Hacker News Reader

Comment by digdugdirk | Hacker News Reader

It's a conductor of electricity. But super good at it.

i.e. - It has zero resistance to electricity.

Currently, the best superconducting materials we can create have to be chilled to near absolute zero, which means designing them to work in liquid helium baths. This is expensive, and difficult. If a material can superconduct at room temperature, now we're talking usage in general purpose consumer goods.

As for why we want a superconductor? Real cool stuff happens when there's zero resistance to electrical current. I'm sure other people can add on to this, but for an immediate benefit - electricity transmission wouldn't have any losses. Imagine offshore wind turbines that could transmit power to Kansas from the Atlantic. It'd be a big deal.

View on HN

Hmm. Losses from HVDC transmission are on the order of 3% per 1000km, so I'm not sure how much of a big deal it'd be for that kind of use case. Your example would only save ~6% transmission losses. An improvement yes but not really a big deal, unless the cables were far cheaper to make than current HVDC cables (which I'm doubtful about).

I think there are other use cases within devices themselves that are far more interesting for energy storage.

3% but keep in mind they can only push so much current through those wires before they start losing energy to heat, regardless of the voltage.

The same cable diameter can now power an entire state.

Superconductors have a critical field, you can't pump unlimited amounts of current through a superconductor.

(I think there were some comments going around that this material has quite a low critical field, so there would have to be some substantial improvements on this even if it is superconducting)

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

I remember going down the rabbit hole on superconductors a few years ago and finding out that they were limited by a critical field. It was both reassuring and disappointing and largely for the same reason - there's no truly "free lunch" in nature.

ok but 3% when you're talking about MWs or GWs of power is still a lot of wasted energy.

Whether it's worth doing also depends on how much energy it would take to make thousands of miles of superconducting cable of similar capacity and how long such a cable would last.

Not as much as is wasted in generation and transforming, both of which would benefit from superconductors.

The benefit might lie less in the wires and more in the equipment.

Tough to say with a trans Atlantic cable though. Those kinds of distances have never been tried to my knowledge.

It probably has no applications in transmission. Trans losses arent that high; not enough to justify refurbishing the grid.

The electrical resistance per se is actually not that interesting. Certainly not for energy loss. Electronics would benefit, especially CPUs if transistor switching doesn't heat the interconnects above the transition T (the actual cpu is much hotter than the package where the thermocouple is).

High quality (as in high Q) passives would be cool. Think very good capacitors and inductors for filtering. Super cond. caps wouldn't be great for energy dumping since high B fields kill the superconducting effect.

The magnetic properties are more interesting. MRIs w/out crygenic cooling, mag levitation without stabilization.

Apparently there are quantum applications too, but Im not too sure about those but my physicist friend is super excited (in a bad way) for quantum computers now.

If this pans out we're looking at an unexpected revolution.

Superconductor means low resistance. Low resistance means less loss due to heat on a wire. Room temperature superconductor also means more efficient magnets for motors, coils, ending up in cars, MRI machines, etc.

Not just low... _zero_. That's where things get weird.

Well, you still lose current over time... for example, we had to dump a bucket of electrons into our superconducting, supercooled magnet about every month ago to keep things swirling properly.

(The EE I worked with later didn't believe me. See https://en.wikipedia.org/wiki/Superconducting_magnet#Persist... and note that the loss was due to details of magnetic superconductors, not superconductors in general)

Yeah,

> Experiments have demonstrated that currents in superconducting coils can persist for years without any measurable degradation. Experimental evidence points to a lifetime of at least 100,000 years. Theoretical estimates for the lifetime of a persistent current can exceed the estimated lifetime of the universe, depending on the wire geometry and the temperature. In practice, currents injected in superconducting coils have persisted for more than 27 years (as of August 2022) in superconducting gravimeters.

(from https://en.wikipedia.org/wiki/Superconductivity)

If you can extract work from the field generated by the supercurrent, it must come from somewhere. Small supercurrents make small fields, so things like adiabatic CPUs seem interesting.

Can you extract work from a constant magnetic field? As I remember my physics education, constant magnetic fields don't do any work, since they apply a force perpendicular to the direction of motion.

I'm not a physicist, but I play with circuitry... two nearby loops of wire are magnetically coupled. If one is a superconductor with some stored current, and the other is a normal conductor with some resistance, then it stands to reason that the supercurrent will burn heat off in the resistive loop.

What happens in the scenario where the superconductor coil is just replaced with a permanent magnet? I'm pretty sure the energy that the loop dissipates comes from the energy required to move the loop into position, which the inductor experiences as a changing magnetic field.

It'll be hard to make traditional motor windings out of this particular material because AFAIK it's a ceramic, but perhaps with thin films on flex PCBs it would be possible.

I'm imagining a future where a superconducting layer on a PCB is just another checkbox you can choose when ordering small runs of boards.

