XC Voyagers to get battery packs: How could this be implemented and how can the technology be best utilised?

[BayPaul]

Moderator note: Split from https://www.railforums.co.uk/threads/cross-country-get-three-year-extension.210296/

See following link for official DfT press release including basic details of battery trial-
https://www.gov.uk/government/news/...ted-through-new-deal-with-arriva-crosscountry

The Department for Transport will also continue to work with the owners of the Voyager trains to trial the use of on-train batteries when they enter and leave stations so that engines are turned off when they’re at platforms further improving air quality.

Batteries on Voyagers sounds like a very clever idea - it would be good if the engines could be shut down well before the station, coast in, recharge the batteries with regenerative braking (are the Voyagers so fitted?), and then accelerate clear of the station before having to restart the diesels. It does like it will put a lot of wear onto the engines with constant restarts and shut downs.

It will be interesting to see how this will work and exactly what it will achieve. The announcement implies that design work is already underway.

Although there is a mention of capacity benefits, you would think there would be a song and dance if that meant that they were taking the Avanti Voaygers and or the EMR 222s in 2022, as they should both be available within this extension period. Sadly, I suspect this capacity benefit is the already announced middle coaches for a few turbostars and better utilisation of the HSTs

 

[ainsworth74]

recharge the batteries with regenerative braking (are the Voyagers so fitted?)

Yes, the big roof racks on each carriage are, I believe, the heat sinks/resistor racks for the rheostatic brakes (that's why you can often see a massive heat haze over the top of them just after a Voyager has come to a stand in station, it's dissipating the heat from braking). It would therefore, one assumes, not be impossible to redirect that energy and turn it into regenerative braking for traction batteries.

 

[37424]

Batteries on Voyagers sounds like a very clever idea - it would be good if the engines could be shut down well before the station, coast in, recharge the batteries with regenerative braking (are the Voyagers so fitted?), and then accelerate clear of the station before having to restart the diesels. It does like it will put a lot of wear onto the engines with constant restarts and shut downs.

Although there is a mention of capacity benefits, you would think there would be a song and dance if that meant that they were taking the Avanti Voaygers and or the EMR 222s in 2022, as they should both be available within this extension period. Sadly, I suspect this capacity benefit is the already announced middle coaches for a few turbostars and better utilisation of the HSTs

According to Mr Miles on WNXX the Dft don't want to tie in Avanti Voyagers at this stage it depends on how passenger numbers recover.

 

[Ianno87]

Batteries on Voyagers sounds like a very clever idea - it would be good if the engines could be shut down well before the station, coast in, recharge the batteries with regenerative braking (are the Voyagers so fitted?), and then accelerate clear of the station before having to restart the diesels. It does like it will put a lot of wear onto the engines with constant restarts and shut downs.

Although there is a mention of capacity benefits, you would think there would be a song and dance if that meant that they were taking the Avanti Voaygers and or the EMR 222s in 2022, as they should both be available within this extension period. Sadly, I suspect this capacity benefit is the already announced middle coaches for a few turbostars and better utilisation of the HSTs

It would hardly be "constant" restarts, if it was just applied at New Street (the station on their network that most needs it for air quality); that would be each Voyager passing through maybe 3-4 times per day at most, given the length of their journeys (I think the Bristol-Manchester-Bournemouth-Manchester-Bristol cycles get through the most).

On capacity, I think Covid probably solves that one until at least 2023 at this rate....

 

[BayPaul]

It would hardly be "constant" restarts, if it was just applied at New Street (the station on their network that most needs it for air quality); that would be each Voyager passing through maybe 3-4 times per day at most, given the length of their journeys (I think the Bristol-Manchester-Bournemouth-Manchester-Bristol cycles get through the most).

On capacity, I think Covid probably solves that one until at least 2023 at this rate....

If the kit is fitted, it probably makes environmental and economic sense to use it in most stations (which the DfT release implies), rather than wasting heat on the resistor banks, however, I was probably exaggerating using the word constant, given that XC don't stop all that frequently.

