Battery units - are they really going to fix everything?

[N1]

Battery buses were introduced on the Leeds-Harrogate-Ripon route in March. Already I have seen with my own eyes two services that have run out of charge on the country roads. Diesel buses breaking down was very rare.

New operators do have a bit of a learning curve when introducing new electric buses. But Coventry still being targeted as all electric bus by the end of the year (subject to some of the Reform led councils re-issuing tenders for supported bus services e.g. Warwickshire), and that Ember can operate intercity electric coach services across Scotland show that it is completely possible.

Schrodinger's BEMUs, are the future and reduce need for electrification but won't commit funding to allow their large scale rollout as not sure the technology is quite ready yet apparently.

Ignoring the 28 sets in use in Japan, orders in the US, Latvia, Lithuania, Denmark and across Germany, as well as 31 on order for use on DART+ in Ireland. For light rail you can see battery trams in Birmingham.

And again, a fleet of over 200 battery railcars were in use in Germany for 40 years from 1955 to 1995.

 

[Brubulus]

Schrodinger's BEMUs, are the future and reduce need for electrification but won't commit funding to allow their large scale rollout as not sure the technology is quite ready yet apparently.

The technology is ready, what isn't is the power supply around major stations and unless that's sorted, a substantial order can't happen.

Though I suspect batteries are also a solution that will help relieve power supply issues.

 

[eldomtom2]

Ignoring the 28 sets in use in Japan, orders in the US, Latvia, Lithuania, Denmark and across Germany, as well as 31 on order for use on DART+ in Ireland.

Those tend to be for quiet branch lines or off-wire extensions of suburban services though - not something that can replace electrification for lines like the MML or GWML.

 

[stevieinselby]

Why would a pure emu have better acceleration? This will be more a factor of range.

My guess would be weight.
A BEMU will have the same drivetrain as an EMU, DEMU or EDMU*, and so – subject to battery capacity – should be able to put down the same amount of power to the wheels, but the extra weight of the battery pack will slow the train down compared to the pure EMU which is lighter.

* I think those are the correct acronyms! Electric multiple unit, diesel-electric multiple unit (think Thumper or Voyager), electro-diesel multiple unit (bi-mode that can run on diesel or electric)

 

[HSTEd]

My guess would be weight.
A BEMU will have the same drivetrain as an EMU, DEMU or EDMU*, and so – subject to battery capacity – should be able to put down the same amount of power to the wheels, but the extra weight of the battery pack will slow the train down compared to the pure EMU which is lighter.

* I think those are the correct acronyms! Electric multiple unit, diesel-electric multiple unit (think Thumper or Voyager), electro-diesel multiple unit (bi-mode that can run on diesel or electric)

I think, in the case of purporse designed battery units, this is debatable.

A battery unit could potentially accelerate independently of any fixed power supply limitations.
It is likely possible, with current technology, to design a unit that is truly adhesion limited on essentially all of the UK railway.

A conventional EMU that tried that would start collapsing power supplies in relatively short order.
You'd end up with a 200m train that draws a peak power comparable to a 400m Shinkansen set!

 

[Zomboid]

My guess would be weight.
A BEMU will have the same drivetrain as an EMU, DEMU or EDMU*, and so – subject to battery capacity – should be able to put down the same amount of power to the wheels, but the extra weight of the battery pack will slow the train down compared to the pure EMU which is lighter.

* I think those are the correct acronyms! Electric multiple unit, diesel-electric multiple unit (think Thumper or Voyager), electro-diesel multiple unit (bi-mode that can run on diesel or electric)

Up to a point. There is a limit on the amount of power which can be drawn from the contact system, so in theory a BEMU (or any bi-mode, if the control system is configured to allow it) could draw current from the battery as well as the OLE and put down more power than a straight electric that's at the current limit.

Though that is such an edge case in normal use as to be irrelevant.

 

[N1]

My guess would be weight.
A BEMU will have the same drivetrain as an EMU, DEMU or EDMU*, and so – subject to battery capacity – should be able to put down the same amount of power to the wheels, but the extra weight of the battery pack will slow the train down compared to the pure EMU which is lighter.

* I think those are the correct acronyms! Electric multiple unit, diesel-electric multiple unit (think Thumper or Voyager), electro-diesel multiple unit (bi-mode that can run on diesel or electric)

Battery weight is about 6-8kg per kWh. So for example Alstom X'Trapolis units for DART+ have 840 kWh batteries. At 8kg per kWh that is 6.72 tonnes, round up to 7 tonnes for any extra electrical equipment. These are to be 83m trains, so comparing to a class 710/2 dual voltage 83m EMU which is 151 tonnes total, 7 tonnes is not going to make a massive difference in terms of acceleration.

 

[Zomboid]

Though I suspect batteries are also a solution that will help relieve power supply issues

That could also be at the substations of course. Cowley national grid sub has a battery bank to help supply the electric bus charging and spread the load around.

 

[N1]

Those tend to be for quiet branch lines or off-wire extensions of suburban services though - not something that can replace electrification for lines like the MML or GWML.

True, still need electrification of Main Lines. However, the whole sequence can be changed. Can order grid connection points, which drive all current electrification programmes, and build out electrification from there, and avoid the most costly civils interventions.

 

[HSTEd]

Railway electrification designed for battery charging has different optimisation criteria to conventional or even electrodiesel electrification.

Charging is likely limited by time available for charging more than anything else, whilst the primary cost driver for electrification is distance, so we want locations where trains are on relatively heavily trafficked lines that are slow.

As an example, the ten route kilometres between Saltash and Laira depot provides ~20 minutes even for a train not turning in Plymouth station. And at least a few of those route kilometres are single track, with the remainder being double track. Even if the Royal Albert Bridge costs several times what open line does per unit distance, the 15mph speed limit and single track may still make it attractive. Especially if the electrification covers the eastbound platform at Saltash, where trains will wait during disruption. You'd probably do both platforms at Saltash for simplicity.

Such electrification would likely be sufficient to fully recharge a battery train running from the South West to London.

Most urban areas have suitable 400/275/132kV supply points, at least if we assume the use of Static Frequency Converters, so I don't see power supply as a huge issue.

 

[CMS1]

Rather than short sections of overhead lines around stations, could 'flash chargers' be developed which the train slots into at stations? Saving the cost of overhead infrastructure at all and reducing hazards (as whilst the best place for recharging, from a safety perspective stations are the least desirable place for overhead lines with level crossings etc. common).

 

[Zomboid]

Rather than short sections of overhead lines around stations, could 'flash chargers' be developed which the train slots into at stations? Saving the cost of overhead infrastructure at all and reducing hazards (as whilst the best place for recharging, from a safety perspective stations are the least desirable place for overhead lines with level crossings etc. common).

That's what's happening at West Ealing, using rails in the 4'.
It'll probably be part of the solution, but more likely to be used in that kind of application than anything on a longer distance through route.

 

[MarkyT]

That's what's happening at West Ealing, using rails in the 4'.
It'll probably be part of the solution, but more likely to be used in that kind of application than anything on a longer distance through route.

The fairly short self-contained branch use case, with range sufficient for periodic visits to a mainline maintenance depot.