The Anonymous Widower

Is A Bi-Mode Aventra A Silly Idea?

In How Long Will It Take Bombardier To Fulfil Their Aventra Orders?, when discussing the new London Midland franchise, that has recently been awarded to West Midlands Trains, I said this about the proposed eighty new carriages for the Snow Hill Lines.

As it is unlikely that the Snow Hill Lines will be electrified in the near future, could we be seeing an Aventra bi-mode for the Snow Hill Lines?

So is the bi-mode Aventra a silly idea?

The Five-Car Aventra

It looks like the formation of a five car Aventra like a Class 720 train is something like DMSLW+MS+MS1+PMS+DMSL

The codes are as follows.

  • D – Driving
  • L – Lavatory
  • M – Motor
  • S – Standard Class
  • W – Wheelchair

So this means the following.

  • All cars are motored for fast acceleration and smooth regenerative braking.
  • As all cars are motored, there must be a heavy-duty electrical power bus running the length of the train.
  • Both driving cars have a toilet.
  • The wheelchair area and the fully-accessible toilet are probably together in one driving car.
  • The pantograph is on one of the middle three cars.

It should also be noted that the Aventra has a slightly unusual and innovative electrical layout.

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-ion batteries if required.

This was published six years ago, so I suspect Bombardier have refined the concept

It would appear that this could be the reason, why in the document I found MS1 was used for one of the intermediate cars, as this is the car with space for the energy storage.

Do Aventras Have Batteries For Regenerative Braking?

Until I get a definitive statement from Bombardier, that they don’t, I will believe that they do for the following reasons.

But the main reason, is that as an Electrical Engineer, I believe it to be stupid and seriously bad design to not use some form of energy storage to handle the energy produced by regenerative braking.

Energy Storage In A Bi-Mode Train

If you look at the five-car Class 720 train, all axles are motored. This will give fast acceleration and smooth regenerative braking, which is just what both train operators and passengers want.

If a bi-mode train had energy storage, if say its speed was checked by a yellow signal, it would be able to regain line speed using the energy stored when it slowed down. So passengers wouldn’t have to endure the vibration of the diesel engine and the jerks as it started.

No competent engineer would ever design a modern bi-mode train without energy storage.

Where Would You Put The Power Pack On An Aventra?

Although space has been left in one of the pair of power cars for energy storage, as was stated in the Global Rail News article, I will assume it is probably not large enough for both energy storage and a power pack.

So perhaps one solution would be to fit a well-designed power pack in the third of the middle cars, which would then be connected to the power bus to drive the train and charge the battery.

This is all rather similar to the Porterbrook-inspired and Derby-designed Class 769 train, where redundant Class 319 trains are being converted to bi-modes.

Diesel Or Hydrogen Power Pack

Diesel will certainly work well, but London and other cities have hydrogen-powered buses.

The picture is from 2013, so the technology has probably moved on. This Fuel Cell Bus section in Wikipedia gives the up-to-date picture.

Automatic Power Source Selection

Effectively, the ideal bi-mode train will be a tri-mode and will have the following power sources.

  • Traditional electrification.
  • On board diesel or hydrogen power.
  • Energy storage, charged from the electrification or from regenerative braking.

The power source would be chosen automatically to minimise the use of both diesel/hydrogen power and electric power from the electrification.

Modern trains like an Aventra can raise and lower the pantograph automatically, so they can do this to make best use of what electrification exists to both power the train and charge the energy storage.

Techniques like these will be used to minimise the use of the diesel or hydrogen power pack.

Intermittent And Selective Electrification

On lines like the Snow Hill Lines sections could be electrified, where the engineering is easy and affordable, to with time reduce the use of unfriendly diesel or expensive hydrogen.

Strangely, one of the first places to electrify, might be the tunnels, as after the electrification of the Severn Tunnel, our engineers can probably electrify any railway tunnel.

I also don’t see why third rail electrification can’t be used in places like on top of viaducts and in well-designed station installations.

Conclusion

A five-car Aventra bi-mode is definitely not a silly idea.

It would be a sophisticated train with the following characteristics.

  • Electric drive
  • Regenerative braking.
  • 25 KVAC overhead and 750 VDC third rail capability.
  • Automatic pantograph deployment.
  • Onboard energy storage.
  • Automatic power source selection.
  • Diesel or hydrogen power-pack

The first four are probably already in service in the Class 345 train.

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August 21, 2017 - Posted by | Travel | , , , , , ,

2 Comments »

  1. […] I discuss the concept of a bi-mode Aventra in Is A Bi-Mode Aventra A Silly Idea?. […]

    Pingback by How Long Will It Take Bombardier To Fulfil Their Aventra Orders? « The Anonymous Widower | August 22, 2017 | Reply

  2. […] In Is A Bi-Mode Aventra A Silly Idea?, I outlined what I believe the ultimate bi-mode train will be like. […]

    Pingback by Electrification ‘Very Unlikely’ To Come Back Into EWR Scheme « The Anonymous Widower | August 26, 2017 | Reply


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