The output power of the thermoelectric generator was evaluated by its output voltage. Substituting
the measured output voltage in Figure 8 and the resistance R = 8 kΩ into Equation (2), the maximum
output power of the thermoelectric generator was obtained. Figure 9 shows the maximum output power
of the energy harvesting thermoelectric generator. The results showed that the output power of the
thermoelectric generator was about 1.1 μW as the temperature difference of 5 K and was about 9.4 μW
as the temperature difference of 15 K. The power factor of the thermoelectric generator was