According to Siemens, all city buses equipped with the new hybrid drive system they released, Elfa (a combination of electric motors and a diesel engine), consume 33% less fuel compared to conventional buses.
The diesel engine from the Elfa system drives a generator that uses power electronics to provide energy to one or more drive motors. Normally, the rear axle is powered by the diesel engine via an automatic transmission, but the new system seems to be more efficient.
The electric motors also feed electricity back to the batteries, acting as generators during braking. This way, the vehicle powered by the Elfa hybrid system generates fewer emissions. The full-electric mode range can vary from a few hundred meters to several kilometers, depending on battery capacity.
As the company said, combined with a clever power management system, Elfa reduces the noise and also the fuel consumption, being able to save around 10,000 liters of diesel at 60,000 kilometers a year.