[ ] 1 oz copper

[ ] 2 oz copper (+$2)

[X] 10 micron LK-99 (+$10)

Another thought - I think the first place we'll see this widely rolled out is in IC's (waiting for the Asianometry video on it). IC's are already planar, they're small so exotic materials aren't a big contributor to costs, and they're very power dense. Replacing a metal layer with a superconducting one could enable greater gate density and potentially significant improvements in efficiency. I don't know by how much because switching losses are probably where most energy is dissipated, but it's an incremental change that seems compatible with the process.

The theoretical papers I've seen (linked here in recent days) suggest that pure crystals of LK-99 would superconduct only in one dimension so it's likely to be fussier than that.

Perhaps it will be like a "tape" laid down with the proper orientation for each conductor. Perhaps you'll need separate north-south and east-west and maybe diagonal layers with special attention to inter-layer connections.

And the issue being that it takes a lot of energy to super cool those superconductors, and thus they can only be used in highly specialized applications. A room temperature superconductor would be like any other conductor, just much, much better.

Thanks to everyone. I understand this much better.

Would a room-temp superconductor make it feasible to cover desert regions with solar panels and transport the electricity long distances?

Yes it makes it more feasible. But even with superconductors, you still need to build out the long-distance grids. With ceramics, manufacturing that much powerline might be the challenge. With the maximum current density reported for this material, you might need a huge x-sectional area.

You still have to worry about batteries. Unless if you place equal numbers of panels separated by 120° meridians for example.

And then there is coordination between governments. This is probably where such an initiative might fail.

>You still have to worry about batteries.

I keep hearing mixed things about superconductors being useful for energy storage.

I imagine that carbon footprint could be reduced substantially by this too, at least on a per-watt of utilized energy basis. Imagine if all computer chips used semiconductor materials - then more of the input electricity is actually put towards computing, and cooling fans are a thing of the past!

If they could get it down to modern chip scale, does that mean you could run a processor very very fast and not generate heat? Or at least a lot less heat? So that would mean much faster clock speeds? What would be the limit on clock speed if you had a superconducting processor?

No, it only works for direct current. While superconducting processors could, in principle, operate more efficiently and perhaps at higher speeds than conventional processors, they won't be completely free of energy losses. AC can induce losses due to electromagnetic fields.

Yeah but sadly that would need a ungodly amount of research and time to implement, electric grids and engines would come much faster

I think a lot of the losses happen in the semiconductors in the CPU, not the wires. Even if LK-99 is a room temperature superconductor, it's probably not usable as a semiconductor.

They are also very good energy storage media. Combine that with zero transmission losses - you can now highly efficient EV powertrains that are significantly more compact. 1000 mile EVs become actually viable.

Secondly, superconductors are one of the most promising platforms for qubits. Big boost for quantum computing - and these are just two applications off the top off my head.

Can you point to a source of these superconducting energy storage mechanisms? How do they work? I briefly looked into it and found out that at least the current ones have very high power density, but low energy density.

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

That's what I meant. It states energy density as 40 kJ/L. Lithium batteries have energy density up to 2.5 MJ/L. Fossil fuels and hydrogen way more.

That 40kJ/L is for the entire system including the cyronics. Get rid of the cyronics and the system gets far far more energy dense.

Yes, that's quite likely how they come up with this number. But is it enough? What's the most energy dense configuration that can be made with room temp SC and does it compete with lithium batteries?

I just took a look at the source paper [0]

""" Although the attainable magnetic flux density limits the energy per unit volume given by Equation (1) ( B2 /2μ o), the real limit of the energy stored in a SMES is mechanical. [...] The relation defines the minimum mass of the mechanical structure in pure tension to support the radial electromagnetic forces. Force-balanced coils [5] minimize the working stress and thus the mass of the structure. """

So it looks like they 1) don't look at cryo and 2) the limiting factor is the stress due to EM fields.

[0] https://snf.ieeecsc.org/sites/ieeecsc.org/files/CR5_Final3_0...

Ah, ok. It seems that this SMES thing is not a solution at all for dense energy storage.

Do you have a source for this?

Except the energy is stored in the magnetic field. Superconductivity or not, you don't carry tesla-scale electromagnets around without becoming a target for high-velocity metallic projectiles and wreaking havoc with every electronic device in the neighborhood. Storage facilities for regulating grid power fluctuations are probably a much more realistic use case.

Would help with fusion, right?

It would make fusion experiments cheaper, but not more successful.

It would definitely help with the commercialization of fusion power.

Why not? Higher temperature for magnets means magnets less susceptible to neutron flux right?

Yes, huge for fusion and would allow tokamak miniaturization too.

If this pans out fusion energy would be completely viable with enough investment. Right now tokamaks don't really have a pathway to being commercially viable and are basically 40 years away. For starters, If you can cut the cost by 2-4x you are right in the ballpark of what you would need to build a working tokamak fusion power plant. You would need to do better than that for fusion to be a viable power source but tokamak fusion was always only a magnitude away unlike other hypothetical fusion energy alternatives.

The limiting factors for superconductors in fusion power generation efficiency is the strength of the magnetic field they can generate which is limited by how much force the superconductor can withstand since the strong magnetic field induces enormous forces on the material. It also requires very high currents. This material seems fragile and can carry very little current.

is this material cheap enough to make such a power line economically feasible

Reply on news.ycombinator.com