Characterisation of Dust Particles Deposited on Photovoltaic Panels in the United Arab Emirates

Abstract

The United Arab Emirates (UAE) experiences up to 50% power losses in photovoltaic (PV) panels caused by frequent dust accumulation over the panels trailed by extreme temperature. Compositional and morphological insights into dust particle can potentially help design PV cleaning mechanisms inclusive of self-cleaning explored in the current article. Five different locations were studied to discover potential differences in dust samples. The collected samples were characterised employing Optical Microscopy, Scanning Electron Microscopy (SEM), X-ray Powder Diffraction (XRD), and Elemental Composition Analysis (Energy Dispersive Spectrometry, EDS). The micrographs revealed that the majority of particles were irregularly shaped, providing interlocking for the dust to stay over the surface. The particle size ranged from 0.01 to 300 µm, and some of the collected dust exhibited cavities. XRD analyses revealed variations in the chemical composition among the samples studied. Elemental Composition Analysis via EDS revealed both consistent patterns and variations in element presence among the dust samples, highlighting specific detections of chlorine (Cl) at some sites.

1. Introduction

The photovoltaics (PVs) are rapidly being integrated into the energy mix globally and more specifically in the Middle East context in a bid to limit the impact of global warming and safeguard the environment. However, the Middle East being predominantly a desert climate witnesses severe dust accumulation over PV panels, thereby leading to significant power losses. Dust, classified as any particulate matter with a diameter of less than 500 µm, originates from a range of sources including wind-borne dust, vehicular exhaust, volcanic eruptions, and air pollution. It can contain various substances such as pollen, fungi, bacteria, vegetation, microfibers, and most commonly, organic minerals such as sand, clay, and eroded limestone [1]. Darwish et al. emphasises the importance of creating a comprehensive model to understand how different types of dust affect solar panel performance, considering various pollutants and PV technologies, particularly focusing on key pollutants like limestone, ash, red soil, calcium carbonate, silica, and sand [2].

Mehmood et al. investigated dust composition on samples collected from PV modules in Dhahran, Kingdom of Saudi Arabia, through scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS), XRD, UV-visible spectroscopy, Dynamic Light Scattering (DLS), and Fourier Transform Infrared Spectroscopy (FTIR). The results revealed the presence of Na, K, Mg, Ca, O₂, Si, and Fe in dust particles and locally scattered white dense regions on the surface [3]. Javed et al. characterised dust collected from PV panels in Doha, Qatar, over a ten-month period employing X-ray Florescence (XRF), XRD and SEM. The authors determined the dust composition, dust accumulation rate (DAR) and the Cleanness Index Change Rate (CICR) indicative of PV power output degradation due to soiling. The results revealed the presence of Ca, Si, Fe, Mg, and Al in descending order which provides insight to devise effective soiling mitigation technologies [4]. Hachichi et al. investigated the impact of dust on the performance of PV systems in Sharjah, UAE, under indoor and outdoor conditions. They established a general correlation between soiling loss and the degradation of PV performance [5].

The impact of atmospheric particulate pollutants and dust deposition on PV module power generation has been investigated experimentally. Results reveal that both types of dust deposition reduce power generation efficiency, with atmospheric dust having a greater impact. A correlation equation is derived for power efficiency reduction due to dust deposition, and a link between solar radiation decrease and atmospheric PM2.5 concentration is established, underscoring the combined impact of particulate pollution on PV module performance [6]. Another study conducted in Isfahan, Iran, highlights factors influencing dust accumulation and its effects on glass transmission. Results show up to 25% reduction in transmission coefficient due to dust accumulation, proposing a generalised equation that relates transmission reduction to dust density for various regions and weather conditions [7].

