Anti-reflection coated spectrally selective carbon nanotube solar absorbers

Zhonghua Chen,Tobias Boström

doi:10.1051/rees/2016002

Abstract

Multi-walled carbon nanotube (MWCNT) solar absorbers on aluminium substrates have been prepared by electrophoresis. The MWCNT absorbers exhibit a good spectral selectivity over the visible and infrared wavelengths. However, to further enhance the solar absorption, an anti-reflection coating made from porous silica was spin-coated on top of MWCNT solar absorbers. Porous silica precursor was prepared using tetraethyl orthosilicate (TEOS), and Pluronic F127 was used as a pore-forming agent. A maximum solar absorptance gain of 0.02 was achieved, which improves the spectral selectivity of MWCNT absorbers. The effect of anti-reflection layer depends on not only its thickness/refractive index but also the roughness of aluminium substrate.

Highlights

The solar thermal absorber is the key component of a solar thermal collector
We have used multi-walled carbon nanotubes (MWCNT) in the absorbing layer, which can be coated on top of an aluminium substrate by electrophoretic deposition (EPD)
Simulations using single-walled carbon nanotubes (SWCNT) as absorbing layers was done by the authors previously, and indicated that they can be good candidates as spectrally selective solar absorbers (SSSA) owing to their high absorption over the solar spectrum [5]

Summary

Introduction

Effective solar thermal absorbers should have a low reflectance in the UV/Vis/NIR region of solar spectrum and a high reflectance at wavelengths >2.5 mm. They are called spectrally selective solar absorbers (SSSA). We have used multi-walled carbon nanotubes (MWCNT) in the absorbing layer, which can be coated on top of an aluminium substrate by electrophoretic deposition (EPD). Simulations using single-walled carbon nanotubes (SWCNT) as absorbing layers was done by the authors previously, and indicated that they can be good candidates as SSSA owing to their high absorption over the solar spectrum [5]. Carbon nanotubes have excellent stability against heat, water, oxidizing environments and standard chemicals

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