The Anonymous Widower

Do Aventras Use Supercapacitors?

In 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. The intention is that every car will be powered although trailer cars will be available.

Unlike today’s commuter trains, AVENTRA will also shut down fully at night. It will be ‘woken up’ by remote control before the driver arrives for the first shift

This was published over seven years ago, so I suspect Bombardier have refined the concept.

The extract makes three interesting points.

All Or Most Cars Will Be Powered

In A Detailed Layout Drawing For A Class 345 Train, I give the formation of a Crossrail Class 345 train.

DMS+PMS+MS1+MS3+TS(W)+MS3+MS2+PMS+DMS

Note.

  1. M signifies a motored car.
  2. Eight cars have motors and only one doesn’t.
  3. The train is composed of two identical half-trains, which are separated by the TS(W) car.
  4. There are four wheelchair spaces in the TS(W) car.

Are the MS!, MS2 and MS3 cars identical?

In addition, I have been told, that all cars in Class 720 trains are motored.

It does seem that Bombardier have fulfilled their statement from 2011.

Remote Wake-Up

This is mentioned in the extract, but there are few other references to it. I quoted a report from the Derby Telegraph, which has since been deleted, in Do Bombardier Aventras Have Remote Wake-Up?.

Supercapacitors And Lithium-Ion Batteries

According to the extract, the trains have been designed to accept supercapacitors or lithium-ion batteries if required.

As the other two statements in the extract appear to be likely, I will continue to believe that all Aventras can have some form of energy storage.

Crossrail

I’ll look first at Crossrail’s Class 345 train.

In How Much Energy Does A Crossrail Class 345 Train Use?, using the train’s data sheet, I came to the conclusion, that electricity usage of the trains is 2.67 KWh per car per kiometre or 3.29 KWh per car per mile.

In the linked post, I also calculate the kinetic energy of a fully-loaded nine-car Crossrail train.

I’ll repeat it.

  • If I take a nine-car Class 345 train, 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 a kinetic energy of 101 KWh.

As the Class 345 trains are effectively two half trains, with two PMS cars with pantographs, it is likely that they have at least two cars that are ready for supercapacitors or lithium-ion batteries.

The Design Of Crossrail

Crossrail could best be described as the Victoria Line on steroids.

  • Both lines were designed to run in excess of twenty-four trains per hour (tph) across London.
  • The Victoria Line was built to deep-level Underground standards, with one of the most advanced-for-its-time and successful train operating systems of all times.
  • Crossrail is a modern rail line being built to National Rail standards, with world-leading advanced technology, that takes full account of modern environmental standards and aspirations.

Costs were saved on the Victoria Line by leaving out important parts of the original design..

Costs were saved on Crossrail, by using high-quality design.

  • Crossrail and the Great Western Main Line electrification share a sub-station to connect to the National Grid.
  • The number of ventilation and access shafts was reduced significantly, with one in a new office block; Moor House.
  • Electrification uses a simple overhead rail, which is only fed with power at the ends.

I also believe that the Class 345 trains, which were designed specifically for the route, were designed to save energy and increase safety in the tunnels.

Regenerative braking normally saves energy by returning braking energy through the electrification, so it can be used to power other nearby trains.

Batteries For Regenerative Braking

However, in recent years, there has been increasing interest in diverting the braking energy to onboard energy storage devices on the train, so that it can be used when the train accelerates or to power systems on the train.

The system has these advantages.

  • Less energy is needed to power the trains.
  • Simpler and less costly transformers  can be used for the electrification.
  • The onboard energy storage can be used to power the train after an electrification failure.
  • In tunnels, there is less heat-producing electricity flowing in all the cables.

Obviously, keeping the heat down in the tunnels is a good thing.

A Station Stop On Crossrail Using Regenerative Braking And Energy Storage

Imagine a fully-loaded train approaching a station, at the maximum speed on 145 kph.

  • The train will have a kinetic energy of 101 kWh.
  • As it approaches the station, the brakes will be applied and the regenerative brakes will turn the train’s energy into electricity.
  • This energy will be stored in the onboard energy storage.
  • As the train accelerates away from the station, the electricity in the onboard energy storage can be used.

The only problem, is that regenerative braking is unlikely to recover all of the train’s kinetic energy. But this is not a big problem, as the train draws any extra power needed from the electrification.

To make the system as efficient as possible, the following must be fitted.

  1. The most efficient traction motor.
  2. Onboard energy storage capable of handling the maximum kinetic energy of the train.
  3. Onboard energy storage with a fast response time.

The train will probably be controlled by a sophisticated computer system.

What Size Of Onboard Energy Storage Should Be Fitted?

