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Invention Idea - Cheap Room-Temperature Superconductors Now?

  1. Mar 1, 2012 #1
    "Invention" Idea - Cheap Room-Temperature Superconductors Now?

    I propose that if you encase a superconducting material along with liquid helium (or some other coolant) inside a Dewar flask or Thermos and then insert liquid helium, and then cool the superconductor+liquid helium once down to below its critical temperature, it will sustain that subcritical temperature without any further energy inputs. In essence, continuous cooling is not required as long as the insulation that isolates the superconducting material from its ambient environment is very good. Dewar flasks that are currently manufactured are good enough insulators for everyday and typical commercial uses, but they still slowly leak in or out heat. But most of the heat is lost or gained through the cap and the neck.

    However, if one is using a Dewar flask to cool a superconductor, it is not necessary to have to even open or close the flask (although it wouldn't hurt either), since it will be manufactured with the single purpose of creating a highly insulating environment for the superconductor. If there is no reason to have to remove the superconductor from the flask, and insert some new object, then it is not necessary to even have the neck and cap that are responsible for the the great majority of heat transfer in a Dewar flask.

    I hypothesize that a Dewar flask that is specially engineered to never be opened can be engineered to not have a neck/cap region that is much poorer at insulation than the remainder of the flask’s surface. If the insulation can be made as good as it is on the Dewar flask’s “good insulation” portion on the entire surface of the flask, I think it’s possible to insulate a superconductor’s local environment in such a way that its temperature increases so slowly that it can have a shelf-life of at least 10-20 years before it needs to be “replaced.”

    If this process is viable, are commercially viable superconductors still a technology of the future? I understand that if the conductor needs to be cooled throughout its entire operating time, that the costs would be significant at least and excessive at best, but if it was insulated so well that it remained below the critical temperature for a century by a one-time cooling at the time of manufacture, that would eliminate a great deal of the variable costs. There seems to be no limit, at least in principle, to the quality of an insulator, even though there is no such thing as a perfect insulator.

    Moreover, it is a fact that a superconductor, which has exactly zero resistance (there are some types of superconductors for which this is not exactly true), when coupled with a enclosed shell/tube/etc. that has almost zero thermal conductivity, the superconductor’s operation will not generate any additional heat other than the almost zero heat flow from the environment, provided that it is below its critical temperature. Again, this is unlike a regular conductor which would also generate waste heat on top of any heat flux from the environment so that even if you could encase the conductor in a perfect (and nonexistent) heat insulator, its own operation would generate waste heat. T

    The great thing about superconductors is that by minimizing one source of waste heat, you completely eliminate the other source, literally to zero. It’s somewhat like if you insulated your home really well with respect to the internal environment and cooled it down, all of the wiring inside your home would no longer generate heat either – “for free.” Then, the lifespan of the superconductor, commercially speaking, would be limited only by how close to zero you could get that heat conductivity to be.

    Is this already the process by which present superconductors are cooled below their critical temperature? I wasn’t sure, because I’ve read from many sources that double-layered metallic encasings are used with vacuum in between to minimize heat loss (i.e. in presently existing MRI machines and in the utilities industry), but also that the cooling process, nevertheless, requires a continuous input of energy rather than my idea which entails a one-time cooling, and hence a reduction of variable costs to fixed costs. Is this distinction between “continuous” and “one-time” cooling even of any significance? Most importantly, can insulation that lasts on the order of many human generations be constructed at a reasonable price?

    Thanks very much.
     
    Last edited: Mar 1, 2012
  2. jcsd
  3. Mar 1, 2012 #2
    Re: "Invention" Idea - Cheap Room-Temperature Superconductors Now?

    Clarification and an Analogy with Chemical Processes:
    In physical chemistry, an equilibrium state is defined as a state that is eventually reached through a spontaneous process, after which no net change will occur. But the fact that a (future) equilibrium state can be reached spontaneously does not mean that it will be reached quickly; spontaneity says nothing about the time it will take to reach that equilibrium state.

    I am suggesting, by analogy, that keeping a superconductor cooled to below its critical temperature entails opposing a spontaneous process. There are, broadly speaking, two ways to do this. The first way is driving the reverse, nonspontaneous process of heat transfer from a cool reservoir to a hot reservoir by expending energy continuously (analogous to driving a nonspontaneous chemical reaction by coupling it with a spontaneous one that provides the necessary heat).

