Not as green as 25kv overhead
And those tanks take up a lot of room.
Hot on the heels of commercial aviation, Britain's rail industry has hailed planned trials of a hydrogen-powered train as "welcome news". Converted out of a 1980s electric train that was displaced from the unloved Bedpan line's* rolling stock, the Hydroflex train ignores its 25kV overhead electrical wire pickup in favour of an …
No downvote, but the "green energy to production hydrogen" is at best a miniscule part of the problem.
Industrial hydrogen production follows from coal gassification, steam reforming of natural gas, and oxidizing methane. All of these are highly energy intensive and filthy.
This is green washing.
Perhaps there is scope for scaling back those carbon sources, whilst scaling up the use of excess power from sustainable sources.
Who knows what is possible when people put their minds to it and theirs money to be made. Not to mention the possibility of catastrophe around the corner if we all just sit around moaning and harking back to 'the good old days' when cheap children got stuffed up chimneys and orphans kept the navy and the army well supplied with expendable muscle.
Clean, industrial scale hydrogen could come from electrolysis from excess wind and solar rather than reforming methane (which is, as you say, a bad thing).
The principle problem for hydrogen is storage and pipelining it to where it's needed; for it leaks through the interstices of just about everything. Also, if there is any sulphur and water present (reasonably likely!) hydrogen will very conveniently turn itself into a virulent corrosive that will eat your system from the inside out.
Powering stuff by hydrogen is fine, which these tests prove. Bulk scale transportation and storage are horrendous problems however and I'm not convinced anyone is really researching them in anger.
I am not sure if storage and transport is really unsolved, the European pipeline network for natural gas is already in place. While hydrogen molecules are smaller than methane the loss shouldn't be too bad.
Don't quote me on the exact figures but something like 5 % hydrogen is already completely fine in natural gas and the current actual amount is more like 2 %. Why not topping it up with otherwise wasted energy from wind mills? Many mills have to be stopped quite often because the electricity is not consumed, why not use the excess energy for electrolysis?
Natural gas is easy in comparison to hydrogen. The problem with hydrogen is that the molecules are so small that they can pass through just about any material used to enclose them. It also is quite reactive (which is why you don’t find pure Hydrogen on earth in nature - it has always reacted with something else). Natural gas is hydrogen bonded to carbon, which both helps stabilise it and forms a much larger molecule that can be contained with much less trouble.
>Natural gas is hydrogen bonded to carbon
Obvious solution is to combine the hydrogen with carbon = green carbon capture tech
Then distribute the resulting methane safely by pipeline into tanks on the train = simple existing technology
Use solar, wind or reliable nuclear electricity sent over low-loss 25KV overhead lines to split the methane into carbon and hydrogen. the hydrogen can then be fed to the fuel cell.
A future Britain could then develop some technology to allow trains to be powered by the waste carbon byproduct
"You may as well have sent electricity over power lines than pumped hydrogen gas in whatever form, the losses involved are much lower."
Yeah, I was thinking along similar lines. Why would there be a need to pump hydrogen around the country when the wind power produces leccy which can be sent to the power stations where they can use the excess to store hydrogen ready for peak times and pump it through fuel cells to convert back to leccy.
I'm not convinced that hydrogen is the answer, but I'm even less convinced that pipelines and local or mobile storage is the answer for the various leakage and brittle metal reason already mentioned above. Larger, more central tankage, (possiblely glass lined?) might be doable.
Clean, industrial scale hydrogen could come from electrolysis from excess wind and solar rather than reforming methane (which is, as you say, a bad thing).
Unfortunately no, it couldn't. Electrolysis is inherently inefficient - except at very low rates, when it is endothermic and therefore effectively over 100% efficient if you are only paying for the electricity. On any industrial scale the round trip from electricity to hydrogen (electrolysis) to electricity (fuel cell) is about 50% efficient, which is a grotesque waste of the useful energy in electricity
It may be wasteful of energy, but it is clean. If we want net zero; lossy hydrogen storage procured from excess renewables is an option.
