birchesgreen
Established Member
I suspect the extra weight of sliding fairings and supporting systems would negate the minimal aerodynamic benefit. Plus it would be something else to go wrong.
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Discontinuous Electrification - RUK's thoughts?
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Richard Scott
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Not an assumption, the energy consumption required for high speed running on battery power would require vastly superior battery technology to what we have now.
On a train aerodynamic benefits are generally only of any value above 90mph so extra weight and complexity would negate any gains whilst running in battery mode.
It doesn‘t. It’s a question of scale. A mate of mine has a Polestar 2 that chucks out 350kW. Multiply by 10 and you have more power than a Class 395 that can hit 225km/h with horses to spare.
HSTEd
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The electron rocket uses lithium ion batteries to power its turbopumps, that drains the entire battery flat in a handful of minutes.
Richard Scott
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Yes, but it won't produce that for very long before it runs out. It's not the power that's the issue but total energy contained.
“we need to get a bigger battery”…
Trainbike46
Established Member
Bigger batteries are easy - the more important question is where would you run at 200 km/h that isn't already wired - I suspect that would mostly be short stretches
Peter Wilde
Member
Precisely. It is the extra weight of batteries being unnecessarily carried around that is the problem.
Technologist
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Read back up the thread, I used IET energy usage specs (which represent a do not exceed value not a target) then looked at the mass of the engine and fuel and replaced it with a commercially available LFP battery pack.
This gives us a range of 125 miles off the wire assuming the rate of energy usage on the East Coast mainline. That is a functionally useful amount of range which I then showed would allow an IET to run to Sheffield from where the current electrical ends at Kettering. Ergo such trains could cross very large gaps in electrification.
That's with a IET which is adequately aerodynamic but hardly designed with extreme attention to detail.
You make my earlier point for me with the 90mph comment. With diesel and electric it made less of a difference, with a battery train it makes a big difference to how useful it is:
I did just run some numbers:
At 100mph a Thameslink sized EMU with a flat front would use 47% more energy than a train with the aerodynamics of an ICE Evo. At 60mph it's 26% even at 40mph the difference is 14%.
Aero makes a big difference at most speeds and intercity train will go at.
Cars can go very long distances with battery power, intercity ones. To do so they need battery packs with masses of around 1/4 their unladen mass. In many cases with weight reduction and the removal of unnecessary components EVs are similar in weight to a ICE car of equivalent performance.
Trains are more energy efficient so are able to get similar levels of useful range with a smaller proportion of the mass devoted to batteries.
With a combination of weight reduction and the use of the battery as a structural member (rule of thumb you can remove, structure equal to around 10-15% of the pack mass if you use it as a structural member) it should be possible to add greater battery mass to a train than in that IET example from earlier.
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Trainbike46
Established Member
Why on earth would you not use the OHLE, that is already in place, on the ECML?
Sticking with LNER services, for them batteries would be useful for the north of Edinburgh/Stirling services, as well as the various off-wire extension (Harrogate, Hull, etc.). Those are either lower speed (as in Scotland) or relatively short distances (the other extensions) or both. The assumption of long distances on battery at 125 mph you make is certainly not reasonable.
There are certainly ways to improve rolling stock, but you make a lot of unstated assumptions, and cite numbers that appear to be made up (unless you work in rolling stock design? if so my apologies).
But it‘s barely anything as a % of train weight, and weight is much less important in energy use terms for a battery train.
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And, as before, batteries are not dead weight. If you're not going to have giant spikes in demand ( like trying to accelerate heavy freight - although even then, freight motive power is looking towards batteries too, no? ) you can run the power infrastructure targeting a lower constant draw per train rather than the maximum possible - so more trains on the same infrastructure, or - perhaps, I suspect for OLE this would be fairly marginal - cheaper infrastructure.
This isn't a radical idea, it's what a hybrid car does.
This isn't a radical idea, it's what a hybrid car does.
Why would you not use the energy profile of an electric train to define how far a battery trains could run?
Yes, that electric train is using wires and you wouldn't use the BEMU to do that, however that's not what is being suggested - it's just using real world data to confirm the energy needs.
However as you point out there's not likely to be a need on the ECML for a train to ruin at 125mph. Yet that's kind of the point, by only needing to run at lower speeds it's likely that the range would be a bit further.
That leads to the question, how much further than 125 miles do we need to go to bridge the diesel running sections of the 80x fleets?
ECML, probably not much. WCML, other than North Wales (which the current government has suggested they might do) again not all that much. TPE routes, not that much (especially with the electrification being out in as part of TPU). MML there's probably a bit more (but again the electrification of the MML is reducing that). The GWML (ignoring the B&H for now) doesn't have a lot either.
