Energy

Hydrogen vehicles

In this sector both internal combustion engines and fuel cell engines are being developed. The latter are essentially important in order to obtain a transport system with a minimum environmental impact. In the first case, the engine has cylinders and pistons, it burns hydrogen instead of petrol or gas oil and does not force to review the internal combustion engine technology. In the second case, fuel cells produce power and supply electric engines. One of the advantages in the use of fuel cells for vehicle propulsion is their energy performance. In fact, 50% of the energy produced by the fuel can be used to move the vehicle, while with petrol engines the maximum percentage amounts to 40%. Moreover, in urban traffic, energy performance of hydrogen vehicles is twice as much as traditional cars. Finally, exhaust materials only consist of aqueous vapour, therefore with no environmental impact. Hydrogen is supplied to the vehicle cells from a tank where it is kept in liquid or gaseous state. As an alternative, it can be extracted from hydrocarbons, such as methane or methanol, directly on board, through a reformer. At present the possibility to use sodium boronhydride and sunflower oil is being evaluated. The characteristics of fuel cells allow to build vehicles of different dimensions (from bicycles to cars, buses, locomotives) by using the same technology and with a similar performance, consumption and environmental impact. At the moment many car manufacturers are making experimental models of hydrogen cars and buses (see image). Some prototypes are already circulating in several Italian and foreign cities. The problem related to the development of hydrogen vehicles, as well as the production of this fuel, is that there is no distribution network and there is a lack of refuelling stations for this gas. Today hydrogen refuelling stations are very rare. The only two are in Berlin and Munich, and a third one is being built in Milan, close to Bicocca “fuel cell” plant. Among technological problems, one of the most critical difficulties is the storage of hydrogen on board, as it heavily affects the autonomy of the vehicle due to the excessive weight and tank volume.