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Comment by Reason077 | Hacker News Reader

From the article:

> “It is bad enough that Germany is keeping some outer regional rail branches in the exurbs of Berlin and Munich unwired; that New York has not fully electrified is unconscionable.”

There is a strong argument that battery-electric trains will replace the need for overhead electrification on shorter routes and branch lines.

Track electrification can be very expensive, and hard to justify on less-busy lines. But with batteries, a train can charge while running on an electrified trunk line, then continue onto smaller branch lines.

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Battery trains aren't a new thing. Prussia had been using them since 1907 and German federal rail later used the newer Class 515 [1] for decades. They had a reach of about 300 km (theoretically and in level areas).

For the 515, costs were a big factor. The lead based batteries had to be rented from the manufacturer.

But even if you take current technology into account: A train isn't a Tesla. It needs much more energy to accelerate. Currently, an engine and a diesel tank are much cheaper to buy and especially maintain. They will give you decades of use. How long are your batteries going to last?

Also keep in mind that batteries add tremendous weight, reducing reach again. More weight is especially painful in hilly areas. All of this needs to be factored in.

Bottom line: It's feasible and has been done. Operating costs, however, are a big factor, especially compared to what other technologies get you.

edit: There's a battery version of the Stadler FLIRT [2]. It went 224 km (at about 80 km/h) on one battery charge recently [3]. They will be in operation for DB from the end of 2022 on.

[1] https://en.wikipedia.org/wiki/DB_Class_ETA_150

[2] https://en.wikipedia.org/wiki/Stadler_FLIRT

[3] https://www.youtube.com/watch?v=m0Z7H3fv4Bc

> "Currently, an engine and a diesel tank are much cheaper to buy and especially maintain."

Yes, diesel is cheaper to buy than battery trains. But pretty much everyone, including the main article here, agrees that maintenance costs are much lower with electric trains compared to diesel. I'd expect that (at least once the technology matures) this will also be true of battery electrics.

The point is, if you start with the assumption that diesel is unacceptable and routes must be electrified - for reasons like climate change, toxic air pollution, route reliability, passenger comfort, etc, then there are many routes where battery electrics are going to greatly reduce costs compared to installing overhead wires on every section of track.

> "There's a battery version of the Stadler FLIRT [2]. It went 224 km (at about 80 km/h) on one battery charge recently [3]. They will be in operation for DB from the end of 2022 on."

Yes, I expect we'll see a lot more battery electric units introduced in Europe in the coming years. There are so many routes where they make perfect sense.

The big acceleration points are predictable. Electrify those areas. Then you only need enough batteries to maintain speed and get through the lesser acceleration points.

They would still want enough batteries to accelerate from a dead stop to prevent a 5 minute delay from becoming a 5 hour delay. Energizing the acceleration points would be more about reducing wear on the batteries and prolonging their life.

I don't think constantly raising and lowering the pantograph is a practical solution. Having lines with spotty overhead is very error prone and reliability is a big factor in rail. If we're talking about longer sections that are either electrified or not, things are different. E.g., extending the line for 100 km into an unelectrified part. Trains like the Stadler LINT (see my edit above), could make that happen.

> "I don't think constantly raising and lowering the pantograph is a practical solution."

I don't see why not. There are actually urban routes in London (London Overground) that do this multiple times on every journey! Switching between overhead AC electrification used in North London and the older third-rail DC electrification used in South London.

> "Having lines with spotty overhead is very error prone and reliability is a big factor in rail. "

But that's where batteries come in. Being able to keep moving under your own power if there's a problem with the overhead wires adds a lot of robustness/redundancy.

It depends on how long these sections are. We're probably of the same mind but thinking of different dimensions. If we're talking just for electrified sections of up to 2 km, alternating a dozen times or more, I'm not sure if it's worth it. For longer sections, yes, it's an absolute killer feature.

The cost of raising the panto slightly too early even once is tremendous. You would have to close the track for maintenance. So you need a safety margin of a few seconds. That's several 100 meters. Frequent changeovers would necessitate the system to be fully automated in order to factor out human error.

The changeover on London Overground is usually done while standing at a station (by the driver). According to [1] it's possible to switch while moving. The speed limit is given as 25mph, however.

[1] https://www.railforums.co.uk/threads/changing-from-dc-to-ac-...

Yes, you'd certainly make sure everything was automated or at least have a software lock-out to ensure the pantograph is only raised on the correct sections. But having a battery makes this a lot simpler, there'd be no need to stop or coast during the changeover.

