Modeling and optimization of radiative cooling based thermoelectric generators

Generating power at night has recently stimulated interest in using the radiative cooling mechanism with thermoelectric generators (TEGs). These low temperature and passive devices have been shown to generate electricity at night with no active input of heat needed. Here, we optimize both the geometry and operating conditions of radiative cooling driven thermoelectric (RC-TE) generators. We determine the optimal operating conditions, including the maximum power point and maximum efficiency point, by developing a combined thermal and electrical model. Our results show that the optimal operating condition results in larger power output than was previously expected. Moreover, we show that maximum power density occurs when the area ratio between the cooler and P or N element reaches an optimal value and can be improved to nearly 2.2 times larger than what has been achieved with commercial TEGs. Finally, we perform a parametric study that takes account of environmental and structural parameters to improve the performance of the RC-TE device, including enhancing heat transfer between the hot surface and ambient air, suppressing the cooling loss of the radiative cooler, and optimizing the geometry of individual thermocouples. In summary, our work identifies how to maximize the output of RC-TE devices, providing universal guidance for this passive power generation method.