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This discussion relates to Technology Review's article More-Efficient Thermoelectrics.

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  b_calder
  

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  07/25/2008 08:04 AM

  reply to both posts

  The technology is most likely to be used in places where other heat recovery technology is impractical. Automobiles have relatively huge possibilities for alteration in dimension and function. This makes the automobile the perennial favorite for adding new gadgets. Always be critical of altering automobiles because their design is market driven.

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  jvmoye
  

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  07/25/2008 08:30 AM

  In the home

  How about generating some energy from the high heat available from a home heating appliance.  It would be nice to use some of the energy as electricity before it's used as space heating, using it twice in the home or work place.

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    browni
    

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    07/25/2008 10:33 AM

    Re: In the home

    I wonder how much electricity could be harvested from the heat in an attic.

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      mbloore
      

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      07/25/2008 11:47 AM

      Re: In the home

      if your insulation is good, not much.  if it is bad, then fiberglass is cheaper.  and remember, you can expect to get back at most 20% of that waste heat; better not to waste it in the first place.

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        cripdyke
        

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        07/28/2008 02:02 PM

        Re: In the home

        hello? If your insulation is good then all summer long you have tremendous temperatures in your attic space from sun on your roof eventually contaminating the attic space but then being unable to pass into the living space.
        
        As for PV being more efficient...PV efficiency is low enough that the vast majority of light will still become heat. Most of that heat will be passed on to the attic space. And, of course, in few cases will all the available roof space be covered in PV anyway. So your attic continues to overheat from the uncoverted solar radiation. That heat is then easily converted to electricity through TV.
        

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      Manuvidya
      

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      07/28/2008 08:17 AM

      Re: In the home

      We're talking large arrays then, I'm not sure if that can in any way compete with current solutions like PV, that even generate current without big temperature difference in terms of costs. Seeing as the thermoelectric item under discussion here can last several car lifetimes, I'd say it'd well last my lifetime as well (I'm talking european cars here ofc ;)).
      For the long run, this kind of product seems well more suited for longterm additions to existing means of powerconversion.

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  DrZook
  

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  07/25/2008 11:25 AM

  Thermoelectric energy

  Two things to add. 1) How about using heat from from waste nuclear fuel rods.  Thermocouples could be attached to a metallic heat transfer structure that surrounds the used uranium and waste product.  The whole device then could be encapsulated in concrete as a barrier with two wires that would supply a steady stream of electricity forever.
  2)Look up a company called Borealis; they have an electron tunneling device that they are developing that attains better than 90% thermal efficiency.  It uses what they call the Avto effect.

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    sjbob
    

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    07/25/2008 02:07 PM

    Re: Thermoelectric energy

    I think there is a problem about this following aspect of what you said: "The whole device then could be encapsulated in concrete as a barrier with two wires that would supply a steady stream of electricity forever."
    
    That concrete barrier would contain the heat within the concrete, thereby leaving the entire thermoelectric device at the same temperature, that of its concrete walls.
    
    In order to extract power there must be a heat source and a heat sink at two different temperatures. One of the terminals of the device must be colder than the other. So to get energy out of the concrete tomb that you envision, a cooling liquid would have to be pumped in. The comments submitted by others all assume an open environment wherein the atmosphere would serve as the heat sink.
    
    This is not to say your idea can't be made to work, once a cooling scheme is designed into the idea. But an entombment in concrete just makes this problem worse. Without active cooling there is a limit to the rate at which electrical power can be extracted. And that limit is dependent upon the surface area of the containment vessel, which for radioactive waste would be as small as possible.

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      Siphon
      

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      07/27/2008 06:24 AM

      Re: Thermoelectric energy

      And nuclear waste has to be kept reasonably cool for safety reasons. If we're talking about spent fuel ponds then water is the primary heat sink (secondary probably atmospheric). High temperature waste is highly undesirable in this application. As such, high efficiency isn't possible (and these thermo-electrics arent' efficient even at big delta Ts in the first place).
      
      The potential impact for turbine exhaust heat to electricity could be really big though. Nuclear, coal, solar thermal...
      
      It would have to be cheaper and more efficient than organic Rankine cycles to be competitive in this application.

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      Manuvidya
      

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      07/28/2008 08:23 AM

      Re: Thermoelectric energy

      Darn, I keep forgetting that we're basically talking about inverted peltier elements, thanks for the heads up in your article :)

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