A Brief Review on Self-cleaning Coatings for Photovoltaic Systems
01 Jan 2021-pp 197-234
TL;DR: In this article, a brief review regarding the recent progress of bio-mimic self-cleaning coatings on photovoltaic solar systems is presented, and a brief introduction on the types of selfcleaning coating and their properties, such as wettability, optical transparency, mechanical durability, and environmental durability characteristics, is discussed.
Abstract: Solar energy is the most efficient and economic gateway for power generation. The development of solar research and technological innovation, and corresponding decline in the prices of solar power harnessing devices, has paved the way for low-cost energy generation in developing country, India. It is estimated that if at least 10% of the total geographical area are effectively utilized, the available solar energy would be 8 million MW, which is equivalent to ~6000 Mtoe per year (https://www.indiaenergyportal.org/subthemes.php?text=solar). However, installed photovoltaic systems including the solar panels in desert areas and in the industrial areas are prone to the accretion of dust and dirt particles. This resultant fouling hinders the conversion of incident light into electricity, causing a decline in the energy conversion efficiency up to 50%. To maintain a steady performance of PV panels, the surfaces of which must be cleaned regularly. However, current methods of cleaning are expensive, inefficient, and potentially harmful to the surfaces. With recent progress in nanotechnology research, nanostructured coatings have become multifunctional, efficient, and smart. Particularly, self-cleaning coatings have gained considerable attraction owing to its application in a wide range of fields. In this chapter, a brief review regarding the recent progress of bio-mimic self-cleaning coatings on photovoltaic solar systems is presented. A brief introduction on the types of self-cleaning coatings and their properties, such as wettability, optical transparency, mechanical durability, and environmental durability characteristics, is discussed. A short note on the considerations and developments regarding the fabrication of durable, self-cleaning coatings for photovoltaic systems has been presented.
TL;DR: In this article , the authors investigated three commercial coatings for use as self-cleaning glass technologies and investigated optical and thermal properties (reflectivity, absorption, and transmission) for each coating as well as their surface wettability and particle size.
Abstract: Solar panel performance can be impacted when panel surfaces are coated with substances like dust, dirt, snow, or ice that scatter and/or absorb light and may reduce efficiency. As a consequence, time and resources are required to clean solar panels during and after extreme weather events or whenever surface coating occurs. Treating solar panels with chemical coatings that shed materials may decrease the operating costs associated with solar panel maintenance and cleaning. This study investigates three commercial coatings for use as self-cleaning glass technologies. Optical and thermal properties (reflectivity, absorption, and transmission) are investigated for each coating as well as their surface wettability and particle size. Incoming solar radiation was continuously monitored and snow events were logged to estimate power production capabilities and surface accumulation for each panel. In terms of power output, the commercial coatings made little impact on overall power production compared to the control (uncoated) panels. This was attributable to the overall high transmission, low absorption, and low reflection of each of the commercial coatings, making their presence on the surface of solar panels have minimal impact besides to potentially shed snow While the coatings made no observable difference to increase power production compared to the control panels, the shedding results from video monitoring suggest both the hydrophilic or hydrophobic test coatings decreased snow accumulation to a greater extent than the control panels (uncoated). Controlling the wettability properties of the solar panel surfaces has the potential to limit snow accumulation when compared to uncoated panel surfaces.
TL;DR: In this article, it has been shown that for each combination of a solid and a fluid, there is an appropriate angle of contact between the surfaces of the fluid, exposed to the air, and to the solid.
Abstract: It has already been asserted, by Mr. Monge and others, that the phenomena of capillary tubes are referable to the cohesive attraction of the superficial particles only of the fluids employed, and that the surfaces must consequently be formed into curves of the nature of lintearias, which are supposed to be the results of a uniform tension of a surface, resisting the pressure of a fluid, either uniform, or varying according to a given law. Segner, who appears to have been the first that maintained a similar opinion, has shown in what manner the principle may be deduced from the doctrine of attraction, but his demonstration is complicated, and not perfectly satisfactory; and in applying the law to the forms of drops, he has neglected to consider the very material effects of the double curvature, which is evidently the cause of the want of a perfect coincidence of some of his experiments with his theory. Since the time of Segner, little has been done in investigating accurately and in detail the various consequences of the principle. It will perhaps be most agreeable to the experimental philosopher, although less consistent with the strict course of logical argument, to proceed in the first place to the comparison of this theory with the phenomena, and to inquire afterwards for its foundation in the ultimate properties of matter. But it is necessary to premise one observation, which appears to be new, and which is equally consistent with theory and with experiment; that is, that for each combination of a solid and a fluid, there is an appropriate angle of contact between the surfaces of the fluid, exposed to the air, and to the solid. This angle, for glass and water, and in all cases where a solid is perfectly wetted by a fluid, is evanescent: for glass and mercury, it is about 140°, in common temperatures, and when the mercury is moderately clean.
TL;DR: In this paper, the basic concepts and strategies adopted to minimize reflectance of anti-reflective coatings (ARCs) are described in greater detail and state-of-the-art fabrication techniques have been fully illustrated.
Abstract: Anti-reflective coatings (ARCs) have evolved into highly effective reflectance and glare reducing components for various optical and opto-electrical equipments. Extensive research in optical and biological reflectance minimization as well as the emergence of nanotechnology over the years has contributed to the enhancement of ARCs in a major way. In this study the prime objective is to give a comprehensive idea of the ARCs right from their inception, as they were originally conceptualized by the pioneers and lay down the basic concepts and strategies adopted to minimize reflectance. The different types of ARCs are also described in greater detail and the state-of-the-art fabrication techniques have been fully illustrated. The inspiration that ARCs derive from nature (‘biomimetics’) has been an area of major research and is discussed at length. The various materials that have been reportedly used in fabricating the ARCs have also been brought into sharp focus. An account of application of ARCs on solar cells and modules, contemporary research and associated challenges are presented in the end to facilitate a universal understanding of the ARCs and encourage future research.
TL;DR: In this paper, the synthesis of silica nanoparticles, characterization on size-dependent properties, and surface modification for the preparation of homogeneous nanocomposites, generally by sol-gel technique are discussed.
Abstract: Application of silica nanoparticles as fillers in the preparation of nanocomposite of polymers has drawnmuch attention, due to the increased demand for new materials with improved thermal, mechanical, physical, and chemical properties. Recent developments in the synthesis of monodispersed, narrow-size distribution of nanoparticles by sol-gel method provide significant boost to development of silica-polymer nanocomposites. This paper is written by emphasizing on the synthesis of silica nanoparticles, characterization on size-dependent properties, and surface modification for the preparation of homogeneous nanocomposites, generally by sol-gel technique. The effect of nanosilica on the properties of various types of silica-polymer composites is also summarized.
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