Surface modification of porous antireflective coatings for solar glass covers

Preparation of Antireflective Silica Coating by the Sol-Gel Method for Heliothermic Power Plants

“…To produce electricity, either in heliothermic power plants or photovoltaic systems, antireflective coatings play an important role reducing losses due to reflection of sunlight. Calculations have shown that the yearly energy produced in a solar thermal plant, where the temperature of the solar collector fluid is 100°C, can be increased by about 20% with the application of an antireflective coating on the solar glass cover 5 . Heliothermic plants are responsible for the solar irradiation conversion and subsequent use for the production of electricity.…”

“…With the insertion of a porous coating layer it is possible to provide a more gradual transition of light from one medium to another, thus eliminating much of the reflection 6 . The absorber tube (Fig.1) Various materials and processes have been studied for obtaining antireflective surfaces, and silicon oxide (SiO 2 ) obtained by the sol-gel process is the one that provides the best results of reflectance [1][2][3][4][5] . In the sol-gel process is a transition occurs from a sol system to a gel system through the establishment of connections between colloidal particles or polymeric chains with the formation of a three-dimensional solid network 8 .…”

“…Thus, it is possible to have a precise control over the film microstructure, such as surface area, volume and pore size 1,8,11 . The low reflectance of the silica film obtained by the sol-gel process is a result of the porous structure formed during the film deposition; it makes the layer's refractive index achieve sufficiently low values reaching up to zero reflection of light by the surface, for a single wavelength [1][2][3]5 . Different techniques can be employed in production of antireflective films, such as dip-coating, sputtering and spin-coating.…”

“…Different techniques can be employed in production of antireflective films, such as dip-coating, sputtering and spin-coating. Among these the dip-coating technique is the most indicated and used to produce antireflective coatings by sol-gel process, especially when it is required the coverage of large areas or materials with complex shapes, furthermore it has low cost of deployment and operation if compared to the others techniques [2][3]5,9,12,13 . The Federal Center for Technological Education of Minas Gerais (Cefet-MG) was the first in Brazil to develop a project for the creation and operation of a heliothermic power plant.…”

Nanofilme Antirreflexivo De Sílica Confeccionado Pelo Processo Sol-Gel Para Aplicação Solar

“…Na geração de eletricidade através da energia do sol, quer seja em sistemas térmicos de energia solar ou fotovoltaicos, os revestimentos antirreflexivos desempenham um importante papel reduzindo perdas por reflexão da luz. Cálculos mostram que a energia produzida anualmente por uma usina termossolar, onde a temperatura do fluido do coletor solar é 100ºC, pode ser aumentada em até 20% através da aplicação de uma camada antirreflexiva na cobertura vítrea 5 . Diferentes processos e materiais vêm sendo estudados na obtenção de superfícies antirreflexivas, sendo o óxido de silício (SiO2) obtido mediante o emprego do processo sol-gel aquele que apresenta melhores resultados de refletância [1][2][3][4][5] .…”