Radiative cooling with selectively infrared-emitting ammonia gas

Spectrophotometric measurements are reported for NH3 gas layers, and the potential use of this substance in radiative cooling devices is evaluated. The basic cooling parameters and the radiated power versus temperature drop are computed: the cooling power at near-ambient temperature can be exceptionally large. The radiative properties are discussed from the configuration of the NH3 molecule. Typically a 2-cm-thick NH3 gas slab can provide 26 Wm−2 useful cooling power at 15 °C below ambient temperature in a device with a moderate nonradiative loss (heat transfer coefficient of 1 Wm−2 K−1).