Discussion
Ye fucking gods, just like how techbros keep reinventing the bus, it seems in solar circles, the idea of putting solar panels in transport surfaces is an idea that a) should never had be got off the fag packet sketch, b) keeps coming back.
We had the trial of a 100m long 18KW install in Switzerland. Which unsurprisingly, did generate power. Noone is surprised by that. It's quite hard to fuck up a solar install so you don't get power from it. But. Does it mean it's a good idea ?
Fuck no.
1/n
You put solar on railway tracks and roadways when you run out of better places to put it!
At present there are still plenty of places where solar can be safely installed like building roofs, car park shades, covers over walkways, along wall and fence boundaries etc.
We can also usefully rip up biofuel crops and put panels there to produce far more energy than burning the crops would ever produce with the side benefit of improving biodiversity below the panels.
Unfortunately because it hasn't resulted in fire and death, the company behind it are trying to do it again. This time in Italy.
The problem is, it's still a fucking stupid idea. Railways are a really bad place to do anything. Vehicles weighing hundreds of tons doing high speeds on rails, with stopping distances measured in kilometres. Railways are safety critical infrastructure. Which means there's processes and procedures to follow everytime you need access.
2/n
@quixoticgeek It seems to me that if you're going to do such a thing, next to the lines makes a hell of a lot more sense.. in that picture there's loads of space around it.
I thought all the solar roadways companies went bust when it became obvious how stupid it was..
If you ever look at the area of track between the rails. You'll see it's covered in all sorts of crap. Oil, lubricants, and all sorts of other fluids fall out the bottom of trains into this space, along with dust, sand (from brakes), leaves, litter, etc... This will all need to be cleaned off to keep the panels operating at peak performance. Except you can't just send a student down with a mop and bucket. You need to arrange track possession, and do all the risk assessment stuff.
3/n
@quixoticgeek Someone described this solar panel scheme as "the world's most expensive dragging equipment detector" because sooner or later something will be dangling below the rail level and they will find out because the power output from the solar panel suddenly drops to zero.
@quixoticgeek Whenever track maintenance needs to come in and adjust thr tracks on the ballast, this hypothetical solar panel assembly needs to come off and afterwards needs to be put back in. It's so impractical and bonkers that people think this would be practical. Putting these things nearly anywhere else makes so much more sense. Gareth Dennis has done a lengthy critical rant on this and he's a railway engineer, so he knows what he's talking about.
@mdione @quixoticgeek Already forgot that it was as a part of collab with Justin Roczniak called Trainsatlantic. Anyhow, it's trained engineers talking. https://www.youtube.com/watch?v=n7Ufb9cE_uQ
@paavi @mdione @quixoticgeek ooh I didn't know that Justin and Garreth has a new podcast! Already listened to the first episode
@trainguyrom @paavi @mdione do you have a link to the RSS feed ?
@quixoticgeek @paavi @mdione this is the feed URL the podcast app I use found: https://anchor.fm/s/113ca11b0/podcast/rss
@quixoticgeek RAIB report 07/2026 (Near-miss at Bookham Tunnel, UK) and SUST report 2024090301 (deadly workplace accident near Schlieren, Switzerland) come to mind as some examples of what happens when the possession is not appropriately managed
@quixoticgeek surely a branch line trial should be the option. Lower frequency, lower risk.
I don't think this is a good idea for high frequency, national critical infrastructure
Railways also come with a lot of extra gubbins beyond the two rails nailed to wood planks (or more often bolted to concrete these days). In more modern networks, rather than burning dinosaurs, the railways have power which comes from all that knitting above the tracks. The above here is the problem. Cos it's going to shade the panels. "But it's only a thin wire, so a small shadow" I can hear some techbro angry typing. You don't need to fully obscure a whole panel to reduce it's output.
4/n
Partial shading of panels is a big problem that is often overlooked by solar installers. Any shading of a section of a panel not only stops they bit of the panel generating electricity, but it turns it into a higher resistance section of panel, reducing even further the output of the rest of the panel. Having support posts and knitting and all that other gubbins above and around the track to shade the panels is a really suboptimal situation to build solar.
5/n
@quixoticgeek it's worth noting that on a two track railway in Switzerland the knitting will only rarely shade the panels, because the sun is never overhead. This is still a stupid idea though, for all the other reasons.
@quixoticgeek
You’ve convinced me! 😀
There are better places for solar panels.
@Su_G @quixoticgeek yes, I am a strong proponent of Solar Panels but I did feel that at current efficiency rates it was a best a novelty installation.
However, if they complimented those with solar fencing on either side of the railway using double sided vertical solar panels it might make a bit more sense.
