Modelling, fabrication and experimental testing of an heat sink free wearable thermoelectric generator

For a first functional investigation, a prototype of 45 thermocouples into a footprint area of about 2.2 × 10−3 m2 was fabricated and tested to evaluate its thermoelectric performance stand-alone and coupled with the DC-DC converter. A mean Seebeck coefficient of about 60 μV/K for pn couple was calculated from experimental data, and a power of about 27 nW was measured at 10 K on matched load of about 6.8 kΩ. A temperature difference of about 1.8 °C was achieved between the junctions in working conditions next to those typical of human body wearing in indoors (quiescent air at room temperature, constant temperature of 34.8 °C applied on the TEG hot side). The investigation shown that a thermopile of 450 couples requires a minimum thermal gradient of about 2 °C between junctions to be able to switch on the custom voltage boost DC-DC converter.