Fuel Cell Systems Explained - from and for SET students

To summarize the irreversibilities due to their importance in different conditions. Concentration and mass transport losses are important only at higher currents. The should bevery small in well designed systems. In low temperature hydrogen fuel cells activation overvoltage and ohmic losses areimportant Fuel cells using mixed fuel, as methanole, the activation overvoltage at anode and cathodedominates. In higher temperature fuel cells the ohmic losses are the major factor.4. Proton Exchange Membrane Fuel Cell PEMFCA PEMFC, also called solid polymer fuel cell, consists of an ion conducting polymer electrolytebonded at each side with a catalysed porous electrode. These membrane electrode assemblies MEAsare very thin and connected in series with bipolare plates. The mobile ion is an H + ion or a proton.The basic reactions are at the anode2H 2 → 4 H + + 4e -and at the cathodeO 2 + 4 H + + 4e - → 2H 2 OThe polymer electrolyte works at low temperature, so that the fuel cell can start very quickly.Further advantages are, that the design can be very compact, no corrosive fluid hazards are used andthe cell works in every direction. This means that the PEMFC is very suitable for a wide range ofapplications, like vehicles and portable electronics, but can also be used in CHP power plants.Similarities for applications: electrolyte electrode structure and catalystDifferences for applications: water management cooling the fuel cell connecting the cells in series operating pressure used reactants