PERFORMANCE AND CHARACTERISTICS OF AL-PBS/SNO2-F SELECTIVE COATING SYSTEM FOR PHOTOTHERMAL ENERGY-CONVERSION

Thin films of SnO2:F (a transmitting selective surface) and PbS (a selective absorber) are evaluated in this study. The coatings are prepared by a spray pyrolysis technique. SnO2:F is prepared on glass slides at a temperature of 400°C, with a thickness of 0.6 μm while PbS is prepared on aluminium substrates at a temperature of 250°C with a thickness of 0.9 μm. Properties of each surface are investigated separately. SnO2:F films showed 90% optical transmission at solar maximum (550 nm) and high infrared reflectivity indicating that the film is a good heat mirror with low sheet resistance of 3 ω/□. Chemically deposited PbS films on chemically etched aluminium substrate have high absorptance (α = 0.92) in the visible spectrum and small thermal emittance (ε{lunate} (100°C) = 0.12). This indicates the film is a good solar selective surface. Comparison studies of the stagnation temperature of different absorbing systems showed some improvement related to the transmission selective properties of the tin oxide film. Such an improvement can be more pronounced with high temperature collectors where radiative losses are greater. © 1990.