That's the vast majority of the routes served by 80x's which could probably be served by BEMU's within the weight of the existing trains.
Yes it leaves the B&H (and parts if the XC network, which whilst they don't run 80x's many have suggested that they should and even if they shouldn't it's the rest of the intercity TOC's so it's reasonable to include in the list) and that's a big problem as the distances are just too big.
However, if we're using this train to show where we need to focus our electrification of the rail network (if we exclude Scotland as they are doing this already), we're likely to conclude the next priority should likely be schemes in the southwest to allow us to bridge the gap.
Where there's capacity issues with the electric grid in exporting renewables from the southwest, arguably it could be sensible to create a section of electrification so as to use some of that generation capacity without having to export it up country (or possibly even to act as a grid upgrade to transport the power to somewhere else to allow further renewable schemes to go ahead).
Technologist
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Who said anything about using battery trains on the electrified sections of the ECML? Go re read my posts:
I used the figures for energy usage for the IET/Class80x train to help with the scoping of power usage. The fact that those figures are for the ECML is irrelevant other than that as a fast line they are likely to result in conservative assumptions.
Your assertion that a battery powered train couldn't run at 125mph is based on what exactly?
My numbers come from the following sources:
Energy consumption of IET from Newcastle to London. This is a spec so actual train will be better. 4600 KWh for 268 miles
This shows that the Bimodal train is 10 tonnes heavier than the pure electric, it also carries 4.5 tonnes of fuel. Ergo we could fit 14.5 tonnes of battery pack without affecting overal weight. If we want to keep the same axle load we could add a lot more battery mass as the coaches with the diesels on are much heavier and we could fit batteries to every coach. Ergo 14.5 tonnes is a conservative estimate.
CATL launches CTP 3.0 battery “Qilin,” achieves the highest integration level in the world
On June 23, CATL launched Qilin, the third generation of its CTP (cell-to-pack) technology. With a record-breaking volume utilization efficiency of 72% and an energy density of up to 255 Wh/kg, it achieves the highest integration level worldwide so far, capable of delivering a range of over...
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CATL Quilin LFP battery pack, has 160wh/kg. Obviously battery capacity goes up overtime so picking a tech already in cars is conservative.
I used an estimate of 150wh/kg for conservatism.
Put that all together our BEMU has a range of 268/4600*(14500*0.15)= 126 miles.
That is with conservative numbers. I then showed that the train could operate London to Sheffield and back without the train going below 10% state of charge, this assumes that we install a small piece of OHL to charge the train at stations, though we could get by without it except at the terminal.
To summarise BEMUs can make long journeys off the wires at mainline speeds. Dedicated BEMUs will probably do a lot better as train design and battery technology improves. Electrification plans should be built around these observations.
FYI I'm not a rolling stock engineer but I am a 20 year veteran of aerospace, nuclear and automotive. All the companies I've worked at are cross pollinated with people from rolling stock design. That experience is enough to be able to observe that rail vehicles and especially UK rail vehicles have a great deal of potential optimisation in the field of aerodynamics and integration.
There's some interesting studies around about defining the most economic driving profiles for rail routes you may want to dive into. I've forgotten the details right now but I vaguely remember a study of a spanish route showing you could probably save 17% or so without degrading the service. If trains carried full route knowledge, aside from the safety benefits that sort of thing could be built in.
GRALISTAIR
Established Member
Not too dissimilar to Scotland's strategy then?
Worth adding here that a couple of electric buses have caught fire recently. Luckily no one hurt, I think.
InTheEastMids
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The most recent story, about recall of 1,800 electric buses due to fire risk was relating to their HVAC systems provided by Hispacold, not the traction system/battery, despite what some hysterical tabloid coverage tried to imply...
That is not to say that EV powertrains can't catch fire, but the latest evidence suggests that they are much less likely than traditional power trains (see link below):
https://www.fleetnews.co.uk/news/tusker-fleet-data-reveals-the-truth-about-ev-fires
"A study by the Swedish Civil Contingencies Agency backs up Tusker’s findings. It concluded that EVs are 20 times less likely to catch fire than petrol and diesel cars."
GRALISTAIR
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this is definitely worth me bookmarking and requoting
The impressive range and charging times being displayed by the class 230 under tests which have exceed the expectations change the electrification debate.
86 miles on one charge and ultrafast charging speeds mean this technology should allow significant electric operation of secondary and branch routes without incurring the cost of full electrification.
