An improved model for performance predicting and optimization of wearable thermoelectric generators with radiative cooling

Wearable thermoelectric generators (WTEGs) have shown great potential for harvesting low-grade body heat. However, inappropriate design of cold side heat sinks leads to unsatisfactory power generation efficiency. To overcome this, radiative cooling cold side has been introduced by some earlier researchers. Nonetheless, a reliable performance evaluation model lacks for WTEGs with radiative cooling at outdoors. In this paper, we propose a novel analytic model, which considers comprehensive thermoregulatory mechanisms and detailed radiative heat transfer process. The model demonstrates good accuracy with less than 9% error in a variety of conditions. Furthermore, the proposed dynamic model greatly outperforms the constant model and static model in terms of WTEG output performance prediction at outdoors, which can reduce the deviations by up to 196.4% and 71.6%, respectively. Among the three types of cold side structures (bare, finned, and radiative cooling), we found that the radiative cooling cold side performed best. Accordingly, the output performance of the WTEG with radiative cooling was further investigated, and the influences of climatic conditions and spectral properties of radiative cooling on WTEG were obtained. Different human body segments were also considered in outdoor simulations, with the shoulder giving the best performance. Finally, based on the proposed model, the thermal resistance improvement indicates that 220% output performance enhancement is possible, which could be beneficial for device design and utilization in many other applications.