The project, financed by the Gipuzkoa Provincial Government, involved using a bicycle kindly provided by the ORBEA bicycle manufacturing company and the pedalling action of which is assisted by a motor. The novelty lies in that the battery power source for the motor is substituted by a fuel cell which, for its operation, only needs oxygen from the air and hydrogen contained under pressure in a small tank. The fuel cell employed is of the PEMFC (polymer electrolyte membrane fuel cell) type, a technology considered to be cutting edge in this field. The fuel cell is, in reality, a series of numerous MEAs (membrane-electrode assembly) layered one on top of each other in order to reach useful power values, given that the voltage generated by each MEA is less than 1 V. Each MEA is made up of an anodic electrode, where hydrogen molecules break up into protons and electrons. The membrane used enables the passage of protons, but not electrons, thus obliging the latter to travel around an exterior electric circuit made up of the equipment itself that is being supplied with power. Finally, at the cathodic electrode, the electrons recombine with oxygen from air, thus producing water. This involves an electrochemical reaction that does not generate any contaminating waste; there is, thus, no combustion. At Cidetec, Centre for Electrochemical Technologies, intensive work on the development of home-grown fuel cell technology, energy sources that, in the not too distant future, will power cars, mobile phones, telecommunication centres, etc.