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Comment by walrus01 | Hacker News Reader

It's worth nothing that the economics of the labor to remove "old" solar panels, transport them, recycle them, and install new panels may not make sense. Current technology monocrystalline silicon stuff can be guaranteed to have 80% of its original STC (standard test condition) power output after 25 years. Usually at which time the panels will be long since paid off and whatever power they are making for the roof owner is free money.

80% of original test-conditions rated power is still a lot - if you were to theoretically install a 40kW rated array composed of about 112, 360W panels, that would still be a 32kW array after 25 years.

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That depends on how much more efficient the new panels are, and how much they cost. You only have so much roof area, so if you can generate enough power with the new panels over the old ones to more than recoup the costs, it's worth it.

We only have so much roof area, but we have almost no shortage of non-roof solar farm area.

Only so much bare roof area, but to say there is plenty left still would be an understatement.

USA Interstate network has a total length of 77,556 km. A 1m wide strip of PV along the dividing barrier in the middle is, eyeballing the solar irradiance graphs, something like 77.5e6 m^2 * 1500 kWh/m^2/y = 116.250 TWh/y compared to USA annual use of about 25 TWh/y for all power not just electricity. Even accounting for PV efficiency, that’s basically enough from just one possible currently wasted location.

Obviously every country is different — my country, the UK, much worse annual average light, and higher population density, but the point still applies. Almost every nation can do this without worrying about land use.

I agree that most countries are not critically limited by land when it comes to solar power, but there are a couple of problems with your figures.

The US consumes nearly 29000 TWh of primary energy per year, of which about 3700 TWh ends up as usable electricity:

https://flowcharts.llnl.gov/content/assets/images/charts/Ene...

(1 "quad", quadrillion BTU, is 293 TWh.)

The other is that you're estimating the energy of the sunlight that falls on 77.5e6 m^2 rather than the achievable electrical generation. The most efficient terrestrial solar panels are just a little above 20%.

Rooftops are also conveniently close to the demand.

Yes, we do. Covering the ground with solar panels means that land can't be used for other things, such as farming, or natural habitat.

I suppose if you want to just cover totally barren places like the Sahara with solar panels that would be OK, but there's political and engineering problems with that (transmitting power long-distance incurs losses, and getting power across the Mediterranean wouldn't be easy).

Solar farms are just as much of an eye sore as coal plants.

I’m all for renewable energy but I don’t want huge solar plants everywhere either.

You actually think this is as ugly as a coal power plant? I just don't know what to say.

http://apsolarracking.com/images/ground-large_13.jpg

Perspectives can differ. One of the greatest soaring sites in Europe (Aspres in the French Alps) is fighting for survival against a solar farm. An irreplaceable loss, given the topology in the area. Which is also why a flat plateau at the top of a mountain is suitable for solar production. Economics wise of course a small bunch of glider pilots will not stand a chance against the inevitable economic needs of the area. So yes, a solar farm can be a land wart, depending on where you stand.

No panels visible here, but they are marching towards sacred ground: https://goo.gl/maps/8kagR6UNXXG2

Considering they are taking green spaces yes they are.

This doesn’t look like a commercial solar farm also it’s a pretty small installation which looks private.

Solar farms will have fences, battery storage, support structures, access roads and essentially everything any industrial installation needs.

They won’t be pretty and you need to be really up there to advocate for taking even more space away from the public.

That picture isn't comparable to a big ugly coal plant, you need to show a couple square miles of panels.

A coal power plant is also a central spreading point of ... well poison really (sulphur oxides are essentially poison). The ugliness of coal power plants just begins with their looks.

They've got large coal dumping grounds. They usually have a freight train station that had coal dumped all over it, so everything within 10 meters of it died. They just let all of this sit in open air usually, plus there's the massive amount of smoke, so you can smell them from kilometers away even when there is wind (and let's just not discuss when there isn't, just visit Beijing).

No one said coal was better or that we should even use it.

But commercial scale solar farms are fucking ugly they take spaces away from people and advocating for more of them at the expense of green spaces is terribly short sighted.

Put solar everywhere we already have ugly box buildings and roads don’t take up even more shared spaces some of them due to current laws are written can even be nature reserves because we’re green after all.

Yeah, they are big and ugly, way to emphasize something I said.

But solar takes up a huge amount of space, it's worth admitting it.

I do. I drive by one of those solar farms regularly and it’s an eye sore.

IMHO this coal plant in the distance is easier on the eyes: https://cdn.arstechnica.net/wp-content/uploads/2017/10/Getty...

