Radiative cooling and thermoregulation in the earth’s glow

• Published in: Cell reports physical science Vol. 5; no. 7; p. 102065
• Main Authors: Mandal, Jyotirmoy, Anand, Jyothis, Mandal, Sagar, Brewer, John, Ramachandran, Arvind, Raman, Aaswath P.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 17.07.2024; Elsevier
• Subjects: broadband emitters; building energy efficiency; differential atmospheric transmission; passive radiative thermoregulation; radiative cooling; selective longwave infrared emitters; textiles; thermal photonics; walls; windows; radiative cooling; differential atmospheric transmission; walls; thermal photonics; selective longwave infrared emitters; textiles; building energy efficiency; windows; passive radiative thermoregulation; broadband emitters
• ISSN: 2666-3864; 2666-3864
• DOI: 10.1016/j.xcrp.2024.102065

Efficient passive radiative cooling of buildings requires an unimpeded view of the sky. However, vertical facades of buildings mostly see terrestrial features that become broadband-radiative heat sources in the summer and heat sinks in the winter. The resulting summertime terrestrial heat gain by buildings negates or overwhelms their narrowband longwave infrared (LWIR) radiative cooling to space, while the wintertime terrestrial heat loss causes overcooling. We show that selective LWIR emitters on vertical building facades can exploit the differential transmittance of the atmosphere toward the sky and between terrestrial objects to achieve higher summertime cooling and wintertime heating than conventionally used broadband emitters. The impact of this novel and passive thermoregulation is comparable to that of painting dark roofs white and is achievable with both novel and commonplace materials. Our findings represent new and remarkable opportunities for materials design and untapped thermoregulation of entities ranging from buildings to human bodies. [Display omitted] •A novel, passive radiative thermoregulation mechanism for walls and windows•Buildings lose narrowband heat to the sky but exchange broadband heat with the earth•Vertical LWIR emitters stay cooler than broadband ones in hot weather and warmer in cold•Thermoregulation by this simple and static design yields untapped energy savings Mandal et al. propose and demonstrate that selective longwave infrared-emissive exterior envelopes can keep walls and windows of buildings cooler than traditional exterior envelopes in hot weather and warmer in cold weather. Achievable by simple means, this passive radiative thermoregulation can enable untapped energy savings in buildings.