An Engineer in Wonderland – Thermoelectricity and photons

25feb09nextremeshrunk.jpgTo be fair, I cannot say I know as much about photons as an earth worm because I have no idea how much worms know about quantum physics.

So instead I will say I know almost nothing about photons*.

This has not stopped me being puzzled by this article

It says infra-red solar cells are called thermophotovoltaic generators and convert photons to electricity,

whereas clusters of thermocouples are called thermoelectric generators and convert heat into electricity.

The question I am stuck on is:

Although they sound different, is there a photon argument for thermocouples – do they have a bandgap?


If you can answer this, respond below, or to alice@electronicsweekly.

* The bit I do know, although the theoretical physicist who told me may have been mistaken, is that there only needs to be one photon in the universe to make all the light work.

Tags: Alice

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1 Comment

  1. Steve Kurt
    February 20, 2009 17:56

    Interesting question….
    For PV’s, photons are an applicable concept. If you are going to bump electrons across a gap, then you need quantized energy to do it. Photons work well as a method of explaining it.
    For thermocouples, do you need quantized energy? Doesn’t the voltage vary with the applied temperature delta? I would assume that if one wanted to really examine the phenomenon, you might run into quantized energy, which would require photons. For the usual macro view, photons aren’t needed, so do they really exist?? :-)
    One of the applications of thermocouples that I am intrigued by is the use of a nuclear pile to generate warmth, which in turn causes a thermocouple group to generate electricity, which powers a deep space probe/vehicle. It’s a wonderful design with no moving parts or even semiconductors. Since it does rely on radioactive decay to generate the warmth, it does seem to imply that photons are part of the process.
    Steve K.

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