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This fuel cell is a matured in technology and commercially available. PAFC has platinum or platinum alloys used as the catalyst at both electrodes. The stack consists of a repeating arrangement of anode and cathode. As the freezing point of phosphoric acid (H₃PO₄) is 40 °C, the PAFC must be kept above this temperature once commissioned, to avoid the thermal stresses. For PAFC, water cooling is used for larger power generation systems [6, 7]. The operating current densities are 150 to 400 mA/cm. The operating cell voltages are 600–800 mV. The ohmic losses in PAFC are quite small. The ability of PAFC to sustain impurity and its voltage–current and power–current characteristics makes it highly suitable for micro-grid. Figure 2.2 shows typical characteristic of PAFC plotted for 1 kW stack. Figure 2.3 shows the average cell voltage vs current density of PAFC after testing for 50 and 250 h [2].