Full-scale experimental assessment of a radiant-capacitive cooling system driven by nocturnal and diurnal radiative cooling

We demonstrate a full-scale radiant-capacitive cooling system (RCCS) capable of maintaining continuous thermal comfort during hot summer conditions without using mechanical refrigeration, thanks to a combination of sky radiators with water-filled radiant-capacity ceiling panels. Tested in twin full-scale cells under clear-sky conditions, the RCCS maintained operative temperatures within the adaptive comfort limit for 94% of the monitoring period when uncoated and for 100% when the radiators were coated with a commercial passive daytime radiative cooling (PDRC) material. The experimental cell exhibited temperatures on average 6–7 K cooler than the control cell, with peak daily reductions in indoor maximum temperature up to 12 K. Sky radiators produced a median cooling potential of about 56 W m⁻² (43–74 W m⁻² across the series), while the ceiling panels removed an average of 2.8–3.2 kWh per day (432–494 Wh/m²∙day), depending on configuration. Applying the PDRC material extended effective cooling by 2–4 h per day and increased daily delivered cooling energy by more than 10%. Multiple-regression models based on climatic and operational variables explain the observed temperature reductions and cooling potential of the sky radiators. These results indicate that a low-complexity, water-based radiative cooling system built from widely available components can significantly improve thermal comfort in well-insulated buildings during extreme heat without mechanical refrigeration.