Highly Selective Solar Thermal Sprayable Coating Based on Carbon Nanotubes

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.