MODEL RELEASED. Hydrogen car. Technician working on the tank of a low-emission BMW hydrogen car. To keep the hydrogen as a liquid it is stored at -253 degrees Celsius by the 70 insulating sheets of aluminium and fibreglass in the fuel tank. The hydrogen is burnt in a type of conventional vehicle engine. Although nitrogen oxides are formed during the combustion, and carbon monoxide is created from the vaporization of engine lubricants, the main product is water. Photographed in Germany.