Aluminium Nitride Doping for Solar Mirrors Self-Cleaning Coatings

Abstract

Soiling severely reduces solar mirror performance, requiring dispendious water consumption for cleaning operations and causing an increase in the levelized cost of energy (LCOE). An emerging technology for facing this problem consists of developing transparent self-cleaning coatings, able to be washed with a small amount of water by virtue of the modulation of surficial wetting properties. Nevertheless, the beneficial effects of coatings decrease in the first year, and coated mirrors show even higher soiling than non-coated ones. Moreover, it is important that coating production processes are economically convenient, consistent with the intended reduction of overall costs. The aim of this work is the research and development of a cheap and scalable solution, compatible with mirror fabrication steps and, in such a sense, economically advantageous. It involves the substitution of the alumina last layer of solar mirrors with more hydrophobic, potentially auxetic aluminum compounds, such as nitrides. In particular, 2D inorganic aluminum nitride thin films doped with metals (such as aluminum and silver) and non-metals have been fabricated by means of reactive sputtering deposition and characterized for the purpose of studying their self-cleaning behavior, finding a trade-off between wetting properties, optical clarity, and stability.

Self-Cleaning Solar Mirrors Coatings: From the Laboratory Scale to Prototype Field Tests

“…This last aspect of the economic evaluation of water saving in ordinary solar field maintenance operations is difficult because each site has its own peculiarities, that make comparison and an absolute evaluation difficult, but which nevertheless allow to draw an indication of the fact that any water saving, especially in desert areas, is always profitable [6]. In a previous work it has been explored the feasibility of changing alumina, that is the most diffuse last layer in all mirror architectures, with AlN compounds obtained by means of sputtering deposition [7].…”

Silver nanoparticles incorporated polydimethylsiloxane nanocomposite film as hydrophobic infrared filters

“…This ability to reflect IR radiation helps to keep solar cells cooler, thereby reducing the phenomenon of thermalization. These films have been implemented in various applications such as surfaces of mirrors, concentrators, solar panels, and other optical components 9 . When selecting an IR reflective film for solar energy harvesting, it is important to consider the film's reflectivity, durability, light transmission, and compatibility with the particular solar energy system 10 …”

“…solar panels, and other optical components. 9 When selecting an IR reflective film for solar energy harvesting, it is important to consider the film's reflectivity, durability, light transmission, and compatibility with the particular solar energy system. 10 Numerous methods to achieve improved solar reflectance have been explored by various researchers, Wang et.al 11 and Ao et.al 12 developed a composite material incorporating PDMS as a matrix for dispersing metal oxides and microcrystal bars demonstrated this capability.…”

Sensing Properties of Metamaterials Utilized as Self-Cleaning Coating for Solar Mirrors

“…In this regards, in a previous work, we demonstrated that it is possible to change wetting properties of solar mirrors applying transparent and auxetic metamaterials on reflectors surfaces by means of scalable processes, with the purpose of reducing water consumption in cleaning procedures [6]. In particular, auxetic nitrides obtained by sputtering deposition on metallized low iron glasses were proposed as selfcleaning solution ideal for back surface mirrors (BSM) [7], while hybrid organic-inorganic nanocomposites, deposited on a lab scale by spin coating and on a pre-industrial scale by spraying, were proposed for front surface mirrors (FSM). Both developed coatings were transparent, hydrophobic, and produced by means of cheap and scalable techniques onto large substrates, as shown in Fig.…”