  In this work we solve approximately the radiative heat transfer problem in
one dimension to perform a comparative analysis of the time averaged
performance of the partially transparent radiative windows and radiative
coolers. Our physical model includes the atmosphere, the window, and the
backwall that are all in the thermal equilibrium with each other, and that can
exchange energy via radiative heat transfer or convection. Moreover, we use a
simplified two-state model for the optical properties of an atmosphere and a
window material which assumes two distinct sets of the optical
reflection/absorption/transmission parameters in the visible/near-IR versus
mid-IR spectral ranges. Furthermore, we have distinguished the design goals for
the partially transparent windows and radiative coolers and provided optimal
choice for the material parameters to realize these goals. Thus, radiative
coolers are normally non-transparent in the visible, and the main goal is to
design a cooler with the temperature of its dark side as low as possible
compared to that of the atmosphere. For the radiative windows, however, their
surfaces are necessarily partially transparent in the visible. In the cooling
mode, therefore, the main question is about the maximal visible light
transmission through the window at which the temperature on the window somber
side does not exceed that of the atmosphere. We believe that our simple, yet
in-depth comparative analysis of the radiative windows and coolers can be
useful for a large number of scientists and engineers pursuing research in
these disciplines.

Applied Physics;Optics