Sky cooling-driven radiant-capacitive hydronic system for all-day building cooling

Year: 2026

Authors: Forte D., Gonzblez-Cruz E., Pattelli L., Belotti C., Pyrez G., Asinari P., Fasano M.

Autors Affiliation: DOE, Politecn Torino, Corso Duca Abruzzi 24, I-10129 Turin, Italy; CSIC, Eduardo Torroja Inst Construct Sci IETCC, Serrano Galvache 4, Madrid 28033, Spain; Ist Nazl Ric Metrolog, Str Cacce 91, I-10135 Turin, Italy; CNR, INO, Ist Nazl Ottica, Via Madonna Piano 10, I-50019 Sesto Fiorentino, Firenze, Italy.

Abstract: Daytime Radiative Cooling (DRC) surfaces enable heat rejection by emitting infrared radiation to the sky while re flecting solar radiation, allowing for sub-ambient cooling even under direct sunlight. This study develops and vali dates a transient numerical model of a DRC-based hydronic cooling system designed for building applications. The system integrates ceiling-mounted radiant capacitive modules (RCMs) with outdoor sky radiators (SRs) that dissi pate indoor heat to outer space, cooling down a heat transfer fluid. The model is validated using experimental data from a full-scale demonstrator using a commercially available DRC emitter and is employed to assess system per formance for a single-family building during a typical cooling season in the cities of Madrid and Rome. Compared to a system limited to nighttime radiative cooling, the DRC-enhanced setup delivers seasonal energy performance improvements of +6.2 % with a commercial DRC material and +10.3 % with an ideal broadband emitter. The study further investigates the effects of varying the surface area ratio between SRs and RCMs and alternative SR placements (rooftop vs. external surface). A fully passive building model with a DRC roof is also considered for comparison. Results show that the DRC-hydronic system can consistently maintain indoor thermal comfort throughout the cooling season, achieving seasonal energy efficiency ratios (SEER) up to 35 times higher than those of conventional air conditioning systems for the case studies analyzed, although the two systems differ in controllability and application scenarios. These findings highlight the strong potential of DRC-integrated hydronic cooling as a highly energy-efficient and sustainable alternative for the climate control of residential buildings.

Journal/Review: APPLIED ENERGY

Volume: 406      Pages from: 127260-1  to: 127260-16

More Information: The authors acknowledge the project PaRaMetriC (21GRD03, Metrological framework for passive radiative cooling technologies) , which received funding from the European Partnership on Metrology, co-financed by the European Union’s Horizon Europe Research and Innovation Programme and the Participating States.
KeyWords: Radiative cooling; Hydronic cooling; Building; Sustainability; Heat and mass transfer
DOI: 10.1016/j.apenergy.2025.127260