There are experimental facilities running such capabilities up already in Germany - if they are able to turn a profit on margin trading that's a good thing.
Also, consider what happens when there's an excess of Wind in the UK at the moment. The market arrangements are such that consumers via the ESO are paying the wind farm to switch off! Better to throw that cash at a storage facility than the windmills for delivering zero (at that time!)
Better yet reinvent the energy market, but that requires a competent government.
Hydrogen at moderate pressure is not difficult to transport - those of us old enough to remember the old coal gas in the UK may not have realised it was about 50% H2, and about 10% CO and the rest methane,ethane and other odd bits of H and C etc . While leaks were indeed a thing, as they are with methane, the carbon monoxide was the most dangerous aspect in terms of accidents, when coupled with meters that cut the gas off, until you put a coin in, and when you did, the gas just came back on again immediately . Leaking through the sides of pipes and valves, at least at low pressure, is no worse than methane. At hundreds of bar, as you may need for storage, another matter altogether - and at high pressures leaks can self ignite as well.
For bulk transportation in the kinds of energy quantities used in the UK, on a network comparable to the existing national gas network, you are talking about a system that needs to run in the range 50 to 100 bar. Leaky networks are a fact of life; but a hydrogen leaky network - good luck getting a safety case together for that - it's both a lot more leaky (through the steelwork never mind just at flanges) and a lot more explosive.
New materials are needed for operating at those kinds of pressures and bulk volumes that, right now, do not exist.
There are probably better ways to use excess elecricity on a local basis than pay for yet another pipeline network on unproved technology...
That maybe the case currently however the article states that the overall impact of using hydrogen is better than diesel taking refinery to point of use. The production impact of fossil fuels is often conveniently forgotten.
It may not be perfect but work done now will pay dividends later. Anything that moves the focus from batteries to something that can be refuelled in minutes has to be worthwhile.
They are IDIOTS! Some prof at a Canadian University 15 years ago was really big on Hydrogen.
He suggested that "they" produce Hydrogen from electricity at those big Mega/Tera Hydro dams in northern Québec. And then?
Why they then pump the hydrogen though pipes 500 KM to Montréal and then use it to- wait for it...
We make clean electricity! No pollution!
Hello, PhD idiot! We already have these pipes! They are called WIRES!
I kid you not: The guy was a senior PHYSICS professor at a major Canadian university. He MUST have had tenure...
If I had been in charge of that university, I would have used the Saddam Hussien method: had him taken out behind the student union and shot.
Remember the video (about 20 years ago - it might still be on YouTube) by the engineer who wanted to see just how quickly he could get his charcoal BBQ roaring hot after lighting it? As usual, the wife must have been impatient...
So he tried pouring liquid Oxygen on the BBQ after lighting it.
Gee - those BBQ coals were hot and ready in 3 seconds! Unfortunately not much of the steel BBQ (or was it a hibachi?) was left to put your steaks on.
I assume this is the kind of video you (and I) desire.
An off the wall thought here, why not use a "tender" coupled to the back of the train to contain the fuel cell, then it can be uncoupled and moved into a recharging yard overnight, ready to be coupled to another train next day. I'm sure that having several tenders for each train would be more cost effective that having several trains sitting idle whilst being recharged. Just a thought.
How long does it take to "re-charge" a gas tank? Although the tender idea might be better than underbelly tanks from a safety and maintenance perspective. We already know hydrogen makes metals brittle so the tender may have a much shorter lifespan than the train.
Why not try using an overhead wire (as in a trolley) to provide electricity to the train?
This electricity could be used to "crack" water (Hey! The oceans ARE FULL OF IT!) provided to the engine, in much the same manner as was provided to Steam Engines 100 years ago. Don't knock this. - it is tried and proven!
The H2 could be used to power the fuel cells with their exotic platinum catalysts! These would then drive ELECTRIC MOTORS at each wheel! Any oxygen produced (I'm told there may a bit of it) could be captured, bottled, and used to treat elderly people with asthma, and those unfortunates with Covid-19.
