Honeycomb Cell Structures Formed in Drop-Casting CNT Films for Highly Efficient Solar Absorber Applications

Area of Science:

• Materials Science
• Nanotechnology
• Renewable Energy

Background:

• Solar thermal absorbers are crucial for renewable energy applications.
• Enhancing absorption efficiency requires advanced material coatings.
• Multi-walled carbon nanotubes (MWCNTs) offer promising optical and thermal properties.

Purpose of the Study:

• To investigate MWCNT coatings for improved solar thermal absorption.
• To analyze the effect of self-organized honeycomb structures and cell area ratios (CARs) on absorption.
• To evaluate optical properties and thermal performance under varying irradiance.

Main Methods:

• Fabrication of MWCNT-coated absorbers with honeycomb structures using drop-casting.
• Varying CARs from ~60% to 17%.
• Optical property measurements (400-1651 nm) and solar thermal performance assessment (0.04-0.39 W/cm²).

Main Results:

• Honeycomb structures with ~17% CAR achieved high-temperature absorption despite moderate visible reflectance (8.4% at 550 nm).
• Infrared reflection increased significantly (80.5% at 1321 nm) for the 17% CAR structure.
• The 17% CAR structure consistently reached higher absorption temperatures (52.5 °C to 285.5 °C) across all irradiance levels.

Conclusions:

• Optimized MWCNT honeycomb structures, particularly with a ~17% CAR, are effective for high-temperature solar thermal absorption.
• A lower visible-to-infrared reflection ratio correlates with higher temperature absorption efficiency.
• This approach offers potential for cost-effective, large-scale production of efficient solar thermal absorbers for water heating and purification.