Alkaline fuel cells

These are devices in which the electrolyte is an aqueous solution of sodium hydroxide or potassium hydroxide. The oxidizer is nearly always oxygen (or oxygen in the air), while the fuel is almost always hydrogen gas. However, if the by-product oxides were efficiently removed and the metal was supplied constantly as a strip or as a powder, zinc or aluminum could be utilized as an anode. Fuel cells are made of metal and some polymers and work at temperatures below 100 degrees Celsius (212 degrees Fahrenheit). Carbon and a metal, such as nickel, are used to make electrodes. Water must be removed from the system as a reaction product, which is commonly done by evaporating the electrolyte via the electrodes or in a separate evaporator. The operating support system has a serious design flaw. Most plastics are attacked by the strong, hot alkaline electrolyte, which also tends to penetrate structural seams and joints. However, this issue has been solved, and alkaline fuel cells are being employed aboard US space shuttle orbiters. Depending on the fuel and oxidizer used, as well as the calculation method used, overall efficiencies range from 30 to 80 percent.