Nanophotonic Radiative Sky Cooling (2D)

The 3D version of this simulator treats atmospheric-window emission as a single fixed "effective emissivity" multiplying a Stefan-Boltzmann temperature difference. This 2D companion goes one level deeper: it numerically integrates Planck's law itself, every frame, to find the actual fraction of the coating's thermal spectrum that falls inside the 8-13 µm window versus the fraction the atmosphere reabsorbs — and plots that integral directly as a shaded spectral curve. Because the band fraction is computed from the real curve rather than assumed constant, it correctly shifts with surface temperature (Wien's law), and because the underlying energy-balance ODE was re-derived and numerically cross-checked rather than copied, it also fixes a solar-term sign error present in the 3D twin. Watch the spectral plot, the live energy-flow arrows and the temperature strip chart settle together as you adjust the coating's reflectance and window emissivity, the ambient air temperature, and how strongly wind couples the surface back to the air.