Fuel in a combustion device for releasing chemical energy directly into electrical energy. Battery difference, is that it can be external to the two electrodes are continuously added fuel and oxidizer without charge. Fuel cell consists of a fuel (such as hydrogen, methane, and so on), oxidant (such as oxygen and air), four parts such as electrodes and electrolyte. The electrode has catalytic properties and porous structure to ensure larger active surface. Work will fuel into the negative, the oxidizer into positive, their respective electrochemical reaction at the electrode catalyst in order to gain power.
Released by combustion of fuel cell energy directly into electrical energy, so it has a high energy efficiency, equal to about twice times the efficiency of heat engines. In addition, it has the following advantages: ① equipment lightweight; II noise, less pollution ③ can run continuously about higher output power per unit weight. Therefore, it has been applied in space, in the areas of military and civilian has been shown widely in future.