From Treehugger.
Just about everyone agrees that the best way to power a train is with electricity from overhead wires; the only problem is that it is really expensive to install. Even in Europe, which is pretty dense and has a great rail system, as much as 40% of the 25,000 miles (40,000 kilometers) of track is not electrified, and on many of these lines, the demand isn't high enough to ever justify the cost, which can be huge. There isn't only the wiring, but often all the bridges have to be rebuilt higher to handle the height of the catenary wires and pantographs on the roofs of the trains.
European governments want to get rid of diesel-powered trains as part of the fight against global heating, so they have been buying hydrogen-electric multiple units (HEMU), which are electric trains powered by fuel cells running on hydrogen.
But there is another player in the game: battery electric multiple units (BEMU) – trains powered directly from giant batteries, which are getting better and cheaper by the day. They are now pushing 75 miles (120 kilometers) in range; Rail Journal quotes Brahim Soua of Alstom, who says “This was not the case several years ago where the level of autonomy was close to 40km. This is thanks to an improvement in the battery’s capability to store more energy for the same mass of battery.” This is good enough range to skip through many non-electrified sections of Europe.
Now Oliver Cuenca of International Railway Journal reports that the battery-powered trains cost 35% less to buy and operate than hydrogen trains. The batteries don't have to be replaced as often as fuel cells, either, so maintenance costs will be lower. Cuenca notes some caveats:
However, the study assumes that only ‘green’ hydrogen made by electrolysis using electricity from renewable sources will be used. In reality, the cheaper so-called ‘grey hydrogen,’ made as a by-product of the chemical and oil industry, will be used in some cases.
The problem is, there is no point in replacing the diesel trains if they run on gray hydrogen, which is made from natural gas and emits 9.3 kg of CO2 for every kg of H2 in the process. The hydrogen-hype people say this is just an intermediate step, that "The plan is that hydrogen will be produced on site via electrolysis and wind energy at a later stage of the project." But as we noted before, "while Germany's renewable electricity supply has grown dramatically, they still get half their power from coal and are closing their nuclear reactors. It will be a very long time before they are making hydrogen from electrolysis."
Unless it was made at night...
"The study also assumes that hydrogen will be more expensive than electricity because electricity is needed to produce the hydrogen in the first place. This may not be true, as electricity used to produce hydrogen generated at night will likely be significantly cheaper due to much lower demand compared with the daytime electricity used when most electric regional trains operate."
Except that if the trains operate during the daytime, they can be charged at night with the same cheap electricity, just like people do with their electric cars. [Well, not quite: most ppl travel less than 100 km per day, while a battery electrc train could do 10-20 tmes that, so will have to charge during the day as well as overnight]And it will store a lot more of that electricity. Hydrogen is a lousy battery; the efficiency of splitting it from the oxygen is now up to about 80%. Then there are losses compressing and cooling it, and then the fuel cell is only about 50% efficient, giving an overall efficiency at the wheels of about 35%. This all might get better with improved technology, but batteries are running at 80% efficiency now[Musk has said that Tesla's batteries were 90% efficient] and they are getting better too. As energy expert Paul Martin notes,
"A technology which uses 3x as much energy as its competitor, at bare minimum, will have a hard time competing—if they share the same energy source. So if H2 is going to be competitive, beware— it won't be "green" hydrogen they reach for. It'll be the only kind you can currently buy—BLACK hydrogen made from fossils without carbon capture. And that's a highly questionable way to "green" a diesel."
See also :Battery-powered electric trains
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