Engineering a polyvinyl butyral hydrogel as a thermochromic interlayer for energy-saving windows

Area of Science:

• Materials Science
• Nanotechnology
• Sustainable Building Materials

Background:

• Thermochromic materials are key for energy-saving glazing but face cost, durability, and recycling challenges.
• Existing smart window technologies often lack a comprehensive set of desirable properties for widespread adoption.

Purpose of the Study:

• To develop a cost-effective, durable, and recyclable thermochromic hydrogel interlayer for smart glazing.
• To overcome limitations of current thermochromic materials for building applications.

Main Methods:

• Fabrication of a polyvinyl butyral (PVB)-based hydrogel swollen with LiCl solution.
• Characterization of the hydrogel's thermochromic properties, frost resistance, recyclability, and mechanical toughness.
• Integration of the hydrogel into a glazing prototype and performance evaluation through simulations.

Main Results:

• The developed hydrogel exhibits a rapid, reversible transparency-to-opacity transition above comfortable temperatures.
• The glazing demonstrates high luminous transmittance (~90%) even at sub-zero temperatures.
• Significant modulation of solar (80.8%) and infrared (68.5%) radiation was achieved.
• Simulations predict a 36% reduction in window energy consumption in warm seasons.

Conclusions:

• The nanostructured PVB-LiCl composite gel offers a unique combination of thermochromic performance, frost resistance, recyclability, and toughness.
• This hydrogel presents a promising, scalable solution for energy-efficient thermochromic glazing in buildings.
• The material's properties align with the need for sustainable and high-performance building materials.