An experimental setup investigated dust accumulation’s impact on PV modules, with analysis, optical, and electrical experiments conducted using natural dust. The results highlight the substantial reduction in transmittance (35.0%) compared to reflectance (1.1%) due to shading effects, which lower electron–hole pair generation, ultimately reducing power output. The proposed “dust layer” concept explains the decrease in short-circuit current, underscoring the need for accurate dust deposition monitoring to optimise cleaning strategies for efficient PV module operation [8]. Another research reviewed the impact of dust on PV system performance, addressing its lesser-known significance and providing a framework for understanding dust settling, assimilation, and potential mitigation measures. Mani et al. reported a PV power loss of up to 17% due to dust deposition on PV modules in Kuwait City after only six days of dust exposure [9]. Another study assessed efficiency losses in polycrystalline silicon modules due to industrial dust deposition. Various dust types from different industries were analysed, and outdoor experiments with covered and clean modules were conducted to compare performance. Efficiency loss, up to 64%, varied based on dust type, with coal dust having the highest impact due to its absorptivity. Finer dust particles showed greater efficiency reduction, and rising temperatures further deteriorated performance. The research highlights the significant economic implications of dust-induced power output drop in large-scale solar power plants [10].

Solar PV cell performance is influenced by factors such as dust, soiling, humidity, temperature, and wind, which can lead to significant power reduction of up to 60–70%. A previous study [11] examined these effects, presented advanced mitigation approaches, and proposed a comprehensive guideline to optimise solar PV cell performance, accounting for various environmental and operational challenges. In another study, Athar et al. compares seven dust samples under varying radiation levels (650, 750, and 850 W/m²) and weights, revealing substantial reduction in solar PV system efficiency due to dust accumulation. The research confirms that even a thin layer of dust significantly diminishes power output, with the smallest particles blocking sunlight, leading to up to 60% efficiency reduction in desert regions with abundant sunlight potential [12]. The experimental evaluation of a PV module system was conducted under fixed and variable loads using five dust types indoors, with constant solar radiation of 600 W/m² by [13]. Notably, the load current reduction reached up to approximately 95.9%, with significant variations observed among different dust types and densities, impacting both load current and power, presenting crucial findings for system performance. Another study [14] explains that the efficacy of PV panels in electricity generation is notably hindered by the accumulation of dust, diminishing solar radiation that reaches the cells and shortening their lifespan through corrosion. The size, structure of deposited dust, environmental factors, and lack of removal schedules influence PV system efficiency. Innovative passive and advanced cleaning technologies offer efficient solutions, while interdisciplinary approaches involving physics, impact analysis, machine learning, and thermal conductive coatings can optimise solar–wind hybrid systems, ensuring sustained power generation and reduced loss due to dust deposition. The research in [15] analyses dust effects on solar PV stations in Sichuan’s Ganzi region. SiO₂ and CaCO₃ are identified as primary dust phases, with unique trace elements like Rb, Y, and Sr. Microscopic examination reveals disorderly distributed nano- and micro-particles with pores. Computational simulations show uneven dust accumulation from back to front rows of PV panels. The findings provide insights for clean management of PV power plants in low latitude, high altitude plateau areas. The study in [16] investigates the impact of dust accumulation on PV modules at the American University of Sharjah, UAE, over a 15-week period in the summer of 2018. A custom setup collected dust samples from outdoor panels, and various analytical techniques were employed to characterise the dust’s morphological and elemental properties. The results indicate that the dust particles are rich in carbon, oxygen, calcium, and silicon, suggesting the presence of silica and calcite. UV–Vis spectroscopy revealed a 30% decrease in transmittance after 15 weeks of soiling. The findings are crucial for developing effective self-cleaning techniques for PV modules in Sharjah.

Another study by [4] in Doha, Qatar, investigated dust accumulation on PV panels over ten months. Characterisation techniques, including particle size analysis, XRF, XRD, and SEM, were employed. The cleanness index changes rate (CICR) showed a strong negative correlation with the dust accumulation rate (DAR). Calcium dominated the elemental composition, with calcite, dolomite, and quartz as the primary minerals. These data provide essential insights for understanding and mitigating the impact of dust on PV performance in arid climates. The research in [17] investigates PV power losses due to soiling in Lahore, Pakistan, considering variable tilt angles and manual vs. automatic cleaning methods. The soiling rate for 30° tilted panels was consistently around 0.8% per day, one of the highest reported in South Asian and Gulf regions. Dust accumulation rates were recorded at per day for panels fixed at 30° tilt. Dust composition, analysed through SEM, XRD, and EDX, revealed high carbon and quartz contents attributed to air pollutants.