It's a Win-Win-Win-Win! And a 5th Win for good luck!
Suggest this method to your local politician or MP. I bet
he.. uh, she will most certainly go for it! After all, It's HYDROGEN!
It would be certainly better to install more overhead lines but they are not cost effective on sparsely used branch lines: Those are typically only feasible with diesel trains. While the hydrogen cycle is far from perfect (still mostly sourced from natural gas iirc) fuel-cell powered trains can be theoretically operated more green.
A few hydrogen-powered LINTs are used in northern Germany* and the most noticeable and positive experience using them was the silence. The same type of train with diesel engines is so fucking loud compared to the fuel-cell version.
*) not my part of the country, no idea if they have now more than the couple of test trains
A few hydrogen-powered LINTs are used in northern Germany*
They've also been testing a hydrogen-powered iLINT in the north of the Netherlands, resulting in an intention to order them as replacements for the diesel units currently servicing the lines in Groningen province.
Quietness is NOT a virtue when discussing thousands of tons of steel and plastic moving at significant speeds.
You may well blame "the idiot yoof" for having their earbuds in all the time, paying primary attention to their phones, etc, but like it or not that's the way things are done nowadays. Attempting to modify the public's behavior by commandment is nearly impossible, even when the behavior in question is transparently idiotic - see also Covidiots refusing to mask up, or wearing them in the "does not understand science" position with their noses wholly uncovered.
It takes truly draconian measures to change public behavior by decree. And while, frankly, I am all in favor of getting so draconian that Vlad Dracul rises from his crypt, points at you and gives a thumbs-up in BREAKING the Covidiots of their Covidiocy by force, it seems to me that it's a wholly wasted effort to employ legions of rozzers with insulated scissors to roam the breadth of the land looking for earbud cords to snip - and airpods to seize.
> Quietness is NOT a virtue when discussing thousands of tons of steel and plastic moving at significant speeds.
The thing is still a train... The fuel cell variant is comparable to an electrical unit of similar size, not as quiet as, say, a cat hunting mice.
"Quietness is NOT a virtue when discussing thousands of tons of steel and plastic moving at significant speeds."
I had a shop near some busy freight lines where the trains were usually accelerating. The diesel exhaust note resonated really well with the inside of the building to the point where it was quieter outside than in. I'm dead certain that a pure electric train would have been much better.
"It would be certainly better to install more overhead lines but they are not cost effective on sparsely used branch lines:"
That's where a battery tender car could be a good fit with recharging from the overhead lines when available. A diesel generator could be a backup, but I'm not sure there is a branch line long enough to make those necessary in the UK. In the US, China or Russia, it's likely going to be needed at least in the short term.
The third rail stops either side of the crossing. Same goes for points - and nothing is as complex as those outside Waterloo or London Bridge. EMUs are long enough so power is still being picked up down the line. Remember all of England south of the Thames with the densest electrified network of lines gets its power this way (apart from HS1) .
Maybe some kind of hybrid supply, with batteries or fuel cells to power the set in tunnels and on longer bridges too low to fit an overhead wire; it should be able to coast through shorter tunnels and bridges, although they should be able to deal with getting going from a full stop in those places.
Tunnels and bridges are expensive, but this is a very long twitter thread on why electrifying them beats coasting: https://twitter.com/25kV/status/1187817155385090048
Basically: making coasting work safely and reliably is a pain in the arse which lands up costing as much as electrifying the section.
Using batteries for discontinuous electrification is also under active consideration and a test train which does exactly that ran for a while. One example is: https://www.railway-technology.com/projects/independently-powered-electric-multiple-unit-ipemu-essex/
Hydrogen is rather covered by the original article, but the applications for which it's being considered are much more "discontinuous electrification" and not really actually looking to replace OLE at all, despite the wording of the article. OLE is always better, but historically in this country we a)built lines before it was an idea then b) didn't spend the money adding it, so now adding it will be very expensive and disruptive. It's a good idea though.
