Enhanced high-temperature thermal stability of the novel MoAlSiN-based solar selective absorbing coatings by optimizing the multilayer structure

Abstract

Solar selective absorbing coating (SSAC) plays an important role in the high-temperature concentrated solar power system. The high thermal stability of SSAC above 600 °C has been a big open question for molten salt concentrated solar power projects. In our work, the TiN/Mo/MoAlSiN/MoAlSiON/SiO2 and the TiN/Mo/MoAlSiN/Si3N4/SiO2 SSACs are developed for getting high-temperature thermal stability, besides excellent spectral selectivity. The solar spectral absorptivities of the MoAlSiN/MoAlSiON and MoAlSiN/Si3N4 SSACs are 95.2% and 93.2%, respectively. While the infrared emissivities of the MoAlSiN/MoAlSiON and MoAlSiN/Si3N4 SSACs are controlled below 10.6% and 10.5% at 400 °C, respectively. The novel MoAlSiN/Si3N4 SSAC deposited on quartz can maintain thermal stability even after heat treatment at 800 °C for 200 h in vacuum, which is one of the best results in the research field for high-temperature SSACs. It is found that the choice of suitable materials without oxygen and the elimination of interfacial thermal stress are very important for improving thermal stability. Furthermore, the practical total energy conversion efficiencies of the MoAlSiN/Si3N4 SSAC at 600 °C–800 °C are always above 57%. When the activation energy is assumed as 180 kJ/mol, the estimated service life of the MoAlSiN/Si3N4 SSAC at 600 °C is more than 25 years.