Obviously, they produce most in direct sunlight, but light (even reflected light) is enough to make them produce.
@peterbrown @Su_G originally it was a demo install. A gimmick, something to point and laugh at, but maybe it would give empirical evidence on how much of a bad choice it is. Yet if you read the news article. They've decided it's such a success they are going to do it again in Italy...
@quixoticgeek @peterbrown @Su_G
As far as they are concerned, the demo was a success!
They got more funding! :|
@quixoticgeek @peterbrown @Su_G @BillySmith
Just because it got funding, doesn't mean it's a success. What really needs to happen to kill these daft projects, is to benchmark the performance of a standard roof install, and have them compete on efficiency.
It's one of those ideas that sounds good, but where roof or overhead installs would be more efficient, and less vulnerable to damage.
Any attempt to ruggedize the panel for traffic, just reduces efficiency more.
@latelesley @quixoticgeek @peterbrown @Su_G @BillySmith Two thumbs up for metrics and competing on efficiency, but I'd also want them to compete as a function of impact of power generation on usage and impact of increased usage on power generation.
Assume the panels optimized for roadways, rails, and paths are just as efficient panels optimized for roofs / shade.
By definition, all of the "put the solar panels in the surfaces things go over" projects have misaligned metrics: the more those areas are used (the more conventionally successful they are), the less useful the solar installation will be (decreased illumination, increased maintenance and replacement costs, increased downtime). If certain types of footwear or tires aren't allowed on certain surfaces, the presence of the panels themselves will discourage usage.
By definition, all of the "use the solar panels as a roof/shade" applications align the conventional success metrics with the power generation metrics. Usage doesn't impact power generation, and in the worst case, power generation won't impact usage. In the best case, power generation may increase usage in pedestrian spaces and parking lots due to increased shade and protection from precipitation.
@latelesley @quixoticgeek @peterbrown @Su_G @BillySmith
I did see they embedded it into a road & footpaths it worked well (stillettos not wanted!)
@PabloMartini @quixoticgeek @peterbrown @Su_G @BillySmith
My point is, yes they work - but they work less efficiently than cheaper plain solar panels would. They'd be far better installing cheaper ordinary panels on poles as a canopy overhead paths and car parks. It would overall be cheaper, and harvest more energy in the same amount of time as a ruggedized, more expensive, ground mounted panel.
@PabloMartini @latelesley @quixoticgeek @peterbrown @Su_G
IIRC, the panels that reacted to pressure from the people waling on them are made from a different material to the panels used in the railway tracks.
The railway track panels are still a daft idea.
@PabloMartini @latelesley @quixoticgeek @peterbrown @Su_G
I'm not denying that it's an interesting approach, but there are already-proven methods that are already profitable.
Agro-voltaics, where you combine solar panels with farmland which means that you get improved crop yields from warmer climates, and you get the solar-generated electricity as well, giving the farms more than one revenue-stream.
It works very well, which is one of the reasons that the fossil-fuel lobby keeps attacking it.
IIRC, during the 1970's, they calculated that setting 10% of farms in Africa to growing sunflowers, the farms could become self-sufficient from fossil-fuels, by growing the ingredients for making bio-diesel.
Now that those temperature bands have moved North, it should be feasible in the UK and the EU... :D
@BillySmith @PabloMartini @latelesley @quixoticgeek @peterbrown @Su_G While you can, of course, grow crops to convert into fuel, you're using land which could grow human food to do so, and I question the morality of that.
#Agrivoltaics are a very much better idea.
https://www.journeyman.cc/blog/posts-output/2025-01-29-the-potato-famine-and-aviation-fuel/
@simon_brooke @PabloMartini @latelesley @quixoticgeek @peterbrown @Su_G
We already have the technology to grow more food whilst re-wilding our planet.
Using these self-contained planters we can increase the amount of growable land on our planet by 40% without causing any extra damage to our biosphere:
https://wickcuriosityshop.net/collection/plant-regulated-growing-system
The planters are an open version of these syetms created in the 1970's:
https://earthbox.com/learning-center/instruction-manuals
No-one on our planet should be going hungry.
As for the aviation fuel, we can cut out the fossil part of the hydrocarbons be makig them directly from atmospheric CO2:
Renewably-generated electricity, captured CO2, and water, means that we can manufacture all of the hdrocarbons that we need, without adding extra CO2 to the atmosphere. :D
Any half competent installer would spot this and recommend against such an idea. But then such people aren't trying to get VC funding.
The next suboptimal part of this setup is one of wire lengths. By it's nature, a solar install in between railway tracks is long and thin. The news article says it's 100m long. Assuming that it's 1m wide (there's only 1435mm between the rails anyway). So essentially that's a 100m² install. But that means you have to run 100m long wire to connect the panels.
