Optical selective coating for solar absorbers

Solar thermal energy is generally accepted as very energy efficient in providing space heating and cooling, desalination of sea water or solar thermal electricity generation. For all these applications, one of the key elements is the optical selective coating for solar absorbers. The process that we developed to produce such multilayered coating for solar thermal absorbers is sol-gel dip-coating; this chrome-free and low-cost process works at atmospheric pressure and temperature. The optical properties of the thin films have been characterized by spectrophotometry and ellipsometry. Coatings deposited on stainless steel substrate exhibit more than 94% of solar absorptance and 11% of thermal emittance at 100°C. These results are particularly interesting since the samples show a very promising durability.