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by icegreentea2 2367 days ago
From mucking about with the device efficiency formula from wiki (https://en.wikipedia.org/wiki/Thermoelectric_materials#Therm...), and a change of zT from 2.5 to 5, we see a maximal possible efficiency increase of 38% (when T_c == T_h).

Wiki also tells me that the best TEG modules currently lock in around 8%, so we're looking at like 10-11% at best with the new material.

So from a bulk scale electricity standpoint... the needle probably hasn't shifted at all. From a small scale? In the IoT like applications (as mentioned in the press release), that extra 30-40% is nothing to sneeze at.
2 comments
makomk 2367 days ago
Also, this seems to suffer the same problem that most high-zT thermoelectric materials do: the total power handling capability is too low to be worthwhile. From a large-scale waste heat recovery standpoint, you're probably better off with a less efficient solution that can actually handle a useful proportion of your total heat output.
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amluto 2367 days ago
You have some kind of error here: with T_c = T_h, not only does Wikipedia’s formula give 0% efficiency, but it must: any power at all generated with no temperature difference would make a perpetual motion machine.
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icegreentea2 2367 days ago
Sorry, I was ignoring the left side (the T_h - T_c / T_h) part of the formula to see the relative change from changing zT from 2.5 to 5.0. Effectively I was looking at the relative efficiency of the high zT material in the limit as T_h approaches T_c. Which as you point out, drives the real individual efficiencies to zero. I was just trying to get the "best case" scenario.

Would also point out that for the IoT like applications, the assumption of T_c ~= T_h isn't so bad. For example, if you wanted something powered off residual body heat, you're looking at something like 293/310 = 0.945. For

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abdullahkhalids 2367 days ago
For T_c=293 and T_h=303, you get efficiency = 1.4% for zT=5 and efficiency = 1.0% for zT=2.5. So about a 40% relative increase as OP calculated and negligible absolute change.
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amluto 2360 days ago
Improving from 1% to 1.4% is a huge improvement. It’s 40% more cooling for a given power input or 40% more power output for a given amount of heat consumed. Alternatively, it means you consume only 1/1.4 the resources to achieve your goal.

This does not imply that 1.4% efficiency is enough to be useful for most applications, of course.

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