Characterization of Soiling Bands on the Bottom Edges of PV Modules

Abstract

Soiling of photovoltaic (PV) modules, especially non-uniform soiling, can lead to PV power loss. For example, soiling bands at the bottom edge of framed modules are caused by the accumulation of water and dirt at a lower tilt angle. However, few studies have investigated this issue. In this study, industrial and commercial metal rooftop PV power stations in central and eastern China were investigated, with a focus in Xi’an and Kaifeng cities. The results show that (1) soiling bands were widespread, even in Guangzhou city, where annual rainfall is approximately 1,800 mm; (2) soiling bands were found during every month in Xi’an city, even from July to September when heavy rainfall occurs frequently; (3) three types of soiling bands were observed on modules (rectangular, transverse trapezoidal, and triangular), with double triangular, arch, and shallow U-shape types also being observed in landscape-oriented modules; (4) the mean relative difference of the maximum direct current due to soiling bands between one maximum power point tracking system and its control from June 19 to October 2, 2019 in Kaifeng city was approximately 4.7%.

Effect of non-uniform soiling on solar panel output and revenue analyzed through controlled experiment

“…The collection of soiling and bird droppings, which is strongly associated with the soiling accumulating region (Kazmerski et al, 2017), can also cause this localized overheating hotspot of the PV module. Moreover, during the field research, the entire region covered by nonuniformly distributed deposited soiling and bird droppings revealed a high temperature (Cui et al, 2021). These panel hotspots may cause irreversible damage to the PV system.…”

“…The cleaning water flow is frequently insufficient to move these dust particles, resulting in a constant buildup of dust in various forms near the bottom edges of the PV module. The PV module is often installed in portrait or landscape orientation (Cui et al, 2021;Karthick et al, 2020). Rectangular, triangular, and transverse trapezoidal forms of accumulated soiling band morphologies have been detected at the bottom edge of the PV module (Cui et al, 2021).…”

“…The PV module is often installed in portrait or landscape orientation (Cui et al, 2021;Karthick et al, 2020). Rectangular, triangular, and transverse trapezoidal forms of accumulated soiling band morphologies have been detected at the bottom edge of the PV module (Cui et al, 2021). Partially shading and soiling bands generated at the bottom edges of the PV module restrict incoming sunlight penetration into the solar cells, resulting in a hotspot (AlDowsari et al, 2014).…”

“…These panel hotspots may cause irreversible damage to the PV system. Compared to the non-soiling region, the fixed area covered by accumulated soiling may store some water after cleaning or raining for a long period on the module surface, which can weaken the PV module seal and reduce the PV panel's service life (Cui et al, 2021). Solar farms are planned with row-to-row shadowing panels in mind.…”

Investigation of dust pollutants and the impact of suspended particulate matter on the performance of photovoltaic systems

“…Because dust particles lower and disperse the intensity of the solar irradiation impacting on the photovoltaic modules, as a result, the conversion efficiency is reduced by accumulated dust. It was observed that the rate of dust accumulation on photovoltaic modules depends on a number of factors, like local weather conditions, airborne particle concentration, type and size of particle distribution, composition, shape, and density (Javed e t al., 2017;Cui et al, 2021). Dust accumulation on the surface of any photovoltaic module will depend on the dust type, weather, surrounding environment, PV module characteristics, and installation design (Konyu et al, 2020).…”