HomeElectrificationIs hydrogen the answer?
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Rail Engineer’s feature on hydrogen trains in the January issue (issue 159) raised the possibility that, despite its good green credentials, the rail industry’s use of rail diesel traction could soon become unacceptable. A few weeks later, Transport Minister Jo Johnson said exactly this in a speech stating that he wished to see “all diesel-only trains off the track by 2040” and saw “alternative-fuel trains powered entirely by hydrogen” to be a prize on the horizon. His speech also called on the industry to provide a vision for how it plans to decarbonise and report back by the autumn.

That recent feature on hydrogen trains concluded that, in the long-term, the replacement of DMUs by HMUs is a realistic goal. Readers may also have gathered that Rail Engineer is a fan of hydrogen. Not only does it provide zero emissions and a possible zero-carbon means of transport but, as an energy vector, it also offers large-scale energy storage to absorb excess off-peak wind power generation.

The tiny Orkney island of Eday provides an interesting example. The island has installed a 0.5MW electrolysis plant to export its surplus wind power as hydrogen to Kirkwall, on Orkney’s mainland, where it is used to power the grid.

Part of the solution

For these reasons, hydrogen has got to be part of the solution, although it cannot be the only one. As with all technologies, it should only be used when appropriate. A limiting factor for hydrogen is its energy density of 2.7MJ/litre (at 350bar on Alstom’s hydrogen iLint train) which is less than a tenth that of diesel (35.8MJ/litre).

Alstom’s iLint hydrogen train is a hybrid unit that makes clever use of a 225kW traction battery to supplement the power of its 200kW fuel cell to give the same performance and range as a diesel multiple unit train.

For much of the time, the fuel cell keeps the batteries fully charged. When accelerating, the iLint is powered by both its traction battery and fuel cell to deliver a maximum power to weight ratio of 8kW /tonne, comparable with a diesel-powered Hitachi bi-mode.

Battery-powered trains also offer zero emissions at the point of use. However, they are limited by the low energy density of batteries which ranges from 0.56MJ/litre for lead acid to 2.63MJ/litre for lithium ion. Furthermore, unlike diesel trains, batteries cannot be instantly refuelled. For this reason, battery-powered trains are generally only suitable for journeys from an electric line onto a short non-electrified branch.

Such an IPEMU (independently power electric multiple unit) application was recently trialled on the Harwich branch where it ran for 50km under electric power and 30km powered solely by battery, as described in our “Batteries included” feature (issue 125, March 2015).

Liquid Natural Gas (LNG) offers lower fuel costs and reduced carbon and particulate emissions. There is significant interest in its use on North American freight railroads, which spend around $12 billion a year on diesel. Last year, the Florida East Coast Railway became the first US railway to operate its entire mainline fleet on LNG. The company claims that this results in an eighty per cent reduction in Nitrogen Oxide (NOx) emissions. In Russia, LNG is used to power a fleet of gas turbine locomotives.

An extensive refuelling infrastructure is required for LNG-powered locomotives, which need a separate tender vehicle containing an insulated double-walled tank in which the fuel is kept refrigerated at -160°C. At 22MJ/litre, LNG’s energy density is two-thirds that of diesel and the performance of LNG trains could be comparable to diesel trains.

Russian Railway's LNG-fuelled gas-turbine locomotive.
Russian Railway’s LNG-fuelled gas-turbine locomotive.

Alternative fuel limitations

LNG is unlikely to be a practical proposition for rail passenger units. If used to power locomotives, it would require the train to be lengthened by an extra vehicle to carry the LNG tank.

Hydrogen and battery technologies offer significant benefits, which will no doubt be developed further. However, their low energy densities will always be a significant constraint. For this reason, there is no prospect of self-powered rail traction using alternative fuels for high-power rail traction. Rail Freight Group executive director Maggie Simpson made this point in her response to Johnson’s statement. She noted that, whilst battery and hydrogen ‘may show promise for lightweight passenger trains, their application for heavy duty freight is at best unproven and setting an arbitrary deadline of 2040 could well therefore be counterproductive, damaging the case for investment’. She advised that RFG would like to see the “continued affordable electrification of the strategic freight network”.

Yet, in his call for the railway to decarbonise, Johnson expects that batteries and hydrogen will replace the diesel engines on bi-mode trains. His advisers would seem to be unaware of the fundamental constraints of these technologies. In his speech, Johnson also seemed to dismiss electrification by stating that it was “unlikely to be the most cost-effective way to secure these vital environmental benefits”.

