Electrochemical device in which the hydrogen is combined with oxygen to produce electricity originating steam and heat. The natural gas is frequently used as a source of hydrogen with air and as the source of oxygen. Once the electricity is produced by a chemical reaction and not combustion, the fuel cells are considered green energy producer. The fuel cell technology is ancient, dating years before the spacial program. The commercial use of fuel cells has been sporadic, meanwhile, the use of fuel cells in vahicles and on buildings as the tendency to grow in the future decades.