Abstract: The dirt deposited on the surface of the solar collector tube directly affects the light transmittance, and then affects the heat collection efficiency of the vacuum tube. In this paper, a SiO₂ coating was applied on the outer tube of a solar vacuum tube by sol-gel method. The results show that the coating has both anti-reflection and anti-fouling properties. The vacuum tube anti-reflection and self-cleaning functions were integrated, making the transmittance of the glass cover tube reach 96% in the sunlight range (300nm to 2600nm).

Key words: solar collectors, heat collection efficiency, AR coating, sol-gel, transmittance