Optical and Thermal Investigation of Selective Coatings for Solar Absorber Tube

Abstract

In this paper three kind of common coatings in solar systems including the matt black painting, black chrome and black nickel-chrome coating were used on the absorber tube of the parabolic trough collector (PTC). These coatings are compared by optical absorbance and thermal conductivity.  Plating chrome and nickel-chrome coatings are carried out at optimal condition for operating temperature, time coverage and cathodic current density. After coating the inside and outside temperature were measured and the thermal conductivity was studied by applying uniform heat flux to the coated absorber tube. The results showed black chrome coating with 98% purity had the highest absorption in the ultraviolet and visible range and the matt black paint had the lowest thermal conductivity. SEM images in the result section show the pore spaces in black chrome cover and prove the high thermal conductivity.