Our new ticketing site is now live! Using either this or the original site (both powered by TrainSplit) helps support the running of the forum with every ticket purchase! Find out more and ask any questions/give us feedback in this thread!
I am very much of the lay people. But people also don't talk about battery degradation very much either. And what that means for whole life cost if the battery needs replacing only a third of the way into the lifespan of the vehicle. Sounds like just pushing an even higher cost into the mythical future. And the whole premise of this way of working is all about conventional electrification being considered too expensive. It's not like trains really "need" to run of batteries in the way that cars do. Some might argue it's a questionable use of rare earth metals.
There is also the other potential issue of battery operation requiring certain amounts of turnaround time which surely makes you're timetable unreliable if you can't use that time to make up small to medium delays from the inbound service. Is there any actual significane to this particular issue in BEMU planning or is fast charging much better than I expected? Also - relatedly - is there any extent to which 25kV OLE is maybe not the best for fast charging at a stand since the contact distance is quite small. I recall hearing a lot of current flow is facilitated by the characteristics of the pantograph specifically in motion.
So a little more like the CVL model. The route is by default electrified, but with small holes poked in to avoid "difficult" enabling works. This is rather different than the 10s of miles off wire approach that people seem to really want.
If the GWR 230 range trialPR day had actually involved sensible Hotel and aux loads e.g. having the lights and HVAC on then very optimisation different decision would have been made on optimal cruising speed
Siemens had a fairly educational advertorial in MR late last year pointing out that BEMUs would need a minimum of 25-30% of the route electrified. If it wasn't the right 25-30% then you would need even more electrification overall. [I agreed with both their comments]. But Siemens could help you get the right 25-30% with their SFC and supply battery tech if the problems was lack of power in the right place(s) which it isn't on Borders or Fife as there are simple enough options on supply (even if only one sensible option, there was an option without innovate power supplies).
I'd be surprised if power supply was often the problem in these cases. More so I'd assume that the optimal stretch to be wired does not line up with the optimal part of the route to not wire up. Because the whole point is to avoid difficult clearances as that is percieved as pushing up the price of OLE, it'd be rather unfortunate if the optimal lines to be wired from the rolling stock perspective don't line up with that. I wonder if this is what happened to EWR? Surely from an infrastructure intervention point of view you'd want to electrify the brand new bits of railway since you can make sure all the clearances are correct from the get-go. However, their actual plan at the moment is to electrify pretty much only the Marston Vale Line which forms the centre of the route.
I am very much of the lay people. But people also don't talk about battery degradation very much either. And what that means for whole life cost if the battery needs replacing only a third of the way into the lifespan of the vehicle. Sounds like just pushing an even higher cost into the mythical future. And the whole premise of this way of working is all about conventional electrification being considered too expensive. It's not like trains really "need" to run of batteries in the way that cars do. Some might argue it's a questionable use of rare earth metals.
There is also the other potential issue of battery operation requiring certain amounts of turnaround time which surely makes you're timetable unreliable if you can't use that time to make up small to medium delays from the inbound service. Is there any actual significane to this particular issue in BEMU planning or is fast charging much better than I expected? Also - relatedly - is there any extent to which 25kV OLE is maybe not the best for fast charging at a stand since the contact distance is quite small. I recall hearing a lot of current flow is facilitated by the characteristics of the pantograph specifically in motion.
So a little more like the CVL model. The route is by default electrified, but with small holes poked in to avoid "difficult" enabling works. This is rather different than the 10s of miles off wire approach that people seem to really want.
Interesting to know!
I'd be surprised if power supply was often the problem in these cases. More so I'd assume that the optimal stretch to be wired does not line up with the optimal part of the route to not wire up. Because the whole point is to avoid difficult clearances as that is percieved as pushing up the price of OLE, it'd be rather unfortunate if the optimal lines to be wired from the rolling stock perspective don't line up with that. I wonder if this is what happened to EWR? Surely from an infrastructure intervention point of view you'd want to electrify the brand new bits of railway since you can make sure all the clearances are correct from the get-go. However, their actual plan at the moment is to electrify pretty much only the Marston Vale Line which forms the centre of the route.
Also a lay person here, but the model Scotrail are using is about 50% route distance electrified, Dundee is 59.7miles from Waverley and will have 25.8 miles electrified, I think that will be one of the lowest % electrified, so the trains can recharge while moving on parts of the route so don't rely on layovers for this.
