High Power Output of Passive Radiative Cooled Thermoelectric Generator Based on Body Heat

Advancements in flexible and micro-powered wearable sensors have led to the demands of energy generating devices. Frequent charging and limited life of the battery can be replaced by thermoelectric generators (TEGs) which can continuously power the wearable sensors by harvesting body heat. Further integration of heat sink with TEG can enhance power generation. However, reported TEGs utilized large sized and bulky heat sinks, which make the device heavy and inconvenient to wear. Hence, high-quality flexible thin heat sinks are required for compact TEGs to generate high power output. Here, a TEG integrated with a flexible, micron-thin P(VdF-HFP) radiative heat sink, showed excellent performance. Radiative heat sink reflects most of the incident solar radiation owing to high reflectivity in the ultraviolet range and due to high emissivity in longwave infrared, it dumped the heat into the outer cold space, i.e., a temperature of 3K through the transparent atmospheric window (8-13 µm). Radiative heat sink creates lower temperature than ambient and generates high power output through passive radiative cooling. Thus, TEG delivered a power density of 12.48 µW/cm², which is higher than previously reported works from body heat under natural convection. Further, radiative TEG is not only two times more compact but also delivers higher power output compared to TEG with a finned heat sink. Moreover, a Li-S flexible pouch cell battery was coupled with radiative TEG to store the fluctuated generated power with the help of a DC-DC voltage booster to achieve a self-powered wearable system. [1]<br/>[1] S. Khan, J. Kim, K. Roh, G. Park and W. Kim, “High power density of radiative-cooled compact thermoelectric generator based on body heat harvesting”, Nano Energy, vol. 87, pp. 106180, 2021