The Anonymous Widower

The Mathematics Of A Hydrogen-Powered Freight Locomotive

If we are going to decarbonise the railways in the UK and in many countries of the world, there is a need to replace diesel locomotives with a zero-carbon alternative.

In looking at Airbus’s proposal for hydrogen powered aircraft in ZEROe – Towards The World’s First Zero-Emission Commercial Aircraft, it opened my eyes to the possibilities of powering freight locomotives using gas-turbine engines running on liquid hydrogen.

A Hydrogen-Powered Equivalent Of A Class 68 Locomotive

The Class 68 Locomotive is a modern diesel locomotive used on UK railways.

This is a brief specification

  • It can pull both passenger and freight trains.
  • It has an operating speed of 100 mph.
  • The diesel engine is rated at 2.8 MW
  • It has an electric transmission.
  • It has a 5,000 litre diesel tank.
  • It weighs 85 tonnes.
  • It is 20.5 metres long.

There are thirty-four of these locomotives in service, where some haul passenger trains for Chiltern Railways and TransPennine Express.

Rolls-Royce’s Staggering Development

Staggering is not my word, but that of Paul Stein, who is Rolls-Royce’s Chief Technology Officer.

He used the word in a press release, which I discuss in Our Sustainability Journey.

To electrify aviation, Rolls-Royce has developed a 2.5 MW generator, based on a small gas-turbine engine, which Paul Stein describes like this.

Amongst the many great achievements from E-Fan X has been the generator – about the same size as a beer keg – but producing a staggering 2.5 MW. That’s enough power to supply 2,500 homes and fully represents the pioneering spirit on this project.

This generator is designed for flight and the data sheet for the gas-turbine engine is available on the Internet.

  • It has a weight of under a couple of tonnes compared to the thirteen tonnes of the diesel engine and generator in a Class 68 locomotive.
  • It is almost as powerful as the diesel.
  • It looks to be as frugal, if not more so!
  • Rolls-Royce haven’t said if this gas-turbine can run on aviation biofuel, but as many of Rolls-Royce’s large engines can, I would be very surprised if it couldn’t!

Rolls-Royce’s German subsidiary; MTU is a large producer of rail and maritime diesel engines, so the company has the expertise to customise the generator for rail applications.

Could this generator be modified to run on liquid hydrogen and used to power a Class 68-sized locomotive?

  • The size of the generator must be an advantage.
  • Most gas-turbine engines can be modified to run on natural gas and hydrogen.
  • Its power output is electricity.
  • There’s probably space to fit two engines in a Class 68 locomotive.

In addition, a battery could be added to the transmission to enable regenerative braking to battery, which would increase the efficiency of the locomotive.

Storing Enough Hydrogen

I believe that the hydrogen-powered locomotive should carry as much energy as a Class 68 locomotive.

  • A Class 68 locomotive has a capacity of 5,000 litres of diesel fuel.
  • This will have a mass of 4.19 tonnes.
  • Each kilogram of diesel can produce 47 Mega Joules of energy.
  • This means that full fuel tanks contain 196,695 Mega Joules of energy.
  • Each litre of liquid hydrogen can produce 10.273 Mega Joules of energy

This means that to carry the same amount of energy will need 19,147 litres or 19.15 cubic metres of liquid hydrogen.

  • This could be contained in a cylindrical tank with a diameter of 2 metres and a length of 6 metres.
  • It would also weigh 1.38 tonnes.

The E-Fan-X aircraft project must have worked out how to store, similar amounts of liquid hydrogen.

Note that I used this Energy And Fuel Data Sheet from Birmingham University.

Running On Electrification

As the locomotive would have an electric transmission, there is no reason, why it could not run using both 25 KVAC overhead and 750 VDC third-rail electrification.

This would enable the locomotive to haul trains efficiently on partially electrified routes like between Felixstowe and Leeds.

Hydrogen-Powered Reciprocating Engines

When it comes to diesel engines to power railway locomotives and big trucks, there are few companies bigger than Cummins, which in 2018, turned over nearly 24 billion dollars.

