The crux of the problem for superconductors used as power delivery is the "critical field" problem. [1]

Super conductors are superconductive to a point. Once that point is crossed they turn into regular conductors. (I've seen ~1A cited. For context, EVs charge at around 500A).

To make them useful for power transmission, you'd have to up the voltage to insane levels to avoid collapsing the field.

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

or just go the straightforward way and use several transmissions in parallel, as it is already done for existing superconducting lines in production.

The AmpaCity project in Essen, Germany, gives insights about the implementation details, as the involved parties were required to publish their work.

https://www.enargus.de/pub/bscw.cgi/?op=enargus.eps2&q=%2201...

for the specific aspect under discussion, the Karlsruhe Institute of Technology report is of interest:

https://www.tib.eu/de/suchen/id/TIBKAT:872231372/Ampacity-10...

Superconductors have a critical current density (Ampere/m^2) that varies with temperature and external magnetic field[0]. So if you want more current, you need to use a bigger wire (and/or make it cooler). YBCO HTS tapes have enough current density for power transmission[1].

[0] https://en.wikipedia.org/wiki/Yttrium_barium_copper_oxide#/m...

[1] https://www.amsc.com/comed-and-amsc-announce-successful-inte...

Am not the author of that comment, but the fact that comes to mind is that aluminum is used for virtually all transmission and distribution lines - for price reasons - even though copper has better conductivity.

If we did discover a room-temperature superconductor, I suspect it would be a while before the cost to produce it in the bulk quantities required for electrical transmission are economically attractive compared to what’s already available.

> it would be a while before the cost to produce it in the bulk quantities required for electrical transmission are economically attractive compared to what’s already available.

Note that there is no guarantee that that would ever happen. Electrical resistance is not the only thing you need for something to be an economically efficient power line. While superconductors are by definition excellent in terms of electrical resistance, there is nothing to guarantee that they wouldn't be too brittle, or too heavy, or too hard to mould into the required shape, or simply require materials that are too rare on Earth. And all of these would not be things that can just be worked around with better production processes or smart engineering - they would be fundamental limitations of the specific material, just like the low temperature requirements of currently known superconductors will never be improved with more research.

So this isn't a matter of when they would reach the point of being better economically, it's also very much a matter of if they would ever reach that point. Hopefully, we'll get lucky one day and find a material that is superconducting at room temperature and above, that is study and light and easy to make into wires and made out of abundantly available elements. LK-99 certainly wasn't most of these things. Even if it had been superconducting, it wasn't a good candidate for any of the other properties we want anyway, so it likely wouldn't have been much better than other known materials for most applications.

The pace of development of computing seems to have trained people to think in terms of "when" for science and engineering problems. The normal paradigm is to think in terms of "if," and that aligns well with most non-computing inventions.

There is a good chance that they never reach the exponential breakpoints that everyone likes to fantasize about.

Yeah. There’s a lot of wishful thinking about science and sciencing up solutions to the world’s problems — especially here. The fact is, most progress is slow, and even if there is progress, it’s not necessarily economical in either financial or energy perspective.

In theory, we could have had a much better power grid with more transmission. The reasons we don't have nothing to do with the price of aluminium, or the resistive losses of it. It's just difficult to build large-scale infrastructure. Transmission projects typically spend longer in court than actually building them. Superconductors would not change a thing, unless it changed that.

Aluminum vs copper is a good example. Another is that we already do use superconducting transmission lines in a few places. We could do more of that, but presumably it's expensive to install and/or maintain otherwise we'd be using it everywhere. I'm not sure what the longest or highest capacity superconducting links currently in existence are.

That have to be kept cool with liquid nitrogen, so it would have to be pretty darn short.

Actually no: they have to be insulated well. People forget that it doesn't actually take energy to stay cool, just to remove the heat. The issue is what's your heat gain from insulation inefficiency per length - and it does get better then thicker your cable gets, because volume increases more rapidly then surface area.

If you're dealing with usecases that need to be cooled anyway, you may well be better off with the tradeoff of needing liquid nitrogen cooling and better insulation in exchange for entirely eliminating resistive heat.

I wonder if we can use these superconducters on spacecraft and probes. Maybe we can place superconducting links on the outer hull of a spacecraft heading to Mars, or a probe heading into outer space.