It does make the pantograph pickup more complex and, if it fails to lower, prone to being ripped off by low bridges or tunnels (the default method being to use spring loaded pressure to push up against the variable height of the overhead line)
About 3 weeks ago, Politico-EU did a piece about the French planning to use their nuclear reactors to produce Hydrogen.
Seems to make sense, in that the reactor provides electricity for peak demand, and produces Hydrogen off-peak, so can be run at a steady output.
On-board power (be it diesel or hydrogen) makes the trains independent of overhead lines (or ground rail), as noted by others.
So no cost to electrify the lines and no on-going maintenance of the overhead lines. Also, no visual intrusion. It's worth noting that overhead lines do come down on occasion (due to weather or fault with the catenary), which then puts a delay until the line can be re-opened.
Further, the overhead lines are a distinct health and safety hazard, and while generally safe in operation, doing without them (all other factors being equal) is safer.
Yes, I was going to suggest standard nukes for electrolysis, but the real win is with a very high temperature gas reactors. Japan is leading the world in VTGR technology right now, but the UK atomic energy industry is far more than capable of giving this a go. My own county not so much.
Above 900DegC process temperature, one can use a closed cycle utilizing iodine and sulfuric acid to split water into H and O. Basically one uses the Bunsen reaction for hydrogen iodide and sulfuric acid production; the iodine and sulfuric acid are recycled in the process, minimizing waste. Carbon has no role in such a system.
The extremely high process temperatures from a HTGR/VTGR can also potentially make other processes that thermodynamically disadvantaged under "normal" circumstances economical. Examples include cracking of non-recyclable plastic crap into useful hydrocarbons, detoxifying waste streams, and so forth.
Mines the one with the borated polyethylene foam blocks in the pocket. Thanks!
Oh, gimme a break!
All that hydrogen? Install a small Tokamak. It could probably fit under the engin., uh.. the TRAIN-DRIVER'S seat! And would easily power the train, as well as even heat the whole train!
Any excess electricity could easily FED BACK via the overhead wires to power the train-station, nay, even the whole primitive village that the train just left from.
From my North-American Acorn-TV subscription, I have noticed that there are many such derelict villages in England!
Why, in Canada, we have installed many, many Tokamaks that now power our Eski... uh,, I mean- our "First Nations" Cities!
Ah yes, the Snow Hill line. I moved into a house on Farringdon Street which had a 12-foot chimney from the line passing through it, occasionally inspected by a BR steeplejack. The real surprise was that, in the deepest winter, the house somehow conspired to be colder than outside. Well, that and the unexpected mercury leak from a disused basin U-bend.
ANYTHING is good news, given... brexit :)
Yesterday I saw a man doing rounds around a hill in a jetpack, today hydrogen-powered train, I wonder what tomorrow shall bring, wide availability of covid-testing for UK population?! Flu jab? Boris resigns? My head's spinning :D
'In the next 20 years'. Hydrogen has all sorts of problems. About it's only redeeming feature is burning it or consuming in a fuel cell produces only H2O.
It's a small molecule so it leaks much more easily than methane or propane.
It's light so the energy density - Joules/kg - is low, also see next point - storage cylinders are heavy.
It won't liquefy easily so practical storage is just gas at pressure, so energy density - Joules/litre - is low
No distribution infrastructure so that's a large capital cost to get it going.
I saw the BBC report - said it took most of the day to fill it with enough H2 for 100 miles... Admittedly it's still an experiment but it looks very much at the 'alpha' stage. Certainly nowhere near the basis for production.
> No distribution infrastructure so that's a large capital cost to get it going.
If they use electrolysis to provide the hydrogen then they only need to run a power cable along where the tracks go as that is where the trains are. Better still, they could run that power cable overhead to save digging up the track!
"We've made it slimmer and tidied up the navigation bar. We felt the previous masthead was quite chunky and took up space -- no, not just for ads but also articles."
