Tuning Optical Properties of Metamaterials by Mie Scattering for Efficient Sub-ambient Daytime Radiative Cooling

TL;DR

This paper presents a novel eggshell-based film that leverages Mie scattering and mid-IR emission to achieve efficient daytime radiative cooling, turning waste into a sustainable energy management resource.

Contribution

The study introduces a new eggshell biowaste-derived film with enhanced optical properties for radiative cooling, combining environmental waste management with energy efficiency.

Findings

Achieves 0.96 solar reflectance and 0.95 mid-IR emission.

Drops temperature by 5°C during day and 12°C at night.

Exhibits flexibility and self-cleaning for outdoor use.

Abstract

The management of the abundant eggshell biowaste produced worldwide has become a problematic issue due to the generated odor and microorganisms after directly disposing eggshell biowaste in landfills. Herein, we propose a novel method to convert the hazardous eggshell biowaste to valuable resources for energy management applications. Eggshell-based films are fabricated by embedding eggshell powders into polymer matrix to achieve highly efficient sub-ambient daytime radiative cooling. Benefiting from the Mie scattering of eggshell particles/air pores in the solar spectrum and strong emission of eggshell in the mid-infrared (mid-IR) range, the eggshell-based films present high reflection of 0.96 in the solar spectrum and high emission of 0.95 in the mid-IR range, resulting in significant average temperature drop of 5{\deg}C and 12{\deg}C below the ambient temperature during daytime and nighttime, respectively. Moreover, the eggshell-based films exhibit excellent flexibility and self-cleaning properties, which are beneficial for practical long-term outdoor applications. Our proposed design provides a novel means for an environmentally friendly and sustainable management of the eggshell biowaste.