Investigation of a Self-adaptive Hybrid Passive Radiative Cooling System for Building Energy-saving Performance

Passive radiative cooling has gained prominence as a promising energy-saving technique that leverages the coldness of outer space to achieve cooling without power input. However, conventional daytime passive radiative cooling techniques (PRCs) provide cooling power year-round, resulting in increased heating demand during cold winter seasons. Despite recent proposals for thermally controllable methods, challenges in terms of instability and limited versatility hinder their practical application. This study introduces a thermal-adaptive hybrid film (TA-HF) to overcome these limitations. A protective layer is incorporated in the TA-HF to enhance durability against solar radiation. The TA-HF is applied on top of a particle-based polymeric PRC, which possesses exceptional solar reflectivity and high thermal emissivity properties. This integration forms a thermal-adaptive passive radiative cooling system (TA-PRC) that possesses the remarkable ability to passively adjust its spectral properties based on the ambient temperature, thereby effectively controlling the radiative cooling power. A mathematical model validates the thermal power modulation of the TA-PRC, demonstrating its efficacy in generating effective cooling power during hot days and heating power during cold days, with an impressive modulation power exceeding 200 W/m². Furthermore, energy-saving simulations using EnergyPlus show that TA-PRC applied to buildings outperforms white PRC buildings and original buildings in terms of energy savings across various climate zones. The results highlight the TA-PRC's significant potential for thermal management and energy saving in smart-green building applications. © 2024 Begell House Inc.. All rights reserved.