Spectrally selective visible and solar transmitting heat barrier coating for flat-plate collector

• Main Author: Muli, Reynaldo C.
• Format: text
• Language: English
• Published: Animo Repository 2002
• Subjects: Solar heating; Optical films; Coating processes; Energy Systems
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/2959
• Institution: De La Salle University

Solar energy is one of the promising alternative sources for the future. The challenge is how to utilize it properly and efficiently. Presently available flat-plate collectors use uncoated glass covers that reflects a considerable amount of light energy that should have been transmitted and converted into heat energy. Spectrally selective coatings on glass covers of flat-plate collectors can reduce the reflected light energy and prevent the escape of infrared energy, thus increasing the collection efficiency of the solar flat-plate collector.The study was composed of four major activities: the design of the antireflection thin-film coating using the Macleod software, the preparation of the substrate and coating materials, the actual coating process using the high vacuum coating machine, and the characterization process using an optical spectrophotometer and the Macleod software.The study concluded that the design and fabrication of the spectrally selected antireflection coating Solar2 successfully reduced the reflectance of the flat-rate collector glass cover and increased its transmittance by nearly 3 percent on the visible band of the spectrum. This will mean an increase of 3 percent of solar energy added to the capacity of a solar flat-plate collector. Low reflection at a single reference wavelength can easily be accomplished with one layer of antireflection coating. However, for a greater bandwidth or a selective spectrum, multiple layers with refined thicknesses of each layer would be required. The 93 percent transmittance of solar energy of the coated Solar2 is equivalent to 12.96 percent increase in collector efficiency if applied on the thermosyphon solar water heater designed and fabricated by Culaba, 1998.