Another study in [18] investigates the impact of different dust components on the performance of PV cells in Sohar, Oman. The collected dust, primarily consisting of sand (65%), cement (5.25%), gypsum (4.94%), ash (4.92%), and other components, was analysed. The study finds that while most dust components have limited effects on the current of the PV cell, they noticeably influence the cell voltage. The decrease in power generation is particularly evident with ash, cement, and new garments, with sand having the most significant impact. Iron powder and red sand were found to have the least effect on the PV cell’s performance.

To address the adverse effects of dust on the efficiency of PV systems, the present study extensively examined dust particles across five distinct sites in the UAE. The primary objective was to comprehend the composition and variations among the dust types prevalent in the region. The findings from this investigation are crucial for the development of targeted and efficient cleaning strategies, as well as the design of specific soiling mitigation technologies tailored to the unique climatic conditions of the UAE. By understanding the characteristics of dust in this environment, this research aims to minimise power losses in PV systems, providing valuable insights for the optimisation of solar energy generation in the region.

2. Materials and Methods

This investigation involves dust samples collected from five distinct locations in Mohammed bin Rashid Al Maktoum Solar Park. This park spreads over a total area of 77 km² in Saih Al-Dahal, about 50 km south of the city of Dubai, UAE. It is situated in the arid desert region of Dubai, UAE, where sunlight is abundant. It is one of the world’s largest solar parks, with a planned capacity of 1013 megawatts, designed to expand further. The park employs various solar technologies, including PV panels and concentrated solar power systems, to convert sunlight into electricity. The park significantly contributes to reducing carbon emissions and promotes sustainable energy in Dubai. It often incorporates innovative technologies for optimising solar energy production in a desert environment, such as dust mitigation strategies and advanced tracking systems. The dust samples were collected in the month of October from five specific locations within the park: the ground surface of the outdoor test facility (GT), the ground surface of the 13 MW plant (GS), the panel surface of the 13 MW plant (S), the panel surface of the outdoor test facility (T), and the rooftop panels at the outdoor test facility (R). The description of the five locations are provided in

Table 1. Description of the characterised samples from the Solar Park, Dubai, UAE.

Sample Name *	Description
GT-10	Ground surface of the outdoor test facility. It is located near the building of indoor labs and offices. This area is partially paved, resulting in lesser dust deposition compared to the main power plant.
GS-10	Ground surface of the 13 MW plant. This area exhibits a higher concentration of sand and larger particles, particularly rich in silicate content.
S-10	Panel surface of the 13 MW plant. In a solar power plant environment, fine particles transported by air currents tend to settle on the surfaces of photovoltaic (PV) panels, making the panel surface of the 13 MW plant more prone to dust deposition.
T-10	Panel surface of the outdoor test facility. Due to the paved ground surface of the test facility, the panel surface is less susceptible to dust compared to the panel surface of the 13 MW plant.
R-10	Rooftop panels at the outdoor test facility. Being installed at the rooftop, these panels primarily attract only smaller or fine particles for deposition.

* This indicates the location, while number 10 represents the month of collection.

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The purpose of this investigation was to identify potential variations in the dust samples from these different locations in the Solar Park and gain insights into their respective compositions and characteristics. Optical images of the collected dust samples were acquired using an optical microscope with suitable magnification and resolution. Images were captured for both the PV surface dust samples and the ground dust samples from each site.

