High-Temp Superconducting Tape

DrLudicrous writes "The NYTimes is running a little overview of the current state of mass produced superconducting materials. A company named Superpower (another blurb on them here) is making a layered superconducting tape out of ceramic materials- ceramics that are high-temperature superconductors (no resistance at liquid nitrogen temperatures, 77K). This is much cheaper to maintain than technologies based on superconducting metals, which tend to require liquid helium (~4 Kelvin) temperatures. A note of contention: the article mentions that superconductivity is not well understood -- high-temperature superconductors are not, but classical 'low-temperature' superconductors are well-described under the Bardeen-Cooper-Schrieffer (BCS) theory."

Comments

Still only liquid nitrogen temps?

[dankjones]

Man! We had that when I was in high school (late `80's)

Looks like room temperature superconductivity is impossible. Have we made any progress in new superconducting materials in the last 15 years?

Re:Still only liquid nitrogen temps?

[PaulBu]

Search for MgB2 , though it is not much better (except possibly for digital apps where HTS sucked big time...)

And I actually used to work in SCE...

Paul B.

Re:Still only liquid nitrogen temps?

[deglr6328]

Pardon, but wtf are you talking about?

Search for MgB2...

Yes....and...? MgB2 is a standard low temp. superconductor with a Tc of only ~40 Kelvin. ...except possibly for digital apps where HTS sucked big time

Whaaa? HTS (high temp. superconductors) are perfectly suited to "digital apps" in many situations. A company called STI makes HT superconducting filters for cell phone antennas in order to increase data bandwidth and and decrease service dropout by making their recievers more sensitive. And Josephson Junctions make up some of the fastest digital IC's in existance at many hundreds of gigahertz.

And I actually used to work in SCE...

Am I the only one who has no idea what this is?

Re:Still only liquid nitrogen temps?

[deglr6328]

It's worth noting that there are no theories (so far as I've heard anyway) that expressly forbid superconductivity at room temperature. The BCS theory of conventional superconductors forbids Tc's beyond about ~50K if I recall correctly, but high temp. superconductors don't follow BCS and have much higher Tc's, who knows if there's another class of electron superconductors with even higher Tc's. In fact it is thought that certain parts of the insides of neutron stars have superconducting protons floating around in a sea of superfluid neutrons at many millions of Kelvin!!

Re:Still only liquid nitrogen temps?

[PaulBu]

MgB2 is a standard low temp. superconductor with a Tc of only ~40 Kelvin.

As pfdietz pointed out below, MgB2 is so much easier to work with than HTS ceramics. Its discovery is considered the next big thing in the field since the discovery of high-temperature superconductivity, not because of increased Tc, but because it can be deposited using standard semiconductor tools and one does not have to worry about grain size/orientation/etc.


Whaaa? HTS (high temp. superconductors) are perfectly suited to "digital apps" in many situations. A company called STI makes HT superconducting filters for cell phone antennas in order to increase data bandwidth and and decrease service dropout by making their recievers more sensitive.

STI/Conductus filters are purely passive devices, there is not a single Josephson junction nor a single cold logic gate. As a matter of fact filters themselves are rather simple, their main achievement is development and mass-production of relatively low cost and reliable cryocoolers. And of course they are not used in "cell phone antennas", rather in "cell phone *base station* antennas", big difference! :-)

But when I was talking about "digital" I meant exactly the stuff from your second link. Search for a guy named Paul Bunyk there , look at my user ID and then decided if I have something to say about those matters... ;-)

Am I the only one who has no idea what this is? SuperConductor Electronics.

Paul B.

Irritating article snippets

[Daniel Dvorkin]

Fascinating stuff, but some of what's in the article really makes me grit my teeth. I love this bit:

Even now, they have yet to develop a comprehensive theory to explain its appearance in materials as diverse as metal and ceramics.

Such scientific conundrums are of only passing interest at Superpower, a four-year-old subsidiary of Intermagnetics General, and at other companies like it. After years of false starts and setbacks, these companies say they are closing in on the goal of producing relatively inexpensive superconducting wire for power generators, transformers and transmission lines.

Success requires making yard after yard of wire, and eventually mile after mile. The focus at the companies, at national laboratories and at many universities is on questions that call for a genius more like Edison than Einstein.

Uh, bullshit. If they don't understand how it works, they're never going to move this stuff beyond the applications possible at liquid nitrogen temps. I'm not selling that short -- it's neat, and has a number of industrial applications -- but we're not going to be making power lines, or even wiring our houses, with that kind of cooling.

