Highly Selective Solar Thermal Sprayable Coating Based on Carbon Nanotubes

Abstract

A key component in solar thermal energy conversion system is the light collector that is coated with an absorbing material. Optimal performance is accomplished by high absorptance and low emittance. The best collectors are fabricated by vacuum deposition processes, which are limited to small size and flat objects. Here, the formation and performance of a new three‐layer solar selective coating, which is formed by a simple wet‐deposition process is reported. The solar absorbing layer is based on carbon nanotubes, which are considered the most absorbing material. This layer is coated by a second layer of ITO, which functions as an IR reflecting layer, followed by an AlOOH anti‐reflective layer. The resulting CNT/ITO/AlOOH coating exhibited the best‐reported spectral selectivity by wet deposition process, with high absorptance of 0.941 ± 0.004 and low emittance of 0.13 ± 0.02 at room temperature. Furthermore, the multilayer sprayable coating is stable at elevated temperature for a prolong time and therefore, shows promise for application in large scale and on‐site solar thermal facilities.

CNT-Based Solar Thermal Coatings: Absorptance vs. Emittance

“…In our recent studies, CNT coatings were deposited on aluminum and Inconel substrates from solvent-based dispersions [27,28]. Since pipes for solar selective absorbers are usually manufactured from SS, we studied the efficiency of CNT coatings on this substrate as solar selective absorbers.…”

“…Previous liquid formulations developed in our group for solar selective coatings [26][27][28] were directly applied on Inconel or aluminum substrates by spraying. The coatings had a multilayer structure composed of different materials with specific optical properties.…”

Nanostructured Black Aluminum Prepared by Laser Direct Writing as a High-Performance Plasmonic Absorber for Photothermal/Electric Conversion

“…However, considering the practical application, the material cost and preparation rate of products should be further optimized. In addition, a solar absorber material with high-efficiency absorption should have other necessary properties such as good mechanical strength, sufficient plasticity, high thermal conductivity, excellent corrosion resistance, and thermal stability. ,, However, aluminum (Al) and its alloys were widely used in daily life and possess the aforementioned excellent properties, which have great potential for application in high-efficiency solar energy utilization. , …”

Fabrication of Self‐Cleaning CNT‐Based Near‐Perfect Solar Absorber Coating for Non‐Evacuated Concentrated Solar Power Applications

“…[15] As a rule of thumb, a decrease of 10% in emittance is equivalent to an increase of 1% in absorptance at high concentration ratios. [16] Hence, in CSP systems, increasing the value of solar absorptance is more significant than reducing the IR emittance. [15] CNT is the best absorbing material ever produced as stated by NASA.…”