Batteries and Fuel Cells

Batteries can be classified into primary and secondary types. A primary battery stores electrical energy in a chemical form that is introduced at the manufacturing stage and a secondary or rechargeable battery absorbs electrical energy, stores this in a chemical form, and then releases it when required. The secondary batteries that are widely used currently include nickel cadmium and lead acid batteries that are formed by connecting a number of cells in series. The insulator in nickel cadmium batteries is formed from vertical plastic rods that may be separate or as grids that are inserted between the plates and the separators in lead acid batteries are normally microporous sheets of plastic that are usually combined with corrugated and perforated spacers. This chapter concludes with the discussion of fuel cell that converts the energy of a chemical reaction directly into electrical energy. The process involves the oxidation of an external fuel that is normally a hydrogen-rich gas, and the reduction of an oxidant, which is usually atmospheric oxygen. The two main types of fuel cells being developed at present are the solid polymer electrolyte fuel cell (PEFC) and the solid oxide fuel cell (SOFC).These two main classes are distinguished by the type of electrolyte used by them.