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What is the judicious mix?

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The Rail Engineer feature “Getting electrification done: the net-zero imperative” with its electrification map attracted a great deal of interest. An updated version of this feature has also been published in Modern Railways magazine.

The magazine’s editor, David Shirres, also gave a sell-out Zoom presentation on this topic to the Railway Division of Institution of Mechanical Engineer on 2 July. This was entitled “What is the judicious mix?” in view of the recommendation in the report by the rail industry decarbonisation task force that a judicious mix of electric, hydrogen and battery traction is needed to decarbonise rail traction.

The presentation answers the judicious mix question as well as addressing wider decarbonisation issues such as modal shift to rail, zero-carbon electricity generation and the supply of hydrogen. It showed how the electrolyser plant that supplied Aberdeen’s fleet of ten hydrogen buses offers lessons for hydrogen trains.

The IMechE’s Railway Division has seven Centres throughout the UK (Midlands; Milton Keynes; North East; North West; Scottish; South East and South West) which each provide regular technical presentations. During the Covid emergency, the Centres are planning to hold virtual presentations until at least December.

For further information about these events google the Centre name, IMechE and Railway.

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. Some steam engines use to refill with water and coal more than once a day, Alstom Cordia iLint 2 car train has a 600 mile range, enough for ten 60 mile trips terminus to terminus stations, if a hydrogen pump is installed at or near one terminus then the same amount of hydrogen could power and refuel a 10 car train 120 miles. A study commissioned by the European Commission, EU reasearch program Horizon 2020 and Hydrogen Europe from McKinsey & Company, titled Hydrogen-powered aviation: Preparing for take-off study, published recently, found that liquid hydrogen which has a higher energy density than hydrogen gas can be used for mid and long haul airliners. Liquid hydrogen has been used for decades to power spacecrafts such as some stages of the NASA Apollo moon missions and Reaction Engines Ltd, UK is developing rockets using liquid hydrogen for Skylon single stage to orbit space plane and wants to develop engines for hypersonic airliners so I don’t see why liquid hydrogen doesn’t have the energy density to power high speed and freight trains. Ammonia which is made with the Haber-Bosch process from nitrogen in the air with hydrogen that can be green, has higher energy density than liquid hydrogen especially at -35°C and doesn’t need to be cooled to -253°C and was used for trams in New Orleans 1870s & 80s, Belgium buses in WW2 and the Reaction Motors XLR99 rocket engine that powered the North American X15 experimental aeroplane, hydrogen gas turbines are being developed for trains so why not ammonia turbines ? Ammonia fuel cells are also being studied.
    Mobile wireless charging was demonstrated powering electric cars at 81 mph near Paris a couple of years ago, as I think the motorway speed limit in France is 81 mph I believe that faster vehicles can be powered. Mobile wireless charging current record is 93% effecient, higher than 3rd rail that can be as low as 75%, that Network Rail’s Peter Dearman claimed, and I think it is Tam Hunter that calculated trains need 40% less electricity per passenger than evs, Robert Llewellyn, Fully Charged Show, youtube said the 2 car solar powered train in Byron Bay, Australia consumes less power than a small electric car he has owned so wireless charging must be powerful enough to propel some if not all trains. I don’t know the cost of mobile wireless charging pads but BMW was going to sell static charging pads for £3,500 so dynamic charging could be a lot cheaper than overhead cables with very low maintenance costs due to a lack of wear and tear of the charging pads due to the contactless power. Wireless charging unlike 3rd rail/ohc won’t be effected by the weather, heavy snow falls which I have seen in a tv documentary damaged overhead cables in Norway, frost which caused a 3rd rail to freeze resulting in a train to breakdown in winter 2019 at Lewshiam Station, London, storm damage and heat from the sun in a summer heatwave which can buckle rails and expand cables and is frictionless useful for high speed trains. The rail industry should conduct a feasibility study to ascertain if wireless charging can power trains and if it is or will be cheaper as charging pads are likely to drop in price in the future, to install and maintain than overhead cable electrification.

  2. In the context of mobile charging, have you tried doing the sums on the amount of energy transmission required for a train, compared with a car or a mobile phone?


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