 

[Mikey C]

It would hardly be "constant" restarts, if it was just applied at New Street (the station on their network that most needs it for air quality); that would be each Voyager passing through maybe 3-4 times per day at most, given the length of their journeys (I think the Bristol-Manchester-Bournemouth-Manchester-Bristol cycles get through the most).

That would be an ideal solution for New Street. Lets hope it's something which can be easily added, and reliable too, as the history of train modifications is that there are always unforeseen problems and they end up late and over budget!

 

[Bletchleyite]

It would hardly be "constant" restarts, if it was just applied at New Street (the station on their network that most needs it for air quality); that would be each Voyager passing through maybe 3-4 times per day at most, given the length of their journeys (I think the Bristol-Manchester-Bournemouth-Manchester-Bristol cycles get through the most).

On capacity, I think Covid probably solves that one until at least 2023 at this rate....

In any case, restarting engines doesn't cause wear, it's restarting from cold. A short station stop won't cause any appreciable cooling down.

 

[Ianno87]

If the kit is fitted, it probably makes environmental and economic sense to use it in most stations (which the DfT release implies), rather than wasting heat on the resistor banks, however, I was probably exaggerating using the word constant, given that XC don't stop all that frequently.

Certain in "air quality" urban areas. Bristol and Leeds would be the other obvious ones.

 

[raetiamann]

Certain in "air quality" urban areas. Bristol and Leeds would be the other obvious ones.

Looking like the electrical shore work is to be depot based and for the Turbostar fleet.

 

[greatvoyager]

Batteries on Voyagers sounds like a very clever idea - it would be good if the engines could be shut down well before the station, coast in, recharge the batteries with regenerative braking (are the Voyagers so fitted?), and then accelerate clear of the station before having to restart the diesels. It does like it will put a lot of wear onto the engines with constant restarts and shut downs.

Although there is a mention of capacity benefits, you would think there would be a song and dance if that meant that they were taking the Avanti Voaygers and or the EMR 222s in 2022, as they should both be available within this extension period. Sadly, I suspect this capacity benefit is the already announced middle coaches for a few turbostars and better utilisation of the HSTs

Certainly looks like voyagers are going to be around for a while if this trial is going ahead, good to see their looking at reducing emissions at stations though.

 

[ForTheLoveOf]

It does like it will put a lot of wear onto the engines with constant restarts and shut downs.

The same engine (Cummins QSK19) is used on 185s. The 185s have a "Hybrid" mode (which is normally enabled) whereby they run on only 2 out of 3 engines, to save fuel and wear & tear.

To balance things out the engine that's off get swapped around every so often. I'm sure there's a method to it, but it seems like it happens at least once an hour or so. 185s have a very high "miles per technical incident" (MTIN) ratio these days, so this clearly has little or no ill effect on reliability.

Voyager engines are different in multiple ways to the 185 engines (not least how they're controlled and the kind of loads they undergo) but it certainly shows that the model of engine is mechanically capable of tens if not hundreds of stops and starts in a given day.

 

[Mikey C]

I'm sure many passengers who use New Street will be very happy to have the use of noisy and polluting diesel engines drastically reduced in that environmental "hot spot"

 

[bengley]

The same engine (Cummins QSK19) is used on 185s. The 185s have a "Hybrid" mode (which is normally enabled) whereby they run on only 2 out of 3 engines, to save fuel and wear & tear.

To balance things out the engine that's off get swapped around every so often. I'm sure there's a method to it, but it seems like it happens at least once an hour or so. 185s have a very high "miles per technical incident" (MTIN) ratio these days, so this clearly has little or no ill effect on reliability.

Voyager engines are different in multiple ways to the 185 engines (not least how they're controlled and the kind of loads they undergo) but it certainly shows that the model of engine is mechanically capable of tens if not hundreds of stops and starts in a given day.