Zero-carbon electrification

Although Johnson’s expectation that greener alternatives will replace diesel is not unreasonable for lightly used lines, this aspiration is unrealistic for busy core routes that require high-powered traction. For these, electrification is the only option that offers the prospective of zero-carbon rail traction as an increasing proportion of Britain’s electricity becomes generated by renewals. The use of wind turbines to provide all the power for electrified railways in the Netherlands shows what can be done.

Furthermore, busy electrified routes carry far more traffic than rural lines, and so offer far greater environmental benefits than alternative-fuelled self-powered vehicles.

Whilst electrification’s high initial capital cost gives it a poor business case for rural routes, this is not the case for busy main lines. The economic case for electrification is recognised by many countries that have a high percentage of their rail network electrified. These include Netherlands (76 per cent), Italy (71 per cent) and Spain (61 per cent). In the UK, just 42 per cent of the network is electrified.

Electrification offers improved passenger benefits with its greater acceleration and speed. For example, a bi-mode class 800/2 has a power to weight ratio of 11.2kW/tonne in electric mode and 6.9kW/tonne in diesel mode.

Electrification also offers enormous operational cost savings. A recent report by the Office of Rail and Road (ORR) on rolling stock costs showed that, whilst the Virgin Trains fleet portfolio includes only 15 per cent diesel rolling stock, diesel accounts for 40 per cent of its total energy costs, making it around four times the cost of electric traction. One reason for this is that, unlike diesels, electric trains can absorb the huge amount of energy required to brake a train and regenerate it back into the grid.

The high maintenance and capital cost of diesel trains is illustrated in a National Audit Office report that considered the procurement of Hitachi IEP bi-mode trains, which includes a 28-year maintenance contract. This showed that the Great Western IEPs, which frequently operate under diesel power, cost £4 million more per vehicle than the mostly all-electric East Coast IEPs.

Unnecessarily high electrification costs

The Government, not unreasonably, considers the current high cost of electrification to be unacceptable and has cut back electrification schemes as a result. The recent feature “Electrification as it used to be” (issue 158, December 2017) showed that, at today’s prices, the cost of electrifying the Great Western main line is seven times the track-mile-cost of British Rail’s East coast electrification. Whilst this is not a totally fair comparison, given changes to standards and the increase in traffic since the days of BR, it does show the need to understand why Great Western electrification cost so much.

In its report ‘A breath of fresh air: new solutions to reduce transport emissions’, the Institution of Mechanical Engineers recommended that the “DfT instructs Network Rail to develop an appropriate specification for railway electrification, which will achieve an affordable business case for a rolling programme to complete the electrification of main lines between Britain’s principal cities and ports, and of urban rail networks through our major city centres.” In making this recommendation, the Institution believes it should be possible to drive down electrification costs and is also suggesting that having a rolling programme, as is the case in Scotland, is one way of doing this.

Jo Johnson is right to suggest that hydrogen and batteries can decarbonise rail traction. However, for very real engineering reasons, they can only be part of the solution.

The politics of electrification are such that the Government is forced to make misleading statements to justify its cutbacks. For example, Chris Grayling’s recent statement that, with bi-mode trains, “we no longer need to electrify every line to achieve the same significant improvements to journeys”, ignores the laws of physics – improved journey times requires more powerful trains. An electrically powered bi-mode is almost fifty percent more powerful than a diesel bi-mode.

The industry’s response to Johnson’s call for decarbonisation solutions must focus on engineering issues. If so, it can only reach the same conclusion that the Institution of Mechanical Engineers has, which is that cost-effective electrification is the only way to deliver significant carbon and emission reductions.

This article was written by David Shirres.

Read more: Hydrail comes of age


David Shirres BSc CEng MIMechE DEM
David Shirres BSc CEng MIMechE DEMhttp://therailengineer.com

Rolling stock, depots, Scottish and Russian railways

David Shirres joined British Rail in 1968 as a scholarship student and graduated in Mechanical Engineering from Sussex University. He has also been awarded a Diploma in Engineering Management by the Institution of Mechanical Engineers.

His roles in British Rail included Maintenance Assistant at Slade Green, Depot Engineer at Haymarket, Scottish DM&EE Training Engineer and ScotRail Safety Systems Manager.

In 1975, he took a three-year break as a volunteer to manage an irrigation project in Bangladesh.

