The Anonymous Widower

Could There Be A Bi-Mode Aventra for Commuter Routes?

The London Overground has ordered a fleet of four-car Class 710 trains.

The Gospel Oak to Barking Line is being extended to a new Barking Riverside station.

In an article in the October 2017 Edition of Modern Railways, which is entitled Celling England By The Pound, Ian Walmsley says this in relation to trains running on the Uckfield Branch, which probably has a terrain not much different to the lines in London.

A modern EMU needs between 3 and 5 kWh per vehicle mile for this sort of service.

The proposed Barking Riverside Extension is about a mile, so this could need up to 20 kWh each way.

This could easily be done with a battery, but supposing a small diesel engine was also fitted under the floor.

Would anybody notice the same 138 kW Cummins ISBe diesel engine that is used in a New Routemaster hybrid bus? I doubt it!

It is revealing to calculate the kinetic energy of a fully-loaded Class 710 train. I estimate that it is around forty kWh, if it is travelling at 90 mph.

That speed would rarely be achieved on the Gospel Oak to Barking Line.

If a Class 710 train, had only one 75 kWh battery from a New Routemaster bus, the charge levels would be as follows, as it went to Barking Riverside and back.

  • Joining the new line to go to Barking Riverside and leaving the electrification – 75 kWh
  • Starting braking for Barking Riverside station – 55 kWh
  • Stopped at Barking Riverside station, after regenerative braking, which generates perhaps 30 kWh.- 75 kWh
  • At line speed after accelerating away from Barking Riverside station – 35 kWh
  • Joining the electrified main line – 15 kWh

Note,.

  1. I have assumed that the train needs 20 kWh for the journey, but this figure will probably be lower, as the Aventra is a very efficient train.
  2. Regenerative braking is not hundred percent efficient, so that explains generating only 30 kWh. But it could be more.

It would appear that the diesel engine would not need to be used.

I come to the conclusion, that there is no need to electrify, the Barking Riverside Extension!

Here are a few other thoughts.

The Size And Number Of Batteries

The total capacity of the battery or batteries must be such, that they can handle, the maximum amount of energy that will be generated in braking.

This has the following benefits.

  • The train may not have any need to be fitted with resistors on the roof or other means to use the generated eectricity.
  • Any electrification will not need to be given the ability to handle return currents from the train.
  • The train will use less energy on a given trip.

As an engineer, I like the concept of putting a battery in all cars with traction motors.

  • Each battery will have shorter cables to where energy is used and created, which will cut losses.
  • More batteries probably improves reliability.
  • Distributing the weight might be a good thing.

I would suspect that only unmotored trailer cars might not have batteries.

Supposing a Class 710 train had three 75 kWh batteries.

This would give a capacity of 225 kWh and the following ranges on battery against energy usage in k|Wh/per mile/per car.

  • 5 kWh – 11 miles
  • 4 kWh – 14 miles
  • 3 kWh – 19 miles
  • 2 kWh – 28 miles
  • 1 kWh – 56 miles

These figures show that an efficient train is key to a longer range.

The ultimate Class 710 train might have the following.

  1. Two 75 kWh batteries per car.
  2. Energy usage of 3 kWh/per mile/per car.

This would give a range of fifty miles.

With a small and almost silent Cummins diesel engine from a New Routemaster, it could go as long as you wanted.

Should A New Routemaster Bus Diesel Generator And Battery Be Used?

Consider.

  • There are a thousand New Routemaster buses on the streets of London, so the reliability of the power train must be known very accurately.
  • The Cummins diesel engine and generator are very quiet and are only noticed on an empty bus, when they start and stop.
  • The engine and generator are under the back stairs.
  • The battery is fitted under the front stairs.

The power train doesn’t appear to be large.

Using these components would certainly be a good place to start and they could probably be easily fitted under the train.

In the rest of this post, imagine a Class 710 train with a single 75 kWh battery and a Cummins diesel and generator,

Would Be The Maximum Speed On Diesel Power Be The Same As On Electricity?

