Passive Daytime Radiative Cooling by Thermoplastic Polyurethane Wrapping Films with Controlled Hierarchical Porous...

Area of Science:

• Materials Science
• Nanotechnology
• Sustainable Energy

Background:

• Global warming and greenhouse gas emissions necessitate energy-efficient cooling solutions.
• Passive daytime radiative cooling (PDRC) offers a promising, energy-free alternative to conventional cooling methods.
• Existing PDRC materials face challenges including structural complexity, poor flexibility, and degradation under stress.

Purpose of the Study:

• To develop a high-efficiency PDRC material with improved flexibility and durability.
• To create a PDRC film using a simple fabrication process suitable for large-scale application.
• To evaluate the cooling performance of the developed material on complex surfaces.

Main Methods:

• Fabrication of a porous thermoplastic polyurethane (TPU) film with bimodal pores.
• Characterization of the film's solar reflectivity and emissivity within the atmospheric window.
• Testing of the PDRC performance under simulated solar intensity and ambient conditions.
• Evaluation of the material's performance on 3D-printed models compared to commercial white paint.

Main Results:

• The TPU film achieved a solar reflectivity of 0.93 and emissivity of 0.90.
• An ambient cooling of 5.6°C was recorded at midday under 800 W/m² solar intensity.
• The flexible TPU film demonstrated superior indoor cooling efficiency (8.76°C) on 3D-printed models compared to white paint.
• The material exhibited excellent elasticity and suitability for application on complex shapes.

Conclusions:

• The developed porous TPU film is a highly efficient and flexible PDRC material.
• The simple fabrication process and robust performance make it suitable for various urban infrastructure applications.
• This technology presents a viable solution for reducing energy consumption and mitigating urban heat island effects.