Re:Irritating article snippets

[stvangel]

Success requires making yard after yard of wire, and eventually mile after mile. The focus at the companies, at national laboratories and at many universities is on questions that call for a genius more like Edison than Einstein.

Uh, bullshit. If they don't understand how it works, they're never going to move this stuff beyond the applications possible at liquid nitrogen temps. I'm not selling that short -- it's neat, and has a number of industrial applications -- but we're not going to be making power lines, or even wiring our houses, with that kind of cooling.

I tend to disagree. Edison, arguably one of the greatest and most prolific inventors, wasn't really an scientific man and didn't understand how many of the things he discovered really worked. He was very persistent and intuitive in the way he would develop things. He'd just keep plugging away at different experiments till he found something that worked. Many famous inventions were an accidental discovery that worked without really understanding the underlying physics. Vulcanized Rubber, Penicillin, and even high-temperature superconductors themselves come immediately to mind. The majority of medicines and drugs were all developed this way. The first of the high-temperature semiconductors was found this way and was against everything known about semiconductors at the time. Many initial breakthrough discoveries were initially called impossible or impractical by conventional knowledge.

There is nothing to say there will even be superconductors at much higher temperatures anyway. What we really needed is an innovative thinker who can come up a unique way of using the existing superconductors we have. Perhaps an innovative refrigeration process to keep them cool in practical applications... Perhaps blending them with non-superconducting materials to make a semi-superconducting material with much higher strength and current carrying capacity? What about a way of encapsulating them in something like a nested Peltier Junction to keep the interior at superconducting temperatures? What about a way to incorporate the superconductors into the junction itself? There are many possibilities to experiment with. Even if you don't discover what you're looking for, there are lots of other things you might find.

Super Conduction

[Arngautr]

That floating magnet experiment/demonstration they describe is one of the coolest physics phenomena I've witnessed, for those without subscriptions you chill the superconductor below its critical temperature and place a small magnet with high magnetic field strength to mass ratio above the superconductor and it floats or sits in mid air spining slightly, pretty cool to see.

This article is low on actual content, it fails to even mention what the Tc is for this tape. The highest Tc I'm aware of is in the 130K while room temperature is on the order of 300K. If we can find materials with high enough Tc and without bad qualities it will revolutionize the world, imagine an electric motor with near zero resistance, unfortunately it could be used for evil too.

High Tc Superconductivity explained

[Goldsmith]

High Tc superconductivity actaully has the begginings of a good theory to explain it.

In BCS theory, electrons interact with phonons (lattice vibrations) to coordinate into pairs and form bosons.

In much the same way, electrons in high Tc superconductors interact with spin waves in an antiferromagnetic material to coordinate into pairs and form bosons.

An antiferromagnetic material is one where the magnetic moments of neighboring atoms are opposite

up down up down up down up down up

You could imagine trying to move the middle electron over one position (trade with the electron to its right):

up down up down down up up down up

Now our magnetic order is screwed up, and this defect can propogate:

up down down up down up down up up

Each pair of "up up" or "down down" next to eachother is a spin wave, which is a boson, with a spin of 1.

Of course, really proving this theoretically is much harder, I don't think it's been done in 3D.

Re:For what?

[barawn]

Interesting. Is copper really that expensive?

Yes, actually. It's about $20-25/kAm right now.

But it's the recurring cost that's a big deal: at kiloampere levels, the power burned off by copper resistance starts to become more expensive than the cost of cooling. Since superconductors have strictly zero resistance, the cooling cost is fixed as the current scales, whereas it's linear in copper. At some point it becomes more economical.

The problem with high-Tc superconductors is that they have a current limit as well, and it's quite moderate, so the scale isn't quite there yet, when you work out all of the factors involved.

There are other reasons to switch, though: simply physical size: in Detroit, where they're replacing copper with superconducting cable in a few areas, they're replacing 18,000 pounds of copper with 250 pounds of superconductor - they replaced 9 cables with 3, and left 6 empty cable lines. This gives them 3 times the energy capacity without having to dig new cable lines at all.

The capacity issue is really what's been driving cities to replace them, though - digging new power lines, especially in cities, is simply ludicrously expensive, and so any option to replace with higher capacity lines without digging is a win.

So yes, really, they will replace copper with superconductors ... and they have, actually. Copenhagen was the first, if memory serves. All of them quoted the capacity increase without digging as being the main reason. Per kA, it's probably more expensive, but the costs savings from not digging will probably make it cheaper over the lifetime of the cable.