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For fun, I am designing a electrical generator powered from natural gas.

I have ordered 20 count of these devices: https://www.ebay.co.uk/itm/Thermoelectric-Power-Generator-Peltier-Module-TEG-40x40mm-High-Temperature-150-/172159882510

  • 20 degree temperature difference: open-circuit voltage 0.97V, generated current: 225MA
  • 40 degree temperature difference: open circuit voltage 1.8V, generated current: 368MA
  • 60 degree temperature difference: open circuit voltage 2.4V, generated current: 469MA
  • 80 degree temperature difference: the open circuit voltage 3.6V, generated current: 558MA
  • 100 degree temperature difference: open circuit voltage 4.8V, generated current: 669MA

My intended design is a stack over a natural gas flame on the stovetop, with a cast iron heat sink, copper plate, TEG array, and then topped with a copper plate with a heat exchanger for cold water flow from the tap.

The max rated temperature on the TEGs is 150˚C and I expect the wintertime tap water to come in around 5˚C.

Here is my question: Assuming I will achieve 150˚C / 5˚C, can I expect even more power than 4.8V * 669MA? Or a different result?

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  • $\begingroup$ Well, your thermoelectric stack could fail (crack or something else). It certainly will at some point. $\endgroup$ – Jon Custer Jan 21 '18 at 0:26
  • $\begingroup$ You are saying, the temperature gradient will put a mechanical stress on the material as possibly more than designed? $\endgroup$ – Douglas Held Jan 21 '18 at 8:48
  • $\begingroup$ Many thermoelectric materials are not very strong. Plus you have all the other materials in a module with different thermal expansion characteristics. They are actually pretty complicated inside. $\endgroup$ – Jon Custer Jan 21 '18 at 16:20
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Well from someone else's research, https://www.sciencedirect.com/science/article/pii/S2214157X1500012X we can see in Figure 4: Figure 4: temperatures vs. power output

that an increasing temperature gradient brings more power but a lumpier line - meaning to me some factors that don't present in smaller temperature deltas start to have a measurable impact at higher deltas. It's easier to see in my annotated picture, where the straight line is delta100˚C, middle line is delta150˚C and the curvy line, delta200˚C.

annotated graph

Neither my design nor the researchers' will exceed the rated temperatures of the devices, but it is interesting to see what will likely lie "off the graph" of the documented characteristics.

A second point that is interesting to me is that although my devices are described by the manufacturer as much more efficient at cooler overall temperatures, that is not clearly evident in the researchers' graph.

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