The morphology of the dust sample was characterised using SEM by visual inspection of the surface topography of materials at high magnification. In this study, a JCM-5000 SEM was operated under high vacuum conditions (10⁻² Pa) to ensure a stable and fine electron beam. The sample was prepared by fixing it onto the top of the specimen block with conductive tape, and excess dust particles were removed by blowing air onto the sample surface.

The chemical composition of the dust sample was investigated using XRD to identify the crystal structure and phase composition of the dust materials of each dust site sample. The diffracted peaks were converted into d-spacing and subsequently compared to standard reference d-spacing patterns database to identify the mineralogical composition of the dust sample.

Elemental composition analysis was conducted through EDS. The selected technique allowed for the identification and quantification of the elements present in the dust samples. The instrument recorded the X-ray emission spectra from the samples, capturing the characteristic X-ray peaks for different elements. The collected data were then analysed to identify the presence of elements and their respective peak intensities.

Overall, the combination of Optical Microscopy, SEM, XRD, and EDS provided valuable insights into the visual appearance, morphology, crystal structure, phase composition, and elemental composition of the dust samples. These findings contribute to a deeper understanding of the characteristics of dust on PV panels and the surrounding environment, aiding in the development of effective cleaning and maintenance strategies for PV facilities.

3. Results and Discussion

3.1. Optical Microscopy

The optical images obtained from the dust samples present several intriguing findings.

The dust collected from the surfaces of PV panels exhibits a distinct colour that differs from the colour of the ground sand at the same site. This visual dissimilarity suggests that the dust on the PV panels might have unique origins or compositions compared to the surrounding ground dust.

Despite variations in the locations from which the PV surface dust samples were collected, there is a remarkable uniformity in their colour. This consistency in colour across different sites indicates that the dust on the PV panels possesses a consistent composition, regardless of the specific site of collection.

Conversely, the ground dust samples gathered from each site display a diverse range of colours. The varying colours of the ground dust grains suggest the presence of different compounds across these samples, hinting at possible variations in their sources and compositions.

The existence of multiple colours in the ground dust samples, as shown in Figure 1, sparks interest and highlights the need for further investigations. This diversity in colours could be indicative of a wide range of compounds in the dust, making it an intriguing subject for deeper analysis. Some compositions might interact with the polymer top cover on the PV panels, leading to potential effects on their performance and functionality. Moreover, tainted compositions may not respond effectively to conventional cleaning agents, necessitating tailored cleaning approaches based on the specific dust characteristics [19].

To gain a comprehensive understanding of the dust samples, XRD analysis was conducted to discern the phases present in the dust. The XRD study allowed us to identify the crystalline structure and phase composition of the dust materials, providing valuable insights into their properties.

Remarkably, despite the variations in the collection sites, the dust samples collected from the PV panels exhibited a consistent composition. This consistent indication of the same composition across different locations within the PV facility offers valuable information. It suggests the possibility of devising a unified approach for PV cleaning that would be effective across various sites. To enhance our knowledge and precisely quantify the degree of homogeneity or deviation across the dust samples, it would be highly desirable to analyse the samples throughout the entire year. Such longitudinal studies would enable us to observe potential seasonal variations and gain a comprehensive understanding of the dynamics of dust accumulation on PV panels.

Finally, the optical images have revealed fascinating insights into the colour and composition of the dust samples, both on PV panels and the surrounding ground. These findings present exciting opportunities for further research to optimise PV cleaning methods and enhance the overall efficiency and performance of PV systems across different locations.