I drive 185s and I can assure you that the large majority of drivers drive without Eco mode on (and as such all three engines are normally running throughout the journey). There is no requirement to use Eco mode and indeed often in the winter and summer months we are told not to use it as it can affect HVAC performance.

 

[DynamicSpirit]

In any case, restarting engines doesn't cause wear, it's restarting from cold. A short station stop won't cause any appreciable cooling down.

Is there any possibility that, on balance, it could reduce wear - since you'd basically have a battery doing all the work in accelerating the train from start to - maybe, something like 50mph, which is presumably the point where the heaviest load would otherwise normally be being put on the engine?

I imagine, aside from the reduction in pollution, the potential fuel savings would be quite significant too.

 

[MarkyT]

Is there any possibility that, on balance, it could reduce wear - since you'd basically have a battery doing all the work in accelerating the train from start to - maybe, something like 50mph, which is presumably the point where the heaviest load would otherwise normally be being put on the engine? I imagine, aside from the reduction in pollution, the potential fuel savings would be quite significant too.

I imagine the ability to recover braking energy will be useful in this respect. I read some articles on stop-start tech and the important thing seems to be that engines should be specifically designed or modified for frequent starts and stops. Techniques involving special bearing materials and lubricants reduce wear significantly. Anecdotal evidence from taxi drivers using hybrid cars like the Prius suggests that their engines exhibit very little wear and achieve prodigious trouble-free mileage. It might be sensible to consider replacing the Voyagers' diesels with slightly smaller and cleaner engines of more modern design when the batteries are added. That might also help in finding space to accommodate the battery and its management and cooling systems. The 220s, in particular, might be considered somewhat overpowered at the moment considering they have exactly the same traction equipment as, despite being around 20% lighter than, the 221s due to the latter's heavy tilt-capable bogies.

 

[jayah]

That would be an ideal solution for New Street. Lets hope it's something which can be easily added, and reliable too, as the history of train modifications is that there are always unforeseen problems and they end up late and over budget!

I am not impressed myself.

The majority of their large stations already have OLE, as does a very considerable proportion of their route mileage.

Me thinks a large dollop of hyperbole here. I have travelled extensively on Cross-Country in the last decade, almost all on journeys north and south of Birmingham New Street. I have not experienced 'absolute shambles'. Yes, sometimes trains have been late, but where in the core of our overcrowded system has this not been the case? Yes, I have been on some overcrowded trains, but if you travel at peak times to and from major cities you will encounter passengers standing on many trains, irrespective of operator. Yes, I have encountered poor service by the tea trolley, but it has not been the end of my world. Have I had pleasant journeys by XC? Yes, plenty. Take a train from Birmingham NS shortly after 9am on a weekday going South West - plenty of seats, pleasant scenery [pre-covid of course, but probably even more empty seats now!]

Would XC benefit from more carriages on some trains? Yes, but I doubt this will be a big issue for sometime to come.

Outside London most peak trains that don't serve London are undersized.

Much work has been undertaken over the years across various franchises e.g. TPE, Scotrail, Northern etc... to acquire new stock and lengthen the trains, but with one notable outlier...

 

[Mikey C]

I am not impressed myself.

The majority of their large stations already have OLE, as does a very considerable proportion of their route mileage.

Of course we'd like a new fleet of bimodes, but they're not going to bin 20 year old trains just like that, especially in the current financial climate AND with passengers numbers well down on pre Covid levels

If a short term solution can help air quality in stations like New Street that has to be a good thing until the longer term solution can be implemented

 

[jayah]

Of course we'd like a new fleet of bimodes, but they're not going to bin 20 year old trains just like that, especially in the current financial climate AND with passengers numbers well down on pre Covid levels

If a short term solution can help air quality in stations like New Street that has to be a good thing until the longer term solution can be implemented

A new fleet is not required. The existing fleet wanted extending anyway and making them Bi-Mode would have met both needs.

 

[Domh245]

A new fleet is not required. The existing fleet wanted extending anyway and making them Bi-Mode would have met both needs.

