Thermoelectric generator placed on the human body: system modeling and energy conversion improvements

Abstract

Abstract. 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, T b = 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.

SIW antennas as hybrid energy harvesting and power management platforms for the internet of things

“…Specifically, the UltraTec Series UT6,24,F1,5555 component by Laird Technologies is selected [10]. Its hot side is tightly attached to the skin of the wearer's arm, whereas its cold side is exposed to the ambient air, in order to harvest thermal body energy based on Seebeck's effect [8]. However, multiple TEGs, potentially stacked, or a heat sink could be used to further increase the amount of harvested energy.…”

Substrate integrated waveguide textile antennas as energy harvesting platforms

“…It implements an ultralow-voltage stepup converter, of which the output is connected to a linear harvesting input of the CPMS. This enables thermal body energy harvesting via an externally connected TEG, based on Seebeck's effect [6], exploiting the thermal gradient between human skin and ambient temperature. The power available from these three different energy sources is combined by the CPMS to charge the micro-energy cell (MEC), in the meantime protecting the MEC and providing a regulated output voltage.…”

“…All these reasons point to SFIT systems as prime candidates to be partly, or even solely, powered by energy harvesting techniques [5]. By extracting energy from the user's activities [6], [7], or from ambient sources at the place where the SFIT is worn by the user [7], [8], life-threatening situations, due to batteries running out of power during interventions, could be prevented. Preferably, energy is scavenged from multiple different energy sources [5], [7] to increase the amount of harvested energy and to obtain a higher continuity in energy scavenging.…”

Textile SIW antennas as hybrid energy harvesting and power management platforms

“…In this work, a single TEG ( the UltraTec Series UT6,24,F1,5555 from Laird Technologies) is connected to the LPS. Its hot side is tightly attached to the skin of the wearer's arm, whereas its cold side is exposed to the ambient air, in order to harvest thermal body energy based on Seebeck's effect [7]. However, multiple TEGs, potentially stacked, or a heat sink could be used to further increase the amount of harvested energy.…”

“…Hence, they allow burst measurement and transmission, resulting in low duty cycle operation, yielding a low average power consumption and making SFIT systems prime candidates to be partly, or even solely, powered by energy harvesting techniques [4]. For instance, energy could be extracted from ambient sources at the place where the SFIT is worn by the user [5], [6], or from the user's activities [7], [8]. Preferably, energy is scavenged from multiple diverse energy sources [4], [5] to be able to harvest more energy in a more continuous way.…”