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A room-temperature superconductor? New developments

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Re: A room-temperature superconductor? New developments

#651

Post by cogman10 »

somerandomqaguy wrote: post #626
marcosdumay wrote: post #529

Earlier quoted context omitted.

Nah, the GP is just completely out of reality. We won't see lossless transmission in a very long time, and no place where an aluminum cable is too expensive today will become viable because something a million times more expensive is 9% more efficient. Batteries won't see a revolution because of this, there's simply no reason for them to (but they are currently in a revolution, and there are more to come). AC storage…

>This won't replace metal layers in CPU for a really long time. Superconductors are hard enough to make, CPUs are absurdly hard to make, and the wins on power savings aren't very large. If people make superconducting chips, it will be ones where the superconductors do active switching, what is much farther away and can enable much faster CPUs too. I would've thought the main wins would've been reduced heat generation…

> I would've thought the main wins would've been reduced heat generation.

Most of the heat in a data center is coming from power burned in the devices themselves not the power transmission to those devices.

Sort of like how a space heater is hot at the heater portion, not the power cable going into the heater.

You aren't losing more than a W or so to transmission for every kW of power delivered. (in fact, you are generating more heat from the AC->DC transformation)

Typically, power cords and wiring is 15 AWG, which has a 10 milli-ohm/meter resistance and runs as 120V AC (maximum of 15->20A). So, 1000m of power cord running at full load would result in 150->200W of heat from the power cable. Meanwhile the server is generating 1.6->2.2kW of heat. (Assuming a single very long 1kM route is servicing the server).

Cut the cabling distance to a couple of meters and you can see why nobody worries at power consumption at that point.

Re: A room-temperature superconductor? New developments

#653

Post by robot_no_421 »

whimsicalism wrote: post #525
pizzalife wrote: post #517

Earlier quoted context omitted.

Look at the actual age distributions rather than collapsing the data into a single number. https://en.wikipedia.org/wiki/Demographics_of_China https://en.wikipedia.org/wiki/Demographics_of_the_United_Sta...

I see a country with triple the young people we do.

You should be measuring that population as a % of their total population. Not sure why you're comparing absolute numbers.

China has triple the young people we do, but quadruple the old people that depend on the young people.

Re: A room-temperature superconductor? New developments

#654

Post by dragonwriter »

nonethewiser wrote: post #542
dragonwriter wrote: post #307

Earlier quoted context omitted.

Because “smart” and “monomaniacally focused on financial gain” are two separate things?

What is monomaniacally focused about maintaining a login page for $350k?

Choosing the $350K job isn't necessarily monomaniacally focussed on money, there's plenty of combinations of priorities that would favor that.

But when you don't assume all smart developers are monomaniacally focussed on money, there’s also plenty of combinations of priorities that might favor an $80K lab job over the $350K login screen job.

Re: A room-temperature superconductor? New developments

#655

Post by cogman10 »

derefr wrote: post #432
klysm wrote: post #422

Earlier quoted context omitted.

> Batteries that don't take any time to recharge Huh? Is this actually a thing that this enables? I don't initially see how

Resistance is what makes things hot, and heat is what makes dumping huge amounts of charge current into batteries a bad idea. No resistance → no heat → no need to charge with low current†. Another way to say it is that, with a superconducting wire, you can make the wire as thin as you want and still pass the same amount of current through it, without melting the wire. Picture using a USB-C cable to charge your car. †…

Heat from power transfer is not the problem with current battery tech. We are already capable of delivering 350kW worth of power into EV batteries. The limiting factor is not the power cable delivering that power.

Thick cable, high voltage (900V typically) and everything is fairly manageable. Assuming we could consistently charge at that 350kW we could fully (0->100%) charge an 80kWh ev battery in 13 minutes. That's not slow.

The limiting factor is the battery chemistry, not the wire chemistry.

Re: A room-temperature superconductor? New developments

#656

Post by adw »

montecarl wrote: post #576
badman2001 wrote: post #171

the dft results are definitely interesting, but i note that with the caveat that my background is in experimental condensed matter physics for materials like this and not theoretical, my understanding is that the dominant feature of the conclusions (the flat bands) is a necessary but not sufficient condition for superconductivity in the way the authors describe. again, in experimental condensed matter physics it's ac…

The thing that stands out to me is that the DFT simulations show that the flat bands only occur in a particular crystal structure of the material and it is not the most stable state (at least according to the simulation). This would explain the synthetic challenges involved. These simulations are not perfect, but they can be VERY useful when guided by experiment and when they correlate strongly it is a good sign that…

The way I'd characterize it is that they're usually _directionally_ (and mechanistically) correct. On something as sensitive as a band gap the error bars are larger; if the DFT simulations said "yeah, no way this has band density at the Fermi level" I'd regard it as strong evidence against the LK-99 claims, but the fact this is in the ballpark is – to be clear, pretty weak – evidence in favor.

Re: A room-temperature superconductor? New developments

#658

Post by r2_pilot »

Vicinity9635 wrote: post #623
jtchang wrote: post #418

The ramifications of the inflection point we are currently at is mind boggling. I had a hard time explaining this last night but we may very well be witnessing the beginnings of a technological transformation era much like when the p-n junction was invented. From the 1940s standpoint it would be hard to envision all we had today. - Lossless transport of energy - Batteries that don't take any time to recharge - Faster…

> The ramifications of the inflection point we are currently at is mind boggling. No joshing, I just got done posting this on facebook: "If this is practical it will change the world like the transistor; maybe more."

Ha, I just posted about a dragonfly I saw while walking, and how it seemed unperturbed by the possibility of room temperature superconductors on Earth. I added that I should probably learn from the dragonfly.

Re: A room-temperature superconductor? New developments

#659

Post by heisenzombie »

cogman10 wrote: post #633
fsh wrote: post #516

Earlier quoted context omitted.

None of the things you listed are limited by the conductors in them. The efficiency of high voltage AC power lines is limited by capacitive coupling to ground. Battery charging is limited by the cell chemistry. CPU heat output is limited by the resistance of the semiconductors. Turns out metals (in particular copper) are already incredibly good conductors.

> The efficiency of high voltage AC power lines is limited by capacitive coupling to ground. And to this point, HVDC has been slowly rising as a viable alternative beyond just undersea transmission. A mistaken belief is that AC is more efficient than DC. What AC is is more easy to transform from one voltage to another (until somewhat recently). That makes it easier to run AC at 1 MV and then step it down to 240V for…

Minor nitpick — "now we can run 1 billion amps at 100V" — there is a limit to how much current you can put down a superconductor. For example I think commercial YBCO superconductor tape will do roughly 1000A/mm^2 (and even that requires being significantly below its critical temperature).

That’s a pretty high current density compared to what’s feasible with copper — don’t get me wrong — but a billion amps would still require a pretty huge cable even with a superconductor.

Re: A room-temperature superconductor? New developments

#660

Post by heisenzombie »

entropicdrifter wrote: post #581
jacquesm wrote: post #552

Earlier quoted context omitted.

Also used for grid stabilization.

So superconductor supercapacitors

More like superinductors than supercapacitors - the energy is stored in a magnetic field (inductor) and not an electric field (capacitor)
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