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Power struggle: what is the best way forward?

Considerable capital investment. Erecting masts and wires, arranging supply points and replacing rolling stock all need money.

Project planners need to carefully assess which tracks need wires above and which do not. A railway with
bi-directional tracks will need crossovers wired, whereas one that only uses crossovers for engineering trains will not, for example.

Thoughts are now turning to leaving sections of running lines without wires. This could save money, particularly where there is little space for overhead line equipment, such as under bridges and through tunnels. The key to this is reliably moving the electric train from one side of the gap to the other.

Trains can coast, as Virgin Trains East Coast occasionally demonstrates when problems force Network Rail to isolate current from overhead wires. Any coasting driver will be hoping he does not need to brake and stop, because the train will then be marooned. Given favourable gradients and signals, a train can coast for several miles.

Longer gaps can be bridged by providing secondary power supplies on a train. This might be a diesel engine (as in Hitachi’s bi-mode trains that are about to enter service), batteries (as tested a couple of years ago by NR in East Anglia), flywheel energy storage or hydrogen power.

However, unless those secondary sources can supply the same power as a train’s primary electrical system, performance will be worse. Top speed might be lower or acceleration more tardy, leading to longer journey times when compared with electric operation. Even so, an end-to-end journey might still be quicker using a mix of power supplies than it is today on diesel alone.

Cost is the driving force behind consideration of partial, or discontinuous, electrification. This cost is not so much in erecting masts and wires, as in altering structures to provide sufficient space around those wires to satisfy electrical clearance rules. 

Britain traditionally used 2.75 metres as its clearance distance, but latest European rules demand 3.5 metres. Imagine a station that sits by a tunnel - or worse, between two tunnels. Without rebuilding the tunnels, the OLE might stand closer than 3.5 metres to platform tops. Although the rules permit clearances under 3.5 metres, Network Rail would need to provide a risk assessment to justify any derogation. 

To date, standards body RSSB has received no application from NR for derogations. Instead, the network owner has opted for expensive rebuilding work which, in turn, led Government to postpone or cancel electrification work in the face of rocketing costs.

Return to our imaginary station sitting between its tunnels, and discontinuous electrification would remove the overhead wire from the platform line. There may just be a gap or an isolated and earthed wire. 

If there’s a gap, then the train will need to have a pantograph that doesn’t extend to its full height when it leaves its contact wire, but remains at a suitable height to regain contact with the OLE after the platform. Using an earthed cable allows the pan to continue running as normal, but designers will need to consider the possibility of the earthed cable becoming live as the train bridges both live and earthed OLE. 

Batteries could provide the power to restart the train and see it back under the wires. Those batteries could have been charged from regenerative brakes as the train slowed to a stop.

This concept could be extended to the complicated trackwork approaching a major station and into the station itself, to save the cost of erecting equally complicated wiring. Trains moving in and around the station would run on secondary power before regaining their OLE. 

This might make the OLE cheaper, but it adds costs elsewhere. Any electric train running through the station would need to have a secondary power source - standard EMUs would not be permitted. NR and Government would save money, but train operators would face higher costs which might cut premium payments to Government or increase the subsidy it needed to provide. 

Such decisions demand detailed analysis. And this analysis should extend to considering what secondary sources trains use, because passengers will be unimpressed if trains run on diesel in stations.

Hydrogen is an alternative. Used in a fuel cell, it directly generates electricity with water as its only emission. It has been the subject of considerable research from the University of Birmingham - Senior Lecturer Stuart Hillmansen tells RailReview that the university built a narrow-gauge locomotive powered by hydrogen five years ago.

This is an extract from a feature published in RailReview. If would would like to read the full article, send an email to stefanie.foster@bauermedia.co.uk and we can send you a copy.

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  • Anonymous Widower - 26/10/2017 14:42

    I am pretty certain, that modern trains like Aventras and Class 80x trains use batteries to capture the energy from regenerative braking, as this means it can work all the time even under dirsel power. Certainly, a traction ststem diagram published in 2014 on Hitachi's web site shows this. If battery power can be used for short distances, then it can be used to bridge gaps where the track is complicated. I also believe that electrifying tunnels could be a lot easier than some people think, if a rail is used on the roof. The Severn Tunnel has been done this way, as has Crossrail.

