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For many years, our consumer society globalization has contributed to intensifying, has demanded products in quantity, quality, and variety, accelerating both a state of dissatisfaction, health concerns, and environmental pollution with no thought given to improving living conditions. There has been a formidable industrial development, which has been growing in installed facilities for the synthesis and manufacture of products that meet various needs. Today, new processes and new products are in the markets to satisfy new needs developed every day, which will test the creativity, innovation, science, and technology, but going to endanger ecosystems, human health, and doubtless going to stress every single person now and in each generation to come.
Given this perspective, in 1997 the governments agreed on the Kyoto Protocol to the UN Framework Convention on Climate Change (UNFCCC), which sets legally binding targets so that, during the 2008-2012 period, industrialized countries reduce 5.2%, on the 1990 levels, the emissions of the main greenhouse gases. There are alternative energy sources, such as sun, wind, wastes, etc., which are renewable every year, do not run out, and also do not pollute the environment, which means a double advantage.
Solar energy is very attractive because it is clean, renewable, affordable, and with lower impact on the environment (Liu, 2016; Carrillo, 2019). The reduction of gases is an advantage of using solar energy. Solar thermal collectors are environmentally friendly and do not pollute as a way to collect energy. The efficiencies of solar thermal collectors have been improved and its absorbent systems or coatings increased the operating and inactivation temperatures (Bagmanci, 2019; Wu, 2019).
Further development of collectors and new applications of solar energy, such as refrigeration and industrial solar heating, are raising the operating temperatures of absorbent materials even further. Since the first collectors, absorbing solar coatings actively have been developing, using advanced designs with improved efficiencies (Bagmanci, 2019).
The degradation processes in solar absorbers are caused by high temperatures, high humidity, water condensation, chlorine, and sulfide. In the case of moisture, corrosion mechanisms have been reported in absorbent coatings on aluminum substrates (Kotilainen, 2014).
The selective coatings are used on black absorbent surfaces to reduce radiative energy losses (Lizama-Tzec, 2019; Thappa, 2020). Such selective coatings require to have a low emittance ε (<0.2) of infrared wavelengths that, combined with the black surfaces that have high solar absorbance α (> 0.9) together, reach higher solar energy harvesting efficiencies. Super absorbent black coatings help us to have better absorption and concentration of solar energy for the different areas where it is intended to be used. The parabolic trough collectors are systems that require selective black absorbing surfaces that receive and transfer the energy (Tzivanidis, 2015).