Considering almost everyone has widescreen displays these days, why not try a paradigm shift and have a vertical "masthead" up the side? Many of us are short (pun intended) of vertical space but have horizontal space to spare.
Hydrogen powered fuel cells are a bit pie in the sky because hydrogen is tricky stuff to store and distribute. A far more economical way of cleaning diesels is to run them on natural gas. I've seen this everywere except the UK; where I live CNG is used to power buses and trucks that are used in urban environments (such as the trash pickup that's just happened).
Methane is naturally occuring and needs to be processed because its a powerful greenhouse gas.
Looking at the video on the BBC website the hydrogen and fuel cells do take up a whole carriage, but if this were to covert a diesel-electric loco such as a class 88 to run of hydrogen I guess this could all fit inside the locomotive and could then be used for freight as well as passenger routes
Hopefully science can work out to produce hydrogen cleaner and store it more densely to make hydrogen more viable as a replacement fuel.
The inside of the carriage is dominated by Fuel Cells, tanks and a massive battery pack to smooth out spikes in demand. They picked this class of loco, because it had a handy power bus that wasn't a million miles from the voltage kicked out by the fuel cell if I recall correctly.
The target is 2021 for getting that lot under the body where diesel tanks etc reside.
Source: I'm in the same research group, but haven't worked on it.
I'll post it as nobody else seems to have done yet.
Network Rail's recent proposals for Traction Decarbonisation (PDF - link below) proposes only about 1,300 Single Track Kilometeres (STK) of the network would be served by hydrogen fuelled passenger trains, as against 13,000 STK proposed for electrification For the rest of the currently un-electrified network, perhaps 800 STK for battery operation and 300 STK where they can't make their minds up yet.
Energy density means that hydrogen is unlikely to be viable for main-line freight and future shunting locomotives are likely to be plug-in electric and battery.
They are referring to the Snow Hill tunnel, which I think crosses the River Fleet at some point. These links may help:
http://www.adeadendstreet.co.uk/2014/11/river-fleet-cso-london.html < amazing images here
"It's light so the energy density - Joules/kg - is low, also see next point - storage cylinders are heavy."
wrong. Energy per Kg is 3 times higher than gasoline fuels. The fuel-cells are 3 times more efficient than an iCE engine, so in mass terms it's a very good energy store.
Then the storage issue. LPG is kind of scary, methane tanks no better and petrol has a nasty habit of forming dense explosive vapour clouds. Anyone want to drop their lithium batteries in water?
All energy stores have issues. Some are just more familiar than others
I came here to say the same.
I used to think that the energy density of hydrogen was awful, but it actually has by far the best energy density (in terms of mass that is). To make it practical though, you have to get the density of the material high enough for practicality. Which means liquification, very high pressure and appropriate storage tech to make sure it doesn't all leak through the walls of the tank.
Hydrogen has the highest energy per mass of any fuel; however, its low ambient temperature density results in a low energy per unit volume, therefore requiring the development of advanced storage methods that have potential for higher energy density.
It may have a great Gravimetric density 35 kWh/kg against diesels of about 12 kWh/kg but it terms of Volumetric density it is rather different with diesel with the higher value at around 10 kWh/L against hydrogens (at 350 bar) of around 1 kWh/L or just over 2 if you liquify it
For a moving vehicle, it's mass that matters the most, as you have to accelerate the fuel mass and that costs. Hence why making cars lighter is a key fuel consumption improver.
Agreed, the storage technology and approach (compression, insulation...) will add to the weight. But on something like a train, the volume is less of an issue.
As to Fuel cell efficiency compared to ICE power plants, https://www.energy.gov/sites/prod/files/2015/11/f27/fcto_fuel_cells_fact_sheet.pdf
Your own PDF shows that a fuel cell can reach 60% efficiency. To produce that hydrogen from water loses you more power - taking this (very optimistic) as true, and ignoring the cost of compressing the gas to 350 BAR for storage and any other losses, that’s 80% efficient, so in combination 48% energy out compared to energy in. Add in the factors I mentioned and you’re closer to 40%.
