Railway: Railway experts: Overhead line is the best solution

When looking for a climate-friendly replacement for the smoking diesel locomotives on Germany’s railway lines, railway experts believe that the familiar overhead line is the best solution. The alternative train drives hydrogen, batteries and vegetable oil are therefore considerably more expensive. In addition, the ecological balance of hydrogen and vegetable oil in particular is in doubt. “Electrification with overhead lines has the best efficiency,” says Professor Markus Hecht from the TU Berlin.

According to the Allianz pro Schiene, only 62 percent of the federal rail network in Germany is electrified. By comparison, Switzerland is the model for Europe, as the entire rail network there is electrified. Austria, Italy and the Netherlands are also further ahead, with more than 70 percent of their rail lines each electrified.

Expensive hydrogen trains

Bavaria wants to start the long-planned test operation of hydrogen trains in the Allgäu region in the autumn. “Bavaria should be climate-neutral by 2040 at the latest. This also means that from 2040 onwards there will no longer be any diesel-fuelled vehicles in local rail passenger transport in Bavaria,” says Transport Minister Christian Bernreiter (CSU). The preferred solution is electrification. For routes without “electrification prospects”, the state government is therefore relying on battery and hydrogen trains.

But skeptics see the high-tech hydrogen trains as political prestige projects. “Hydrogen is the most expensive solution and is less efficient than diesel,” says Berlin rail technology professor Hecht. The fuel cells not only generate water and electricity, but also a lot of waste heat.

Higher electricity consumption in summer than in winter

That is why cooling is a big problem with hydrogen vehicles. “You have to cool a lot in the summer and you also need electricity for the air conditioning to cool the passenger compartments,” says the scientist. “In the winter you can use the waste heat to heat the passenger compartment. That is why it is grotesque that the hydrogen vehicle needs less energy in the winter than in the summer.” Because of the poor efficiency, energy consumption is always much higher than with all other technologies.

The Berlin professor is not alone in his assessment: In 2017 and 2020, the TU Dresden compared the respective advantages and disadvantages of alternative drives in reports for the Bavarian Railway Company. Hydrogen performed worse than batteries, also in terms of the CO2 balance. However, Bavaria is an important chemical location. That is why the state government is planning to build a hydrogen network, which could then also benefit the railway.

Lower Saxony has already tested hydrogen – and then decided to buy over 100 battery trains because battery-powered trains are cheaper to operate. “Battery trains are also much more expensive to operate than pure electric multiple units,” says Hecht. The efficiency is lower and the vehicles are heavier. The battery only has a finite lifespan and needs to be heated in winter and cooled in summer.

Battery trains are also not ideal

“That’s why battery trains can only travel short distances, today it’s usually 80 kilometers. Then there has to be an intermediate charging section.” One solution is hybrid trains: pantograph and battery combined. These trains can recharge empty batteries on sections of track with overhead lines. In Germany there are routes with many tunnels that date back to the steam locomotive era – too narrow for overhead lines. “There, the costs of converting the tunnels for the overhead lines can be saved by driving battery-electrically,” says Hecht.

Used cooking oil – from the fryer into the tank

The third option: used vegetable and cooking oil as a replacement fuel for diesel locomotives, known in technical jargon as HVO 100. Since diesel locomotives can also run on French fry fat without major technical effort, this has the advantage that no new locomotives have to be bought: “Diesel vehicles can be operated with the climate-friendly fuel without complex conversions,” says a spokeswoman for DB Regio Bayern. “This means we can continue to operate them until the end of their service life, protect the climate and save resources.”

However, there are doubts about how climate-friendly HVO is. “When HVO is burned, just as much CO2 escapes from the exhaust as with diesel,” says Hecht. “The environmental benefit only comes from the certification of the HVO fuel. This proves that the fuel comes from biological material, that all the CO2 that comes out of the exhaust was previously absorbed from the air.”

But there are two major drawbacks: “The certificates can be fake, and then there is a scandal all of a sudden. And the second is: you don’t know what would have happened to the material otherwise.” The concern is that the HVO fuel for trains in Germany could then be replaced elsewhere by coal or oil or other CO2-emitting material.

There are also practical concerns. “Although HVO has an environmental advantage, it is currently around 30 percent more expensive than conventional diesel,” says a spokesman for the Lower Saxony Ministry of Transport. “In addition, the engines must be approved for the new fuel and sufficient availability must be ensured. This is difficult or sometimes not possible, especially with older engines.”

The permanent solution will be electrification

The passenger association Pro Bahn sees HVO as a temporary solution. “We can’t eat as many fries as it would take to convert all diesel vehicles,” says Bavarian state chairman Lukas Iffländer, who is a computer science professor at the Dresden University of Applied Sciences. Compared to hydrogen, however, HVO is the more sensible temporary solution for dual-fuel locomotives with diesel engines and pantographs.

With increasing electrification of the rail network, Iffländer believes that hybrid drives with batteries and pantographs will also be a practical solution for freight transport. “We therefore assume that fully electric drives will prevail.” Where overhead lines are not available, the range problem will be solved with batteries. “Almost all routes that are still problematic and have regular freight traffic are planned for electrification.”