The current plans are very much 'minimum viable electrification' so if infill happens in time then that would potentially allow for battery degradation over time without being a problem. So eventually we would have the Forth and Tay Bridges, plus a few other difficult structures which weren't electrified, but never exceeding a 5 mile stretch on battery. After Fife and Borders I think the next sections planned are Dunblane to Aberdeen, so on the same basis, Gleneagles-Perth (Hilton Junction if the tunnel is difficult), Dundee-Arbroath and Stonehaven-Aberdeen would probably cover those, then move onto infill.
After Fife and Borders I think the next sections planned are Dunblane to Aberdeen, so on the same basis, Gleneagles-Perth (Hilton Junction if the tunnel is difficult), Dundee-Arbroath and Stonehaven-Aberdeen would probably cover those, then move onto infill.
This may be either old news to some or outdated news, but the old plans from either 2022 or 2024 show the interim electrification plans for the future sections being:
- Barnhill (Outside of Perth?) to Barry Buddon (just west of Barry Links station)
- Kinnaber Junction (just north of Montrose) to Stonehaven
- Faskally (north of Pitlochry) to Dalwhinne (presumably following the dual tracked section)
- Avielochan (just north of Aviemore) to Inverness
Those last two sections could be different now, as the highland mainline would require more wiring than that to facilitate battery electric trains I assume.
Other sections mentioned include:
- Nairn to Keith
- Huntley to Aberdeen
The feeder stations mentioned include:
- Invergowrie for Dundee (now likely Stannergate)
- Drumlithie for Stonehaven (SECML FS)
- Faskally for Dalwhinnie (South HML FS)
- Avielochan for Inverness (North HML FS)
- Beauly for Inverness (FNL FS)
- Elgin for Nairn (A2I West FS)
- Kintore for Aberdeen (A2I East FS)
- Greenloaning for Perth/Hilton Jn (Dunblane Perth FS)
- Thornton for Fife Circle North (SECML/FCL North FS)
But people also don't talk about battery degradation very much either. And what that means for whole life cost if the battery needs replacing only a third of the way into the lifespan of the vehicle.
If you get the route characteristics, battery sizing and chose the wrong battery technology/chemistry etc. then you might be doing 6 battery replacements in working life. If you do it right focusing on TCO (but much more expensive up front) then you might get it down to one change in working life (this is where Siemens moved to in 2025) but this needs to choose the right size, careful C-rate management, pack electronics and pack chemistry (e.g. Siemens moved to join the LTO camp (was just ABB) in 2025).
This means you aren't quoting massive off the wires ranges.
And the whole premise of this way of working is all about conventional electrification being considered too expensive. It's not like trains really "need" to run of batteries in the way that cars do. Some might argue it's a questionable use of rare earth metals.
There is also the other potential issue of battery operation requiring certain amounts of turnaround time which surely makes you're timetable unreliable if you can't use that time to make up small to medium delays from the inbound service. Is there any actual significance to this particular issue in BEMU planning
No because you either vastly over size the battery or trash it with a high C-rate! Greenford fast charging is about mini top ups - most of the charge comes from slow charging over night with micro top us during the day. (A bigger cheap battery with no charging in the day would also have done it or having some OHLE in the platform and few hundred metres outside)
Also - relatedly - is there any extent to which 25kV OLE is maybe not the best for fast charging at a stand since the contact distance is quite small. I recall hearing a lot of current flow is facilitated by the characteristics of the pantograph specifically in motion.
OHLE charging is fine. The static pantograph current draw limit is 80A (and 300A while moving), this equates to ~2MW (depending on voltage) which is more than enough for MU battery charging with any sensible battery size. (If you MU is very big you will have two pantographs (one for each half unit) anyway e.g. Cl. 345 or 700). 300A leaves enough headroom for in motion charging for MU in Scotrail type cases.
The need for proprietary fast charging was effectively killed off in RSSB's T1272 project (use OHLE or 3rd rail whatever is local first)
So a little more like the CVL model. The route is by default electrified, but with small holes poked in to avoid "difficult" enabling works. This is rather different than the 10s of miles off wire approach that people seem to really want.
Interesting to know!
I'd be surprised if power supply was often the problem in these cases.
With most routes there is some thing do-able but may be not in the ideal place (lots of Scotland) with some other routes there are no easy options (e.g. Long Marston test track).
CVL power supply is generally pretty good (This shocked Adrian S. when he asked what I though of his CVL proposals - the power supply options were far better than typical) there are plenty of places nationally where it isn't though.
Because the whole point is to avoid difficult clearances as that is perceived as pushing up the price of OLE, it'd be rather unfortunate if the optimal lines to be wired from the rolling stock perspective don't line up with that.
