Instead of a combustion engine, the SauberBus uses fuel cells to produce the energy required to propel it. This is generated by an electro-chemical reaction. Hydrogen and oxygen are fed in to different sides of the fuel cell (anode and cathode). Direct contact between these two elements is prevented by a proton exchange membrane (PEM), which only allows the hydrogen atoms to pass through it. The electrons take a circuitous route and flow as electrical current through an electric conductor. Among other things, the buses' electrical wheel hub motors are driven by this current. The only by-product from this reaction is created on the other side of the membrane by the reaction between the hydrogen-protons and -electrons, and this is water vapour. Oxidation of this kind is known as "cold combustion", as it takes place at a temperature of around 80°C.
The benefit of fuel cells is that they convert chemical energy directly into electrical energy. Unlike in conventional motors, no detours are required due to extremely high-loss combustion processes. Losses in energy are saved as a result, with efficiency levels of up to 60% being attained. The efficiency levels of this method are almost twice as high as for petrol- or diesel-driven motors.
Fuel cells are energy converters. When fed by hydrogen and oxygen, direct electric energy is produced. This means fuel cells can be used to propel the buses and to keep their doors, lighting and air conditioning supplied with current.