Solar-Adaptive Cooling Blocks Composed of Recycled Fabric.

Radiative cooling technologies have had a significant impact on advancing carbon neutrality efforts by significantly improving the passive cooling efficiency. The tandem of conduction and radiation enables solar-adaptive radiative cooling through the insulating effect of materials along with solar absorption, which affects the thermal state of materials and enhances radiative thermal transfer from the surface under solar irradiation. This enhancement is achieved by utilizing the porous polymeric structure of materials, which facilitates improved conduction pathways along with solar reflectance, while maintaining the effective emission of thermal radiation. In this particular scenario, blocks, which were made of recycled fibers, offer a great opportunity as solar-adaptive cooling materials, enabling their easy deployment for cooling applications. Herein, we have fabricated a porous block using fiber wastes that combines strong solar reflectance (92%) at the 1 μm region and high thermal infrared emittance (∼75%) at the 10 μm region. The combination of effective solar reflection and thermal infrared emission allows the fiber block to achieve a high cooling performance of approximately 68 W/m under solar irradiation. In addition, the fiber block works effectively for insulation during the night, thereby enhancing its heat retention capabilities. The economic and environmental advantages of the fiber block make it a cost-competitive and sustainable choice for near-market cooling technologies. This design is anticipated to expand the practical application range of passive cooling.