The Anonymous Widower

Could A Class 450 Battery/FLEX Train Be Used Between Waterloo And Exeter?

When I wrote Porterbrook Makes Case For Battery/Electric Bi-Mode Conversion, Issue 864 of Rail Magazine hadn’t been published. The magazine contained details of Vivarail’s proposed rapid charging facility, which I wrote about in Charging A Battery-Powered Class 230 Train.

Consequently, at the time, I came to the conclusion that a Class 450 train with a Battery/FLEX conversion, similar to Porterbrook’s one for a Class 350 train, couldn’t stretch between Waterloo and Exeter, as it was just too far.

But Vivarail’s proposed rapid charging facility could change everything!

The West of England Main Line is electrified as far as Basingstoke station, from where the route is worked excursively by diesel Class 159 trains.

Between Basingstoke and Exeter St. Davids stations, the trains make fourteen stops.

  • Most station stops,take up to a minute, but could take longer if say the train is busy or there’s a passenger in a wheelchair.
  • The train stops at Salisbury for four minutes, possibly to allow loading and unloading of catering trolleys.
  • The distances between stations range between a few and eighteen miles.
  • In Porterbrook Makes Case For Battery/Electric Bi-Mode Conversion, I said that if a 400 kWh battery were to be fitted to a Class 350/2 train, that this would give a range between twenty and fifty miles.
  • The Class 350 and South Western Railway’s Class 450 trains are the same basic Siemens Desiro train, although the Class 350 train uses 25 KVAC overhead electrification and the Class 450 train uses 750 VDC third-rail electrification.

It would appear that if the train could be charged at each station, it should be able to hop all the way between Basingstoke and Exeter St. Davids stations.

Using a traditional charger, where the train would have to be physically plugged into the charger, wouldn’t be possible in the short station stops on the route.

Even raising a pantograph to connect to a 25 KVAC overhead line would be slow and could distract the driver, whilst they were doing more important things.

But Vivarail’s proposed rapid charging facility, which I am sure is automatic would give the battery a top-up without any driver intervention.

 

The charging system would have a third rail on the opposite side of the track to the platform, as in this picture of Kidbrooke station.

The third-rail would be.

  • Short enough to be shielded by a train stopping on top.
  • Long enough to connect to at least two contact shoes on the train.
  • Automatically earthed, when no train is present and connected.

This would be the sequence, as a train stopped in a station.

  • The driver would stop the train at the defined place in the platform, as thousands of train drivers do all over the world, millions of times every day.
  • Once stopped, the contact shoes on the train would be in contact with the third rail, as they would be permanently down, as they are when running on third-rail electrification.
  • The charging system would detect the stationary train and that the train was connected, and switch on the power supply. to the third-rail.
  • Electricity would flow from the track to the batteries, just as if the train was on a standard third-rail electrified track.
  • If the battery should become full, the train’s system could stop the charging.
  • When passengers had finished leaving and joining the train and it was safe to do so, the driver would start the train and drive it to the next station.
  • When the charging system determined that the train was moving or that the contact shoe was no longer connected to the third-rail, it would immediately cut the power to the rail and connect it to earth.

It is a brilliant system; simple, efficient and fail-safe.

  • Regenerative braking will mean that stopping in the station will help to top-up the batteries.
  • The battery on the train is being charged, as long as it is stationary in the station.
  • Delays in the station have no effect on the charging, except to allow it for longer if the battery can accept more charge.
  • The driver concentrates on driving the train and doesn’t have to do anything to start and stop the charging.
  • The charging system never exposes a live rail to passengers and staff.

The charging system may also help recovery after an incident.

Suppose a fallen tree or a herd of cows has blocked the line and the electricity used to power the train’s systems has used a lot of battery power, so that when the train eventually gets to the next station, the battery needs a long charge before continuing.

The driver would just wait in the station, charging the battery, until there is enough energy to safely proceed.

A Look At The Mathematics

I shall now look at the mathematics of a leg between Basingstoke and Andover stations.

I will assume the following.

  • The train will leave the electrification at Basingstoke with a full battery, containing 400 kWh of electricity, as it will have been charged on the way from Waterloo.
  • The train is running at an operating speed of up to 90 mph between stations where possible, which means it has a kinetic energy of 47.1 kWh.
  • For each mile, the train consumes 8 kWh of electricity, to power the trains services and maintain the required speed.
  • Regenerative braking is eighty percent efficient.