He retired from Network Rail in 2009 after a 37-year railway career. At that time, he was working on the Airdrie to Bathgate project in a role that included the management of utilities and consents. Prior to that, his roles in the privatised railway included various quality, safety and environmental management posts.

David was appointed Editor of Rail Engineer in January 2017 and, since 2010, has written many articles for the magazine on a wide variety of topics including events in Scotland, rail innovation and Russian Railways. In 2013, the latter gave him an award for being its international journalist of the year.

He is also an active member of the IMechE’s Railway Division, having been Chair and Secretary of its Scottish Centre.


  1. Diesel = 45MJ/kg, Hydrogen = 142MJ/kg, or 3 times more.
    Liquefied Stoichiometric Modified Oxygen-Hydrogen (MOH) Gas contains 167kgH2/m3 vs 1m3 liquid H2 (70kg), or 2.5 times more H2.
    MOH could be easily liquefied at 1bar/-178deg.C and stored in LNG cylinders.
    MOH is safe – cannot be ignited by a spark at normal conditions, doesn’t perform embrittlement as the H2.
    MOH could be used as a perfect Hydrogen Storage. Pure 99.99% Hydrogen could be extracted on-board out of MOH and used for Fuel Cells.
    Times more effective is using MOH as it is, for fueling one or more Gas Turbines, which are much cheaper and with much better weight-to-power ratio, compared to the Fuel Cells. Also, Gas-Turbines have unlimited lifespan, while the best Fuel Cells are limited up to 20,000 hours.
    Gas Turbines could be coupled with power generators and drive electric motors, or (better) transmit the rotation DIRECTLY to the wheels, through a Gear-Box.
    No Fuel Cells, no Generators. A super-cost-effective option.

  2. I find it really interesting the massive difference in approach to decarbonisation of transport that automotive and rail seem to be taking. The automotive industry has been trying to make Hydrogen work for at least a decade, more like 2 or even 3. Almost universally they have abandoned it as “not cost effective” and are going down the hybrid or electric only route as batteries improve further. Why does rail think it can do something more cost effectively than the auto industry can? Lets face it, it doesn’t have a great track record in such matters. I appreciate that one of the biggest issues is the re-fuel network for hydrogen cars as well as crash worthiness which is much more simple in the rail area, but still this is something the rail industry have to take notice of too.
    The Alstom iLint is interesting but I thought the performance figures were similar to a DMU, which infers they aren’t quite there yet reading between the lines. (87mph and 370-500 mile range is what is quoted by Alstom). Stats on the DMU’s will vary by class but in general they are faster with significantly higher range.

    I agree with the author that Hydrogen may be part of the solution, but when you consider moving freight I’m afraid another solution is needed. And I think ultimately battery and OLE hybrids will have a significant place in our transport of the future.

    • I suggest some more updated research. The automotive industry is taking up hydrogen technology with vigour – Toyota, GM, Hyundai, Daimler, Honda, Audi. This is mainly going to be for SUVs for range. The battery binge cannot address heavy transport economically as you take away your payload with batteries. Buses, trucks, ferries, trains will all be powered by hydrogen. The barriers for uptake (tech availability/infrastructure availability and cost) are being addressed with massive infrastructure investments, new vehicles coming into the market almost weekly and the increased manufacturing volumes dropping cost. This is then providing the impetus to tech companies to develop even better hydrogen technology…hydrogen is well and truly on the slope of enlightenment of the Gartner hype curve. Google “McKinsey hydrogen” for a good summary of why.

  3. Amazing the U.K. hit with four days of snow and the national grid is screaming for more gas.Closing down the coal fired power station wasn’t clever move.Interesing the U K is sitting on two hundred years worth of Shale Gas. As a child of the 1970s I can remember doing my homework by candle lite ,When the cold starts to bite and Railways ,factories and shops are ordered to close and the lights start flickering the British voter will soon lose their appetite for Green Virtue Signalling.

  4. The Chester to Liverpool line via the Halton Curve, which is scheduled to open in December 2018, is proposed for a trial by Alstom of their zero emissions hydrogen fuel cell trains. The line was chosen as Alstom’s new technology facility is at Halebank on the Liverpool border adjacent to the line, with hydrogen supplied via the nearby Stanlow refinery

  5. THe govt needs to give Network Rail £1bn a year indefinitely to continue electrification so that it has certainty of funding. Network Rail can then continue with electrification of the rail network in an increasingly efficient and planned manner. Given the number of bimodes we now have, focusing on electrifying straigtht and easy to electrify elements of major lines (e.g. the MML, Cardiff to Swansea) and infilling busy local lines (e.g. Didcot to Oxford) and electrifying new lines (East West Rail) should be the focus. Hydrogen is for trundle lines such as Inverness to Wick/Thurso, the West HIghland Line, and the Cornish Branch lines.

