Testing of advanced selective black coating in a prototype of solar water heater

The development of selective coating in solar absorbers is required for higher photothermal energy conservation. Hence, a promising process for producing such an efficient selective coating is the electrolytic coloring of anodized aluminum. It comprises the electrodeposition of tin nanoparticles in the outer porous surface layer of an aluminum strip. In this work, the aluminum surface was anodically anodized in H₂SO₄ and colored with tin. In the coloring step, tin was electrodeposited from sulfate salt-based electrolyte to give a black layer on the aluminum surface. In this research, the scaling up of an advanced black coating in a prototype of a solar water heater was investigated. Realization of practical heating efficiency is performed by constructing and testing two prototypes of a solar water heater. The tested solar absorber was prepared by electrolytic coloring of anodized aluminum after one step of anodization. The other type is prepared by coloring aluminum strips with commercial black paint for comparison. The highest observed temperature of the outlet water was 82 °C for the anodized type. However, the highest temperature for black paint was 62 °C. Furthermore, at 750 W/m² of maximum solar intensity, the black anodized absorber has a higher heating efficiency of 72.3%, while the other kind decreased to 61.3%.