It's a special operation, requiring special signage, and awareness of the driver. Here in Hamburg, where the S-Bahn using third-rail got extended to service Stade, is using multi-system rolling stock now. Which traverses the gaps by rolling without power through that gap. I also remember standing on some platform above ground, where you could see them coming over a ramp, with the pantograph up, on a piece of track using third rail. Wondering how that happened, and what would happen if it goes back into a tunnel (with third rail), like that. Or under a bridge, overpass, all built with low clearance, because: hey, third rail!

Nerd that I am, I walked up to the driver, knocking on the glass and asked: "Moin, do you know your pantgraph is up?" Turned out he didn't, and there wasn't any indication. He got it down by repeatedly switching up/down, and finally it stayed down. Two minutes late!1!! ;-)

> "Battery trains aren't a new thing."

Indeed, and neither are electric cars. But battery chemistry, electric motors and inverters, and controller software and hardware have all come a long way in that time. The technology is far more viable and efficient today than it was back then!

They would also allow 95% of a route to be electrified, leaving tunnels and sections under pedestrian and other bridges un-electrified and covered by small capacity batteries. Especially since the train is unlikely to be accelerating during those sections.

When Network Rail in the UK looked at electrifying the Great Western Mainline, the majority of the cost is actually in a very small % of track length which is where the line goes through Victorian tunnels and under old bridges.

If your battery only needs to be sized to maintain speed for sections a few miles long at the most, you can get away with much smaller batteries.

I know they are running trials of what are effectively "tri-mode" trains already which are diesel/battery/OHL.

There's a strong counter-argument that batteries large enough to power entire trains are also expensive to produce and maintain, especially when battery prices shoot up due to lithium scarcity, and that's not even mentioning the massive carbon footprint of producing those batteries. Diesel-electric trains are probably better emissions-wise.

> “battery prices shoot up due to lithium scarcity”

There is really no scarcity of lithium in the world. If more is needed then it’s easy to just tap new supplies because it’s pretty much everywhere if you go looking.

Battery producers are more constrained by things like nickel and cobalt, but there are alternative, cheaper li-ion chemistries (such as LFP) that do without these.

> “Diesel-electric trains are probably better emissions-wise.”

Definitely not!

Probably safer in the event of a crash or mechanical failure. I would not like to see what electrical fire would look like from a lithium battery big enough to power s train.

Electric buses in Europe and China usually use LFP chemistry, because it's cheap(er) and much safer in a crash or fire because it's not prone to thermal runaway. Electric passenger trains will likely be using the same, or other stable li-ion chemistries rather than the more volatile nickel-based ones.

I think the point the article is making is that you shouldn't be looking at the cost of electrifying based on how busy the lines are, because the introduction of delays in those sections then propagate into the busier sections causing a ripple effect. Quiet sections with low reliability cause delays in the busy sections. So it's not about how busy that line itself is, it's about the downstream impact.

Battery electric trains solve the issue either way, and are likely to be much, much cheaper than electrifying branch lines.

(With batteries, an electric train becomes even more reliable because it can continue under its own power in case of a line power failure.)

Capacitors make much more sense than batteries, since you need to discharge at like 2-4C average, probably 20C peaks, and charge at much higher rate. Some buses are already running with this, for instance: https://www.youtube.com/watch?v=nlJlQprrEmg . So far it doesn't look like there is much interest in it, since I'm not aware of any further development since that 2014 line.

Minsk in Belarus runs a network of super-capacitor powered buses. I travelled on one when there in 2020. Just like a normal bus from the passenger's point of view.

https://eng.belta.by/economics/view/belarusian-electric-bus-...

"The bus is fitted with a system of super capacitors, which get fully charged within 5-10 minutes while the bus is at an end stop. The bus can travel along the entire distance of the line for up to 15 times per day. On the first day it managed to travel for over 40km on one charge."

Capacitors are power dense but not energy dense, compared to batteries. So for a given size/weight, you get a lot more range with batteries.

There has been some work, a few years back, using super-capacitors (alongside storage batteries) in high-performance electric cars to increase peak power output. But really, battery technology has improved so much that it's made that sort of thing unnecessary. Even your standard Tesla is pulling 8-10C if you really put your foot down.

> Even your standard Tesla is pulling 8-10C if you really put your foot down.

How long does your battery keep usable if you do that at every single stop? (so every 2 minutes, let's say 300 times a day ballpark)

Hah! Nobody sane is doing that at every stop. For one thing, it shreds your tires.

But for the ones who are doing it repeatedly (at the track), the answer is: very effective battery cooling! Tesla's software in their performance models actually offers a special "track mode" which, amongst other things, applies max cooling.

You'd almost certainly do better to have the storage at a stationary off-track location rather than as part of the trainset.

