Selective properties of high-temperature stable spinel absorber coatings for concentrated solar thermal application

In concentrated solar thermal (CST) system, receiver tube is one of the key important elements in the photothermal conversion process. The high photothermal efficiency of the receiver tube greatly depends upon the coating type, angular selectiveness of the coating, and radiative, conductive and convective losses. Apart from the efficiency, cost-effectiveness of the components is the major hurdle for the CST system to make it a viable technology. In this regard, we have implemented wet-chemical based spinel absorber coatings in a tandem layer approach to make the coating more selective in terms of high absorptance (95%), low emissivity (13%) and wide angular selectiveness (0 to 60 degrees). The coatings are tested for thermal stability and corrosion resistance to check their stability in open-air atmosphere condition. Further, the photothermal conversion efficiencies of the developed coatings are calculated at different temperatures ranging from 300 to 500 degrees C by considering the actual thermal emissivity values of the absorber coating at that particular temperature.