Because the battery and the diesel generator will work together, I believe this will be possible, if there is a well-programmed computer system on the train.

  • Accelerating to line speed of 90 mph will take around forty kWh, as that will be the energy of the train.
  • This will perhaps take thirty seconds in which time, the 138 kW Cummins generator, will produce just over a kWh of electricity, so the battery will provide 39 kWh.
  • The battery will be charged by electrification where it exists and regenerative braking.
  • In addition, the diesel generator could also top up the battery.
  • In the cruise, energy would need to be supplied to overcome aerodynamic losses, to climb gradients and provide train and passenger services.
  • Under braking, the regenerative braking would charge the battery.

You wouldn’t be able to run on a challenging line, but running on a fairly level line, which was perhaps twenty miles long with a dozen stations, would be a possibility.

Range on a real route, would be increased by adding extra batteries.

I suspect, Bombardier have created a sophisticated computer simulation of various train configurations and routes.

In this article in Rail Magazine, which is entitled Bombardier Bi-Mode Aventra To Feature Battery Power, a company spokesman is quoted as saying.

The bi-mode would have a maximum speed of 125 mph under both electric and diesel power.

So I’m pretty certain, a bi-mode version of a Class 710 train would have a 90 mph operating speed .

And for some easy routes on the similar-sized battery and diesel generator to that of a New Routemaster bus.

The Get-You-Home Train

Imagine a Class 710 train with a single 75 kWh battery and a Cummins generator.

Suppose power is cut to the electrification for some reason.

A normal electric train would just sit there, but the generator would cut in and using the residual energy in the battery, the train would go slowly to the next station.

With just 75 kWh and an energy usage of 3 kWh/per mile/per car, the train would go six miles.

Fast Station Stops

The keys to a fast stop at a station or a short dwell time are down to the following.

  1. Smooth, fast deceleration under regenerative braking.
  2. Efficient loading and unloading of passengers and their baggage.
  3. Fast acceleration away from the stop to regain operating speed.

Point two has nothing to do with the traction system of the train and it can be improved by good design of doors, lobbies on the train and platforms, and by better staff deployment and training.

Will the traction system be designed in a similar way to that of a New Routemaster bus?

The train’s traction, passenger, driving and other systems will be powered directly from the battery.

The battery will be charged in one of four ways.

  • From 25 KVAC overhead electrification.
  • From 750 third-rail electrification.
  • From the onboard generator.
  • From regenerative braking.

Note.

  1. A well-programmed computer system would control the whole traction system.
  2. Fast acceleration to operating speed will probably need the onboard generator or the electrification to provide a backup to the battery.
  3. The battery can probably supply more power for a short period, than an onboard generator or the electrification
  4. When the train stops in a station, the computer will ensure that the battery contain as much power as possible, so that a quick acceleration away is possible.
  5. A lot of power will have come from regenerative braking, but at times, the onboard generator  or the electrification would be used to charge the battery.
  6. At each stop, because of the limitations of regenerative braking, a certain proportion of the electrical energy will not be recovered and stored in the battery. The onboard generator or the electrification would make up the difference.

Note that the train works in the same way with an onboard generator or electrification.

The West London Orbital Railway

The proposed West London Orbital Railway will connect Hounslow and Kew Bridge stations in West London to West Hampstead and Hendon stations in North London using the Dudding Hill Line.

  • It is around twelve miles long.
  • It is electrified at the Western End using third-rail electrification.
  • There is overhead electrification in the North.
  • The middle section is not electrified.

Class 710 trains, with a diesel generator and a battery stolen from a New Routemaster bus could be able to handle the routes proposed.

Conclusion

I am led to the conclusion. that if you fitted the battery and diesel generator of a New Routemaster bus under one of the cars of a Class 710 train, you would have the following.

  • A train capable of 90 mph on diesel and electrification.
  • A useful range without electrification.

The train would need a well-programmed computer system.

The London Overground could use these trains on the Barking Riverside Extension and the West London Orbital Railway.

 

April 3, 2018 - Posted by | Travel | , , , , , ,

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