Design and Experimental Investigation of Thermoelectric Generators for Wearable Applications

Abstract

A critical challenge in using thermoelectric generators (TEGs) for charging the portable or wearable electronics has been their limited outputs, as available temperature differential on human body (ΔText) is typically less than 10 K. Furthermore, the thermal resistance (Rth) at the TEG&#8211

air interface often overwhelms Rth of TEG itself, which makes the temperature differential within the TEG merely a small fraction of ΔText. Here, the designs of TEG systems for wearable applications based both on theory and systematic experiments are studied. First, this study fabricates the TEGs having different fill factors (equivalently, varied internal Rth of the TEGs) and finds an optimum fill factor that is determined by both thermal matching condition and the electrical contact resistance. Next, to investigate the effects of heat sink and external air flow, this study combines plate fin heat sinks with the TEGs and evaluates their performance under three different convection conditions: natural convection, and convection with either parallel or impinging flow. Lastly the effect of Rth at the skin&#8211

TEG interface is studied. Although the TEG system produces an output power of 126 μW cm&#8722

2 (ΔText = 7 K) on a smooth heat source (Cu heater), it generates reduced power of 20 μW cm&#8722

2 (ΔText = 6 K) on wrist (uneven heat source).