The immense difficulty (read: cost) of achieving this has been discussed extensively before, and I find it surprising that people still think it's a good idea

 

[hwl]

I imagine the ability to recover braking energy will be useful in this respect. I read some articles on stop-start tech and the important thing seems to be that engines should be specifically designed or modified for frequent starts and stops. Techniques involving special bearing materials and lubricants reduce wear significantly. Anecdotal evidence from taxi drivers using hybrid cars like the Prius suggests that their engines exhibit very little wear and achieve prodigious trouble-free mileage. It might be sensible to consider replacing the Voyagers' diesels with slightly smaller and cleaner engines of more modern design when the batteries are added. That might also help in finding space to accommodate the battery and its management and cooling systems. The 220s, in particular, might be considered somewhat overpowered at the moment considering they have exactly the same traction equipment as, despite being around 20% lighter than, the 221s due to the latter's heavy tilt-capable bogies.

The voyagers have separate traction, auxiliary (including hotel) and battery charging alternators at different voltages on the engine with pretty much separate electrical systems at different voltages. (On the Meridians the battery charging is fed form the aux supply instead so just 2 alternators). One of the mayor issues is that Voyagers have very limited auxiliary cross feed between vehicles (and no traction cross feed) hence a minimum of half the engines need to be kept running to supply the auxiliary loads (when stationary).
I would be really surprised if they are looking to do major (expensive) work as part of a small trial hence I'd expect the new batteries to be used to supply just the auxiliary system loads in stations with them being charged from power diverted from rheostatic braking or from the engine's auxiliary alternator. I.e. no traction battery use.
This would address quite a bit of the air quality issues at the major stations (not just New Street) for comparatively little spending (this isn't about decarbonisation).

Beacon thought they were getting a bargain when the bought the Voyagers from Voyager Leasing (Lloyds TSB /Angel JV) when Lloyds got out of leasing but didn't read the tea leaves too well and are probably complaining to DfT that DfT should have been more explicit about potentially stranded assets in a world with growing air quality and decarbonisation aims.

The immense difficulty (read: cost) of achieving this has been discussed extensively before, and I find it surprising that people still think it's a good idea

Pretty much agreed.

At the moment DfT are effectively buying themselves time to come up with the medium / long term fleet spec for XC based on the outcome of:
1) where passenger demand levels are a few years into Covid world is.
2) potentially rejigging parts of the the XC network to better meet demand in other ways (this was giving them headaches before the last re-franchising attempt.
3) where the NR decarbonisation strategy is heading including potential times and prioritisations (XC bimodes would be a big early win on reducing CO2). Given the voyagers should last till about 2035-40 if there is a long term need for (diesel) bi-modes till 2060 as part of the plan then getting some new ones now makes sense.
4) What timing NR and TS put on Aberdeen electrification

 

[MarkyT]

The voyagers have separate traction, auxiliary (including hotel) and battery charging alternators at different voltages on the engine with pretty much separate electrical systems at different voltages. (On the Meridians the battery charging is fed form the aux supply instead so just 2 alternators). One of the mayor issues is that Voyagers have very limited auxiliary cross feed between vehicles (and no traction cross feed) hence a minimum of half the engines need to be kept running to supply the auxiliary loads (when stationary).
I would be really surprised if they are looking to do major (expensive) work as part of a small trial hence I'd expect the new batteries to be used to supply just the auxiliary system loads in stations with them being charged from power diverted from rheostatic braking or from the engine's auxiliary alternator. I.e. no traction battery use.
This would address quite a bit of the air quality issues at the major stations (not just New Street) for comparatively little spending (this isn't about decarbonisation).

Interesting. That could be a quick win on all units for the 3-year extension, allowing a complete engine shutdown at longer station stops like Birmingham. If they were to survive on the service group for another decade or so after that under new management arrangements then a more comprehensive traction battery scheme might be implemented. Perhaps one of the Avanti units might be used as an experimental prototype when it comes out of WC service during this 3-year period. I'm convinced a Thor type bi-mode scheme to add a pantograph car will never stack up compared to new trains.

