Design of Double-Sided Optical Coatings for Space Cooling Through Vertical Windows

Passive radiative cooling is a promising energy-saving strategy for space cooling. Dual-sided thermal emitters offer efficient heat removal from enclosed spaces; however, existing studies predominantly focus on rooftop applications, with limited attention to vertical surfaces, such as walls and windows. Here, a dual-sided radiative cooling glass (DSRCG) tailored for vertical applications proposed, enhancing enclosure cooling. The DSRCG incorporates multilayer epsilon-near-zero materials, including Al₂O₃ and Si₃N₄, layered on a double-sided indium-tin-oxide-coated glass. The outward side of the DSRCG exhibits angular-selective emission for efficient heat dissipation, while the inward side minimizes thermal radiation into enclosures. The visibly transparent layers enable a visible transmittance exceeding 72%. The simulation results demonstrate that the DSRCG reduces heat transfer to enclosures by 15 W m⁻² compared with the conventional glass (C-glass) at ambient temperatures above 30 °C. These findings highlight the DSRCG's potential as an energy-saving window for reducing space-cooling energy usage.