Electrodeposited and Sputtered Selective Coatings for Solar-to-Thermal Energy Conversion

In this work, we report on the deposition and characterization of selective coatings for solar-to-thermal energy conversion systems for applications of low to medium temperatures. Both sputtering and electrodeposition were used to deposit the layers of typical multilayer coatings. The completely electrodeposited selective films consist of an infrared reflecting nickel interlayer on stainless steel, and a black nickel solar absorber material. An alumina/molybdenum/alumina (AMA) multilayer absorber material was deposited by sputtering on stainless steel and copper with electrodeposited nickel (Cu/Ni). The optical properties of the films were studied as a function of the thermal treatment and were compared with similar selective coatings with sputtered alumina as antireflective coating. The films were thermally treated and characterized by reflectance spectroscopy, FESEM, DSC, XRD, profilometry and Raman measurements. Finally, we report on the scale-up of these films, and the results obtained on individual fin collectors showed that our selective coatings exhibit a performance close to the benchmark coating in the market.