86 miles on one charge and ultrafast charging speeds mean this technology should allow significant electric operation of secondary and branch routes without incurring the cost of full electrification.
InTheEastMids
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There are practical limits to charging speeds that can be imposed by grid capacity and/or the charger and/or the vehicle, any can be the rate-determining step.
Combine that with the dwell time at the station and you get limits on how much energy you can get, with weight/speed of service translating into the range. Today's ultra-rapid 350kW EV chargers are almost always limited by the vehicle capability, and frequently by the supply capacity from the grid. This means for a given dwell time, you might get less range than you'd expect from looking at specifications.
For recharging battery trains, this highlights a couple of issues that have location/route/service specific answers
- Appropriate grid connections (with/without a lineside battery to support train charging) to charge enough trains, quickly enough.
- Are the dwell times required for recharging at either end greater than other operational limits? i.e. might you need to build more platforms, buy more trains, increase journey times, add passing loops to accommodate extended dwells at recharging locations?
Bletchleyite
Veteran Member
Though with a train you aren't going to be charging constantly, so you can charge a battery in the charger from the grid and use that to charge the train faster than the grid can manage.
I think the voltage drop in the Southern 3rd rail is quite a lot at the London end in peak periods is quite a lot. I am unsure at what low voltage the circuit breakers kick in in substations and trains.
Lets say there is a 100v drop. charging battery trains will make that worse. So sizing the battery to be fully charged on the 3rd rail between Oxted and London and back on 750v may be a bit of a best case scenario.
What we dont want is a battery/electric train arriving at Oxted from London without enough charge to do the return trip to Oxted.
Of course the sane solution is to electrify Oxted - Uckfield
Many of these problems can be offset by installing top-up chargers along the route and then identifying somewhere with suitable capacity for a long deep charge. Also worth pointing out a train would not need to reach 100% every time.
As mentioned a power bank which is trickle-charged from the grid then fast-charges the vehicle is a common solution and is, AIUI, the system being tested at Greenford. Also a train will top itself up with regen braking if fitted (which is nearly ubiquitous now).
Trainbike46
Established Member
And of course, it many places charging while stationary can be complemented with charging while on the move, either with new OHLE, or with existing OHLE or 3rd rail.
Mikey C
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When electric vehicles do burn, the fires do seem to be more serious though.
Trainbike46
Established Member
Sorry, I didn't see this until now.
I did not intend to imply that a battery train couldn't run at 125 mph, but rather that on services along the ECML it wouldn't have to, because all sections where the linespeed allows 125mph are already electrified or a very short distance, and if the electrification is already there why would you not use it? Batteries for ECML services would primarily be useful for the sections that currently run on diesel. If fitting batteries to the ECML services, they would only have to be capable of running the maximum speeds encountered off-wire, and only for the distances encountered there. If you were suggesting using batteries INSTEAD OF the wires already present, which is what I initially thought you meant, I'd say that is a bad idea; we have the OHLE infrastructure and should use it. If you were just using the ECML as an example to show the capabilities of your theoretical battery train, I'd say your assumptions are rather more negative than what would be encountered in real life (as it wouldn't run at 125mph for long distances from batteries, as there are no long sections without OHLE on the ECML services with a 125 mph linespeed)
The GWR class 230 charge ultra fast at up to 2000KW's. Yes they will ramp up and down from that charging speed and environmental conditions will vary it a bit but it's not going to exceed normal turnaround times at terminal stations.
Don't forget you also don't have to charge fully each time and can opportunity charge.
I've seen the charge times for the modelled Thames Valley branches and all are in 2-3 mins range.
With a purpose built and lighter train design than the class 230 I'd expect range to extend by at least 25% as they are not the most efficient design.
InTheEastMids
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Yes, I don't think anybody is saying they are unsolvable issues - I certainly wasn't - but they are issues that need to be considered beyond just measuring how many kWh are in the traction battery. Obviously it makes sense to start with a lightweight, slower train on a short branch line spur, rather than jumping in with both feet and trying - I don't know - the Chiltern Main Line.
This is true. Plane crashes are also more serious than car crashes, yet travelling by plane is much safer!
So this reinforces that identification, management and mitigation of different risks in different contexts are key.
But you're right a battery in thermal runaway is a chemical fire (i.e. the fuel and oxidiser are both in the battery, whereas a conventional fuel fire relies on oxygen from the air).
Although not all lithium batteries are equally prone to this, and the ones (I think) are being used by GWR are of the "LFP*" type, rather than "NMC**" (which are a bit more prone to runaway).
* Lithium Iron Phosphate
** Nickel Manganese Cobalt
Agreed.