Progress always requires energy. Up today, the energy needs have been provided by combustion of fossil fuels and this has increased the air pollution and the emission of greenhouse gasses. Consequently, the greenhouse emission problem could represents a concrete opportunity to promote the high-efficiency design of conventional plants, but also a new approach to energy systems and the consequent dissemination of advanced technologies. One of the most promising energy conversion technology is the fuel cell because it is an electrochemical device in which the chemical energy is directly converted into electrical energy, with low environmental impact. In this paper the losses of the fuel cells has been analysed.