  6. Would DME (Dimethyl Ether/methoxymethane) be a useful interim step for reducing diesel emissions from rail transport, especially for smaller DMU diesel engines?

    In terms of fuel replacement, DME needs similar equipment to LPG (for petrol engines) in terms of tankage (on vehicle/storage), injections, control gear etc. So perhaps not useful for larger “prime mover” locomotives (the “extra carriage/fuel tanker” mentioned above) but could perhaps be squeezed into a small DMU (underfloor, loss of a few seats in often lightly used carriages etc) and “life extend” some older DMUs (and maybe also an option for the Vivarail D-train underground stock re-purposing).

    One challenge is that DME is not yet available in the UK (volume production has started in the US) but rail use could kick start availability for other diesel use cases (cranes, construction, portable electric generation, trucks etc.) especially where it is not practical to replace the equipment with new (powered by less polluting sources).

  7. Ammonia has the advantage that it liquifies at fairly low pressure at normal ambient temperatures. It is theoretically possible to use it in a fuel cell, the waste products being nitrogen and water.

    Another option that is worth considering is hydrogen oxide, since anything that will burn can be used as the energy source, including renewables and waste. Given the better control of the oxidation process that is possible when external combustion is employed, this is an effective and inexpensive way to reduce particulates and NOx.

  8. From all this it appears that a 20 year life or less for diesels now being introduced. This is not financially acceptable and poor value for public money. Compare with BR HST current 40 + years of service and moving on to the next job. Where is the published hydrogen etc development programme to full production in less than 20 years? Electrification does not require this risky pie in the sky speculation, it is feasible right now. There has always been a recognition and concern re the high cost, but look at the payback from the West Coast Route which like the East Coast Route owes little money to anybody. Look to the lead in the rest of the world. ‘Give us the tools and we’ll finish the job’.
    Vaughan Cole FIMechE

  9. The author of the article states “Not only does it {hydrogen.} provide zero emissions and a possible zero-carbon means of transport……..”

    Unfortunately, whilst hydrogen/fuel cell technology may be zero-emission at the tail pipe of the vehicle, that statement ignores the emissions where the hydrogen is produced, and the likelihood that such production will likely produce as much carbon dioxide overall as the use of diesel. Hydrogen is unlikely to lead to true zero-carbon transportation for the foreseeable future.

    That assumes the hydrogen is produced by such as steam reformation from fossil fuels – as the vast majority is at the moment. Yes, it’s true that if there was indeed a surplus of renewable energy from wind/solar etc, such could be used to produce truly green hydrogen. But the example given (Orkney island of Eday) is very, very far from typical. By and large, all electricity from renewables goes into the grid, and every kWh is one less kWh that would otherwise by generated from fossil fuels. Generally, it’s far more efficient to lay undersea power cables to connect to the grid.

    Renewable power generation would have to VASTLY increase before that ceases to be true, and it’s important to appreciate that converting electricity to hydrogen and back to electricity is only about 25% efficient, compared to somewhat over 75% for battery storage.

    Yes, it’s true that a battery rail vehicle may be problematic in terms of battery size and cost to give a sensible range, but there are ideas for a hybrid system of overhead power and battery. Whilst overhead power is available, such can be used not only for traction, but also topping up the battery – then the battery giving power where no overhead power exists. Such a solution may in many instances allow a battery size small enough to be viable, without any huge capital outlay.

    Hydrogen and fuel cells sound seductive, but even they still require quite a large battery, the fuel cells themselves are expensive, and the catalyst may be prone to limited life due to pollution poisoning. Quite apart from (if the hydrogen is produced via electrolysis) roughly 3x the amount of electricity is needed per mile compared to pure battery electric.

  10. The Alstom hydrogen train is now operational in Germany. It reaches just under 90mph. Hydrogen makes sense in large vehicles like trains, ships, buses, big earth movers, etc, not for cars. The hydrogen can be generated at say a train depot using overnight electricity. No transport costs like with diesel. Also it even out the grid by using electricity in the dips and using it in the peaks.

    Overhead wires are very expensive to install…and maintain.


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