 

[hwl]

Interesting. That could be a quick win on all units for the 3-year extension, allowing a complete engine shutdown at longer station stops like Birmingham. If they were to survive on the service group for another decade or so after that under new management arrangements then a more comprehensive traction battery scheme might be implemented. Perhaps one of the Avanti units might be used as an experimental prototype when it comes out of WC service during this 3-year period. I'm convinced a Thor type bi-mode scheme to add a pantograph car will never stack up compared to new trains.

The amount of XC Voyager running under the wires is pretty large (but not as large as Avanti's 85%+) hence bi-modes bring big energy cost savings hence not much point going down the traction battery route (the electrica architecture of the voyagers is a poor starting point).
It is worth remembering that York - Leeds electrification is effectively signed off hence Manchester - Birmingham/ Coventry (80/100miles) and Glasgow/Edinburgh - Doncaster /Leeds (215-250miles) are effectively included for during the 2023--> XC concession. DfT are looking at MML again as one of the of "Accelerate" project which would add Sheffield - Derby and then Didcot-Oxford potentially back on the table means substantial elements of the 3 arms of the XC Voyager network are all or mostly electrified.

 

[jayah]

The immense difficulty (read: cost) of achieving this has been discussed extensively before, and I find it surprising that people still think it's a good idea

vs the cost of electrification Swansea to Cardiff which would save a fraction of the emissions, or the cost of a new fleet of Bi-Mode at £2.5m per vehicle?

 

[Domh245]

vs the cost of electrification Swansea to Cardiff which would save a fraction of the emissions, or the cost of a new fleet of Bi-Mode at £2.5m per vehicle?

I don't know where the Swansea-Cardiff comparison came from, although assuming there was a budget to only electrify ~45mi of track with an intention to cut emissions as much as possible it wouldn't be thrown at Swansea-Cardiff (keeping it XC related it'd get you from Birmingham to Derby)

And no, whilst the headline cost of a fleet of new bimodes is more, it's a far better prospect than faffing around with the Voyagers. A whole fleet replacement of voyagers & HSTs like for like with 5 car 802s would have a headline cost of £750m and delivering a 36% capacity increase* but that'd be on a pretty conventional lease and therefore no significant cost difference to current - for a simple comparison a 30 year life would represent around £25m a year.
For each extended voyager you'd be looking at minimum ~£3m for each of the 58 vehicles** because of the small production run and probably around half a million per existing vehicle for all the various modifications needed to make it work and a general refurbishment, so a headline cost of £300m, but with only a 10 year life that'd come in at £30m a year for Beacon to finance, on top of the cost of leasing the trains in the first place. The capacity gain would also be less, if the new vehicle has 66 seats and you manage to get 8 additional seats per train from the existing fleet by rejigging the toilets etc, you only stand to have a 28% gain in seat capacity.

And that's before considering any sort of risk around timing - an order for Hitachi bimodes placed today would result in new trains entering into service in 2023 with little risk of slippage based on previous performance. Any re-engineering programme would be a lottery as to when it actually enters service as evidenced by 760s, 230s, & HST power door mods, but 2023 for first service it would not be.


*based on a GWR style layout
**not including any cascades from avanti or EMR

 

[jayah]

I don't know where the Swansea-Cardiff comparison came from, although assuming there was a budget to only electrify ~45mi of track with an intention to cut emissions as much as possible it wouldn't be thrown at Swansea-Cardiff (keeping it XC related it'd get you from Birmingham to Derby)

And no, whilst the headline cost of a fleet of new bimodes is more, it's a far better prospect than faffing around with the Voyagers. A whole fleet replacement of voyagers & HSTs like for like with 5 car 802s would have a headline cost of £750m and delivering a 36% capacity increase* but that'd be on a pretty conventional lease and therefore no significant cost difference to current - for a simple comparison a 30 year life would represent around £25m a year.
For each extended voyager you'd be looking at minimum ~£3m for each of the 58 vehicles** because of the small production run and probably around half a million per existing vehicle for all the various modifications needed to make it work and a general refurbishment, so a headline cost of £300m, but with only a 10 year life that'd come in at £30m a year for Beacon to finance, on top of the cost of leasing the trains in the first place. The capacity gain would also be less, if the new vehicle has 66 seats and you manage to get 8 additional seats per train from the existing fleet by rejigging the toilets etc, you only stand to have a 28% gain in seat capacity.

