Every clear night, roof-mounted radiative panels lose heat to deep space through an atmospheric "window" around 8–13 microns, dropping several degrees below the surrounding air even with no power input. Piping chilled water from those panels into an insulated tank lets a building bank that overnight cold, then release it the next afternoon through pipes cast into the floor slabs — a thermally activated building system, or TABS.
Radiative sky cooling works because the 8–13 micron atmospheric window lets a panel's infrared radiation pass almost straight through to the ~3 K of space, bypassing the warm air in between — the same physics that makes clear desert nights feel so much colder than cloudy ones.
A city block whose roof panels radiate heat straight to the night sky, banking the resulting chill in an insulated tank that then feeds a thermally activated slab to blunt the next day's heat load.
At night, clear skies let roof panels lose heat through the atmospheric window, filling the storage tank (blue). By day, the tank discharges through slab piping to absorb the building's heat gain — a full charge/discharge cycle.
Speed up the day/night cycle, size the roof panel array, dial in sky clarity, and set the building's cooling demand. Watch the tank fill overnight and drain as the slab draws on it during the day.
Radiative cooling panels can drop several degrees below air temperature with zero electricity input — they simply exploit a gap in the atmosphere's infrared absorption spectrum around 8–13 microns.