Do Hydrogen trains ever make any sense?
Hydrogen has long been touted a a possible "zero emissions" fuel.
A few weeks ago, my Twitter timeline got filled up with talk from Alstom of its Coradia iLint hydrogen multiple unit train driving nearly 1200 kilometres on onboard hydrogen, and this raised a question that I’ve always found interesting — does hydrogen for trains (or other vehicles) actually make any sense? Why are we still so fixated on it while batteries are showing so much promise?
My thesis is that our mobility future does have hydrogen as a part of it, but that it’s also important to acknowledge where it makes sense when compared to other zero-emissions energy technologies, and well, to stop calling hydrogen zero-emissions, because it does have emissions — just not harmful ones!
Weaknesses of Hydrogen
So hydrogen is not actually a power technology (big surprise there), so when people talk about hydrogen cars, or in our case trains or buses, what they are really talking about is a vehicle that uses a Hydrogen Fuel Cell (HFC) to combine oxygen from the atmosphere and Hydrogen stored onboard to create power.
Unfortunately, herein lies one of the issues with HFC trains and buses compared to even just pure battery — there is additional complexity. Much as with a diesel-hybrid vehicle, an HFC vehicle has an onboard battery that is used for things like regenerative braking and propulsion, while the HFC is used for charging the battery. This means that you’ll have a battery just as a battery vehicle would, but also fuel cells and hydrogen tanks and fuelling components.
At the same time, some of the common criticisms of batteries like their expendability and use of rare earth materials also apply to fuel cells! There is also the issue of the hydrogen itself being well — hydrogen (insert Hindenburg joke here)! Not only is hydrogen flammable, it’s also stored under extreme pressure — this isn’t actually all that novel (Compressed Natural Gas vehicles are a thing) but it adds complexity!
Theres also the issue of actually getting the hydrogen. As you probably know from high school science class, you can get hydrogen by splitting water using electrolysis, and this is the way green hydrogen is made. Unfortunately, electrolysis plus the rest of the energy stack makes turning electricity into hydrogen and then back into electricity quite a bit less efficient than just storing electricity in a battery. This means it’s attractive to get hydrogen from less green methods like reforming natural gas — which releases carbon monoxide. We also just don’t have hydrogen infrastructure readily available, from fuelling stations to transportation, which are all things we do have to varying extents with other zero-emissions technologies.
Strengths of Hydrogen
Of course, I wouldn’t be writing this article if I thought it was all bad — so whats the secret?
Well, hydrogen has one really valuable feature (besides having zero harmful emissions when used on a train or bus) — storing it for medium to long periods of time is entirely doable, and this means that you can really stockpile it. This is really valuable because there are already times — particularly in places with lots of renewables — where more power is being generated than can be used. Even if electrolysis is inefficient, losing fifty percent of your energy is a lot better than one hundred percent! At the same time, as costs continue to drop precipitously for renewables like wind and solar, the cost of hydrogen produced by them might actually pencil out quite well.
As is usually the case, you can spin a lot of the “negatives” of hydrogen as positives. For one, the fact that it can be created by reforming natural gas means the traditional fossil fuel energy industry actually has a way to produce and sell hydrogen. While this might seem bad, it’s possible to actually move to green hydrogen unlike with gasoline for example, and that will probably happen pretty quickly anyway given the climate imperative and the falling cost of renewables. Traditional energy companies might well also subsidize the creation of new uses for their hydrogen, which could then be later used with green hydrogen.
There are also much more practical on-the-ground benefits to hydrogen. For one, compared to charging, hydrogen refuelling can be much faster without having to be weighed against the potential damaging effects it would have on the energy storage onboard a vehicle, and for that fast refuel, it seems hydrogen vehicles still have a substantial range advantage compared to battery electric. At the same time, a fuel cell vehicle is still fundamentally using an electric architecture, so dual mode vehicles using overhead line power for extended range is entirely conceivable (though probably not necessary).
Distribution is an issue with hydrogen, but the good thing is for applications such as with fleets you can produce hydrogen onsite with an electrolyzer and renewables, and this would not be all that different from how a compressed natural gas bus fleet is fuelled (and we already have a lot of those!).
Use for Transit
Now, how do the features and bugs of hydrogen look in transit applications? Well, while I am not convinced hydrogen is likely to be a great solution for urban buses or trams where overhead wires plus some batteries will work fine, I do think long distance coach buses would be a prime candidate for hydrogen given the range. Hyundai actually showed off such buses at the 2018 winter olympics, and hydrogen buses were also used in the 2010, 2012, and 2020-errrr-2021 games.
Another long distance mode of transport where hydrogen seems like it may be promising is ferries, given boats can generally need substantial energy storage capacity.
I also think it’s clear that a lot of rail service — be it rural in Europe or Asia, or Intercity and Regional in the Americas — hydrogen based electrification is a workable solution, especially because it should legitimately be less complex to install; it will probably have a cost advantage on most lines without frequent service in the longer term.
In North America in particular, hydrogen electrification will probably be doable long before we can electrify most of our intercity (not to mention freight) rail by conventional means — both from a construction capacity and cost perspective, and the electric architecture again does not preclude that eventually happening if it makes sense or if we figure out how to build things for reasonable prices. It’s also probably the case that, for less sophisticated operators, the concept of having trains you refuel is probably less of a lift than OHLE even if I don’t like it. At Innotrans this year, Stadler and Caltrans unveiled they were deploying more hydrogen FLIRTs for use across the state of California, and so we actually might see some more hydrogen rail services running in North America in short order (the original hydrogen Flirts are for Metrolink’s Redlands rail service).
That’s another exciting element of the whole hydrogen rail thing, though similar things are true for buses - there is just way more manufacturer support these days. Siemens, Alstom, and Stadler all have similar regional multiple unit trains that run on hydrogen, and other manufacturers like Hyundai and CRRC also having offerings. The fact that there is actually choice appearing in this market is exciting.
It's the clean production of hydrogen that's half the problem, and its large electrolysis energy loses that's the other half of the problem, which is investigated in more detail in my article https://www.londonreconnections.com/2021/hydrail-breezes-in-the-uk/. Unfortunately, very few places in the world have surplus energy to produce green hydrogen consistently.