Thermocouplers

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A thermocouple is an electrical device consisting of two dissimilar electrical conductors forming electrical junctions at differing temperatures. A thermocouple produces a temperature-dependent voltage as a result of the thermoelectric effect, and this voltage can be interpreted to measure temperature. Thermocouples are a widely used type of temperature sensor. when different metals are joined at the ends and there is a temperature difference between the joints, a magnetic field is observed. In practical use, the voltage generated at a single junction of two different types of wire is what is of interest as this can be used to measure temperature at very high and low temperatures.

For Power Generation

The magnitude of the voltage depends on the types of wire being used. Generally, the voltage is in the microvolt range and care must be taken to obtain a usable measurement. Although very little current flows, power can be generated by a single thermocouple junction. Power generation using multiple thermocouples, as in a thermopile, is common. Efficiency is around 4%. Thermopiles are commonly paired with Radioisotope thermal generators to produce power.

It seems to be possible to generate power with these. see 1 and 2. Nasa used Silicon-Germanium thermocouples in their RTGs until 2010 at which point they switched to lead telluride.

Ongoing Questions

  • Does anyone do this? - see above
  • Does anyone do this in space? - For attitude determination and for use in RTGs yes.
  • Has anyone done this in a cubesat? - For attitude determination yes, not for power.
  • How much voltage can we get out of this? - In the range of a few tens to a few hundreds of milivolts
  • How much Current can we get out of this? a few milliapps
  • What is the average power we can get out of this? - In the range of a few tens to a few hundreds of milliwatts
  • Can we get sustained power or will it fluctuate? - Sustained while we are in sunlight / When there are temperature differentials
  • How much will it cost us to implement? Depends, how much we want to try and get out of it. An inital test would be ~$20
  • How many additional ICs would we need? in theory, 0
  • Does the heat decrease when we use this? yes
  • What are the different types we could use? Silicon-Germanium or lead telluride