60% so a bit better than Diesel (50%). What about energey taken to produce H2 vs. the refinery energy used?
Could be interesting.
What is also interesting is we cannot easily get new mid powered Diesel locos now, and have to rely on grandfather rights.
So companies are spending hundreds of thousands on rebuilding 1960s stuff.
Simplz, generate electricity from Green Energy sources (Wind/Solar/Wave) & use national grid to transmit to plants to
generate H2 by electrolysis.
Store the H2 in the form of Ammonia (NH3), which is a *lot* easier to store & if necessary transport, than H2.
There's existing technology & infastructure to do this.
Crack NH3 to release H2 when required to generate electricity where & when required via H2 Fuel Cells, or even better by NH3 Fuel Cells.
No Carbon in the above cycle, therefore no Carbon capture required.
Hydrogen fuel cells are great items and can work well in transport environments. But where do we get the hydrogen from? Chemical and cracking processes are messy and energy intensive (therefore negating one of the reasons to go hydrogen in the first place). Electrolysis seems promising but those who propose using “spare” wind and tidal generated power need to look at the realities of the present UK generation capacity. Basically there isn’t any, as most of our electricity is provided from gas powered equipment. GB nuclear provides a steady 6GW or so – about 15% of consumption. Wind varies between about 6 and 50% depending on the weather. 6% is NOT unusual and is common when high pressure sits over the UK which can be in both hot and cold seasons. Everyone claims wind power is sufficient to keep the UK going but most of the time we rely on gas and even coal as substantial generation sources. https://gridwatch.co.uk/ gives a comprehensive report on sources. We regularly import about 6% from France – presumably from their nuclear resources. The Green supporters revile nuclear sources and simultaneously want gas powered domestic heating and cooking converted to electricity (as well as all transport, including cars, buses and lorries). No one ever checks on the reality of the situation, and our incompetent politicians go along with the fantasies in the pursuit of votes. If we want electric transport then build nuclear stations everywhere and run overhead-cables for rail and in towns for trams. Just don’t put one in N London where I live…..
This post has been deleted by its author
The clamour to remove gas as a method of heating is just bonkers on a cost basis. I still don't understand why people have not joined the dots on this to see the reality.
Average price of gas is 4p/KWh
Average price of electrcity is 14p/KWh
Now modern houses are better insulated and this has reduced heating costs but only if you are on gas. If you only have electric heating then it is unlikely to have been a net saving.
The vast majority of houses are simply not able to be insulated sufficiently for this to be viable for the average person. Hell, it is probably cheaper to switch to LPG or Oil if the mains gas is stopped.
Kerosene 3.5p/KWh (I have seen quite a few new installations using this now)
These policies are only viable if your goal is to reduce carbon emissions at any cost, regardless of the impact on the consumer. I am all for reducing carbon emissions but it has to be done in a sensible way. A lot of the insulation is full of horrendous chemicals where they are foam based. When buildings are demolished I think that all insulation ends up in landfill as there is no effective way of separating and recycling it.
The efficiency savings on insulation have to be huge to balance the cost of switching from gas to electricity for heating. Then there is the cost of actually fitting the insulation.
That assumes a 1-for-1 swap of electricity and gas - e.g. replacing a 27kW gas boiler with a 27kW electric boiler.
The reality is that the replacement for gas is a ground-source heat pump, which generates ~4kW thermal per kW of electricity. Given a comparison of 4:1 then your equivalent heating cost is 16p of gas to 14p electric (albeit that seems cheap, most consumer electric tariffs are closer to 18p/kWh before the standing charge and even on an economy 7 tariff you're looking at 11-12p/kWh for nighttime usage). But with 4:1 then you're more or less at parity with gas, and if you charge a hot water tank overnight on a economy tariff then you could actually save money vs. gas.