Running lots of long trains to Universal Studios means it is worth electrifying (proposed service levels are higher than in recent consultations before the definite US go ahead)
Surely from an infrastructure intervention point of view you'd want to electrify the brand new bits of railway since you can make sure all the clearances are correct from the get-go. However, their actual plan at the moment is to electrify pretty much only the Marston Vale Line which forms the centre of the route.
And the easy bits away from the couple of East Bicester- Swanbourne bridges they didn't touch (oops!). Anything near Oxford is horrific cost which they want to leave to western region (who get the most benefit too)!
== Doublepost prevention - post automatically merged: ==
Also a lay person here, but the model Scotrail are using is about 50% route distance electrified, Dundee is 59.7miles from Waverley and will have 25.8 miles electrified, I think that will be one of the lowest % electrified, so the trains can recharge while moving on parts of the route so don't rely on layovers for this.
A higher % means you tend to trash the batteries less so they last far longer (Sensible choice from Scotrail). Fife is one end and middle, Borders is 2 ends. with sensible turnarounds of 10 minutes you get huge levels of charge and can chose to lower the C rate for that cycle to reduce battery damage, if running late you can go for slightly higher C-rate.
Around 50% it starts to become a big academic as to which sections are electrified and which aren't unless the route section is hugely long overall. All good sensible thinking from Scotrail.
The current plans are very much 'minimum viable electrification' so if infill happens in time then that would potentially allow for battery degradation over time without being a problem.
So eventually we would have the Forth and Tay Bridges, plus a few other difficult structures which weren't electrified, but never exceeding a 5 mile stretch on battery. After Fife and Borders I think the next sections planned are Dunblane to Aberdeen, so on the same basis, Gleneagles-Perth (Hilton Junction if the tunnel is difficult), Dundee-Arbroath and Stonehaven-Aberdeen would probably cover those, then move onto infill.
That's very true, I was thinking about the Harrogate line which seems to have effectively no turnaround time in Leeds. The methodology in Scotland seems to run several miles of wires at the terminus end which basically negates this issue.
No because you either vastly over size the battery or trash it with a high C-rate! Greenford fast charging is about mini top ups - most of the charge comes from slow charging over night with micro top us during the day. (A bigger cheap battery with no charging in the day would also have done it or having some OHLE in the platform and few hundred metres outside)
OHLE charging is fine. The static pantograph current draw limit is 80A (and 300A while moving), this equates to ~2MW (depending on voltage) which is more than enough for MU battery charging with any sensible battery size. (If you MU is very big you will have two pantographs (one for each half unit) anyway e.g. Cl. 345 or 700). 300A leaves enough headroom for in motion charging for MU in Scotrail type cases.
The need for proprietary fast charging was effectively killed off in RSSB's T1272 project (use OHLE or 3rd rail whatever is local first)
Ah so useful battery charging can be achieved on 750V third rail, I was under the impression it wasn't great for it because of the high currents needed to support both the charging and the actual travel of potentially multiple trains in one section.
With most routes there is some thing do-able but may be not in the ideal place (lots of Scotland) with some other routes there are no easy options (e.g. Long Marston test track).
CVL power supply is generally pretty good (This shocked Adrian S. when he asked what I though of his CVL proposals - the power supply options were far better than typical) there are plenty of places nationally where it isn't though.
Yeah I guess the former industrial land-use gives the area lots of supergrid supplies. From a power supply perspective CVL is pretty conventional though. For all the off wire sections, there are feeder cables laid for each OLE circuit which I guess is realistic when the largest discontinuities are about 3 miles. I need to draw a map of the CVL power system at some point, I have all the info but just haven't gotten around to it since it'll be quite a big job to chart all of the permanently earthed sections and mileages off of wire running.
Indeed this lead to different proposals for Fife (middle and 1 end) and Borders (2 ends)
Ideally you would keep wiring further North from Tweedbank (further up the big climb) but they stop at the southern end of a tunnel.
Running lots of long trains to Universal Studios means it is worth electrifying (proposed service levels are higher than in recent consultations before the definite US go ahead)
I also think there's a bit of a chess move involved of using the main EWR project to wire up the "most difficult" bit, while they have the opportunity to build the Bedford-Cambridge route with passive provision for OLE meaning it should be a pretty simple job to finish that section off at a later date. Or at least I hope such provisions would be made like they did with Leven line.
And the easy bits away from the couple of East Bicester- Swanbourne bridges they didn't touch (oops!). Anything near Oxford is horrific cost which they want to leave to western region (who get the most benefit too)!
