The Anonymous Widower

Bi-Mode Ate My Electrification

The title of this post,  is the headline on an article by Roger Ford in the January 2017 Edition of Modern Railways.

The article describes how electrification of the rail line between Selby and Hull has been dropped and quotes Chris Grayling as implying  that it’s all because the train companies have bought Class 802 trains, which are bi-mode, and won’t need electrification between Selby and Hull.

Both train companies; Hull Trains and TransPennine Express need to run high-class services with modern fast trains to Hull.

I will look at Hull Trains need in more detail.

Much of the route used by Hull Trains is along the electrified East Coast Main Line, so a 140 mph capability could be needed in the next few years, as speeds increase on that line.

If the Selby-Hull line were to be electrified, Hull Trains could run electric trains like Class 801 trains, InterCity 225s, or perhaps a version of the Stadler Flirt, that Greater Anglia will be running.

Hull Trains obviously need to increase quality and capacity on the route and it appears that the only train available is the bi-mode Class 802 train.

The only certain way Hull Trains could get new trains in a reasonable time, given that electrification is continually being kicked into the long grass,  is the bi-mode route.

Purists might not like the bi-mode train, but at least it will enable Hull to have a quality high-speed train service.

The Problems With Electrification

Electrification is needed, so that trains can run fast and efficiently, without the noise, pollution and carbon-emissions of diesel power.


  • Electrification in the UK, is like trying to make a Victorian house fit for a modern lifestyle and it is even more expensive.
  • Electrification gantries and wires, ruin landscapes.
  • Much of our railway infrastructure,like stations, bridges and viaducts are beautiful structures in their own right and perhaps electrification will not be for some of them.

As we get further into the future, I think that there will be more reasons why existing lines will not be electrified.

We’re All In It Together

Several countries have a substantial proportion of lines without electrification, of which Germany, India and, the UK and the US are the most notable examples.

So ideas will be developed in these and other countries, that could be replicated in other countries with a pressing need for electrification.

The Problem Is An Opportunity For The Train Builders


  • Hitachi have developed their Class 800 family of trains to include bi-modes.
  • Bombardier are developing trains with onboard electric storage and have a philosophy for all markets that I wrote iabout in Parallel Thinking From Bombardier.
  • Stadler have a Pandora’s box for of ideas and technologies.
  • CAF are supplying trams with onboard energy storage.

I can’t believe that Alstom, Siemens and other fFar Eastern manufacturers are not looking at using self-powered trains to cut down on electrification.

It is also worth noting that others are developing technologies, that will assist train builders in providing the trains that train companies and their passengers desire.

  • Tessla and other companies are developing batteries with a higher storage density.
  • Automatic pantograph up and down is being developed, so trains can use overhead power, where it exists.
  • Automatic coupling and uncoupling will be developed.
  • Trains will be driven automatically, so minimum power is used.

The train of the future will be powered and braked by electricity, and highly automated. It could be driven automatically, but I suspect like the Victoria Line or your average commercial airliner, the driver will be in overall control and  monitoring everything.

Why Trains Need An Energy Storage Capability?

If an electric train has an onboard energy storage capability, it has various advantages.

  • It can store the energy generated from regenerative braking and release it to help get the train back up to speed.
  • On board energy storage can be used with both electric and diesel-electric trains.
  • Depots can be designed with less electrification for safety and to save money.
  • Trains can be given a remote wake-up capability as I discussed in Do Bombardier Aventras Have Remote Wake-Up?, so a train parked in a siding can be warmed up ready for the driver at the start of the day.
  • Trains can recover to the next station using stored power, if electrification power fails.
  • Trains can take diversions without electrification if needed.
  • Depending on the size of the storage, trains could provide a service over a limited distance on stored power alone.

Hybrid cars and buses, which have onboard energy storage,  might suggest even more reasons.

Energy Storage Can Only Get Better

Over the last few decades the energy capable of being stored in a device of a fixed physical size and weight has increased dramatically.

This process can only increase, so onboard energy storage will become more and more viable.

What Is The Kinetic Energy Of A Train?

I ask this question to show the energy values involved.

If I take a nine-car Class 345 train, which will be used on Crossrail, this has a mass of less than 350 tonnes and a maximum speed of 145 kph.

1500 passengers at 80 kg each works out at another 120 tonnes.

So for this crude estimate I’ll use 450 tonnes for the mass of a loaded train.

This gives the train an energy of 365 megajoules or 101 kilowatt-hours.

This amount of energy is only a couple of kWh larger than the largest battery size of a Tessla Model S car.

Can Regenerative Braking Be Handled By Onboard Energy Storage On A Train?

As an example, look at the Stadler Flirts and Bombardier Aventras, that will be running between London Liverpool Street and Cambridge, Colchester, Ipswich, Norwich, Southend and Stansted Airport.

