Ideas for Recharging battery trains

[Bald Rick]

a dozen or so diesel-hybrids travelling around rural Scottish lines isn't going to even register on any global measuring system.

Absolutely, and the same for some other long / remote branches a long way from any juice.

 

[Meerkat]

although my review remains that a dozen or so diesel-hybrids travelling around rural Scottish lines isn't going to even register on any global measuring system.

But its a bad look for the politicians and the "rail is green" campaigners, especially if we are all driving electric cars. And the Greta's of this world will make a big fuss about it, inconsequential numbers or not. Even more so for lines where an electric bus would make more sense to everyone but rail fans anyway!

 

[6Gman]

I think the easiest way, if you are designing a system from scratch would be as follows. Design a train with a compartment at one end with wide access doors. Create a battery pack sufficient to propel the train that is mounted on a industy standard pallet. This can then be loaded at the platform at the start or end of the route, or at intermediate stations as needed. Once the battery needs recharging it would be swapped out for a fully charged one, and then can be trickle charged at the station until needed again. You might need a slightly longer train/platforms for this, and probably a forklift to move a ton of battery, but its still fairly low tech and acheivable, and probably a lot cheaper than for instance, wiring the whole West Highland line.

And somebody to do the plugging and unplugging, and to drive the forklift.

And a safety case.

 

[Nicholas Lewis]

But its a bad look for the politicians and the "rail is green" campaigners, especially if we are all driving electric cars. And the Greta's of this world will make a big fuss about it, inconsequential numbers or not. Even more so for lines where an electric bus would make more sense to everyone but rail fans anyway!

It is now but let the dust settle and the outlook will be different.

 

[Irascible]

Running them on biofuel has the same slightly dubious credentials as burning trees for electricity - doesn't release buried carbon which is good for the figures, but visibly somewhat polluting ( as opposed to polluting someone else's environment like EVs ). Stick giant green "Powered by plants" on the side or something. ( Never mind that fossil oil comes from plamts too... )

 

[jon0844]

I am probably out of date with battery technology, but doesnt fast charging heat up the battery damaging it, and thus, shortening its life.
And delivering 350Kw in a small town may be difficult without major upgrade to the local network. Especially when you want 350Kw for a short time then a long period of no load. Most infrastructure is based on a constant load, not having big local spikes.

Charging tech is improving all the time to reduce heat and other issues, and generally the charging speed falls off a cliff after around 80% - but there are many tricks that can divide the batteries up so as to maximise the fast charging process.

Batteries might need some level of conditioning before rapid charging, given the batteries are exposed the elements, but that's all stuff I think the industry is aware of.

To reduce that peak load, it's possible that charging stations could have their own batteries to deliver the required charging, charged themselves over a slower and more gradual time (which also gives some form of backup if there's a power outage).

Edit: I see much of what I just wrote was already said - that's what happens when you join a thread late in the day! However, I'll keep it so as to show that multiple people agree there are no real issues with battery charging these days!

 

[Bald Rick]

Thats kind of my point with a swappable battery pack. You have a smaller one suitable for 15-20 miles, and swap it out en-route rather than lug the whole lot all the way. There is obviously a trade off between weight of battteries carried, range, and time needed to swap the units. Complete speculation here, but I imagine an electric train with a small battery swapped at intervals could perform similar timings to current diesal DMUs.

I should also have mentioned. A smaller battery pack that, say, could only do 20 miles, would weigh perhaps half a tonne less, on a coach that will weigh at least 50x that. Weight is not really a problem.

 

[mike57]

A question...

You have a 100 mile rural branch line, in typically rolling countryside (i.e. not the Fens or through the pennines), You have a BEMU with current battery technology, charging from OHL where available. How much of the line would need to be electrified to allow the unit to trundle up and down all day. To add some more parameters, lets say 60-70mph line speed throughout, and stops every 5 miles, with a battery thats say 2 years old (or whatever is deemed to be mid life)

Yes I know the above is a 'made up scenario' but its to try and understand where we actually are with the current technology.

 

[jon0844]

Surely the batteries won't be put under any more load than a normal EV? You simply have more battery cells in the case of a train, and more motors.

Their life should still be between 5 and 10 years and quite possibly more, with a drop in quality to maybe 80 or 85% capacity by then that could be worked around.

The future isn't replacing the entire battery pack either, but individual cells or modules - and they'll go on to work elsewhere after, and ultimately fully recycled.

