The hybrid train

One of the most debated topics of our time is the use of renewable energies. By definition, energy that can be renewed comprises a circular scheme – energy is taken from a source, the source itself is self-sustainable so that the energy is regained. But how to find such a miraculous energy source and how to supply all our daily necessities with it? In Europe, there is hardly a second country attempting to find solutions to these problems like Germany does. Under the motto “Die Energiewende” (the energy switch), politicians and institutions are pushing forward society’s deep endeavour to run the country on green energy. At least at some point, so people dream, shall Germany be free of nuclear plants. But is there any evidence yet that we could take to evaluate the efforts carried out so far?

The train as an energy saver

Yes there are and we will focus on one in particular. The German Railways, called “Die Bahn”, is Europe’s most extensive train network – carrying more passengers per year than any other mobility service. Thereby, a lot of electricity is required. To power the trains including the electricity needed for the interior and to power train stations, the Bahn uses as much electricity per year as the entire capital of Berlin.[1] So, scientists and engineers pondered over this problem and realised the following: when the train speeds along the countryside, relatively little energy is used up. However, accelerating such as when departing from a station requires the biggest portion of total energy. Therefore, the Bahn developed a hybrid train that creates energy when the train brakes. How does this work? Well, lots of energy can actually be harvested from braking. When the train starts to slow down the remaining velocity can power a generator, which, in turn, produces electricity. The re-gained energy can hence be stored in huge batteries. The train “Desiro” is the first prototype incorporating this technology. But how beneficial is this recuperation of energy? The answer is: very. The “Desiro” uses the braking energy to power the notorious acceleration of the train. Although this only contributes to the total energy required that gets the train rolling again, the “Desiro” needs 25% less total electricity thanks to the battery system.[2] Or in other words, the train takes 25% of the total energy needed from a renewable source.

One step at a time

By the way, experts on electric cars among you may now say: wait a minute, such batteries only function with a sophisticated cooling system. Yes, and that’s why they’re installed on top of the train so that the wind does the job. Cleverly, the Bahn’s plans are to only equip regional trains with the hybrid technology. This is because on some regional journeys, the train stops fourteen times, within less than 40 kilometres and thus a lot of braking and accelerating occurs. Hence the energy consumption is particularly high on these routes whereby the hybrid technology becomes profitable. Germany may still be far away from the full implementation of the “Energiewende” but the ambition and the spirit is evident. Such a process consists of many puzzle pieces anyway and so the “Desiro” may just be one of them.

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