$E_P$	Efficient power (W)
$F$	Heat transfer area of heat exchangers ($m^2$)
$I$	Output current ($A$)
$K$	Thermal conductance ($W/K$)
$k$	Coefficient of heat transfer ($W/m^2\cdot K$)
$M$	Total number of thermoelectric elements
$m$	Number of first-stage thermoelectric elements
$n$	Number of second-stage thermoelectric elements
$P$	Output power ($W$)
$Q$	Heat flux ($W$)
$R$	Electric resistance ($\Omega$)
$T$	Temperature ($K$)
Greek symbols
$\alpha$	Total Seebeck coefficient ($V/K$)
$\eta$	Thermal efficiency
Subscripts
1	High temperature side of thermoelectric device
2	Low temperature side of thermoelectric device
$E_P$	Maximum efficient power point
$H$	High-temperature heat source
$L$	Low-temperature heat sink
max	Maximum value
mid	Middle connection layer
$opt$	Optimal
$P$	Maximum power point
$T$	Total
$\eta$	Maximum thermal efficiency point
Superscript
$-$	Dimensionless
Abbreviations
DI	Deviation index
FTT	Finite-time thermodynamics
HEX	Heat exchanger
HT	Heat transfer
MOO	Multi-objective optimization
NET	Non-equilibrium thermodynamics
TE	Thermoelectric
TTEG	Two-stage thermoelectric generator