And that's before considering any sort of risk around timing - an order for Hitachi bimodes placed today would result in new trains entering into service in 2023 with little risk of slippage based on previous performance. Any re-engineering programme would be a lottery as to when it actually enters service as evidenced by 760s, 230s, & HST power door mods, but 2023 for first service it would not be.


*based on a GWR style layout
**not including any cascades from avanti or EMR

Swansea Cardiff is relevant because in Bi-Mode age there is little operational or timetable gain, the case revolves almost entirely around how much CO2 is saved at what cost.

Bi-Moding the Voyager fleet would smash that business case out of the park.

I don't know where the Swansea-Cardiff comparison came from, although assuming there was a budget to only electrify ~45mi of track with an intention to cut emissions as much as possible it wouldn't be thrown at Swansea-Cardiff (keeping it XC related it'd get you from Birmingham to Derby)

And no, whilst the headline cost of a fleet of new bimodes is more, it's a far better prospect than faffing around with the Voyagers. A whole fleet replacement of voyagers & HSTs like for like with 5 car 802s would have a headline cost of £750m and delivering a 36% capacity increase* but that'd be on a pretty conventional lease and therefore no significant cost difference to current - for a simple comparison a 30 year life would represent around £25m a year.
For each extended voyager you'd be looking at minimum ~£3m for each of the 58 vehicles** because of the small production run and probably around half a million per existing vehicle for all the various modifications needed to make it work and a general refurbishment, so a headline cost of £300m, but with only a 10 year life that'd come in at £30m a year for Beacon to finance, on top of the cost of leasing the trains in the first place. The capacity gain would also be less, if the new vehicle has 66 seats and you manage to get 8 additional seats per train from the existing fleet by rejigging the toilets etc, you only stand to have a 28% gain in seat capacity.

And that's before considering any sort of risk around timing - an order for Hitachi bimodes placed today would result in new trains entering into service in 2023 with little risk of slippage based on previous performance. Any re-engineering programme would be a lottery as to when it actually enters service as evidenced by 760s, 230s, & HST power door mods, but 2023 for first service it would not be.


*based on a GWR style layout
**not including any cascades from avanti or EMR

Sorry but those figures are made up nonsense.

£500k per vehicle for every *other* vehicle?
Source?

10 years life?
Voyagers are 17 years old and can last at least as long as mk3s however much they are disliked.

 

[Richard Scott]

10 years life?
Voyagers are 17 years old and can last at least as long as mk3s however much they are disliked.

They possibly could but the mk3s trump card is that it's loco hauled and not stuck with thirsty diesel engines slung under it. Unfortunately they were badly thought through when purchased, really be was obvious even 20 years ago that an all diesel intercity unit was not a clever idea. They are a dinosaur in the modern world and not worth salvaging. Better off with new bi-modes.

 

[Domh245]

Swansea Cardiff is relevant because in Bi-Mode age there is little operational or timetable gain, the case revolves almost entirely around how much CO2 is saved at what cost.

Bi-Moding the Voyager fleet would smash that business case out of the park.

Agreed that in this day and age, electrification is now about CO2 reductions than any operational benefit, I just don't see why you brought up Swansea-Cardiff as voyagers don't operate anywhere near there!
With the Voyagers current brilliant performance, the only benefit you'd stand to gain from electrification regardless is CO2 reduction, cost/benefit analysis rides solely now on what the government says 1t of CO2 emissions is valued at. Bi-moding them would reduce the benefit of any electrification schemes but there are very few voyager-only routes, in the fullness of time they'd get electrified

Sorry but those figures are made up nonsense.

