This paper focuses on the production of electricity using a thermoelectric
generator placed on the human body connected to a dc-dc converter. The small
difference in temperature between the hot heat source (e.g. the human body,
Tb = 37 °C) and the cold heat source (e.g. ambient air, Ta = 22 °C), associated with a poor quality thermal coupling (mainly with the
cold source), leads to a very low temperature gradient at the thermoelectric
generator terminals and hence low productivity. Under these use conditions,
the present article proposes an analysis of various ways to improve
productivity given a surface capture system. Furthermore, we demonstrated,
in this particular context, that maximizing the recovered electric power
proves to be a different problem from that of maximizing efficiency, e.g.
the figure of merit Z. We therefore define a new factor ZE, depending
on the physical characteristics of thermoelectric materials, that maximizes
electric power in the particular case where the thermal coupling is poor.
Finally, this study highlights the benefit of sub-optimization of the power
extracted from the thermoelectric generator to further improve efficiency of
the overall system. We show that, given the conversion efficiency of the
dc-dc converter, the maximum power point of the overall system is no more
reached when the output voltage of the thermoelectric generator is equal to
half of its electromotive force.