Efficiency calculation of thermoelectric generator using temperature   dependent material's properties
  Accurate measurement of efficiency for thermoelectric generator (TEG) is of great importance for materials research and development. Approximately all the parameters of a material are temperature dependent, so we can't directly apply the $\eta_\text{max}$ formula for efficiency calculation in the large temperature range. To overcome that problem, we tried to calculate the efficiency of TEG by dividing large working temperature range into a number of small temperature difference. The aim is to make temperature dependent parameter to be constant for that small temperature range. Using maximum individual efficiency of each segment obtained by $\eta_\text{max}$ in the equation of $\eta_\text{overall}$, which gives overall efficiency. The $\eta_\text{overall}$ of TEG using $Bi_2Te_3$ and $TAGS$ as thermoelectric materials come out to be $7.1\%$ and $8.94\%$, respectively, which is close to experimental results. For the high-temperature region, we have used $SiGe$ material in TEG and found out $\eta_\text{overall}=3.5\%$. The cumulative efficiency obtained by keeping one end temperature fixed with another end varying can be applied in real life application, i.e. automobile sector. The present work provides a simple way for the design engineers to calculate the efficiency of TEG by using the temperature dependent materials parameters like thermal conductivity, electrical conductivity, and Seebeck coefficient on which $z\bar{T}$ depends. 
Kumar Gaurav and Sudhir K Pandey
cond-mat.mtrl-sci