ABSTRACT
Our society consumes an important part of the total energy for transporting goods and persons by means of machines based on fossil fuels: cars, trucks, ships, planes, etc. An alternative to
the present gasoline car is the hydrogen car. ™is car uses an electric motor based on a hydrogen fuel cell instead of electric batteries. ™ere are many advantages of hydrogen cars over electric battery and gasoline cars: hydrogen is very abundant and can be produced from water by electrolysis. ™e only emission from a hydrogen fuel cell is pure water. ™e main advantage is that the full recharge times of a hydrogen and an electric car with the same autonomy range, 200 km, are 10 min and about 8 h, respectively, using 110 V (3 h using 220 V). However, the eÀciency of the engine based on electric batteries is slightly larger (72%) than that of an engine based on hydrogen fuel cells (64%). ™e eÀciency of a gasoline engine is smaller (20%). Hydrogen has the highest energy content per mass (120 MJ/kg) compared with any other fuel. Gasoline has a smaller energy content per mass (44 MJ/kg). But it has a larger energy content per volume (35 MJ/L) than gaseous hydrogen at room temperature and 1 atm pressure (0.01 MJ/L) and liquid hydrogen. Electric batteries also have a smaller energy content per mass, but a larger energy content per volume than hydrogen. For instance, nickel hydride batteries have energy contents of 0.11-0.29 MJ/kg and 0.5-1.1 MJ/L.