Batteries can and will work well on many routes.

 

[Bald Rick]

A question...

You have a 100 mile rural branch line, in typically rolling countryside (i.e. not the Fens or through the pennines), You have a BEMU with current battery technology, charging from OHL where available. How much of the line would need to be electrified to allow the unit to trundle up and down all day. To add some more parameters, lets say 60-70mph line speed throughout, and stops every 5 miles, with a battery thats say 2 years old (or whatever is deemed to be mid life)

Yes I know the above is a 'made up scenario' but its to try and understand where we actually are with the current technology.

the answer depends entirely on time on the juice vs time off. And the former depends on where the OLE is located. For example, if the OLE was at stations, particularly the places where there are longer turn rounds, then the amount or wiring could be relatively small.

very, very roughly, for a branch of the characteristics you describe, a battery train charging through OLE would need to be on the juice for between 30-60% of the time, partly depending on battery size.

 

[mike57]

the answer depends entirely on time on the juice vs time off. And the former depends on where the OLE is located. For example, if the OLE was at stations, particularly the places where there are longer turn rounds, then the amount or wiring could be relatively small.

very, very roughly, for a branch of the characteristics you describe, a battery train charging through OLE would need to be on the juice for between 30-60% of the time, partly depending on battery size.

So a thought, and no doubt there will be some issues, but

Wire up each station at 1.5kV DC, Dual voltage operation is tried and tested now.

Advantage is that for rural areas providing a DC supply is easier than AC, as the DC supply can be dervived from a 3 phase supply with less grid balance problems than a single phase supply for AC 25kV. Each station section could then be locally powered, and buffered with supercapacitors, which although bulkier than batteries are better at supplying high peak currents. The increase in bulk/weight over batteries doesnt matter as they are static. These supercapicitors then recharge over time from the local supply ready to supply starting current plus rapid charge current every time a train calls at the station. You then dont need a high power grid connection at every station/OHL section. OHL would maybe extend 1/4 to half mile either side of each station. In addition any long gradients could be wired using a similar technique. This assumes a low usuage, lets say 1tph each way, I am not advocating this solution for busy main lines, its a way of equiping the rural branch lines which realistally will never be electrified. The static installation at each station could be a standard containerised solution, which would accept 3.3 or 11kV 3 phase grid input. Pan up and Pan down managed automatically to avoid disasters

Terminus station would have a beefier installation to allow further recharge during layover. This would go a long way to meeting 30-60% of time.

 

[Bald Rick]

So a thought, and no doubt there will be some issues, but

Wire up each station at 1.5kV DC, Dual voltage operation is tried and tested now.

Advantage is that for rural areas providing a DC supply is easier than AC, as the DC supply can be dervived from a 3 phase supply with less grid balance problems than a single phase supply for AC 25kV. Each station section could then be locally powered, and buffered with supercapacitors, which although bulkier than batteries are better at supplying high peak currents. The increase in bulk/weight over batteries doesnt matter as they are static. These supercapicitors then recharge over time from the local supply ready to supply starting current plus rapid charge current every time a train calls at the station. You then dont need a high power grid connection at every station/OHL section. OHL would maybe extend 1/4 to half mile either side of each station. In addition any long gradients could be wired using a similar technique. This assumes a low usuage, lets say 1tph each way, I am not advocating this solution for busy main lines, its a way of equiping the rural branch lines which realistally will never be electrified. The static installation at each station could be a standard containerised solution, which would accept 3.3 or 11kV 3 phase grid input. Pan up and Pan down managed automatically to avoid disasters

Terminus station would have a beefier installation to allow further recharge during layover. This would go a long way to meeting 30-60% of time.

no need for 1.5kV DC, as that needs more kit on every train. just make it 25kV AC and have an inverter at the charging point. Or 750-800v DC and a conductor rail.

And batteries are more than capable of discharge quick enough.

 

[mike57]

And batteries are more than capable of discharge quick enough.

The reason for suggesting supercapacitors is that they have a much longer life without degrading, and dont suffer with the same thermal issues as batteries during quick discharges, basically you are trading robustness for size and weight, but as they are static size and weight doesn't matter (with in reason)

 

[Bald Rick]

The reason for suggesting supercapacitors is that they have a much longer life without degrading, and dont suffer with the same thermal issues as batteries during quick discharges, basically you are trading robustness for size and weight, but as they are static size and weight doesn't matter (with in reason)

what’s the price difference for a given MWh storage, out of interest?