    The second way is to control the kinetics, or the rate, of the spontaneous reaction; namely, by manipulating the "reaction conditions" (enclosing it by an "ideal" Dewar flask) so that even though the process remains spontaneous, its rate of change is so low that for the net temperature change from some initial temperature to the critical temperature (which is not analogous to equilibrium, but is nevertheless an intermediate step towards it) takes so long that, for all practical purposes, the "reaction" can be considered to be "not happening," much like the reaction of converting graphite into diamond, which is spontaneous at room temperatures but so slowly that it is negligible.
     
  4. Mar 1, 2012 #3
    Re: "Invention" Idea - Cheap Room-Temperature Superconductors Now?

    How would you put the super-conductor in action? You still may need to bring out wires from inside the flask, and wires (metals) are very good conductor of heat.
     
  5. Mar 1, 2012 #4

    f95toli

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    Re: "Invention" Idea - Cheap Room-Temperature Superconductors Now?

    Another problem is that ANY heat leak will cause the helium to boil, which produces a lot of gas, which increases the pressure, which eventually leads to an explosion unless the helium gas can be vented.
    And since there is no such thing as a perfect insulator helium will ALWAYS boil....

    Moreover, the cryogenic part is essentially a non-issue. All that is needed is to collect to helium gas that is boiled off in this dewar, then this helium can be liquefied again (using a pulse tube cooler) and poured back into the dewar.
    These "closed-cycle" systems have been around for a long time. and is how most MRI systems in hospital work (you DO need to top up the helium occasionally due to inevitable leaks, but very rarely).

    Moreover, even a single stage pulse tube cooler will get you down to 20K (and 2 stage to 4K), well below Tc of say YBCO. And single stage coolers are not expensive (although they tend to use a fair amount of electricity).
    There are plenty of "dry" systems out there (that do not use He at all, or only as a heat-transfer medium) that can be used to cool down a superconductor, including dilution fridges that can reach mK temperatures.
     
  6. Mar 1, 2012 #5
    Re: "Invention" Idea - Cheap Room-Temperature Superconductors Now?

    It seems to me that the cost of using room temperature superconductors is really not an issue at all. Why is it that people are always talking about the cooling costs, when the only thing you have to deal with is boiling helium, which as you said is not really a significant concern (non issue)? I'm guessing it's because regular conductors essentially require no upkeep, and because they are so cheap and widely used, transitioning to superconductors will never become truly competitive unless the refrigeration costs are actually zero, as will be the case with true room-temperature superconductors?
     
  7. Mar 1, 2012 #6
    Re: "Invention" Idea - Cheap Room-Temperature Superconductors Now?

    Whats that wrong with copper anyway ? In current house wiring, only 2 to 3% electricity is lost in the wires, majority of losses are done by the equipments themselves. Ok, if you are thinking of re-designing the equipments also and make them use super-conductor, we still don't have much benefit. for example, you could wind motors with super conductors and totally eliminate the copper-loss part, but you would still bear Iron losses.
    We don't still have 'super-conducting' transistors and FETs. :)
    I don't still see any great revolution by room temperature super-conductors, except for few specialty places. But, hey I may be blind ?
     
  8. Mar 2, 2012 #7
    Re: "Invention" Idea - Cheap Room-Temperature Superconductors Now?

    1. Even if you could build a Dewar flask without any conductive heat transfer the liquid helium would still warm up via thermal radiation (infrared EM waves) radiated from the surrounding environment.

    2. You can't build a perfect Dewar flask where the inner walls do not contact the outer walls. Well unless you are going to use some exotic method like magnetic levitation to levitate some kind of ferromagnetic inner wall. So you are still going to transfer a lot of heat through conduction.

    3. True vacuum insulation panels for home insulation were tried (maybe by Owens Corning). They tended to develop leaks and lose their vacuum over a period of time and they certainly didn't give you a house that didn't need to be heated. See point 1 and 2.

    Insulating your cooling jacket with aerogel would be a better, more practical system. Assuming of course that price is no object. Otherwise use polyurethane spray foam or something. TAINSTAFL.
     
  9. Mar 3, 2012 #8

    NascentOxygen

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    Re: "Invention" Idea - Cheap Room-Temperature Superconductors Now?

    I thought the heading here was, "Invention" Idea - Cheap Room-Temperature Superconductors Now?" My concept of room temperature does not extend even to the temperature of liquid CO2, let alone liquid helium, and with all this global warming, I think it never will. I've been duped! https://www.physicsforums.com/images/icons/icon6.gif [Broken]
     
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