Isn't the visual appeal of a power station a secondary factor at best? Just not sure of the relevance of your reply.

Which means the old panels should be reused instead of recycling. Perhaps that's the point. Clean the protective layers and resell on used market.

Having been in possession of more than my share of "used" panels, there are a few practicalities you need to be aware of:

•Used solar panels are off-spec and can't be teamed with other used solar panels properly. They become like two drunks trying to help each other down the street.

•Even used solar panels need mounting/racking hardware.

•Even used solar panels need inverters and wiring (frequently in values that are out of production).

•Used solar panels are a b*@#% to ship.

The glass, if intact, is the most valuable part of the solar panel for recycling purposes. This is followed closely by the aluminum frame.

The EVA (clear rubber) that encases the solar panels is garbage by the time the panel gets recycled. This is the part that turns brown and lets in moisture. I imagine incineration is the best path forward for this stuff, because after 30 years of cross-linking in the sun, it's not going to melt into a liquid.

The solar cells themselves are so enmeshed with the EVA that they turn into inchlong irregular shards attached to tabbing. There's no realistic hope for getting a commercial-grade panel out of them, even if you melt them down.

The tabbing is a valuable mix of tin, copper, and silver, as is the metallization on some cells, though you'd have to be talking tons of crushed cells to get a pound each of the metals. This should be a straightforward matter of crush and dissolve in chemicals, then throwing the stripped silicon into a smelter somewhere.

The "J-box" doesn't count for a lot of weight and is probably too old-fashioned to reuse, even if the plastic hadn't broken down and the contacts hadn't corroded. Best off cooking off the plastic and remelting the copper/tin metal portions.

You might find yourself in a position to say, hey, I'd gladly accept a used 3 ft x 5 ft solar panel that worked 50% as good as new, and was ugly. I doubt you would be in the position to take on 100 more, especially not being able to team them together.

It's not unusual to see brand-spanking-new panels at prices near $0.50/W. Shipping is starting to dominate the cost of panels, used or new.

You certainly wouldn't want to mix and match used solar panels with an existing install. It would be necessary to keep them together in series and parallel configurations somewhat similar to how they were originally installed. Or to break them up into smaller groups of the same consistent age and resell them to offgrid builders (eg: a guy who wants 8 x 60-cell panels for his off grid cabin somewhere).

And yes shipping will be truly a pain in the ass. A brand new pallet of 20 or 22 panels with the special plastic protectors in place, and wrapped up with plastic, is easy to ship. Individual loose panels are difficult to transport loose without damaging them, and labor intensive to move around.

One of the things you can do with used panels is re-use them for off grid applications. There are off grid PV charge controllers now (Schneider, others) which support up to either 600V or 1000VDC on the PV input side, and up to 4800W of panels per charge controller. You can build strings that are basically all of the panels in series together, simplifying the wiring, assuming that the panels are new enough to be also rated for 600V (US) or 1000V (EU) spec, mostly intended for feeding big inverters.

I wouldn't really say that shipping dominates the cost just yet. I recently bought a pallet load of high-efficiency monocrystalline panels (72-cell, 360W) at around $0.62/watt. The shipping for the pallet was about $350. The panels themselves were about $4500 FOB.

Sounds like a further argument for per-panel microinverters

I've seen hobbyists/enthusiast groups get a van full of used panels for surprisingly cheap, which then was split between the members at meetups. Seems like people are happy to just see them gone, which makes sense if they're hard to reuse or repair at scale.

Sure, if I were in that position after 25 years, and I wanted to increase my kWh sold to the grid per month by buying new panels (let's imagine that a 1.99 x 0.99 meter panel in 25 years from now might be rated at 450W)... And I could make the math work for the ROI to pay off the new panels, I could sell the old panels in place as-is where-is, buyer to remove.

> The robots in Veolia’s new plant dissemble the panels to recuperate glass, silicon, plastics, copper and silver, which are crushed into granulates that can used to make new panels.

That's recycling, not reuse. A lot of energy and, I'd assume, water and chemicals go into turning these raw materials into panels again.

But those raw materials are much less raw than sand and metal ores.

Not really. For example it takes similar amounts of energy to turn glass into glass of another shape than sand into glass.

Then why is it profitable to recycle glass?

That still is a 8kW difference that, over decades, may offset the energy cost of recycling the old set of panels.

Also, keeping the old panels means you can’t reuse whatever those panels are mounted on for the new ones. That can make installing new panels alongside old ones more expensive, sometimes significantly more so.

It's also worth noting that economic considerations are not always paramount.

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