Radiative Cooling and Thermoregulation of Vertical Facades with Micropatterned Directional Emitters

• DOI: 10.48550/arxiv.2408.03512
• Publication Date: 2024-01-01
• Authors: Degeorges, Mathis; Anand, Jyothis; Varghese, Nithin Jo; Mandal, Jyotirmoy
• Keywords: FOS: Physical sciences; Physics - Applied Physics; Applied Physics (physics.app-ph)

We demonstrate a micropatterned directional emitter (μDE) with an ultrabroadband, azimuthally selective and tailorable emittance across the thermal wavelengths and over wide angles. The μDE can enable a novel and passive seasonal thermoregulation of buildings by reducing summertime terrestrial radiative heat gain, and wintertime loss. We show several types of μDE, such as metallic, white and transparent variants, made using low-cost materials and scalable manufacturing techniques that are already in large-scale use. Furthermore, we show that its directional emittance can be geometrically tailored to sky-view factors in different urban scenarios. Outdoor experiments show that μDEs stay 1.53-3.26°C cooler than traditional omnidirectional building envelopes in warm weather, including when they are sunlit. In cold weather, μDEs can be up to 0.46°C warmer. Additionally, μDEs demonstrate significant cooling powers of up to 40 Wm-2 in warm conditions and heating powers of up to 30 Wm-2 in cool conditions, relative to typical building envelopes. Building energy models show that μDEs can achieve all-season energy savings similar to or higher than those of cool roofs. Collectively, our findings show μDEs as highly promising for thermoregulating buildings.<br/>This version has been accepted for publication in Joule. Compared to the last version, further details on thermoregulation, new materials, and a transparent micropatterned directional emitter has been demonstrated<br/>