Obviously, this is only speculation and a best guess, but the following conditions must be met.

  • The onboard energy storage must be able to capture the maximum amount of energy generated by braking.
  • The physical size of the energy storage system must be practical and easily fitted under or on the train.
  • The energy storage system should be able to store enough energy to be able to move a stalled train to safety in the event of complete power failure.

Note that an energy storage system with a 100 kWh capacity would probably take the train somewhere around four to five kilometres.

Obviously, a series of computer simulations based on the route, passengers and various other conditions, would indicate the capacity, but I feel a capacity of around 120 kWh might be the place to start.

Where Would The Energy Storage Be Placed?

With nine cars, and with eight of them motored, there are a several choices.

  • One energy storage unit in all motored cars.
  • One energy storage unit in the three MS cars.
  • One energy storage unit in each half train.

I’ve always liked the concept of an energy storage unit in each powered car, as it creates a nice tight unit, with energy stored near to where it is generated and used.

But there is another big advantage in splitting up the energy storage – the individual units are smaller.

Could this mean that supercapacitors could be used?

  • The main need for onboard energy storage is to handle regenerative braking.
  • The secondary need for onboard energy storage is for emergency power.
  • There is no needon Crossrail as yet,to run the trains for long distances on stored power.
  • Supercapacitors are smaller.
  • Supercapacitors can handle more operating cycles.
  • Supercapacitors run cooler.
  • Supercapacitors have a fast response.

If running for longer distances were to be required in the future, which might require lithium-ion or some other form of batteries, I’m sure there will be space for them, under all those cars.

I wouldn’t be surprised to find out that Crossrail’s Class 345 trains are fitted with supercapacitors.

Note, that  a Bombardier driver-trainer, talked of an emergency power supply, when I asked what happens if the Russians hacked the electrification.

Class 710 Trains

London Overground’s Class 710 trains are a bit of a mystery at the moment as except for a capacity of seven hundred passengers disclosed in this article on the International Railway Journal little has been published.

Here are my best guesses.

Formation

Based on the formation of the Class 345 trains, I think it will be.

DMS+PMS+MS+DMS

Effectively, this is a half-train of a seven-car Class 345 train, with a DMS car on the other end.

Dimensions

I have a Bombardier press release, which says that the car length is twenty metres, which is the same as Class 315, Class 317 and Class 378 trains and a whole load of other trains, as twenty metre cars, were a British Rail standard.

I doubt there will be much platform lengthening for these trains in the next few years.

Weight

The Wikipedia entry for Aventra gives car weight at between thirty and thirty-five tonnes, so the train weight can be anything between 120-140 tonnes.

Passenger Capacity

I wrote about this in The Capacity Of London Overground’s New Class 710 Trains.

This was my conclusion.

It appears that seven hundred is the only published figure and if it is, these new Class 710 trains are going to substantially increase public transport capacity across North London.

They are certainly future-proofed for an outbreak of London Overground Syndrome, where passenger numbers greatly exceed forecasts.

As some of the trains are being delivered as five-car units, there is always the option of adding an extra car. Especially, as the platforms on the line, seem to have been built for five or even six car trains.

London Overground have not made the platform length miscalculations of the North and East London Lines.

For the near future they’ll hold around 700 passengers at 80 Kg. each, which means a passenger weight of fifty-six tonnes.

Full Train Weight

For various train weights, the fully-loaded trains will be.

  • 120 tonnes – 176 tonnes
  • 130 tonnes – 186 tonnes
  • 140 tonnes – 196 tonnes

Until I get a better weight for the train, I think I’ll use 130 tonnes or 186 tonnes, when fully-loaded.

Speed

I wrote about this in What Is The Operating Speed Of Class 710 Trains?.

This was my conclusion.

But what will be the operating speed of the Class 710 trains?

I said it will be somewhere between 145 kph (90 mph) and 160 kph (100 mph)

Consider.

  • I think that 145 kph, will be able to handle the two planned increased frequencies of four tph.
  • 145 kph is identical to the Crossrail trains.
  • 160 kph is identical to the Greater Anglia trains.
  • 160 kph seems to be the speed of suburban Aventras.

It’s a difficult one to call!

I do think though, that trundling around the Overground, they’ll be running at the same 121 kph of all the other trains.

Kinetic Energy

The kinetic energy of a 186 tonnes train at 121 kph is 29 kWh.

Could Supercapacitors Handle This Amount Of Energy?

I’m pretty certain they could.

Conclusion

Supercapacitors are a possibility for both trains!

I’ll review these calculations, as more information is published.

 

November 11, 2018 - Posted by | Transport | , , , , ,

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