Radiation cooling technology has become an efficient and passive thermal regulation solution by reflecting solar radiation and emitting infrared radiation. This dual function eliminates the need for external energy input for cooling, making it a promising approach to alleviate global energy and environmental challenges. Radiation cooling conforms to the principles of green and low-carbon development, providing sustainable temperature control alternatives for various applications including buildings, textiles, and personal thermal management systems.
However, the actual deployment of radiation cooling materials (RCMs) is often hindered by environmental factors such as heat accumulation, convective heat transfer, and significant diurnal temperature variations. These challenges may reduce the cooling efficiency of RCM, leading to potential issues such as overcooling or overheating under specific climatic conditions. Integrating phase change materials (PCM) with RCM has been proposed as an effective strategy to address these limitations.
PCM has high latent heat and stable phase transition temperature, allowing it to absorb and release heat during the phase transition process. This inherent ability can stabilize temperature fluctuations, thereby improving the overall efficiency of the radiative cooling system. For example, PCM can absorb excess heat during high temperatures and release it when the temperature drops, thereby reducing the impact of environmental heat inflow and alleviating thermal discomfort. In addition, PCM with phase change temperature suitable for human thermal comfort level shows great potential in improving the applicability of radiative cooling systems in wearable and personal thermal management technologies.
Extensive research has been conducted on the integration of PCM with radiative cooling systems in a range of applications, such as solar stills, photovoltaic thermal systems, air conditioning units, and energy-efficient roofs. These studies emphasize the significant advantages of combining the thermal storage performance of PCM with the optical and thermal emission performance of RCM.
However, there are still some challenges, including limited latent heat, suboptimal phase transition temperature for human comfort, and difficulty in processing PCM integrated materials due to increased viscosity and reduced processability.