  • A large proportion of this revenue could be at risk, if governments around the world, get serious about decarbonisation.
  • Cummins have not let the worst just happen and in 2019, they acquired Hydrogenics, who are a hydrogen power company, that they now own in an 81/19 partnership with Air Liquide.
  • Could all this expertise and Cummins research combine to produce powerful hydrogen-powered reciprocating engines?
  • Other companies, like ABC and ULEMCo are going this route, to modify existing diesel engines to run on hydrogen or a mixture of hydrogen and diesel.

I believe it is very likely, that Cummins or another company comes up with a solution to decarbonise rail locomotives, based on a conversion of an existing diesel engine.

Refuelling Hydrogen-Powered Rail Locomotives

One of problems with hydrogen-powered trucks and cars, is that there is no nationwide refuelling network providing hydrogen. But railway locomotives and trains usually return to depots at the end of the day for servicing and can be fuelled there.


I feel that there are several routes to a hydrogen-powered railway locomotive and all the components could be fitted into the body of a diesel locomotive the size of a Class 68 locomotive.


  • Decarbonising railway locomotives and ships could be a large market.
  • It offers the opportunities of substantial carbon reductions.
  • The small size of the Rolls-Royce 2.5 MW generator must offer advantages.
  • Some current diesel-electric locomotives might be convertible to hydrogen power.

I very much feel that companies like Rolls-Royce and Cummins (and Caterpillar!), will move in and attempt to claim this lucrative worldwide market.

September 25, 2020 - Posted by | Hydrogen, Transport/Travel | , , , , , , , , , ,


  1. There is no doubt Hydrogen is the fuel that we need to maintain mobility in high power forms of transport if we want to maintain what we have without killing the planet. Trouble is it takes more energy to extract it than your left with and even more is needed to get it liquefied. So it needs cheap energy production or an acceptance there is a price to pay to eliminate carbon but then you have the issue of building such plants or trillions of solar panels in itself creates an energy burden as well so there are no simple answers here.

    That said there should be a demonstrator just take an old class 47 and kit it out and get it on the network to see what the issues are fuelling it and operating it.

    Comment by Nicholas Lewis | September 27, 2020 | Reply

    • Hydrogen production will come down in price, as electrolyser technology improves. At least we have a world-class manufacturer in ITM Power. It appears from their web site they are aiming to produce hydrogen at the offshore wind farms.

      There is also going to be a lot of development of hydrogen power for buses and large trucks.

      Some of the generation of hydrogen and refuelling will be co-located.

      There must be any number of diesels, that can be used. It would only need to be diesel electric, with a spacious body.

      I suspect, the choice will seem unusual to some.

      I’d probably pick a Class 66, as there are so many that need replacing.

      Comment by AnonW | September 27, 2020 | Reply

      • You still can’t get past the energy input required in the first place to create Hydrogen although I acknowledge that research is going into seeking more efficient methods. Unfortunately saving the planet still doesn’t have the urgency that solving Covid does where an extraordinary worldwide effort was mobilised over weeks to seek a vaccine. If only the same level of crisis was attached to dealing with climate change im in no doubt we would solve the the Hydrogen conundrum.

        Anyhow thank you for continuing posts many of which i very thought provoking

        Comment by Nicholas Lewis | September 27, 2020

  2. I think the urgency is coming and those with money seem to be backing the technology, even if Trump doesn’t. But most EU nations, the UK, Australia, India, Japan and South Korea seem to be backing it. Eben the Chinese have stated recently, they want to go csrbon-free.

    Comment by AnonW | September 27, 2020 | Reply

  3. Fueling refill speed is a data point not covered, and may be critical to high utilisation and depot layouts.

    I don’t know the answer either way, my guess is H2 might be quite a bit slower or more complex to match speed wise in a safe way.

    Comment by MilesT | September 28, 2020 | Reply

    • There is a lot of work being done by hydrogen companies to improve hydrogen refuelling.

      It should be remembered that hospitals and others have been taking large deliveries of liquid oxygen for decades and there’s not much difference to handling the two gases as liquids.

      Comment by AnonW | September 28, 2020 | Reply

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