Fuel cells are the electrochemical source of power where the energy of fuel and oxidizer continuously supplied to electrodes is directly converted into electric power. Since in case with fuel cells no heat conversion into work presents, the power efficiency of fuel cells is significantly higher matched to conventional power plants. There are several types of fuel cells that differ in terms of operation conditions. However the general principle of their action is the same: the fuel (hydrogen) comes to anode where hydrogen atoms become ionized via oxidation electrochemical reaction; oxidizer (oxygen or air) comes to cathode where it becomes combined with electrons passing from anode through exterior electric circuit and protons passing from anode through electrolyte. This results in electric power and clean water generation. In practice, the fuel cells functioning is supported by a variety of interlinked processes including power and mass transfer, heat exchange and physicochemical reactions.