3.2. Dust Chemical Composition (XRD Characterisation)

X-ray diffraction (XRD) was employed to determine the chemical composition and crystal structure of materials, including dust particles. The XRD methodology for determining chemical composition begins with the preparation of the sample. The material of interest is finely ground into a powder and then typically pressed into a thin disc or mounted on a sample holder. X-rays are emitted from a source and directed onto the sample. When these X-rays interact with the crystal lattice of the sample, they undergo diffraction, producing a distinct diffraction pattern on a detector. The collected data, consisting of angles and intensities of the diffracted X-rays, are then analysed to identify crystallographic planes and the arrangement of atoms in the crystal lattice. This information is crucial for determining the phases present in the sample. The diffraction pattern is often compared to a database of known crystal structures to aid in phase identification. Quantitative analysis can be performed by examining the intensities of the diffraction peaks, allowing for the determination of the relative amounts of different phases. While XRD provides insights into the crystal structure and phases, it is often complemented by other techniques, such as Elemental Composition Analysis via EDS, to achieve a more comprehensive understanding of the material’s chemical composition. For the current analyses, the investigation into the structural properties of the collected samples was conducted with precision using an X-ray diffractometer employing Cu Kα radiation (λ = 1.54 Å). The meticulous diffraction pattern acquisition was executed under specific conditions: a tube current of 30 mA and a target voltage of 40 kV. The scanning parameters, encompassing a range of 2θ values from 5° to 70° (2θ) min⁻¹, were calibrated with a scan speed of 2° (2θ) min⁻¹ to ensure comprehensive coverage of all significant diffraction peaks. Identification of XRD diffraction peaks for the collected solids was based on a rigorous adherence to the theoretical intensity of the three most eminent peaks characterising the respective minerals in their pure state [20,21].

Figure 2 shows the XRD patterns for the five dust samples. Figure 3 shows the outcomes of the XRD analysis conducted on these samples collected from the mentioned geographical locations.

Based on the XRD characterisation results, the dust samples collected from the five locations have different chemical compositions. The XRD analysis depicted in Figure 2 affirms the ubiquity of calcium carbonate (calcite) across all samples, substantiated by the intensity of the most distinguished peak associated with calcium carbonate minerals in their pure state. Silica (SiO₂) was consistently observed in all samples, except S-10. The presence of dolomite (CaMg(CO₃)) in samples S-10, GT-10, and GS-10 is noteworthy, whereas titanium oxide (TiO₂) was selectively confirmed solely in samples GT-10 and GS-10. Sulphate components, exemplified by Anhydrite (or Gypsum), were exclusively located in sample R-10, and the presence of Hypermangan (KMnF₄) was discerned in a singular sample, namely S-10. The minimal composition observed in sample T-10, characterised by the exclusive presence of calcium carbonate and trioxidosilicate components, is of significance. Conversely, samples GS-10 and GT-10 exhibited a diversified array of components, as evidenced by the intricate patterns observed in the XRD analyses. The results in Figure 3 confirm the presence of diversity of the phases across different locations even though the dust was collected from the PV surface which provides a point of departure from the Optical Microscopy results. As can be seen, all the samples contained calcium carbonate and silicon oxide regardless of the site; however, each individual site further possessed unique compositions containing Magnesium Sodium, Aluminium, Titanium and Rubidium in compositions of Carbonates, Silicates and Oxides. However, calcium carbonate and silicon oxide are the predominant compounds in all locations. In another research [22], XRD analysis of dust samples from South Africa revealed a molecular composition potentially comprising quartz (SiO₂), quartz-a (SiO₂-alpha), calcite (CaCO₃), iron oxide chloride (FeOCl), kaersutite (Al₂Ca₂Mg₆NaO₂₄Si₆), and mantienneite (Al₂FeH₃₃K_0.5Mg₃O₃₄P₄Ti).

Further research is needed on the interaction between sand particle composition/morphology, PV surface morphology, wind speed, and relative humidity to help devise suitable cleaning technologies specific to UAE weather environmental conditions.

3.3. Dust Particle Morphology (SEM Characterisation)

The samples were imaged at various magnifications ranging from 500 µm to 10 µm to ensure an in-depth analysis of the particles described below.