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    • FrankH - 26/10/2017 16:22

      The rail on the roof idea is used in Spain and probably elsewhere where stations are underground and has been for years. Coasting over viaducts and under bridges and tunnels is done in France and again probably elsewhere in Europe.

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  • David Hunt - 26/10/2017 17:35

    Hopefully we can save millions when we leave the common market,as we should be able to go back to 2.75 metres gap.

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  • AndrewJGwilt1989 - 26/10/2017 22:03

    Hydrogen trains could be the best solution to reduce CO2 emissions and to reduce pollution. But I find Hydrogen trains could be dangerous as Hydrogen is a dangerous gas and can explode causing disasters and fatalities if a Hydrogen train explodes. Bi-Mode trains are the future for the railways not just in the UK. But in Europe and worldwide. As new Bi-Mode trains are being built. And also Battery powered trains aswell is also good despite they are to be used on shorter journeys unless new charging points are needed at stations where battery operated trains can stop at a station so that it can recharge its own battery. Whilst passengers alight and aboard the train before the train’s batteries is fully recharged and departs to carry on its journey from A to B. Battery operated trains could also be used on local lines in the UK to replace the DMU trains which is also a good thing.

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    • BigTone - 27/10/2017 12:47

      The biggest problem is releasing the hydrogen in the first place. 2 processes I know are both energy intensive. One process, the by product is CO2 (Hydrocarbon gas and superheated steam, I used to work on that process on a benzene refinery). The other is splitting brine with electric, vast amounts of electric. Andrew is right about the handling of hydrogen

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    • FrankH - 27/10/2017 15:46

      Alstom has orders for the Coriada iLint unit which is Hydrogen powered.

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  • Ian Watkins - 26/10/2017 22:07

    Is the extra height in the European regulations because of the extra height of the trains on the continent or is it considered necessary for safety so there is no arc to the ground?

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    • BigTone - 27/10/2017 12:54

      I would guess that is to have a common standard. The British loading gauge is having to be raised anyway for handling 9ft 6 inch containers on standard wagons. Also don't forget the OHLE rises over level crossings to clear lorries

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  • Anon - 27/10/2017 09:55

    The benefits of further electrification were obvious this morning (27/10/17). Disruption between Coventry and Rugby could've been minimised if the line between Nuneaton and Birmingham New Street had been electrified. Only a handful of Voyager's were able to make use of the route and were only a handful of minutes late. All the Pendolino's that had to go via Stafford lost a lot more time than that!

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  • RogT - 02/11/2017 17:46

    This article seems to assume that the only form of electrification worth considering is the 25kV AC overhead system. Why hasn't 750V DC third rail been entertained for short branches off the main AC OHLE electrified sections? With this system masts don’t need erecting, bridges don’t need to be raised. The extra equipment required on the trains themselves is minimal. Rectification at relatively closely spaced electrical substations is necessary - I believe about every 1½ miles - but the branches I have in mind are fairly short. Of the electrification projects "postponed" in July, the ones where this option seems to me feasible are: Oxenholme - Windermere (ca. 10 miles) Didcot - Oxford (ca. 11 miles) Bristol Parkway - Bristol Temple Meads (ca. 6 miles) The use of diesel engines is creating rising levels of nitrogen oxide, which pose a major risk to public health. Hence shortly after the electrification "postponement" announcement, the Government declared that Britain is to ban all new petrol and diesel cars and vans from 2040. The aim ought to be for the vast majority of rail transport in Britain to be electrically powered by 2040. Public transport must not be allowed to lag behind private transport. We should be aiming to minimise the use of diesel engines in both conventional diesel-powered trains and hybrid diesel/electric trains. The latter are heavy and less efficient as well as running in polluting diesel mode for part of each journey. Isn't 750V DC third rail electrification at least worthy of consideration for short branches off the AC OHLE electrified sections?

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