Anti-soiling coatings for solar cell cover glass: Climate and surface properties influence

Abstract

The objective of this study has been twofold: i) to investigate different strategies for CPV module glass surface modification, in particular preparing hydrophilic and hydrophobic coatings in order to reduce the dust accumulation (soiling) on the module surface; ii) to perform a joint comparative soiling testing in Italy, Spain and Brazil in order to understand the limit and advantages of the proposed anti-soiling coatings in different climate condition. Two TiO 2 /SiO 2 films with different titanium content have been synthesized and benchmarked against pure TiO 2 in relation to transparency and hydrophilicity. Moreover, a hydrophobic antireflective material based on functionalized-SiO 2 thin film was also investigated. All these coatings have been deposited over low iron float glass substrates by sol-gel dip-coating and electron-beam evaporation technique. TiO 2 /SiO 2 and functionalized-SiO 2 films showed higher transmittance in visible range than pure TiO 2. TiO 2 /SiO 2 films showed a persistent superhydrophilic character with water contact angles near to 0°, while functionalized-SiO 2 presented hydrophobic property. The joint comparative soiling tests showed the importance of setting anti-soiling strategies in region characterized by more dry climate: in Brazil, which during the soiling test was characterized by a long dry period, the anti-soiling coatings were effective in reducing the soiling deposition and in the removal of the contaminants by rainwater; in Spain and Italy, the more frequent rain precipitation made the soiling effect less relevant, however, the deposition of anti-soiling coating on the module cover glass allowed to fully recover the initial transmittance after rain washing. A chemical and mineral characterization of the soiling has been carried out revealing the dependence of the contaminants from the environment conditions (e.g. car traffic, presence of industries, amount of rain and local minerals in the ground).

Water Saving in CSP Plants by a Novel Hydrophilic Anti-Soiling Coating for Solar Reflectors

“…Coatings 2019, 9, x FOR PEER REVIEW 2 of 10 of application [8]. Solar energy applications are also taking advantage of the efficiency increase over time, due to the soiling reduction in the optical surfaces through this kind of coatings [9], mainly in photovoltaic technology [10][11][12] but also more recently in CSP plants [13][14][15]. For CSP applications, anti-soiling coatings are applied both to the glass tubes of parabolic-trough collectors and to solar reflectors of all different concentrators.…”

Soiling Effect Mitigation Obtained by Applying Transparent Thin-Films on Solar Panels: Comparison of Different Types of Coatings

“…In another studies of de Jesus, SiO 2 sol-gel treated with hexamethyldisilazane (referred to as SM) resulted in a hydrophobic thin film [ 35 ]. In comparison with their previous TiO 2 /SiO 2 composite, it had much higher transparency, which is even superior to the bare glass ( Figure 8 ).…”

“… Transmittance spectrum for uncoated glass plate and glass with the layer of hydrophobic film (SM), hydrophilic Si 86 Ti 14 (ST1), hydrophilic Si 40 Ti 60 (ST2), and pure TiO 2 (T) [ 35 ]. …”

Transparent and Self‐Cleaning Surfaces Based on Nanocomposite Sol‐Gel Coatings

“…However, most contributions have studied the self-cleaning properties in laboratory conditions, [13][14][15][16] while only few ones have investigated the performances of self-cleaning coatings by testing them in atmospheric outdoor conditions. Magnum et al [17] have reported the preparation of anti-soiling coatings composed by superhydrophilic/hydrophobic thin films tested in different locations (Brazil, Italy, and Spain) in out-door conditions. The best performances were obtained with TiO 2 -SiO 2 composite film, which showed a persistent superhydrophilic character with water contact angles near to 0°and transmittance losses of 50 %.…”