This paper proposes a sizing method to guide the design of water-circulating radiative sky cooling systems and water-based energy storage solutions. Following this method, the choice of operational flow rate in the radiative sky cooling (RSC) panels and the water storage is based on four indicators: sub-ambient temperature, cooling power density, minimum storage temperature and useful energy stored. The method is applied to the BaityKool Solar Decathlon Middle East (SDME) prototype in order to design a water-radiative sky cooling system with storage in the climatic conditions of Dubai. We developed passive strategies for the BaityKool prototype, including a multi-functional innovative exterior wall and a semi-indoor courtyard space, combined with active solutions (in particular a hydraulic radiative sky cooling system). The experimental campaign conducted on the RSC system over three successive nights in November (ambient air temperature between 22.7 and 31.4 °C) indicates an average cooling power of 30–45 W m−2 for a maximum sub-ambient temperature drop of 2.8 °C, and shows that great attention to the water pipes and storage insulation can lead to an increase in the thermal performance of radiative sky cooling systems.< Leer menos