A multilayered photonic emitter for high-performance daytime radiative cooling
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TECHNICAL PAPER
A multilayered photonic emitter for high-performance daytime radiative cooling Adil Mohammed1 • Sumith Yesudasan2
•
Sibi Chacko1
Received: 3 September 2020 / Accepted: 1 November 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Daytime radiative cooling devices consisting of various materials are used to transmit and radiate heat energy from a target body outward through the atmosphere and into cold outer space, without using external energy and in the presence of sunlight. In this study, a daytime radiative cooling thin film structure is designed to achieve high emission in the atmospheric transparency window (8–13 lm) and a high reflection of solar radiation. Simple and chemically stable inorganic materials of silicon dioxide, silicon nitride, aluminum oxide, and silver are selected for the initial design of the structure, initially having four layers. The needle optimization technique is used to enhance the initial design to acquire a final structural design of 10 layers of the selected materials. The average emissivity of the cooler in the range of 8–13 lm was numerically found to be 94.5% and the average reflectance for the solar spectrum was determined to be 96.3% according to validated calculations. Lastly, a high net cooling performance of 125 W/m2 is theoretically generated by the structure when it is equal to the ambient temperature and a temperature reduction of 8 °C is achieved from the ambient temperature according to validated calculations.
1 Introduction Cooling systems are an essential requirement in our daily lives as they can be used to remove and dissipate heat energy from almost any kind of undesirable heat source. However, the use of such systems generally requires a significant amount of external energy and results in high greenhouse gas emissions which leads to global warming, which consequently has a harmful impact on the environment of the planet. This has led to the introduction of various novel ideas in the field of passive cooling, or cooling without any external or active source of energy (Daisy 2016). Recent studies have focused on the phenomenon of radiative cooling, a passive cooling approach & Sumith Yesudasan [email protected] Adil Mohammed [email protected] Sibi Chacko [email protected] 1
School of Engineering and Physical Sciences, Heriot-Watt University, Academic City, Dubai, UAE
2
Department of Engineering Technology, Sam Houston State University, Huntsville, TX, USA
that lowers the temperature of surfaces exposed to sunlight, without causing emissions and without using external energy (Ko et al. 2018). Radiative cooling or sky cooling is a phenomenon by which cooling of a surface or a body occurs through the process of radiation. It occurs naturally during the night when sunlight or solar energy is not present. In general, radiation is the emission of energy in the form of electromagnetic waves, caused by the presence of heat energy in a body. Most of the heat energy emitted by
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