Revealed degradation mechanisms in the HSA CSP coatings through accelerated testing and materials characterization enable absorber service life prediction.
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.
A near‐perfect black solar absorber made of carbon nanotubes (CNTs) prepared by a low‐cost wet‐deposition method on a reflective metal surface for mid‐temperature non‐evacuated concentrated solar power (CSP) applications is demonstrated. The dispersed CNTs in an alumina–silica matrix exhibit an absorptance of 0.985 in the entire solar spectrum and emittance of 0.90 in the infrared (IR) region. The coating shows high durability and is super‐hydrophilic (0° contact angle) after plasma treatment, without affecting the solar absorptance and excellent coating adhesion. The efficiency of the coating is evaluated by analytical models, which implies that it has higher efficiency at low temperature and at a high solar concentration ratio than that of previously reported selective coatings.
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