Thermochromic Nanocellulose Films for Temperature-Adaptive Passive Cooling

Area of Science:

• Materials Science
• Sustainable Energy
• Nanotechnology

Background:

• Energy efficiency in buildings is crucial for sustainability and cost savings.
• Passive cooling methods offer a promising alternative to active cooling systems.
• Sustainable materials are needed for advanced passive radiative cooling solutions.

Purpose of the Study:

• To develop adaptive passive cooling films using cellulose nanofibrils (CNF) and thermochromic (TC) materials.
• To explore the potential of hybrid CNF films for temperature-dependent thermal regulation.
• To investigate the application of these materials in enhancing energy efficiency in habitation spaces.

Main Methods:

• Hybrid films were fabricated by doping CNF with black-to-leuco TC particles.
• A thin silver layer was optionally applied to the films for enhanced performance.
• Optical properties, transition temperatures, and cooling potential were measured.
• Outdoor field testing and simulation modeling were conducted.

Main Results:

• The hybrid CNF films exhibited rapid optical property transitions at ~22 °C within 1 second.
• Visible light transmittance ranged from 60-90%, with significant mid-infrared (MIR) absorption (8-13 μm).
• Cooling potentials of 1-4 °C (without silver) and ~10 °C (with silver) were achieved, with a peak of 12 °C in outdoor tests.

Conclusions:

• The developed thermochromic CNF films demonstrate effective adaptive thermal regulation for passive cooling.
• This technology offers a novel application for green cellulose-based materials in energy-efficient building solutions.
• The concept is applicable to standalone films and glass coatings, extending its potential impact.