£500k per vehicle for every *other* vehicle?
Source?

10 years life?
Voyagers are 17 years old and can last at least as long as mk3s however much they are disliked.

£500k was probably a little on the high side, but point is the major refurbishments don't come cheap. Scotrail's HST refurbishment was an estimated £54m for refurbishment, power door installation and limited modification to the powercars, at an effective £300k per vehicle. The 458 conversion was £50m across 180 vehicles, coming out at ~£275k per vehicle. The 455 retraction project was £40m for 91 motor vehicles, ~£440k per vehicle

Considering that for each vehicle in addition to the extensive interior refurbishment to bring it up to an 'as-new' spec, you've got to (at minimum) modify the traction package (or at worst, replace entirely) to enable them to work as EMUs, reconfigure the antiquated TMS system, run buslines through them, recertify etc, it's not going to be towards the lower end of those costs.

The choice of 10 years life was just to equal out the 30 year life I'd arbitrarily chosen for the alternative plan, and isn't entirely unrealistic for intercity type stock. HSTs and Mk3s are the exception to the rule and whilst a voyager could run into the 2040s, I don't think it's a particularly likely scenario. Bi-moding them would make them a more attractive prospect for running into the future but there'd still be capacity concerns and the other issues baked into the voyager design that make them less attractive to run than a new 80x

 

[edwin_m]

The voyagers have separate traction, auxiliary (including hotel) and battery charging alternators at different voltages on the engine with pretty much separate electrical systems at different voltages. (On the Meridians the battery charging is fed form the aux supply instead so just 2 alternators). One of the mayor issues is that Voyagers have very limited auxiliary cross feed between vehicles (and no traction cross feed) hence a minimum of half the engines need to be kept running to supply the auxiliary loads (when stationary).
I would be really surprised if they are looking to do major (expensive) work as part of a small trial hence I'd expect the new batteries to be used to supply just the auxiliary system loads in stations with them being charged from power diverted from rheostatic braking or from the engine's auxiliary alternator. I.e. no traction battery use.
This would address quite a bit of the air quality issues at the major stations (not just New Street) for comparatively little spending (this isn't about decarbonisation).

It certainly seems to be a bit of weasel wording implying that traction would also be included but not actually saying so. Or perhaps they are going to look into all the options.

I also wonder where they will find the space for the new batteries and electronics. When the Meridians first appeared it was said (by Roger Ford I think) that part of the increase in passenger space was because the space taken up by the tilt equipment in the 221s, and empty in the 220s due to the common design above floor, could be used for other purposes. This probably didn't account for very much of the extra passenger space, as most of it was from fitting smaller toilets in the intermediate cars. But I wonder if they plan to use the same space for this work, which would mean removing some redundant tilt equipment on 221s with the possibility that restoring tilt would be more difficult if ever needed.

At the moment DfT are effectively buying themselves time to come up with the medium / long term fleet spec for XC based on the outcome of:
1) where passenger demand levels are a few years into Covid world is.
2) potentially rejigging parts of the the XC network to better meet demand in other ways (this was giving them headaches before the last re-franchising attempt.
3) where the NR decarbonisation strategy is heading including potential times and prioritisations (XC bimodes would be a big early win on reducing CO2). Given the voyagers should last till about 2035-40 if there is a long term need for (diesel) bi-modes till 2060 as part of the plan then getting some new ones now makes sense.
4) What timing NR and TS put on Aberdeen electrification

An obvious option would be to finish electrifying the MML with a new fleet of EMUs (perhaps retaining a few bi-modes if any non-electrified extensions that remain unelectrified are important enough to continue service). The bi-modes could then go to CrossCountry - being shorter than the 80x series they would need less clearance work (although most XC routes are probably cleared for 80x anyway) and being specified to match Meridian performance on diesel they would have no problem keeping to schedules. These could be deployed on the XC diagrams with the largest proportion of running under the wires.