6/n
@quixoticgeek I agree this a stupid idea, but cable length is not the problem. I'm running a pair of PV strings over 50m of cable (for + and -, so 100m in total) and with 6mm², it is just a few percent of loss, very tolerable if the rest of the install makes sense. With a 100m long string, you'd have one end terminate at yourend and the other come back to you via 100m of cable. But you'd probably have at least 2kV of voltage, which might be a problem.
@cm the problem is when you scale it beyond 100m.
At such low voltages, voltage drop over that sort of distance is going to mean quite an efficiency hit. Unless you use really thick cable. Which is expensive. Or run things at a much higher voltage (now you have extra risk assessment concerns)
It's probably a good time to dispell perhaps one of the misconceptions many will have about this install. That the power it generates can power the trains. These solar panels are going to be generating electricity in the 100s of volts range at best.
7/n
@quixoticgeek Yeah, this whole idea seems ridiculous. Random bits of railway track also aren‘t generally well-situated for feeding into the grid.
In Europe we have far too much sealed ground surface dedicated to car parks, which heat up to incredible temperatures from direct sunlight. You‘d think they‘d start by shading those with PV, solving 2 problems at once and without the weird issues of geometry and operations.
@pmdj @quixoticgeek France introduced this as mandatory for new car parks over a certain size since couple of years ago or something.
The UK shelved similar plans recently.
And while there are some countries that run their trains on low voltages (1500VDC in .NL, 3000VDC in .BE). Most overhead electrified lines use either 15KV AC at 16 ⅔hz, or 25KV AC. Taking your tiny 100m² 18KW solar install and trying to make any of those voltages and feed it to the trains is just not gonna work. High voltage electrical engineering is Really Complex!. So instead small installs feed into the local 415v grid.
Now that word local is the next flaw in the idea.
8/n
You might think the railways are lots of space, so this just scales great and we can have oodles of power. Let's take a hypothetical 100km stretch of track, and fill it with a continuous string of 1m wide panels. That gives us an area of: 100000m². At 200w/m² output, that's 20MW! Loads! Except you now have to transmit that power 100km (well 50km to each end). We have technology to do very low loss long distance power transmission. But it all relies on really high voltages.
9/n
@quixoticgeek Ah, but what if we also made a 100km long city to go alongside the railway.... Maybe in the desert somewhere....
@geospacedman a startling lack of ambition. It needs to be at least 500km to get VC funding...
@quixoticgeek Oh of course EEvBlog smashed it - 3 years ago... https://youtu.be/7vItnxhWRqw
@geospacedman yeah, but he's not considered a good source since he's been known to make transphobic comments.
@quixoticgeek Ugh. I don't follow him, just dip in occasionally so missed any of that.
Now if we took say the original 100m² demo array, and instead of putting it in a safety critical location with all sorts of risk headaches. And we made it into a single 10m x 10m square. Our longest cable run becomes about 14m, we can build it say, over the station carpark, which also reduces energy for the cars to cool themselves. The station is of course near homes, businesses, etc... so near demand. Cheaper. Easier to maintain, and no safety critical systems headaches.
10/n
@quixoticgeek better shading the car parks with solar pv
"yeah, but that's the tiny install, what about that 20MW 100ha install you talked about?, that's bigger than your station carpark!!"
Yep. So let's use the local supermarket roof... And maybe their carpark... And some businesses... And some homes. Maybe the local school roof. That'll quickly add up. Simpler installs, no faffing in safety critical environments. No bonkers long cable runs. Power generated near to where its used.
It's just there's no VC funding for such sensibilities...
11/n
@quixoticgeek VC funding wants a growth story, not a better mousetrap.
@quixoticgeek that was so frustrating - just using the right of way _next_ to most rail lines would be an order of magnitude easier but because it’s just routine engineering it’s not exciting enough for VCs because they can’t pretend to have a huge rate of return.
@quixoticgeek "yeah, but what about all the surface car parks in the city"? I'll have the answer tonight, I hope.
Meanwhile, there is a law here in France that surface car parks beyond certain size have to have at least 50% of its surface covered in panels. Unluckily, I know only one:
(fsck, cartes.app is down, gmaps will have to be)
@mdione see the eurodisney example later in the thread.
@quixoticgeek yeah, I read. Unluckily is not on the satellite imagery yet :(
The number that really puts this all into perspective comes from the Wikipedia page on LGV Sud Est. The french high-speed line from Paris to Lyon. The total area of the train line is 16km². By comparison Charles de Gaul airport is 32km². Trains are an incredibly efficient use of space
To throw in another data point. Disneyland Paris has approximately 200000m² of carpark. And they've covered it with solar panels. Local to where the power is needed, no faffing with safety critical systems.
