Multilayer selective passive daytime radiative cooler optimization utilizing memetic algorithm

Abstract

Passive Daytime Radiative Cooling (PDRC) process radiates excess heat by dumping heat into space through Transparent Atmospheric Windows (TAWs). Many structures are proposed for the PDRC but their main constraint is achieving near unity selective emission over 8–13 µm (first TAW, i.e., TAW 1) and 16–26 µm (second TAW, i.e., TAW 2) wavelength regions. In this paper, we have presented two Passive Daytime Radiative Coolers (PDRCs) referred as Design 1 and Design 2 which have respectively maximum 99% and 98% emissivity in TAW 1. While Design 1 is simulated considering only TAW 1, Design 2 is found acknowledging both TAW 1 and TAW 2. Both the models consist of three dielectric layers (i.e., SiN, SiC and SiO2) and a metal (i.e., Ag) back reflector. A genetic algorithm named” Memetic Algorithm” (MA) is utilized to identify the dielectric materials and determine their optimum thickness. The dielectric materials are selected by MA in such a way that their absorption peaks in the TAW 1 do not overlap and destructively interfere with each other, which in turn helps to obtain a high selective emission in that particular window with minimum thickness. This technique can be a new paradigm in designing PDRCs via tailoring material configuration. Additionally, the selective emitters are capable of providing a cooling temperature of 49.8 K and 44 K with a cooling power of 100.72 Wm−2 and 112.27 Wm−2 at equilibrium respectively for Design 1 and 2 when non-radiative heat exchange coefficient hc is 0 Wm−2K−1 and the studied wavelength range is in between 0.3 to 30 µm. The proposed emitters have only 1D planar layers. Therefore, they can be fabricated with promptly accessible materials which make them a better candidate for large scale fabrication.