Forum: The Classroom
Topic: Superconducters
started by: CatKnight
Posted by CatKnight on May 22 2001,11:13
are actually replacing some powerlines today! the technology has been improved so that the wiring will only cost about โ per meter (compared to ษ for regular copper wires). this will lead to uber fast internet connections and also help the power outages in california eventually.
Posted by masher on May 22 2001,11:35
Do you know what the superconductor is?------------------
"Once you have pulled the pin from Mr. Grenade, he is no longer your friend."
-Unknown (cited in nene, 2001)
Posted by Dark Knight Bob on May 22 2001,12:08
guy who came from my school is working on something like that with some big ass power company that involves using the electro conductivity of a crystaline structure and finding a way to implement it into power cables. This message has been edited by Dark Knight Bob on May 23, 2001 at 07:10 AM
Posted by CatKnight on May 22 2001,13:51
its a ceramic composed of bismuth, strontium, calcium, copper and oxygen, surrounded by silver.
Posted by damien_s_lucifer on May 22 2001,16:09
how do they plan to keep 1000's of miles of superconducting cable cold? last I heard they hadn't got anything to superconduct above liquid nitrogen temperatures.
Posted by CatKnight on May 22 2001,16:11
liquid nitrogen isn't all that expensive. infact I think the actual quote from the guy was that it's "cheaper then kool-aid". before this new composite however, they had to use liquid helium which is very expensive.
Posted by damien_s_lucifer on May 22 2001,18:47
That's cool. It hadn't occurred to me that a superconducting cable wouldn't need to be that thick. Hmm... they're still gonna need a pumping station every few miles, though. But since something like 60-70\% of the power is lost just in transport from the plant to the home, I don't suppose it will be hard to justify the added cost - since it would effectively triple the amount of juice you can get from a single power plant.Do you have a link for this stuff? I want to rewire my house with it... 
Posted by DuSTman on May 22 2001,19:12
on the thickness thing.. Superconductors only superconduct when the current flowing through them is lower than a certain critical current density (which is affected by the temperatue.. the more below the superconducting temperaure, the higher the critical current density will be). But in general, they might need quite thick wires, so that they can carry a lot of current and not become resistive, while not making itself impractical by requiring too much cooling equipment..
Posted by damien_s_lucifer on May 22 2001,21:18
isn't the critical current density a hell of a lot higher than the amount of current you can put through an equivelent-size copper wire though?I mean, you shoot 100 amps through some 24 gauge copper wire and *poof!*- no more wire.
Posted by DuSTman on May 22 2001,21:22
i don't know what the order of the critical current density is..just raising it as a point..
Posted by masher on May 22 2001,23:50
Does this sound right? quote:
http://ist-socrates.berkeley.edu/~davisgrp/stm/papers/ZnImpurity/berk_press_rel/02-16-2000.html
copper oxide high-temperature superconductor (Bi2Sr2CaCu2O8+d) - dubbed BSCCO (BIS-ko) because they are composed of bismuth, strontium, calcium, copper and oxygen. This superconductor is made up of a repeating series of layers: two bismuth oxide layers, a strontium oxide layer, and two copper oxide layers with some calcium atoms sandwiched between them.
quote:
http://www.anl.gov/OPA/news96/news960613.html
Researchers at the U.S. Department of Energy's Argonne National Laboratory and the University of Pittsburgh have developed a new
"silver-wire-in-tube" manufacturing technique that consistently produces superconducting wires with "critical currents" (a measure of
current-carrying ability) greater than 100,000 amps per square centimeter -- considered the breakthrough value needed for practical applications. ... In 1994, Argonne and the University of Pittsburgh, following up on University of Wisconsin research, found that supercurrent in powder-in-tube
wires made at Argonne flowed almost exclusively through a thin interface, the layer of superconductor closest to the silver casing. "This interface has just the right grain structure and alignment," Poeppel said. "Since the remaining ninety percent of the superconductor carries no current worth mentioning, we decided to see if we could get rid of it." ... When cooled to about 110 kelvin, it conducts electricity with no energy loss.
That explains why it needs to be so thick. It can handle 100,000 Acm^-2, but it only conducts in the thin outer shell of the wire. Therefore you need to make it thick to allow the area of the outer shell to be thick enought to carry enough current. LN2 is at 77K, so its cold enough, and also cheap enough to use. ------------------
"Once you have pulled the pin from Mr. Grenade, he is no longer your friend."
-Unknown (cited in nene, 2001)
Posted by CatKnight on May 23 2001,01:26
like I said 
Posted by damien_s_lucifer on May 23 2001,05:12
LN is cheap, but what about the cost of keeping it flowing around the wires? How the hell do you do THAT?
Posted by CatKnight on May 23 2001,05:18
the power lines consist of layers of flexible superconducting fibers surrounded by an insulated pipe, which liquid nitrogen is pumped through.
Posted by Bozeman on May 23 2001,22:23
Read the latest Scientific American. People who were fucking around with random compounds found the best superconductor to date by accident. I forget which compound, and I'm too lazy to go downstairs and read the article again, so any subscribers out there please feel free to inform us all.------------------
It's the pop-o-matic bubble, motherfucker!
Posted by damien_s_lucifer on May 24 2001,17:38
100,000A / cm^2 = a cable that carries about 10 GW at 100,000 volts without any loss. holy crap.
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