12/n
@quixoticgeek Very good logical thread that, BECAUSE it is logical and well argued, will be ignored by the techbros. Thanks.
Solar energy is an absolutely incredible technology. It's a key building block of our sustainable future. We need lots of it. But maybe before we start trying to cram it into the safety critical infrastructure of our railway tracks, we start first with every equatorial facing roof top. And maybe some platform shelters to provide shade for passengers as well as electricity.
13/13
@quixoticgeek@v.stLet's to East-West facing, to flatten the daily curve and align production more with times of demand ;-)
See last section in https://www.golem.de/news/gleichmaessige-stromproduktion-alpiner-solarstrom-fliesst-auch-im-winter-2607-210678.html for example or https://next2sun.com/en/
@quixoticgeek Let's do East-West facing though, to flatten the daily curve and align production more with times of demand ;-)
See last section in https://www.golem.de/news/gleichmaessige-stromproduktion-alpiner-solarstrom-fliesst-auch-im-winter-2607-210678.html for example or https://next2sun.com/en/
@quixoticgeek To the lady commenter, they look easy. Roofs can be complicated cos they're often weak. Panels on new, and strengthening money for redone roofs can work.
Ditto the space around trains, it seems?
@quixoticgeek why the fuck don't they put solar panels on posts *over* roadways and train tracks? There's an upper limit to how tall shit being transported on these things can get. Just go a bit higher!
@quixoticgeek Back when I was still on FB, someone wrote a long, technical essay on why paving slabs that double as solar panels are a bad idea. Such negativity about an exciting technology annoyed me at the time, but has been proved correct. 🤷🏻♂️
Put simply, they generate less power at an exponentially higher cost than conventional solar systems, not least because no known material is both durable and cheap enough for them to be practical. Paving slabs endure 👉🏼 massive👈🏼 amounts of wear and tear!
@ApostateEnglishman
I remember a few years ago, someone tried to make solar roadways, it didn't go well...
The surfaces were too slippery, they got dirty really fast, and repair costs were too high
I do like the idea of floating panels in reservoirs and aquaducts
@quixoticgeek
@DelilahTech @ApostateEnglishman @quixoticgeek If they want to run solar along railway lines, why not have elevated panels attached to the existing (which may need reinforcement for the panel weights) support towers that hold the power cables along electrified passenger lines?
Overhead solar makes use of the right of way, can connect to the grid at existing transformer stations, and doesn't carry as much risk of breakage and degraded performance. Between the rails is just a silly maintenance nightmare.
@linuxandyarn
OMG, between the rails—wouldn't that be entertaining?
@ApostateEnglishman @quixoticgeek
@linuxandyarn
Hrm... let's hope it will be viable
@ApostateEnglishman @quixoticgeek
@DelilahTech @linuxandyarn @ApostateEnglishman why? There's much more sensible places to put solar. Hence the whole reason I started this thread.
@quixoticgeek this. So many times this.
I hate that they're now applying similar logic for ✨data centers in space✨. It's all just grift. The only benefit you gain is free area, compared with the innumerable downsides of a hostile environment and being so far away from everything. It's all just grift. They'll swallow up billions in investor money, and then produce something worth a few farts and call it a success.
@Artemis201 @quixoticgeek
Data centres in space sort of make sense, if (a) you truly believe that you will be uploading yourself just before ecosystem collapse claims Earth-based civilisation, and (b) you haven't thought through the need for maintenance and support
@swaldman @Artemis201 or cooling... Or connectivity... Or radiation...
@quixoticgeek @Artemis201
Connectivity and radiation are fairly solvable if not trying to compete on cost, I think. No idea how they plan it cool the things...
@swaldman @Artemis201 radio connection cannot compete with the speed of terrestrial fibre.
@quixoticgeek @Artemis201
I was thinking more of pointing lasers between units. Assuming this is for post-civilisation use, most traffic will be staying in space.
@quixoticgeek It's not as if various railway operators don't have parcels of land here there and everywhere that you could do a much more conventional ground mount install without messing with the track
@quixoticgeek Very interesting but why on earth would anyone think of putting it on the track? Maybe it's obvious because I'm British and I know that's where the "wrong type of snow" belongs. :-)
@woo cos VC funding...
Large solar farms are running 1000V - 1500V these days to minimise losses.
The side effect of all this is things will get interesting when a big train goes bouncy-bouncy over the track on a regular basis shaking the connections and dropping the odd bit of debris on the panels.
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