Batteries are massive (in the weight sense), and frequent acceleration and deceleration as well as safety would be major concerns.

The reason people look to battery trains is to avoid the infrastructure costs of the overhead lines / third rails, substations etc. to get electricity from trackside to the trains. The costs can be difficult to justify for smaller branch lines. A train that can use overhead lines on the main lines, then switch to battery for a branch is (hopefully) greener / more efficient than say running a diesel under the wires all the way[1].

It is a bit of a case of shuffling costs from infrastructure to rolling stocks, trains with batteries would still cost more than a pure overhead line electric, but I guess it comes from a different budget...

I'm not sure of any real reason why you'd use a battery off-track instead of a connection to the electricity grid except as some sort of backup for a power failure?

[1] Bi-mode diesel / electrics also exist of course, which solve the problem in a slightly different way (insert NOX / CO2 v Lithium mining debate here).

You don’t need massive batteries for short regional/suburban branch lines. We’re not talking about long intercity routes here.

It's not the length of the line.

It's the duty cycle of the rolling stock.

Running a trainset four times along a 100 mile route, or 40 times along a 10 mile route, you're still travelling 400 miles.

And the stop frequency is likely far higher on the urban route. It's the acceleration that costs, and batteries only save you so much there, even with regenerative braking.

Add in heating/cooling loads, air handling, etc., and there's a lot to consider.

About the only place batteries make sense on rail is where you're moving a heavy load one-way down-grade. There are operating quarry and logging operations which effectively work as battery storage. Laden cars (or trucks) run downhill, whilst regenerative braking charges the batteries. Empties return uphill, slowly, on that charge.

Other than a Soylent Green operation from a mountain resort, few commute rail systems have a suitably matching travel pattern.

> "Running a trainset four times along a 100 mile route, or 40 times along a 10 mile route, you're still travelling 400 miles."

We're not talking about 100 miles on battery power here - although there are already battery electric transits that are capable of that and more. For the most part, inter-urban trunk lines in Europe are already electrified.

There are many outer-suburban/regional routes that are, for example, 50 miles along an electrified trunk line then 25 miles on an un-electrified branch line. Currently that means whole route needs to be operated by diesel trains. But a battery train only needs to be capable of doing (eg) 50 miles on battery, then it can recharge when it's running under the wires.

Do you have any references for serious studies or proposals for such systems?

Not just proposals: orders have been placed and trains should be in passenger service this year. Google "FLIRT Akku" which is the name of Stadler's battery-electric train.

https://www.urban-transport-magazine.com/en/schleswig-holste...

"The longest non-electrified section on the diesel network is 80 km. Under optimal conditions, however, a battery range of 150 km should be possible."

Could make sense for short distance, low frequency. I know of a few services on branch lines that have long linger times at stations. They will do a 10 minute journey twice an hour and stay in the station between trips.

For NYC diesel trains, you're talking about stretches like the one from Croton-Harmon to Poughkeepsie (by car, it's about 40 miles). I'm not sure whether this counts as "short."

https://www.reddit.com/r/nycrail/comments/l57nw2/map_of_the_...

(LIRR Montauk branch is longer, but I'm less familiar with it.)

Batteries would add a lot of weight and increase energy consumption for whole route, with overhead wires or not.

Batteries will add weight, but you also get rid of diesel engines, traction generator/alternators, fuel tanks, etc which are all pretty heavy too.

On long routes the required size of the batteries might become prohibitive. But we’re talking about outer-suburban branch lines here which are usually pretty short, often only a few miles.

You don't have diesel engine and fuel tank on electric wired train ;) Also, looking at cars, batteries are much heavier than engines and fuel tanks giving same kilometrage. On top of that, fuel tank is heavy only in the beginning of the trip. You can fill up only as much as you need for the trip for better fuel economy. While batteries stay same weight for lifetime.

Batteries make sense for manoeuvre trains working ports, cargo train depots etc. Small batteries and recharge frequently.

> "You don't have diesel engine and fuel tank on electric wired train ;)"

In some cases you do because hybrid (bi-mode) trains exist too! [1] Although as another commenter points out, they are also working on tri-mode diesel/battery trains.

[1] https://en.wikipedia.org/wiki/British_Rail_Class_800

Batteries are still heavier than your typical commuter train diesel engine and tank. The diesel commuter trains are usually diesel hydraulic in Europe, so much less weight than you might expect, e.g. https://en.m.wikipedia.org/wiki/DBAG_Class_612

Batteries (or capacitors) would also allow the rheostatic braking to become regenerative and recharge them instead of just venting it as heat.

Of course, fully electric trains can just regenerate into the power lines.

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