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

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  lkrndu
  

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  07/25/2008 02:13 AM

  Side Benefits

  Intriguing. If it can pan out, not only does it reduce the mechanical complexity of cars or other machinery, the whole notion of a component that has several lifetimes - re-useable across several useful  lives of the machine that employs it - multiplies the savings. Less stuff manufactured, fewer replacements, not so many, one hopes, of calls for help when a cranky alternator goes fffft.

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    boz_hobbs
    

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    07/28/2008 12:12 PM

    Re: Side Benefits

    O'yeah. We need this like we need another nose. Another toxic ditty to carry around at freeway speeds (in the millions of numbers) to replace an item that is proven and not that toxic. Nope. The ICE-driven vehicle is dead; in the thousands of days, not ten thousands as most the writers here seem to imply.
    I do like the concrete encasement idea; although, since the government is running the potential disposal site, it may prove explosive.

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  tedinoue
  

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  07/25/2008 07:20 AM

  other potential uses

  I need to do more research on this. How much power can one convert with this at a reasonable price? Would it be cost effective for use in concentrating solar thermal systems instead of PV cells? What deltaT is required for effective power generation?

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  • 
    hador_nyc
    

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    07/25/2008 09:50 AM

    Re: other potential uses

    I don't think you're looking at it the right way. I don't think 10% efficiency, or even the potential 20% the article mentions, would be good enough to compete with solar PV or solar thermal.
    
    
    Instead, you should think of it as a way to make traditional internal combustion engines and generators more efficient by turning part of a waste stream; their exhaust; into something useful. All traditional power plants, Coal, Nuclear, etc, produce heat to turn a turbine which spins a generator and generates the electricity. The steam, after going through the generator, is useless, hence those massive cooling towers. The combustion exhaust is also just sent up a chimney. You could use these thermoelectric cells to line the pipes leading to the cooling/exhaust towers generating more energy from that waste. The same thing could be done on a smaller scale, as said in the article, in any device that uses an ICE and needs electricity.
    
    
    Honestly, I'm surprised they didn't think of power plants in the article, which would seem to be the best usage to me since they do last 50+ years in most cases.

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      Siphon
      

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      07/26/2008 06:29 AM

      Re: other potential uses

      People are so fixated on research to make thermoelectric more efficient for waste heat applications, when in fact there are far more promising technologies that can be used for this, that don't get much attention.
      
      For example, the article on this site about infrared nano-antennas. Hot objects radiate infrared into the colder ambient. Use this principle in conjunction with infrared nano-antennas and very high efficiency can be achieved, higher than thermo-electrics could ever do.

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      Manuvidya
      

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      07/28/2008 08:10 AM

      Re: other potential uses

      I'm not sure how using heat from exhaustfumes would effectively eliminate the fumes themselves, the technology if used as described above will still be harmfull to the environment. I agree with others though that this technology would be a great asset in conjuction with other technologies that are already in use, increasing overal 'perfomance' of a system.

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    browni
    

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    07/25/2008 10:31 AM

    Re: other potential uses

    Instead of replacing PV, what about using this technology to convert the heat resulting from the use of solar concentrators in existing PV systems.  Using two methods to produce electricity in the same system might lower the overall cost of the installation and raise the total energy conversion ratio.

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      rlounsbu
      

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      07/25/2008 11:03 AM

      Re: other potential uses

      browni gets the point.  Its is not necessarily about replacing one form of generation with another. It is about increasing overall efficiency.  TEs can be used as a bottomin cycle just about anywhere... Residual heat from an ICE, downstream of a steam turbine, heat on the backside of a PV panel,and if your really want a "green" house... how about heat from your roof shingles, waste heat from the back of your refigerator, and even the heat from the hot water going down the drian. I'm thinking TEs on the waste heat side of a 5kW SO Fuel Cell generating electricity for the independant home.

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        mbloore
        

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        07/25/2008 11:42 AM

        Re: other potential uses

        if you put this on the back of your fridge you will be insulating its heat sink, reducing its efficiency.  you won't get as much power back as you'll need to add to keep the fridge as cool as before.

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          cripdyke
          

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          07/28/2008 01:50 PM

          Re: other potential uses

          you missed the point--and the opportunity--with respect to refrigerators.
          
          The cooling coils are still the part of the fridge that extends farthest out. The TEs (or TVs for consistency w/ PhotoVoltaics) go between the coils and the insulation at the back of the cold compartment. This prevents heat extracted from the CC returning to it. Perhaps a certain amount of insulation could even be replaced by the TVs, but at the very least we could now have some of the cooling energy "recycled," lowering the overall electric use of the device.

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    GreenPlease
    

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    07/25/2008 08:48 PM

    Re: other potential uses

    Peak efficiency is reached at a temperature delta of 900F. Very doable in the exhaust of a car, though not so much for a NG or coal fired plant.
    
    Also note that TECs in order to function properly must act as an insulator which makes them a no no for concentrated photovoltaics.
    
    Using them on spent uranium fuel rods would be an excellent idea.

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    • 
      Siphon
      

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      07/26/2008 06:36 AM

      Re: other potential uses

      I'm not sure if this would be suitable for spent fuel. The reason is safety: economical use of thermo-electrics requires high temperatures, and when the thermo-electrics fail, the container could melt and catch fire, releasing dangerous amounts of radioactivity.
      
      It's much better to just use dry cask storage with passive cooling that never fails. The safety risk just isn't worth the relatively small amount of electricity that can be generated from the spent fuel.
      
      Unless of course, we're talking about the spent fuel ponds, where the water acts as passive cooling (and Tlow for the thermo-electrics). That could work I think. That's also the phase where the fuel releases the most heat (short half life isotopes decay) so on second thought it could actually work quite well. The temperature difference would be low though (we don't want the water to boil!), so forget about high efficiency with thermoelectrics. We're still talking about relatively small amounts of power compared to the output of nuclear plants themselves. Nuclear powerplants are inefficient because of the low temperature heat engines (saturated rankines). So there should be a lot of electricity to be had from waste heat to electric conversion from the turbine exhaust itself rather than from the spent fuel.

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      cripdyke
      

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      07/28/2008 01:55 PM

      Re: other potential uses

      they are wonderful for CPV...Just use convection water cooling - long mastered by the navy for sub reactors - to bring the heat to a hot water jar lined with TV materials.
      
      And as for "what if they break down..." Heavens Forfend! These circuits simply cannot break down unless the material physically breaks in half so as to prevent circuit completion - in which case the water bottle will be broken as well.

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    dbdet
    

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    07/31/2008 05:07 AM

    Re: other potential uses

    Just a moment here! Why "instead of PV cells"??
    
    PV cells operate better at lower temperatures, right? Why not simply use such thermoelectrics as a heatsink to cool PV-cell temperature on the one side (increasing PV-cell efficiency), while generating their own additional energy at the same time?
    
    Then, place these "hybrid" thermoelectric-PV-arrays over parking lots, thus creating shade (& lots of solar energy, either for charging elec. cars, or for selling back to the grid).
    
    This would surely work as a magnet for shopping centers. After all, where would you prefer to park your car? In the shade? Where (if elec./hybrid) it could be recharged for free while shopping?
    
    dbd

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