Membrane-assisted radiant cooling for expanding thermal comfort zones globally without air conditioning

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 117; no. 35; pp. 21162 - 21169
• Main Authors: Teitelbaum, Eric, Chen, Kian Wee, Aviv, Dorit, Bradford, Kipp, Ruefenacht, Lea, Sheppard, Denon, Teitelbaum, Megan, Meggers, Forrest, Pantelic, Jovan, Rysanek, Adam
• Format: Journal Article
• Language: English
• Published: Washington National Academy of Sciences 01.09.2020
• Subjects: Air conditioning; Built environment; Cold surfaces; Condensation; Convection; Convection cooling; Cooling; Cooling systems; Cooling water; Dew; Dew point; Humid climates; Low density polyethylenes; Low temperature; Membranes; Physical Sciences; Polyethylene; Radiant cooling; Relative humidity; Temperature; Temperature requirements; Thermal comfort; Thermal radiation; Urban environments; Water supply; Singapore
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.2001678117

We present results of a radiant cooling system that made the hot and humid tropical climate of Singapore feel cool and comfortable. Thermal radiation exchange between occupants and surfaces in the built environment can augment thermal comfort. The lack of widespread commercial adoption of radiant-cooling technologies is due to two widely held views: 1) The low temperature required for radiant cooling in humid environments will form condensation; and 2) cold surfaces will still cool adjacent air via convection, limiting overall radiant-cooling effectiveness. This work directly challenges these views and provides proof-ofconcept solutions examined for a transient thermal-comfort scenario. We constructed a demonstrative outdoor radiant-cooling pavilion in Singapore that used an infrared-transparent, lowdensity polyethylene membrane to provide radiant cooling at temperatures below the dew point. Test subjects who experienced the pavilion (n = 37) reported a “satisfactory” thermal sensation 79% of the time, despite experiencing 29.6 ± 0.9 °C air at 66.5 ± 5% relative humidity and with low air movement of 0.26 ± 0.18 m−1. Comfort was achieved with a coincident mean radiant temperature of 23.9 ± 0.8 °C, requiring a chilled water-supply temperature of 17.0 ± 1.8 °C. The pavilion operated successfully without any observed condensation on exposed surfaces, despite an observed dew-point temperature of 23.7 ± 0.7 °C. The coldest conditions observed without condensation used a chilled water-supply temperature 12.7 °C below the dew point, which resulted in a mean radiant temperature 3.6 °C below the dew point.