolyte membrane fuel cells are used as well for operation at lower energy densities. 

The working temperature of a polymer electrolyte membrane fuel cell is about SO C. The reactant gases are supplied to the battery at pressures of 2-5 bar. This relatively high pressure is needed because, in order to prevent drying out of the 

The thermodynamic electromotive force of a polymer electrolyte membrane fuel cell at a temperature of 25°C is given by e = 1.229 V. The open-circuit voltage (OCV) of a hydrogen-oxygen polymer electrolyte membrane fuel cell has values between 0.95 and 1.02 V, depending on the temperature and gas pressures. 

PROTON-EXCHANGE MEMBRANE FUEL CELLS (PEMFC) 

All these processes must be controlled quite carefully. If water withdrawal is too fast, then there is a risk of water loss from the swollen membrane, which not only leads to a drastic raise in resistance but also to fragilization. Cracks may then develop across which the gases may mix, yielding an explosive mixture, with all the catastrophic consequences that ensue. 

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Fig. 10 A simplified onedimensional picture of the concentration distribution of reacting species across MEA in the operating conditions of PEMFC. (View this art in color at www.dekker. com.)...

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