 

[Ken H]

So how would Settle - Carlisle work? You have to move abaout 40 tonnes up from Settle to Ais Gill. Battery will be a bit discharged having worked from Skipton and made maybe 3 stops. How much battery would you need to drag the train up the long drag?
And all the stations are in well remote places. So a big load from the railway might be difficult for the leccy infrastructure.
I am assuming a battery/25Kv EMU that charged itself between Leeds and Skipton, and while waiting at Carlisle.

 

[mike57]

what’s the price difference for a given MWh storage, out of interest?

I am not sure at MW levels, but at smaller levels I think you are looking about 3 to 8 times the cost, but its worth remembering that their cycle life is measured in millions of charge/discharge cycles, not 1000s or even 10000s, and they can deliver that at a much higher power level for a shorter time, which is what my idea would need (I was thinking 5mins discharge 55m charge time). Roughly speaking a 1MW power delivery over 5 mins would need about 100kW steady state from the grid and that load would be fairly well balanced, which would be acheivable in most places. Supercapacitors are no good for long term (days+) energy storage. The reason you eliminate problems with number of cycles is that the energy storage is charge storage, not a chemical process, which is what causes degredation of the currently available lithium cells. No doubt the economics would be worked out, but if I were designing a system with a potential 30 year life such as I had described I would go the supercapcitor route rather than batteries because you could expect them to last the life of the installation, as by my reckoning assuming an hourly service you would be looking at around 250,000 charge discharge cycles in 30 years

 

[Bald Rick]

I am not sure at MW levels, but at smaller levels I think you are looking about 3 to 8 times the cost, but its worth remembering that their cycle life is measured in millions of charge/discharge cycles, not 1000s or even 10000s, and they can deliver that at a much higher power level for a shorter time, which is what my idea would need (I was thinking 5mins discharge 55m charge time). Roughly speaking a 1MW power delivery over 5 mins would need about 100kW steady state from the grid and that load would be fairly well balanced, which would be acheivable in most places. Supercapacitors are no good for long term (days+) energy storage. The reason you eliminate problems with number of cycles is that the energy storage is charge storage, not a chemical process, which is what causes degredation of the currently available lithium cells. No doubt the economics would be worked out, but if I were designing a system with a potential 30 year life such as I had described I would go the supercapcitor route rather than batteries because you could expect them to last the life of the installation, as by my reckoning assuming an hourly service you would be looking at around 250,000 charge discharge cycles in 30 years

given the scale we are talking, it is similar to grid level storage, which is mostly done with batteries AIUI.

 

[MarkyT]

Here's an interesting video about a promising new use of graphene in supercapacitors.

Whether or not they will eventually be able to store all the energy required for traction and other demands in non-wired parts of a future network, supercapacitors could be used as a proportion of storage in conjunction with more conventional batteries as a buffer for short term storage which can then be trickled to and from the main battery as expedient. That could be particularly useful for fast partial charging at short passenger stops, and for absorbing regenerative braking energy that might otherwise be wasted if the main battery couldn't take all the current quickly enough directly.

 

[Nicholas Lewis]

I am not sure at MW levels, but at smaller levels I think you are looking about 3 to 8 times the cost, but its worth remembering that their cycle life is measured in millions of charge/discharge cycles, not 1000s or even 10000s, and they can deliver that at a much higher power level for a shorter time, which is what my idea would need (I was thinking 5mins discharge 55m charge time). Roughly speaking a 1MW power delivery over 5 mins would need about 100kW steady state from the grid and that load would be fairly well balanced, which would be acheivable in most places. Supercapacitors are no good for long term (days+) energy storage. The reason you eliminate problems with number of cycles is that the energy storage is charge storage, not a chemical process, which is what causes degredation of the currently available lithium cells. No doubt the economics would be worked out, but if I were designing a system with a potential 30 year life such as I had described I would go the supercapcitor route rather than batteries because you could expect them to last the life of the installation, as by my reckoning assuming an hourly service you would be looking at around 250,000 charge discharge cycles in 30 years

supercapitors have low energy density but high power density so they are best used on traction vehicles with high frequency stop starts like trams/metros as you able to size the system to harvest all the energy available from braking and then reuse for next acceleration cycle. The cycle rate for doing this runs into the millions vs batteries which is 100's times lower although by keeping battery in the 20-80% SOC range life can be extended.

