Scania is developing a hybrid ethanol electric bus for trials in Stockholm in 2008. The engine is a high efficiency diesel engine that runs on ethanol. According to Scania the technology is robust, will last for the normal service life of the bus and is an optimal combination for city traffic, with its constant stopping and acceleration.
Mechanical energy is transformed into electrical energy via a generator. The bus is propelled by an electrical motor, which also serves as a generator when the vehicle is braking. Energy is stored in supercapacitors, which have significantly longer service life than today’s batteries. This essentially means the bus is not so much a hybrid but an electrically powered vehicle with an on board generator. It uses a similar propulsion mechanism to modern diesel electric submarines where a generator charges a battery and the battery powers a large electric motor.