4 ms·

This is not a heat engine, as there is no cyclical nature and it's not turning the heat into mechanical energy, therefore the Carnot efficiency need not apply.

Scaevolus 8y ago
Carnot efficiency still applies, even if the thermoelectric effect doesn't have a mechanically cyclical nature. http://www.pnas.org/content/112/27/8205 http://www.pnas.org/content/112/27/8205
- nanomonkey 8y ago
  The article you linked doesn't follow your statement, in fact it suggests a different theoretical limit, and only suggests a engineering formula for high temp TEGs to mesh up with the observed results due to the Thomson effect on heat transfer.
  - Scaevolus 8y ago
    They suggest a new formula because the "the conventional efficiency formula (Eq. 1) often misleads and gives rise to an impractically high efficiency prediction". > The [thermoelectric] conversion efficiency by Eq. 1 is the product of the Carnot efficiency (ΔT/Th) and a reduction factor as a function of the material’s figure of merit Z = S^2 ρ^−1^κ−1, where S, ρ, and κ are the Seebeck coefficient, electrical resistivity, and thermal conductivity, respectively.
theothermkn 8y ago
Interestingly, while the Carnot Limit is derived using heat engines, it applies to any "device" that extracts energy from a temperature difference. If it were not so, then one could place, for example, a thermoelectric device between two energy reserves at different temperatures and use it to power a Carnot heat pump to drive the temperature difference higher, or to sustain the temperature difference and extract work. This is a perpetual motion machine, violating the thermodynamic laws of which the Carnot Limit is a manifestation. (It is a general result, obtained from hypothetical devices.) One can sort of "feel" this result by imagining the voltage pushing a cloud of electrons around a circuit, producing shaft work in an electric motor, and/or heat if there is any electrical resistance.

Scaevolus 8y ago

Carnot efficiency still applies, even if the thermoelectric effect doesn't have a mechanically cyclical nature. http://www.pnas.org/content/112/27/8205 http://www.pnas.org/content/112/27/8205

nanomonkey 8y ago
The article you linked doesn't follow your statement, in fact it suggests a different theoretical limit, and only suggests a engineering formula for high temp TEGs to mesh up with the observed results due to the Thomson effect on heat transfer.
- Scaevolus 8y ago
  They suggest a new formula because the "the conventional efficiency formula (Eq. 1) often misleads and gives rise to an impractically high efficiency prediction". > The [thermoelectric] conversion efficiency by Eq. 1 is the product of the Carnot efficiency (ΔT/Th) and a reduction factor as a function of the material’s figure of merit Z = S^2 ρ^−1^κ−1, where S, ρ, and κ are the Seebeck coefficient, electrical resistivity, and thermal conductivity, respectively.

theothermkn 8y ago

Interestingly, while the Carnot Limit is derived using heat engines, it applies to any "device" that extracts energy from a temperature difference. If it were not so, then one could place, for example, a thermoelectric device between two energy reserves at different temperatures and use it to power a Carnot heat pump to drive the temperature difference higher, or to sustain the temperature difference and extract work. This is a perpetual motion machine, violating the thermodynamic laws of which the Carnot Limit is a manifestation. (It is a general result, obtained from hypothetical devices.) One can sort of "feel" this result by imagining the voltage pushing a cloud of electrons around a circuit, producing shaft work in an electric motor, and/or heat if there is any electrical resistance.