 

[mike57]

Whether or not they will eventually be able to store all the energy required for traction and other demands in non-wired parts of a future network, supercapacitors could be used as a proportion of storage in conjunction with more conventional batteries as a buffer for short term storage which can then be trickled to and from the main battery as expedient. That could be particularly useful for fast partial charging at short passenger stops, and for absorbing regenerative braking energy that might otherwise be wasted if the main battery couldn't take all the current quickly enough directly.

My thinking was to used them in a fixed installation at stations in rural areas where the grid cannot support the sudden load that would be required to fast charge and accelarate away (post 41) 55 mins to charge, 5 mins max to dump that charge into the unit.

 

[Nottingham59]

try and understand where we actually are with the current technology.

In December, a Stadler Flirt AKKU achieved 225km on battery power. Their guaranteed range off the wires is 80km. https://www.railtech.com/rolling-st...ld-record-for-battery-only-range/?gdpr=accept

80km is not enough for Settle-Carlisle, but there are many many branches lines in Britain less than 80km away from the juice.

The great thing about battery charging is that it can use a balanced 3-phase supply, so you don't need massive 400kV transformers to accommodate single-phase OHLE.

Personally, I'd investigate using a 750V DC overhead busbar at branch terminus platforms feeding a dual-voltage pantograph, like you get on a dual-voltage tram-train.

But I'm not an expert (which is why I opened this thread!)

 

[MattRat]

Solar panels could extend the battery range until it goes back onto electrified track.

 

[MotCO]

Solar panels could extend the battery range until it goes back onto electrified track.

And stick a few windmills on the roof - these would whizz round as the train moves along

 

[MattRat]

And stick a few windmills on the roof - these would whizz round as the train moves along

I'm not sure those would fit within the loading gauge. Of course, you could be joking becuase I know solar panels aren't the most efficient, but I'll give you the benefit of the doubt because I clearly said extend and not fully power.

 

[Bald Rick]

Solar panels could extend the battery range until it goes back onto electrified track.

You’d need an awful lot of solar panels!

 

[MotCO]

I'm not sure those would fit within the loading gauge. Of course, you could be joking becuase I know solar panels aren't the most efficient, but I'll give you the benefit of the doubt because I clearly said extend and not fully power.

I had included a smiley face emoji on my post, but somehow it's fallen off

 

[Nicholas Lewis]

In December, a Stadler Flirt AKKU achieved 225km on battery power. Their guaranteed range off the wires is 80km. https://www.railtech.com/rolling-st...ld-record-for-battery-only-range/?gdpr=accept

80km is not enough for Settle-Carlisle, but there are many many branches lines in Britain less than 80km away from the juice.

The great thing about battery charging is that it can use a balanced 3-phase supply, so you don't need massive 400kV transformers to accommodate single-phase OHLE.

Personally, I'd investigate using a 750V DC overhead busbar at branch terminus platforms feeding a dual-voltage pantograph, like you get on a dual-voltage tram-train.

But I'm not an expert (which is why I opened this thread!)

If the unit is battery only a DC supply makes sense to reduce carting around extra weight. The pan would be heavy duty to manage the current transfer so wouldn't necessarily be suitable for running under 25kV. So if your building a BEMU it would make sense to provide 25kV at charging points

 

[Bald Rick]

The pan would be heavy duty to manage the current transfer so wouldn't necessarily be suitable for running under 25kV.

High Speed pans can do 16MW (at 300km/h+), which i would have thought is more than enough power transfer? At that rate you could give a 4 car unit 100k range in a couple of minutes. The challenge will be getting that from the power electronics into the batteries.

 

[Nicholas Lewis]

High Speed pans can do 16MW (at 300km/h+), which i would have thought is more than enough power transfer? At that rate you could give a 4 car unit 100k range in a couple of minutes. The challenge will be getting that from the power electronics into the batteries.

Current is a lot lower at 25kV compared to transferring it at 750V DC though. Also when the pan is static for a long period you will get localised heating of the carbon strips but it all depends on how much power is required to be transferred.

 

[MattRat]

You’d need an awful lot of solar panels!

Well you'd have nearly the entire roof. And again, extend rather than fully power. It just needs to reduce the drain, not stop it.