  • These are fully-electrified lines.
  • The ability to stop and restart quickly is needed as these are very busy lines, with another 110 mph train along in a couple of minutes.
  • All the passenger trains on the lines will have regenerative braking.

The electricity generated by braking can either be returned to the overhead wires using an inverter to get the voltages right or stored on the train in an onboard energy storage device.

Both methods are possible with good electrical engineering and there is probably no weight or installation advantage with either technology.

I don’t know what Stadler are doing, but this article in Global Rail News from 2011, which is entitled Bombardier’s AVENTRA – A new era in train performance, gives some details of the Aventra’s electrical systems. This is said.

AVENTRA can run on both 25kV AC and 750V DC power – the high-efficiency transformers being another area where a heavier component was chosen because, in the long term, it’s cheaper to run. Pairs of cars will run off a common power bus with a converter on one car powering both. The other car can be fitted with power storage devices such as super-capacitors or Lithium-Iron batteries if required.

As this was published five years ago, I can’t believe that an innovative company like Stadler have not been thinking about onboard electrical storage.

As I showed in the previous section, the kinetic energy of a Crossrail Class 345 train is around 101 kiowatt-hours.

So it is not beyond the bounds of possibility that a couple of Tessla batteries could handle the regenerative braking for a fully-loaded Crossrail train!

The same would apply to all of the trains  in East Anglia, which would probably have a bit more kinetic energy.

It can obviously be done on an Aventra, so I feel that the Flirts will do it as well.

If all the trains on the routes handled their own regenerative braking, this could mean that there would be no need for the power supply to the overhead wires to be able to handle it. Whether that would save money, I don’t know!

Can the same technology be applied to a locomotive-hauled train, like a Class 68 locomotive pulling a rake of five Mark 3 coaches at 160 kph?

The kinetic energy is slightly less than that of the Crossrail train, so it might be feasible to put onboard energy storage in the diesel-electric locomotive to reuse braking energy.

Onboard energy storage for regenerative braking will become universal on all electric or diesel-electric trains.

In March 2016, I wrote Will London Overground Fit On-board Energy Storage To Class 378 Trains?, which was based on this article in Rail Technology Magazine entitled Bombardier enters key analysis phase of IPEMU. In the article, Marc Phillips of Bombardier is quoted as saying this.

All Electrostars to some degree can be retrofitted with batteries. We are talking the newer generation EMU as well as the older generation. So, the 387s and 378s are the ones where we have re-gen braking where we can top-up the batteries and use the braking energy to charge the batteries. That gives us the best cost-benefit over operational life.

So it would seem that the Class 378 trains of the London Overground are candidates for fitting with batteries. This would give the following advantages.

  • Electricity savings.
  • Recovery to the next station if the electricity supply fails.
  • Simplified depot layouts with less electrification.

As nearly all lines are electrified in London, the ability to travel on short routes without electrification wouldn’t be needed.

On the other hand, new services might need a new branch line or a chord between two electrified lines, which if worked with trains with onboard energy storage, would not need to be electrified.

In Don’t Mention Electrification!, I noted that in all the documents for the extension of the Gospel Oak to Barking Line to Barking Riverside, there is no mention of electrification, although electric trains are stated to be working the route.

So could this be the first newly-built line in the UK to be worked by electric trains powered by onboard energy storage?

How Far Will Trains Go On Onboard Energy Storage?

This is very much a case of answering these and other questions.

  • How much range do you want?
  • Does the route have lots of stops?
  • Is the route hilly?
  • How much space there is on the train?

In the end, the most important question is can you afford it?

Could We See A Tri-Mode Train?

A tri-mode train would be one that could use the following power sources.

  • Electric power from either 25 KVAC overhead or 750 VDC third-rail.
  • Diesel power.
  • Onboard energy storage.

It could even pick up 750 VDC from a tramway, if it was running as a train-tram.


  • If you look at an Hitachi Class 800 train, I suspect that the engineers could find space somewhere for onboard energy storage.
  • The Aventra double-power-car concept, has probably been designed with a diesel version in mind.
  • A hydrogen fuel-cell would be an alternative to diesel.
  • The power control system would just switch between power sources automatically.

It’s all down to good engineering design and innovation.

I suspect, that a tri-mode train will be launched in the next few years.


I believe there is a lot of scope to cut the amount of electrification that is done, by using alternative technologies.

The bi-mode is in pole position, but with the advance of battery and other technologies, the current lead will not last long.



December 22, 2016 - Posted by | Transport | , ,

1 Comment »

  1. […] Bi-Mode Ate My Electrification, I asked this […]

    Pingback by Porterbrook Launch A Tri-Mode Train « The Anonymous Widower | December 23, 2016 | Reply

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