Cooling them would still be a problem. The sunny side might not be tHe best place for them.

They might find a niche in some instruments in probes, but for wiring it does not make sense. The rest of the probe electronics don't like being that cold.

But why? What is the problem you are trying to solve by placing superconducting links on the outer hull of spacecraft?

High-temperature ones can be cooler with liquid nitrogen. Standard ones, the ones most commonly used, require liquid helium.

Well, I think it comes down to whether the energy cost of active cooling is better or worse than resistive losses. Which one is better doesn't depend on cable length.

In some desperate places, people would cut down aluminum power lines and sell them to scrapyards for some quick buck. But copper power lines? Those would be in a similar danger in many more places.

Not only in desperate places. I heard last year (or the year before) someone stole few km of train wire in Germany. Although to this day some people think it was a Russian sabotage rather than genuine theft. Previously (for example in Poland) I used to hear about things like this all the time until maybe a decade ago.

They steal buried copper cables in rural locations (UK) by attaching one end to a truck and driving off. Mostly seems to be communication lines.

Tying a high voltage power line to a truck is a recipe for an exploding/melting truck, long before someone could pull it down.

Communication/low voltage is a different matter of course.

Aluminum vs Copper is not that simple. Aluminum has worse conductivity for the same area, but area is in no way fixed. And aluminum has actually better conductivity than copper for the same weight. You just have to make the cables a bit thicker.

I think the relevant metric here is conductivity for the same cost.

It may come down to cost, but other physical properties enter the picture. For example: thermal expansion is an issue for overhead power lines, along with how ductile it is.

In other cases it is more important to reduce resistance, not so much because of the power loss but because of what the power loss means: the generation of heat that may be difficult to remove.

Of course you can get around those problems at extra cost, but it is more than a straight up comparison of the material cost of the conductor.

Silver is even more conductive than copper!

And gold too.

Very expensive to build anything sizable out of it

Gold (2.44x10-8 Ω•m) is worse than copper (1.68x10-8 Ω•m), but better than aluminium (2.82x10-8 Ω•m).

It does have excellent anti-corrosion properties.

I wonder what kinds of alloys we will see in the potential future with asteroid mining and thus comparatively cheap gold. Imagine replacing lead with gold in industrial applications. Or the stainless steels with a gold component in them.

Probably the most useful mtal from asteroid mining will be platinum for use in catalysts.

The trouble with asteroid mining is that getting anything there and back is expensive, let alone any heavy equipment needed for large scale mining.

My guess is the main application will be for space missions that find it cheaper to carry mining/manufacturing equipment rather than all the materials they need. Even that seems potentially a ways off. I suppose we could mine asteroids for science sooner, but that's quite a bit different than any mission plan which includes mining as a part of the required logistics. Maybe if there's some materials needed for extending life support capabilities? But still I'd have to wonder why not just take the extra supplies with you.

Maybe a moon or Mars base could change some calculus. As I suspect the break even point of such a plan may require lots of use of any such equipment.

We frequently use aluminum wires with a higher thickness to make up for the lower conductivity as compared to copper. It’s not as simple as cost vs performance though, as aluminum is substantially less dense than copper. Gold and silver are also better conductors than copper, but of course are very expensive, and still have resistance. Zero resistance may be with it on some cases. For instance in projects that currently use high voltage dc it may be worth it due to safety and complexity wins, but that all would depend on how hard (expense and complexity) the superconductor is to deploy.

>We frequently use aluminum wires with a higher thickness to make up for the lower conductivity as compared to copper.

Aluminum wires even made it into residential housing when copper was expensive/rare. https://en.wikipedia.org/wiki/Aluminum_building_wiring

Can confirm, my parents had an aluminium telephone line in the UK until it failed and had to be replaced. Moot point as it's replaced with a fibre optic cable now though.

The problem is with their usage as mains power. I think they are considered a fire hazard in older German homes.

Not surprising, any degradation in the connection leads to intermittent connection/high resistance fault = heat and poof, there it goes.

No only silver is a better conductor than copper. Gold is worse.

A 2" diameter copper wire will have lower losses than a 1" diameter copper wire.

Copper is expensive so over hundreds of miles you may not want that.