Simulation of Water Balance at Cathode and Stabilization of Power for Methanol Fuel Cells

On the methanol fuel cell which uses methanol as fuel directly, the important problem to keep high efficient and stable operation is to exhaust water generated in air electrode appropriately and to keep the best water balance without over wetting or drying in air electrode. Therefore, the theoretical equations were introduced to consider the relation between generated water by electrochemical reaction and exhausted water by the flowing air along the air flow direction. By using these equations, simulation on various conditions of operation and structure were made. As a result, the countermeasure to keep best water balance was found as follows. (1) The increasing of water reservation in air electrode with thicker electrode and the increasing of hydrophilic ability by addition of electrolyte were effective and applicable methods for practical use. (2) The reduction of water permeability in electorolyte layer is effective, which was attained by the system with solid polymer electrolyte and without sulfuric acid. (3) Larger air chamber depth and appropriate humidity control of inlet air are effective. However, these methods are limited to use because of the increasing of size and flow-rate.