  The possibility of night-time power generation has recently stimulated
interest in using the radiative sky cooling mechanism with thermoelectric
generators (TEG). These passive, low-temperature difference devices have been
shown to generate electricity at night with no active input of heat needed,
instead using the ambient air itself as the heat source. Here, we optimize both
the geometry and operating conditions of radiative cooling driven
thermoelectric (RC-TE) generators. We determine the optimal operating
conditions, including 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 cooler and P or N element reaches an optimal value. 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. Our work identifies how to maximize the output of RC-TE devices
and provides comprehensive guidance on making use of this new passive power
generation method.
