The Anonymous Widower

Battery Trains On The Uckfield Branch

The Uckfield Branch is not electrified and it only gets an hourly service to London Bridge.

However a few years ago, all platforms on the line were extended, so that twelve-car trains could run services.

I have always felt that this service was ideal for running using battery trains.

  • Trains would run between London Bridge and Hurst Green using the third rail electrification.
  • The batteries would be charged between London Bridge and Hurst Green stations.
  • South of Hurst Green, the train would run on battery power.
  • Top-up charging could be provided during the eleven minute turnround at Uckfield station.

These are distances and times between stations South of Hurst Green.

  • Hurst Green – Edenbridge Town – 4.33 miles – 6.98 km. – 6 mins – 7 mins
  • Edenbridge Town – Hever – 1.75 miles – 2.81 km – 4 mins – 4 mins
  • Hever – Cowden – 2 miles – 3.21 km. – 4 mins – 5 mins
  • Cowden – Ashurst – 2.77 miles – 4.47 km. – 4 mins – 4 mins
  • Ashurst – Eridge – 2.31 miles – 3.72 km. – 6 mins – 6 mins
  • Eridge – Crowborough – 3.74 miles – 6.01 km. – 6 mins – 6 mins
  • Crowborough – Buxted – 4.71 miles – 7.58 km – 7 mins – 7 mins
  • Buxted – Uckfield – 2.25 miles – 3.62 km – 6 mins – 4 mins

Note.

  1. The first time is Southbound and the second is Northbound.
  2. I only calculated distances to two decimal places.

It appears the route has a generally 70 mph operating speed.

What Is The Performance Of The Current Class 171 Trains?

Class 171 trains have the following characteristics.

  • 100 mph operating speed
  • Acceleration of 0.5 m per second²
  • A weight of 90.41 tonnes.
  • Seating for 109 passengers.
  • On my trip today, the train rarely exceeded 50 mph.

What Would Be The Performance Of A Battery Train?

I will assume that the battery train is something like a Class 701 train fitted with batteries.

  • Ten cars
  • 100 mph operating speed
  • Acceleration of 1.0 m per second² (taken from Class 345 train)
  • A weight of 364.9 tonnes. (An estimate based on data from Weight And Dimensions Of A Class 345 Train.
  • Based on the Class 345 train, I would reckon the train would have at least eight motored cars.
  • I would put a battery in each motored car.
  • Capacity of 546 seated and 673 standing passengers.

I will use this information to calculate the energy of the train.

Assuming each passenger with all their baggage is 90 kg., this gives a passenger weight of 109.71 tonnes

This gives a total train weight of 474.61 tonnes.

Calculating the kinetic energy for various speeds gives.

  • 30 mph – 11.8 kWh
  • 40 mph – 21 kWh
  • 50 mph -30.9 kWh
  • 70 mph – 64.5 kWh
  • 80 mph – 84.3 kWh
  • 90 mph – 106.7 kWh
  • 100 mph – 131.7 kWh

Even the highest energy figure, which is way above the operating speed of the line could be handled under regenerative braking by a convenient size of battery.

How Would A Battery Train Operate?

This Google Map shows Hurst Green station and Hurst Green Junction, where the Uckfield and East Grinstead branches split.

As the East Grinstead branch is electrified, after stopping at Hurst Green station, a train for Uckfield station will have something like two to three hundred metres of electrified track to accelerate it to the operating speed.

At present the operating speed appears to be 70 mph, but if it were higher, the train would enter the section of track without electrification, with more energy.

As it is, the train would probably be entering the branch with batteries, that had been fully-charged on the way from London.

The electrification would have been used like a catapult to impart maximum energy to the train.

At each stop, the following would happen.

  • Regenerative braking will convert the train’s kinetic energy into electricity, which will be stored in the batteries.
  • Battery power would then accelerate the train after each stop.

As regenerative braking is not 100% efficient, there would be a loss of perhaps fifteen percent of kinetic energy at each stop.

So gradually as the train progresses to Uckfield and back, the battery charge will be depleted.

There are seven stations between Hurst Green and Uckfield,so that means that fifteen stops will have to be made before the train returns to the electrification at Hurst Green.

If the train was operating at 70 mph, the kinetic energy would be 64.5 kWh and the losses in the regenerative braking at fifteen stations would be 64.5 *0.15 *15 or 145.57 kWh.

I will assume each battery train has eight 50 kWh batteries, as Bombardier have a 50 kWh PRIMOVE battery that would be suitable.

So if the train entered the Uckfield branch with 400 kWh in the batteries and 64.5 kWh in the train, it would be carrying 464.5 kWh, that could be used to power the train.

As I said, 145.57 kWh would be lost in braking, so that would leave 318.93 kWh to take a ten car train, a distance of 46 miles.

This works out at a figure of 0.7 kWh per car per mile for the journey.