As Basingstoke to Andover is eighteen miles, this means that energy consumption in the leg and the stop at Andover is as follows.

  • 144 kWh is used to power the train and maintain speed.
  • 9.42 kWh is lost in the braking and acceleration back to operating speed..

So the train will lose about 154 kWh on the eighteen mile leg.

I have built an Excel spreadsheet of the route and it looks that if a minimum of 100 kWh can be transferred to the train’s battery at each stop and the train uses no more than 8 kWh per mile, that it should be possible for the train to go from Basingstoke to Exeter on battery power.

Obviously, there are ways to make this journey more certain.

  • Reduce the train’s energy consumption for items like lighting and air-conditioning..
  • Improve the efficiency of regenerative braking.
  • Improve the charging systems, so more electricity is transferred in the short stops.
  • Improve the track, so that it is as smooth as possible with gentle curves.
  • Fit a larger battery.

It requires different teams of engineers to optimise their own area, so all contribute to a more energy-efficient system.

Would Battery Power Work If The Line Speed Was Increased to 100 mph?

I have done this calculation assuming an operating speed of 100 mph, rather than the current 90 mph determined in part by the maximum speed of the Class 159 trains and it appears to be still possible.

Could 100 kWh Be Transferred To The Train In The Short Stops?

In Station Dwell Times On The London Overground, I showed that the London Overground regularly has station stops of under thirty seconds.

Even to me, as an trained Electrical Engineer, 100 kWh does seem a lot of power to transfer to the train in a stop that is that short.

In the related post, I postulated that a thirty-second dwell time, means that the only way to connect the train to the rapid charging system is to use third-rail electrification, as this connects and disconnects automatically.

This was said about Vivarail’s charging system in Issue 864 of Rail Magazine.

The rapid charging concept consists of a shipping container of batteries that are trickle charged from a mains supply. When a Class 230 sits over the short sections of third-rail, electricity can be quickly transferred to the train’s batteries. When the train is away, the power rails are earthed to ensure they pose no risk The concept provides for charging a Class 230 as it pauses at a terminus before making its return journey.

The key is the battery-to-battery transfer of electricity, as batteries have a low impedance and are designed to supply high electrical currents for a short time, as when starting a massive diesel engine in a truck.

This page shows a 12v 250Ah battery available for just over three hundred pounds.

  • This battery alone has a capacity of 3 kWh.
  • It is 518mm x 273mm x 240mm.
  • It weighs 61 Kg.

You’d get a lot of these in a twenty-foot shipping container, which according to Wikipedia has a volume of 33.2 m³.

I estimate that a hundred of these batteries would fit easily into the container with all their control gear and electronics, which would mean a total capacity of 300 kWh.

Running my Excel spreadsheet with a 200 kWh transfer at each station, shows that the train can leave many stations with a full battery.

I have also run a more difficult scenario.

  • For each mile, the train consumes 10 kWh of electricity instead of 8 kWh, to power the trains services and maintain the required speed.
  • The rapid charging system can only transfer 80 kWh in thirty seconds.

The train still appears to get to its destination.

Obviously, Porterbrook, Siemens and Vivarail have better data than I have and will know what the actual performance of their trains and systems are.

How Much Power Can The Third-Rail Handle?

It should also be noted that a Class 450 train has eight x 250 kW traction motors, so the third-rail system of the train, must be capable of handling all of these at full power, when running on lines with third-rail electrification.

Would One Charging System Handle Both Tracks?

The route is double-track, with often platforms on either side of the tracs.

This Google Map shows Gillingham station, which appears to have a typical layout.

Note the three-car Class 159 train in the station.

If both tracks were to have a charging rail, I can’t see why one set of batteries shouldn’t be able to feed both tracks with separate control systems.

Although it does appear that several stations often use the same platforms for both directions.

Conclusion

This could be a very affordable way of electrifying a line with a lot of stations.

 

October 26, 2018 - Posted by | Travel | , , , , , , ,

1 Comment »

  1. This post is password protected. Is it supposed to be…?

    >

    Comment by Rowan Lloyd | October 26, 2018 | Reply


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