The first hybrid train with a new regenerative braking system is being trialled in Germany. The train will be taking passengers on a 37 km (22 miles) route between Aschaffenburg and Miltenberg.
Most trains can work on both diesel and electric motors, depending on the track, and half of Europe’s train-tracks are electrified, so why haven’t we seen hybrid trains before? This is due to high capital investments, the extreme conditions faced by trains on a daily basis and reliability. All these factors ensure that the development of hybrid trains has been limited mostly to shunting locomotives (called switching engine or switcher in the US), which have particularly high energy losses.
The German train, a Siemens Desiro Classic VT 642 locomotive, which is now the first hybrid in the world taking passengers, was originally diesel powered and equipped with two 275 kilowatt engines. The train has been supplied with regenerative braking capacity and two 315 kilowatt-rated hybrid power packs.
MTU, the subsidary of Tognum, a manufacturer of large diesel engines, has developed the braking system that uses a generator to convert the kinetic energy generated during braking into electrical energy. This electrical energy is temporarily stored in lithium-ion batteries before being used again for starting, accelerating or for supplying electrical loads on the train. The battery packs are placed on the roof, where they are cooled by the air streaming across the top of the train whilst it’s in motion.
The new system is intended to reduce fuel consumption and greenhouse gas emissions by 25%. As the trail-route has 14 stops, the train will have plenty of opportunity to use the braking system and to recharge the train’s batteries.
If the system proves to be a success, the authorities hope that all the existing trains can be converted to hybrids in future.
You can see an animation video of how the train works here