Carbon Nanotube Dry Spinnable Sheets for Solar Selective Coatings by Lamination

Abstract

Carbon nanotube, oriented free standing sheets can be laminated on any surface as selective solar absorbers while simultaneously dry spun in a highly controlled process from vertically oriented forests grown by CVD. We have found that properties of a CNT forest strongly correlate with the optical transparency and reflectivity of CNT sheets required for solar selective coatings and can be properly tuned for optimal coatings for solar collectors. We study absorptive and emissive properties of CNT sheets that are laminated by a simple automated and controlled process, developed for coating of cylindrical glass tubes for evacuated solar collectors (ETC). The advantages of Joule heating of CNT coatings are demonstrated and test results described, showing a unique property of fast heating as compared to slow heating in conventional solar water heaters.