The Anonymous Widower

What Is The Kinetic Energy Of A Class 710 Train?

I finally got a good look at a Class 710 train at Gospel Oak station this morning.

The picture shows the plate on the end of a DMS car.

  • The weight of the train is 157.8 tonnes. Note that the four-car Class 378 trains weigh 172.1 tonnes.
  • 700 passengers at 90 Kg each with baggage, bikes and buggies would be 63 tonnes.
  • That would be a total weight of 220.8 tonnes.
  • The operating speed is shown as 75 mph., which is the same as the Class 315 train, that many Class 710 trains will replace.

Using the Omni Kinetic Energy Calculator gives a kinetic energy of 34.5 kWh.

For completeness these are the figures for different speeds.

  • 90 mph – 49.4 kWh – Operating speed of a Crossrail Class 345 train.
  • 100 mph – 61.3 kWh – Operating speed of many electric multiple units.

Note that the amount of energy is proportional to the square of the speed.

What Do The  Kinetic Energy Figures Show?

These are a few of my thoughts.

What Is Regenerative Braking?

A full Class 710 is travelling along at 75 mph, ihas 34.5 kWh of kinetic energy. Whenit needs to stop at a station, this energy has to be dissipated.

With normal friction brakes, the energy will be converted into heat and wasted.

But with regenerative braking, the traction motors are used in reverse to generate electricity.

This electricity is generally handled in one of three ways.

  • It is passed through resistors on the roof of the train and turned into heat and wasted.
  • It is fed back into the electrification and used by nearby trains. This needs special transformers feeding the electrification.
  • It is stored in a battery or other energy storage device on the train.

The last method is the most efficient, as the stored energy can be used to help restart the train and regain line speed.

Can The Lea Valley Lines Electrification Handle Regenerative Braking?

This question must be asked, as if the lines can’t then running trains with batteries could be the best way to handle regenerative braking and improve efficiency and reduce the electricity bill.

It should be noted, that the Chingford and Enfield Town routes are not shared with any other trains, so running Class 710 trains on these routes may have advatages in the maintenance of the electrification, if the trains handle the regenerative braking.

On the Cheshunt route, there are also some Greater Anglia services, but these will generally be run by Class 720 trains, which are also Aventras.

On the other hand, the electrification on the Gospel Oak to Barking Line has probably been installed to handle the reverse currents.

Do Class 710 Trains Have Regenerative Braking?

Search the Internet for “Class 710 train regenerative braking” and you find little in addition to my ramblings.

But other Aventras, like Crossrail’s Class 345 trains have been stated to have regenerative braking.

I also repeated my views in an article in Rail Magazine, which I described in I’ve Been Published In Rail Magazine.

No-one has told me that they disagree with my views and I was talking rubbish!

So I will assume that Class 710 trains do have regenerative braking!

The Aventra’s Electrical Systems

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.

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

But even in 2011, Bombardier were thinking about energy storage on the train.

How Much Storage Would A Class 710 Train Need?

As I said earlier, I train would need sufficient energy storage to store the kinetic energy of a train.

As my calculations show that a full train travelling at the maximum speed of 75 mph, then the energy storage for this version of a Class 710 train must be able to store at least 34.5 kWh, at all times.

The size of the on board energy storage could be around 40-50 kWh, which is readily available in a lithium ion battery, that has been designed for transport use.

Where Would The Energy Storage Be Placed?

The extract above says that two cars hold the electrical systems.

These pictures show the pantograph car and driver car next to it.

Note that underneath the pantograph car is a transformer.

So are these, the pair of cars, the extract describes? They certainly could be!

This is a selection of pictures of the underneath of the driver car.

Note.

  1. There are two large boxes with latches under both driver cars.
  2. Next to these boxes is a smaller box. At the pantograph end of the train, it is open and looks like a cooling system for the two boxes
  3. At the other end of the train, the smaller box appears to have a blanking plate, so perhaps the boxes are empty.

The only sensible use I can think of for the boxesis to store the batteries or capacitors.

I

I would estimate that each of the four large boxes.

  • Is about a metre wide.
  • Is about 0.3 metres high.
  • Is sized to fit within the 2.7 metre width of the train. Perhaps 2.5 metres.

These give a column of 0.75 cubic metres.

Bombardier used to manufacture a Primove 50 kWh battery, which was built to power trams and trains, that had the following characteristics.

  • A weight of under a tonne.
  • Dimensions of under two x one x half metres.

Were these boxes under the floor of the driver cabs of the Class 710 train designed to hold a Primove 50 kWh or similar battery?

Four batteries could give the train as much as 200 kWh of energy storage.

But surely for trundling along the Gospel Oak to Barking Line. a smaller battery capacity would be sufficient. I suspect that you fill the boxes with how many batteries you need and the computer does the rest.

Perhaps, just one 50 kWh battery would be enough! This could explain, why the cooling system appears to be blanked off at one end of the train.

Could The Batteries Be Used To Power The Class 710 Train?

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 is not very challenging.

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

So a 50 kWh bsttery would give the following ranges with these consumption rates for a four-car Class 710 trains.

  • 3 kWh – 4.2 miles
  • 4 kWh – 3.1 miles
  • 5 kWh – 2.5 miles

It looks to me, that battery power would be possible over the extension to Barking Riverside station, which is about a mile long.

Battery power would also other uses.

  • Moving the train to a safe place for passenger evacuation, when the overhead electrification fails.
  • Moving the train in a depot or sidings, without overhead power.
  • Running innovative on-board services for maintenance and train preparation, when the train is parked overnight.

Reliable battery power has a lot of uses on a train.

West London Orbital Railway

The West London Orbital Railway would have less than ten miles of lines without electrification, with several electrified miles on either side.

I believe that Class 710 trains with the right amount of batteries could bridge the gap and make a massive difference to rail transport in North and West London.

I think that jumping a gap of a few miles on battery power, may well be easier than doing an Out-and-Back service..

A Flexible System

As it appears, each Class 710 train has got four battery boxes, I suspect that batteries can be installed as to the needs of the route.

  • Standard operation on Gospel Oak to Barking, Watford DC Lines and Lea Valley Lines could be one or two batteries to handle regenerative braking.
  • Out-and-Back to Barking Riverside station ,might need two batteries.
  • West London Orbital services might need three or four batteries.

These battery boxes also could be designed to allow an easy and quick change of battery, as batteries on buses have given Transport for London trouble in the past.

Conclusion

Bombardier’s design of the Aventra has been designed with battery operation in mind, which opens up lots of possibilities!

May 25, 2019 - Posted by | Transport | , , , ,

2 Comments »

  1. Small plea – please use SI units! mph and especially kWhrs are very confusing.

    Comment by R. Mark Clayton | May 26, 2019 | Reply

  2. The trouble is that when I used to use kilometres etc. I got complaints about not using miles.

    So now I tend to use units that people can relate to, like miles, tonnes or tons (no difference), mph, kWh, which are units most people understand.

    But in my personal life, I always work in SI units. When I went to work for ICI in 1969, they had been metric since the mid-50s and then after I’d left, I found it strange that some big engineering companies worked in Imperial units.

    One guy at ICI said that some serious problems on chemical plants had been caused by conversion of units.

    Interesting, my son is nearly fifty and he works in Imperial units despite having been taught at school in metric.

    I also have a copy of The Times for July 20th, 1969, which has a report on the Decimalisation and Metrication Board, which says that the country will be totally metric by 1984.

    Comment by AnonW | May 26, 2019 | Reply


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