The key problem right now being economies of scale and the number of gas boilers sold in a year vs. the number of heat pumps and associated gear. Plus for GSHP the labour required for installation - but this would be offset if done at point of build (especially for estates) where you already have plant onsite and aren't bringing in hardware and personnel specifically to dig up the garden or bore a hole for a retrofit or one-off (Grand Designer) install. Bringing in a team to bore one hole is expensive. Boring an additional hole per house (e.g. in addition to foundation piles) once the equipment is on site is almost negligibly cheap.
Wind and solar are not green they are low carbon.
Wind kills a lot of wildlife and the switchgear they are gas insulated switchgear which uses Sulphur Hexafluoride. Sulphur Hexafluoride (SF6) is described as the world’s worst greenhouse gas. It’s 23,500 times more potent than CO2. Global annual emissions are 8,100 tonnes, equivalent to the CO2 emissions of 100m cars. It has an atmospheric lifetime of over 1,000 years and its installed base is expected to grow by 75% by 2030. 80% of all SF6 is used in gas insulated switchgear.
Solar panels are not very friendly to the environment, they are made of some rather nasty heavy metals. Today the recycling costs are more than the economic value of the materials recovered, which is why most solar panels end up in landfills.
Exposure to high concentrations of ammonia in air causes immediate burning of the eyes, nose, throat and respiratory tract and can result in blindness, lung damage or death. Inhalation of lower concentrations can cause coughing, and nose and throat irritation. Easier to store and transport yes but it is any safer?
Yes we need to stop burning so much carbon but we also need to make sure to not just create another problem later on.
That's news. Because of course, once you have fusion, spending the near limitless energy on creating hydrogen is a no-brainer.
But without fusion, your hydrogen is mainly created by coal plants, so you gain nothing.
Really people, get going on Thorium.
It's our only hope until fusion gets real.
Metal Hydrides for storing H2 have been in the research labs since the mid 70s.
Problem is the adsorption/desorption rate, you need to heat the MHs to release H2, and
it's slow. Add the problems of heat + H2 issues, thermal degradation of MH structure (and hence storage capacity) and lowish energy (H2) storage density to start with ....
All problems very similar to Li batteries really.
"Current hydrogen production methods are largely reliant on electricity from non-low-carbon sources.."
It's worse than that: hydrogen is not normally manufactured by electrolysis - it is normally manufactured through the steam reforming of oil refinery off gases. After that, as with petrol and diesel, hydrogen must be stored and transported until it reaches the point of use - and that storage and distribution is incredibly energy intensive and adds more pollution.
Given that railway electrification has been implemented sucessfully in numerous countries, this looks like a pretend green solution to a problem that already has a better, proven solution.
One of the major arguments for electric transportation is that it makes no difference how the electricity is generated. Some areas may have lots of wind resources, some may be good for solar and hydro/pumped storage in yet others. A PHEV train can run all over the country without having to plan for specialized refueling. Having some battery capacity is a good thing. It's useful for unnelectrified tracks and shunting yards. If a section of overhead lines are down, the train can continue on even if it means slowing down. Recharging onboard batteries is easy. A battery car can be added to routes with stretches with no overhead lines.
From a pollution standpoint, Hydrogen looks very appealing but it's really only lower pollution at the point of use. It takes an enormous amount of energy to get the H and move it to where it's used. People that nay say EVs constantly state that EVs are coal powered. Even if they are charged somewhere where coal is a major portion of the generation mix, they are far cleaner than petrol/diesel cars will ever be. In fact, grids are getting cleaner and the older a car gets, the worse it pollutes.
There very well could be niches where using Hydrogen as an energy source is useful, but it doesn't appear that it's going to be efficient for large scale transportatoin. It's like an RTG. The Voyager spacecraft RTGs don't generate much power, but they have been working for decades far from the sun. RTGs have also been used for remote sensing in difficult to reach places where a low power supply is needed to run for long periods of time with no refueling and no maintenance. I don't think I've ever heard of somebody advocating for their use for on the Grid.