They suggest a new formula because the "the conventional efficiency formula (Eq. 1) often misleads and gives rise to an impractically high efficiency prediction

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.