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 it looks like running a battery train on the route could be impossible, as there is a large difference between 0.7 and 3.

Let’s see what the mathematics say for various ideas.

Put A 50 kWh battery In Each Car

The larger battery capacity would mean the train will enter the branch  carrying 564.5 kWh, that could be used to power the train.

Thus after deducting the regeneration losses of 145.57 kWh, this would leave 418.93 kWh to run the 460 vehicle miles.

This works out at a figure of 0.9 kWh per car per mile for the journey.

Improve The Efficiency Of The Regenerative Braking

Suppose that the energy lost at each stop can be reduced from fifteen to ten percent, how much difference would that make?

If the train was operating at 70 mph, the kinetic energy would be 64.5 kWh and the losses in the regenerative braking would now be 64.5 *0.10 *15 or 96.75 kWh.

Using the 500 kWh battery would mean the train will enter the branch  carrying 564.5 kWh, that could be used to power the train.

Thus after deducting the regeneration losses of 96.75 kWh would leave 467.75 kWh to run the 460 vehicle miles.

This works out at a figure of 1 kWh per car per mile for the journey.

Charge the Train At Uckfield

Trains take eleven minutes to turn round at Uckfield station.

So how much power could be put into the batteries in that time?

But the Aventra isn’t a normal train.

Crossrail’s Class 345 trains have the following formation.

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

Note that it is symmetrical with two PMS cars, which have pantographs and the heavy electrical gear.

I suspect that the trains are two half trains with a degree of independent systems, so that if there are problems in the Crossrail tunnel, the train doesn’t get trapped.

I wonder if Thameslink’s Class 700 trains are the same?

So will South Western Railway’s third rail Class 701 trains be similarly designed, so that they can bridge gaps in the third rail electrification. If the third-rail shoes were in the second and ninth cars, they would be around 160 metres apart.

So perhaps a charging point based on third rail technology could be a double one, with a connection to each half-train.

This picture shows the exceedingly long platform at Uckfield station.

It could certainly accommodate a double third rail-based charging system.

  • It would be on the far-side from the platform.
  • It would only be activated with a train the platform and connected.
  • It could be designed to have no serious safety problems.

The eleven minute charge would be equivalent to one of twenty-two minutes.

There must surely be the option to adjust the timetable, so that trains spend a few minutes longer at Uckfield and a few less at London Bridge, where charging isn’t necessary, as they charge the batteries all the way to and from Hurst Green.

Aventra Trains Have A Low Energy Mode

A few months ago, I was on a Crossrail train and I got talking to one of the driver/trainers.

I asked him what happens, if the power fails in the Crossrail tunnel.

He told me, that the driver switches systems off to reduce power requirements and switches to emergency power to move the train to a safe place to evacuate passengers.

Suppose though, when the train is running on batteries, power-hungry systems like air-conditioning were turned to a low energy mode. With judicious switching and innovation in design, I suspect that energy use can be lowered when running on batteries and raised when running on electrification to compensate.

Suppose, it was a very hot summer’s day.

The air-conditioning would be cooling the train from London Bridge to Hurst Green, getting more than adequate power from the electrification.

At Hurst Green, the train would be just the right temperature and the air-conditioning would be switched to eco-mode.

The train would be well-insulated and this would help maintain the cool environment, until the electrification was regained.

What about a cold day in the winter?

This post is entitled Aventras Have Underfloor Heating. On a cold day will this act a bit like a storage heating and keep the train warm if the power fails?

As I said I don’t think an Aventra is a normal train and although some of this is my deductions, we should be prepared for surprises as more of these trains start running on the UK’s railways.

Will Battery Trains Be Slower?

Much of the battery running on this route will be short hops of a few miles and minutes between stations.

The longest section will be between Crowborough and Buxted stations, which is 4.71 miles and currently takes seven minutes in both directions.

Both the Class 171 trains and the battery trains, will operate each section in the same way.

  • Accelerate to the line speed, as fast as possible.
  • Run at line speed for a measured distance.
  • Slow down and apply braking to stop precisely in the next station.

As the battery train has 1 metre per sec² acceleration, as opposed to 0.5 metre per sec² of the diesel train, the battery train will get to line speed faster

Regenerative braking will also be smoother and possibly greater, than the brakes on the diesel train.

I am fairly sure, that a well-designed battery train will save a few minutes on each leg from Hurst Green to Uckfield.

These time savings could be used to extend the charging time at Uckfield

Conclusion

Running services on the Uckfield branch using battery-powered trains is a feasible proposition.

But these trains must have the following features.

  • Regenerative braking to the trains batteries.
  • A design where batteries are central to the traction system, not an afterthought.
  • The ability to minimise power use for onboard systems.

But above all, the trains must have energy efficient systems.

Bombardier obviously have better figures and information than I do, so I think we should be prepared for surprises.

 

 

 

 

August 26, 2018 - Posted by | Transport | , , ,

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