A highly abrasive-resistant, long-lasting anti-reflective coating for PV module glass

Abstract

More than 4% of incident light is reflected from the front cover glass of photovoltaic (PV) modules. The industrywide trend to cost-effectively increase the efficiency of PV modules has driven the widespread adoption of anti-reflective coated (ARC) glass. The most common deposition methods for these anti-reflective (AR) coatings are wet sol-gel processes, with a small minority of glass manufacturers using vacuum-based sputtering. Most commercial sol-gel coatings consist of single layer porous silica and are highly transmissive across a broad range of the solar spectrum. The mechanical strength of these coatings is generally derived from high temperature treatment during the tempering of the glass. However, as the PV industry increasingly focuses on project levelized cost of electricity (LCOE), PV module manufactures and system owners are seeking ARC glass with increased durability and long-term performance, particularly for systems operating in medium to high soiling environments, where PV modules are subjected to airborne particle abrasion and repeated washing. In this work, we report durability test results for a new, low temperature curable sol-gel AR coating from Enki Technology, showing significantly improved abrasion-resistance compared to more traditional AR coatings. The new coating is denser than the traditional coatings and chemically derives its abrasionresistance at relatively low process temperatures without sacrificing the optical performance. The samples under test in this work were subjected to extensive testing following the industry-standard abrasion test method in EN1096.2 and accelerated environmental test procedures in IEC61215. Our results show increased coating longevity for the new coating, up to four times greater than existing coatings with comparable optical performance. This increased mechanical strength directly translates to reduced risk of handling during manufacturing and installation, lower O&M costs, increased energy yield and reduced warranty costs.

Sandstorm erosion testing of anti-reflective glass coatings for solar energy applications

“…Like at the lower velocity, the sample AR4 performs the best. Similar results were obtained by Pop et al [25] who investigated the durability of AR coatings for PV modules when subjected to abrasion. The coating developed by their group did initially perform worse than a traditional one but did show a higher durability leading to a transmittance gain in 7 out of 10 outdoor test site campaigns.…”

Recent advances in the mechanical durability of superamphiphobic surfaces: A review

“…Apart from anti-wetting properties, glass should also have good anti-reflective properties so that it can be effectively used in various solar applications. For example, in the case of photovoltaic (PV) panels, low-iron content glasses are used, which has a reflectance of 8-10% 200 in the visible region of an electromagnetic spectrum, which decreases the effectiveness of incident light and therefore, the overall efficiency of the system is affected. 201 Mechanical abrasions due to deposition of dust and foreign particles also decrease the efficiency of the system by degrading transmission of light.…”

Non-destructive Characterization of Anti-Reflective Coatings on PV Modules

“…Single-layer ARCs based on porous silica often have tradeoffs between performance and durability [13], [14]. While coating performance improves as the porosity increases, higher porosity can result in lower coating hardness and wear resistance [9], [15]. Although coating manufacturers use a number of stress tests and technical solutions to develop better coatings [14], [16], third-party module reliability testing programs do not measure ARC longevity [17].…”

“…Many prior studies have used optical techniques to quantify coating performance [18]- [21]. Other work tested ARC longevity under artificial or natural aging [10], [13], [15]. Most of this work uses glass coupons and optical transmittance measurements, a straightforward and reliable method, but one that is not applicable to assembled modules.…”