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Thread: Diodes convert heat into electricity

  1. #1 Diodes convert heat into electricity 
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    There is well known phenomenon such as thermal current in diodes which is 26millivolts at room temperature.And it increases with temperature rise.How good are diodes in converting heat to electricity and what qualities should have diode for perfect heat to electricity conversion?I read that scientists have experimented with quantum tunneling diodes for this purpose and claimed to acheive some results.
    But do they really need quantum tunneling effects?It seems to me that usual solar cells convert light into electricity in similar way and there is no need for quantum
    effects.Diodes in solar cells look quite efficient and don't seem to be a serious limitation.


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  3. #2  
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    I think that since diodes have been understood for a long time, it's unlikely someone hadn't experimented with this yet. First of all, you can't just place a common volt meter and read even 5 millivolts across a diode. The current is so weak, and the impedance so high, that there is no useful energy.

    Did you know there is something like 300 volts per inch in the atmosphere? Again, the current is too weak for any power application.

    I remember seeing plans in Popular Mechanics, or Popular Science in the 70's for radio control airplanes that involved four sensor pads, amplified with FET's, then OP amps, and then controlled the ailerons and elevator. This allowed the plane to somewhat follow the terrain by sensing the voltage differences.


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    Currently some researches are trying to use nanoantennas (infrared rectennas)
    for energy harvesting.
    http://newenergyandfuel.com/http:/ne...hould-be-huge/
    They suppose to create tiny diodes for rectifying of currents.
    Some people wonder if they are able to create diodes that work with such tiny and
    high frequency currents why they need nanoantennas?Maybe it's easier to rectify
    those thermal electron currents which exist in a heated body?
    There is no wonder that you can't use thermal currents in diode which exist under room temperature.Otherwise it would be demon of Maxwell.To get some usefull energy temperature differences should exist somewhere in a system.I would be glad to know what kind of properties in diode we need to have to rectify thermal electrons?Should it be low forward voltage or high frequency or Schottky or some
    other kind?
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  5. #4  
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    Quote Originally Posted by Stanley514
    Currently some researches are trying to use nanoantennas (infrared rectennas)
    for energy harvesting.
    http://newenergyandfuel.com/http:/ne...hould-be-huge/
    They suppose to create tiny diodes for rectifying of currents.
    Some people wonder if they are able to create diodes that work with such tiny and
    high frequency currents why they need nanoantennas?Maybe it's easier to rectify
    those thermal electron currents which exist in a heated body?
    There is no wonder that you can't use thermal currents in diode which exist under room temperature.Otherwise it would be demon of Maxwell.To get some usefull energy temperature differences should exist somewhere in a system.I would be glad to know what kind of properties in diode we need to have to rectify thermal electrons?Should it be low forward voltage or high frequency or Schottky or some
    other kind?
    That would be cool, to help alleviate peoples fear of greenhouse gasses. We could turn the atmospheric heat into electricity, and therefore cool the air.

    Still, there isn't enough power to make it cost effective for electricity production, but producing electricity as a byproduct of cooling the atmosphere might be worth it.
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    Oh...

    As for the "antenna" idea, this does have merit. If you create a mesh of antenna's on a flat surface, you can effectively get electricity from it. the trick is, the effective antenna needs to be 1/2 the wavelength of the IR. Each diode can only rectify a small portion. However, and micro meter sizes, the are trillions in a small area. if the radiative forcing in the atmosphere is in the hundreds of watts per square meter... God.... Big guess here, you might be able to get 100 watts per square meter out of it.
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    Do you know why low heat conductivity is very important for good thermopower while it does not seem to be important for stirling engine?Don't they work in somewhat similar maner?Why Stirling engine is quite efficient when thermopower
    does not?

    Do you know why pyroelectrics react (produce power) only on temperature changes but not steady heat input?
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    what is "The Peltier–Seebeck and Thomson effects" for $400 pls
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    Probably,I need to explain my question.Stirling engine works somewhat similar to thermopower,but instead of electrons it circulates a gas from hot side to cool side.But what is interesting, Stirling engine does not need to be made from low heat conducting material.For example, it could be made completely from metal and ultimately heat will transfer from hot part of engine to cold side and all metal parts of engine will aquire not too different temperatures.But it doesn't seem influence Stirling efficiency very much and it stays quite efficient.Why thermoelectrics can't
    be made similar to Stirling engine?
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