High temperature optically stable spectrally-selective Ti1-xAlxN-based multilayer coating for concentrated solar thermal applications

Abstract

Abstract Spectrally-selective solar absorbing coatings based on the Ti1-xAlxN system were deposited using DC magnetron sputtering. Due to their refractory nature and very suitable optical properties, these were considered for high temperature solar thermal energy conversion. The composition of Ti1-xAlxN, (effectively, the Ti/Al ratio) was optimized to achieve a maximized solar absorptance. The optimum composition was then tested in a tandem absorber which included anti-reflective layers. A stainless steel substrate was used in order to simulate service in parabolic trough-based power plants that use stainless steel pipe to carry the heat-transfer fluid. High temperature annealing of the stack caused structural modifications but the solar absorptance of 92% was retained even after annealing at 900\u202f°C.