OPTIMIZATION AND ANALYSIS OF SOLAR SELECTIVE SURFACES WITH CONTINUOUS AND MULTILAYER PROFILES

Both continuous and multilayer profiles of solar selective surfaces have been analyzed and optimized. The structure having the highest photothermal efficiency has two uniform absorbing layers with two antireflection layers of different refractive index materials. Interference effects were analyzed in terms of optical path length of the sublayers and their combination. The phase cancellation positions for the optimized multilayer profiles are well distributed in the solar radiation range but do not occur at wavelengths above about 2.5 μm. A study of the electric-field distribution in these optimized profiles has shown that the sharp transition at above about 2.5 μm from low to high reflectance is due to the absence of high filling factor sublayers which can act as an effective reflecting substrate. The selective properties of the optimized multilayer structures are not particularly sensitive to the optimized graded profile for thickness variations of ±20%. © 1995 American Institute of Physics.