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Comment by effie | Hacker News Reader

Room temperature superconductivity itself is not revolutionary for anything except academic papers. Lossless power lines and frictionless trains are a gimmick as those losses are small part of their operating cost. Resistance of copper cables is very small and acceptable already. When price of superconducing cables is comparable to copper cables, then it becomes interesting.

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Superconductivity is phenomenologically different than "very low resistance." The excitement about high-temperature superconductors is not only that there will be less power dissipated through power lines, but they will enable new technologies in power generation, high-energy physics research, analog and digital circuitry, sensors, and communications.

As someone who knows nothing about this: what would the most obviously useful applications be, if we discovered practical room-temperature superconductors?

MRI scanners, tiny and mobile, used like ultrasound whenever, wherever at a tiny fraction of the cost. This would be one 'extension' of something we use already.

But the notion of cheap 'extremely powerful' magnets extends into other things - you'd see 'maglev' type stuff everywhere.

I would imagine some kinds of major computational leaps if it could be done at that small scale.

The efficiency of electric generators changes tremendously without resistance - if built into your local windmill it would improve generation quite a lot.

Yes except the last one. Your windmill is not starved of space to make a big dynamo that uses a lot of copper and is very, very efficient. If the superconducting material is cheap you might be able to do it without using nearly as much material or even without magnets. So it might be cheaper and smaller!

The opposite application (generating torque) is already a home for superconductors. The navy has some superconducting motors in its ships. They're way smaller and have high efficiency over a much wider dynamic range of operating torque. Those are cryo-cooled though.

Fusion power becomes a reality, MRI machines get really small and cheap, your computer gets faster and no longer needs to be cooled, better Maglev trains, lossless transmission of electrical power over long distances.

It's a holy grail technology. You would likely solve all energy problems for the human race forever.

Do you realize all those are wishes, not plausible technology right now? Fusion power has more problems than just magnets needed to be kept cold. MRI machines are a niche thing, sure they could get cheaper but why should average Joe care? Computers don't get just magically faster. Computers need semiconductor switches and those operate based on energy dissipation, you can't just remove that and get a better computer. Maglev trains are overpriced gimmick and lossless transmission would be nice but current estimate of energy losses is like 5%, negligible part of the cost.

> It's a holy grail technology.

In the sense lots of people talk about it as something important, but it is never actually seen or used.

Computers would get magically faster, though. You can build standard digital circuits out of superconducting Josephson junctions, which have much higher switching speeds than semiconductor transistors. A flip-flop was demonstrated to operate at 770 GHz.

Josephson junction is a very interesting device with many uses, including low energy consumption per FLOPS.

But one big part of the reason the consumption is so low is low temperature. When you try it with room temperatures, switching energy will go up by 2 orders of magnitude (due to higher thermal noise) and this makes the JJ computer efficiency only somewhat better than CMOS. I agree this would still be interesting as refrigeration can be much simpler then and researching JJ-based computers would be easier.

But if we talk about best power/watt, the 4.2K systems or 77K systems are likely to be better than room temp superconducting computers.

"A flip-flop was demonstrated to operate at 770 GHz."

That's data, but not information - flip-flop Hz is far higher than the processor's Hz (which basically has to synchronise over billions of different circuits and run at the lowest common denominator) - so your figure can't be compared to a normal processor's clock speed, only a normal flip flop's speed.

Anyone know what a normal flip flop's speed runs at?

Energy storage would be pretty useful, the efficiency could be even better than batteries: https://en.wikipedia.org/wiki/Superconducting_magnetic_energ...

The only discipline in which SMES are an interesting option is high-power pulse sources. For storage of power plant production they are not interesting, as their energy density is order of magnitude lower than those of batteries. They are too heavy and too big. This problem does not go away just by having room temp superconductor. It would have to have incredibly high critical magnetic field strength and be very cheap.

> https://snf.ieeecsc.org/sites/ieeecsc.org/files/CR5_Final3_0...

I think it could scale. If you can directly transfer mechanical stress from the cable to the earth, with no concerns over vacuum or thermal insulation, the economics might work. Even if you can only store ~1 Wh per kg of enclosed rock, it seems possible to enclose millions of kgs of granite in a solenoid.

Maybe fusion power:

https://www.psfc.mit.edu/research/topics/high-field-pathway-...

Definitely fusion, room temp super conductors would allow for better magnets that would better contain the plasma.

It depends on more factors than the critical temperature. Keeping the magnets cool is not so difficult, liquid nitrogen is fairly cheap. You want materials that can sustain large magnetic fields before losing superconductivity.

> "power generation, high-energy physics research, analog and digital circuitry, sensors, and communications"

Could you provide some reference to these things that are almost there but wait for temp room semiconductors? Sorry, as written this sounds like a vacuous buzzword drop from MIC contractor.

I think you meant "very low resistance" or "very high conductivity", right?

Yes, definitely. I'll edit the parent to reflect.

Isn’t superconducting a requirement for fusion reactors (for plasma confinement)? I think all the cooling required for that is a major impediment to both the design and the efficiency.

You don't need room temp superconductors to make those magnets. REBCO tape can be cooled by liquid nitrogen. It's what they are using for the various tiny Tocamak projects.

Why is this material not used for MRI's?