Yeah all in all I think Scotland's approach is pretty sensible, actually just using batteries to stage electrification, instead of whatever we're doing in England which is... nothing?
That's very true, I was thinking about the Harrogate line which seems to have effectively no turnaround time in Leeds. The methodology in Scotland seems to run several miles of wires at the terminus end which basically negates this issue.
This should be the default approach everywhere, even <2 miles outside Oxenhome / Twyford / Greenford (e.g. till you get to the first problems structure would solve many challenges.)
Ah so useful battery charging can be achieved on 750V third rail, I was under the impression it wasn't great for it because of the high currents needed to support both the charging and the actual travel of potentially multiple trains in one section.
THe issue with 3rd rail is (existing) power supplies being maxed out in some places so there isn't even the head room to run more EMUs let alone BEMUs (e.g. Hurst Green - South Croydon). Having decent length of 3rd rail to charge from allows the peak power requirements to be managed.
Huge levels of good DNOs supply point opportunities (every former pit and washery all next to railway lines) + Grid opportunities, all most too much choice in most places.
From a power supply perspective CVL is pretty conventional though. For all the off wire sections, there are feeder cables laid for each OLE circuit which I guess is realistic when the largest discontinuities are about 3 miles. I need to draw a map of the CVL power system at some point, I have all the info but just haven't gotten around to it since it'll be quite a big job to chart all of the permanently earthed sections and mileages off of wire running.
I also think there's a bit of a chess move involved of using the main EWR project to wire up the "most difficult" bit, while they have the opportunity to build the Bedford-Cambridge route with passive provision for OLE meaning it should be a pretty simple job to finish that section off at a later date. Or at least I hope such provisions would be made like they did with Leven line.
I often find myself wishing they'd just finish off GWEP! It's missing so many crucial components
Yeah all in all I think Scotland's approach is pretty sensible, actually just using batteries to stage electrification, instead of whatever we're doing in England which is... nothing?
This should be the default approach everywhere, even <2 miles outside Oxenhome / Twyford / Greenford (e.g. till you get to the first problems structure would solve many challenges.)
THe issue with 3rd rail is (existing) power supplies being maxed out in some places so there isn't even the head room to run more EMUs let alone BEMUs (e.g. Hurst Green - South Croydon). Having decent length of 3rd rail to charge from allows the peak power requirements to be managed.
DC substations arent generally the limiting factor in outer areas as their loading is quite low over an hourly cycle so could absorb charging load. The issue is the aggregate load all the substations present to the high voltage distribution system feeding the substations although East Grinstead line is substantially stronger now than when it was electrified nearly 40yrs ago. This is far less of an issue on OLE sites as they can just request increased firm capacity at the feeding stations to support the charging load. Still be interesting to know how ScotRail/NR arrived at the arrangement they've adopted for Fife circle to get the balance optimal between how much battery capacity you carry around (extra weight) vs OLE extent.
One interesting thing they did on the CVL was that when they realised their original electrification plans didn't work (issues with sensitive equipment nearby for example) rather than get the trains power system changed they just used their digital modelling software to work out where they need to electrify to make up for it.
They essentially had a fixed capability train and designed the infrastructure around it.
ScotRail seem to be working the opposite way they're designing a specific infrastructure and presumably are gonna have to hope they can get a train that's fit for it.
It'll be interesting to see how fast they do end up needing infill work.
ScotRail seem to be working the opposite way they're designing a specific infrastructure and presumably are gonna have to hope they can get a train that's fit for it.
It'll be interesting to see how fast they do end up needing infill work.
Didn't Scotrail say the work (on the Highland main lines via Dundee etc) is being based on assuming that further sections to Aberdeen etc would be added in 10-15 years.
So electrification capacity is being sized based on some as yet unbuilt regional express BEMU that can replace the 222s (that are replacing HSTs) in about 2040-2042
A lively Express unit is going to need 800-1000 HP per vehicle, so for a 5car unit, so about 3.5MW per train (and it would be sensible to provide for 6car, so perhaps 4.2MW). Of course will only be using that during acceleration and hill climbing, so can estimate peak load in any section.
The worst case scenario is an emergency all trains stop, then all trains are cleared to resume so everyone accelerates at same time (although sequenced signal release can be used in this situation, to stagger power being applied)
We are aware of an issue with emails from the Forum to Microsoft-based email accounts (hotmail/outlook/live.com email addresses). This is being looked into currently, thanks for your patience meanwhile.
