Start-up Effects in Alkaline Fuel Cell Stacks

Any fuel cell operation relies on successful start. In particular, successful and rapid startup of proton exchange membrane fuel cell (PEMFC) from cold start is of great importance for their commercialization. Unlike PEMFCs, liquid alkaline fuel cells (AFCs) are less prone to freezing problems due to the use of aqueous potassium hydroxide solution as electrolyte. The aqueous potassium hydroxide solution has low freezing temperature which prevents the blocking of pores at sub-freezing temperatures to a certain extent. However, the successful start-up in liquid alkaline fuel cells is subjected to other issues which are not common in solid membrane type fuel cells. In liquid electrolyte AFCs, the only barrier between fuel and oxidant is the liquid electrolyte. If during startup the electrolyte is not fully filled within the electrolyte chamber, the reactant gases can enter into the said chamber and creates gas pockets. This phenomenon is highly non-desirable as combustible gas mixture can be trapped and the useful voltage from the cell declines. Few experiments were designed to understand this startup effect and to prevent the failure. The results show that filling-up all the electrolyte chambers prior to reactant gases entry prevents this phenomenon. Furthermore, a relatively high pressure electrolyte chamber filling at startup evacuates the static air from the chamber.