This material only appeared in the last 10 years as a practical way of creating strong magnetic fields. Give it enough time and you'll see most MRIs transition away from the large hulking behemoth machines that we have today into much smaller and more portable machines. Also, as an added benefit you can use liquid nitrogen to cool them instead of helium.

As sibling post noted, likely time. Existing designs have 4 decades of inertia behind them.

South Korean and Japanese researchers definitely have it on their radar.

https://ieeexplore.ieee.org/document/9000570

And MRI-machines. Are you able to make superconducting self sustaining outside the laboratory it can have a lot of great implications: Reduce the cost of MRI (huge helium cost), make extremely fast batteries for regeneration of power, very efficient and small motors +++

MRI machines don't necessarily need helium even today. It just the common model family using Niobium-Tin wires you see in hospitals or media. There are permanent magnet MRI machines.

What do you mean by "fast batteries"? For regenerative breaking one can already use supercapacitors. Will room temp SMES cheaper than that?

Electric motors are pretty efficient and small already, there is 0.6mm motor from Namiki. Sure they can get smaller. How does room temp superconductor help that? Smaller motors have better cooling than big motors so ohmic heating is not a problem.

I think you are right for tokamaks, room temp superconductor would change the design somewhat.

In existing superconductors, you break superconductivity if your magnetic field reaches a certain threshold. That limit decreases, the closer you are to the temperature limit.

So yeah, higher-temperature superconductors could either give you higher-temperature supermagnets, or same-temperature stronger magnets. The latter is being explored with relatively new materials, for smaller tokamaks, which enabled by stronger magnetic fields.

Having another data point will help in shaping their understanding of the phenomenon, which may lead to future more practical developments. So don't discount the fact this is an academic result.

Power line losses are not insignificant, and put a limit on how far power can be shipped. Solar and wind variability is a problem, but if power could be shipped anywhere on the grid with no transmission line losses (there would still be other losses) it would do a lot to smooth out local variations in power generation.

https://www.eia.gov/tools/faqs/faq.php?id=105&t=3

5% is not insignificant, and it is that low because electricity is routed to nearby consumers as much as possible.

I don't think the elimination of cable losses is near the top of the list when it comes to discussions around why high temperature SC is revolutionary.

And what is top of the list, then?

Stronger magnets! Better magnetic bearings! RF circuits.

If superconductors were feasible on integrated circuits, I'd expect the TDP to get lower, enabling higher frequencies and integration (3D?). Frequencies would still be limited by propagation delay, but we have some room to grow. Classic FET wouldn't work, I think, at least not without bringing back switching losses, but there's probably a way to create a magnetic transistor using a few superconductor wires (locally increasing resistance above 0, for instance). Or use FETs with adiabatic computing, who knows? Future seems bright, and applications for room-temperature superconductors are aplenty. It's just that everyone thought of them as a pipe dream, so they aren't really being investigated that I know of.

I wish that link had a better list:

https://en.wikipedia.org/wiki/Technological_applications_of_...

At least with a PoC, we might see a revival of real interest in them. Not sure how long it will last, though.

Superconducting computer will still dissipate heat, as there is minimum cost per element switch due to thermal noise. This makes superconducting computers more efficient at lower temperatures. Room temp superconductor would be cool for making research simpler though.

I imagine energy storage would be up there.

To be fair, the article takes some care to point out that cables are likely impossible

... with this method. My point is, even if we have room temp room pressure superconductors, this isn't as revolutionary by itself. The price is key and ordinary copper is likely to win in most places except where price does not matter, or where we need the very strongest magnets.

I'm imagining if superconductors become widely used it will be in small quantities and for their unique properties that cannot be achieved otherwise. Not for minor benefits over alternatives?

But what about energy storage? How much current you can pump in a closed circuit?

The current has some limits, but with enough copper you can probably put some serious amperage on it, and a superconductive magnet in "persistent mode" can apparently keep going for months. Not sure how I'd feel about several MWh in a single circuit though.

It might be easier to just build a big flywheel.

Issue with flywheels tends to be containment when they explode, flashing a MWh of metal due to containment failure I would hope to be safer. Additionally a superconductor wouldnt have gyroscopic forces to worry about.

1MWh is almost 1 ton of TNT. If you have that energy in a flywheel or in a electric circuit and something goes wrong, you need containment in both cases.

If the circuit losses superconductivity and a part overheats, it will release 1MWh in a very short time, that will cause an explosion.

You should look up what happened at Cern when they had a superconductor meltdown. And that one wasn't even a burst of power it was a continuous current (admittedly one with enough to power a small city).

Of course anything with that much energy is possibly violent, but at least a flywheel is easy to control. I haven't the faintest idea what that amount of electromagnetic energy would do, I'm not sure I want to find out.

At the very least I suspect you'll find that electromagnetic current also has angular momentum at those scales.

Cern has blocks of metal to contain the heat in these scenarios.

There’s no way to quickly transfer the energy from a flywheel however.

In a superconducting coil there are similar repulsive magnetic forces, which can easily disintegrate the superconducting wire at very high currents.

Therefore the coil assembly must be designed to support the wire and resist to the highest forces expected.

So there are similar problems with flywheels and superconducting coils, in the case when the stored energy densities are also similar.

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