3.3.1. Dust T-10

Figure 4 depicts SEM micrographs representing dust particles identified as T-10. The micrographs illustrate varying sizes and morphologies of the dust particles, characterised by irregular shape distribution and rough surfaces. Some particles exhibit an oval shape while others present a square or rectangular shape. The particle size ranged from 0.01 to 30 µm, with a Gaussian distribution centred around 15 µm, and a higher concentration of medium-sized particles. The SEM micrographs reveal the presence of small cavities, with other areas mainly composed of closely packed dust particles. Observations of the magnification at 10 µm suggest that larger particles are predominantly covered and surrounded by smaller particles, measuring less than 5 µm.

The presence of small cavities and closely packed dust particles revealed by SEM micrographs suggests that these particles may be cohesive, potentially due to electrostatic forces, and could possibly form aggregates. Furthermore, the observation that larger particles are mostly surrounded by smaller particles (<5 μm) suggests that there may be a size-based sorting mechanism in place, whereby smaller particles tend to accumulate around larger particles.

3.3.2. Dust S-10-22

Figure 5 presents the SEM images of dust particles sample S-10. In comparison to T-10, the particles in S-10 exhibited a more compact arrangement. The SEM images reveal that the particles display different sizes and morphologies with irregular shapes and rough surfaces. Some of the shapes identified include square, rectangular, spherical, and cylindrical, while the majority of the particles are irregular in shape. At 500 µm magnification, the cavities observed for the sample are less prominent than those seen in the T-10 sample. The particle size distribution ranges from 0.01 to 30 µm with the Gaussian distribution centred around 10 µm, with a greater number of small-sized particles observed. The analysis of the 10 µm micrographs shows that larger particles are mostly covered with and surrounded by several smaller particles (<5 µm).

3.3.3. Dust R-10

Figure 6 presents the SEM micrographs of dust particles identified as R-10, which reveal a distribution of irregularly shaped particles with few closely packed particles and some irregular-shaped cavities. The majority of the particles exhibit an irregular shape resembling spheres, ovals, or ellipses, and the surfaces of the dust particles can be characterised as rough. The dust particles exhibit a wide range of sizes and morphologies, with the majority of the particle size falling within the 0.01–30 µm range, and a Gaussian distribution centred around 10 µm.

Further analysis of the micrographs at a magnification of 10 µm reveals that the larger particles are typically surrounded by several small features measuring less than 5 µm in size. This observation is noteworthy, as it suggests that the small features may play a role in the physical behaviour and properties of the dust particles.

3.3.4. Dust GS-10

Figure 7 shows the representative SEM micrographs of dust sample GS-10. The particles are of various shapes with different morphologies. On comparison with the previous particles, the main noticeable differences are that the particle size is much larger in GS-10, the surface is smoother, and the particles are brightly illuminated compared to previous samples, thereby indicating increased reflection of light. The particles resemble a stone-like structure with some of the larger particles comprising cavities. Different shapes observed are elliptical, oval, spherical, and rectangular, with smooth edges. The particle size ranges from 30 to 300 µm, with the Gaussian distribution centred around 100 µm. A high proportion of the particles is either small or large sized. On closer examination of the particles (magnification 20 µm), the surface appears to be slightly rough. The particles are very closely packed. This densely packed arrangement could suggest that the particles were transported together as a mass, and they settled at the site in close proximity to each other.

3.3.5. Dust GT-10

The SEM images presented in Figure 8 depict the characteristics of dust sample GT-10. It is noteworthy that all the observed particles are either small or medium sized. The images indicate that the dust particles exhibit variations in size and shape, with a predominantly regular distribution in shape and smooth surface texture. However, a small fraction of the particles has an irregular shape.

The particles can be broadly categorised into oval, elliptical, square, and rectangular shapes, resembling stones with smooth surfaces. On closer examination at higher magnification, slight roughness is discernible. The particle dimensions are smaller than those of GS-10, and no cavities are observed on the surface or among the particles.

The particle size distribution ranges from 20 to 100 µm, with a Gaussian distribution centred around 50 µm.

Based on the findings of previous studies and the current investigation carried out, it is evident that the different sites in UAE harbour dust particles with unique characteristics and morphology. These features have significant impact on shading caused by the dust particles on the PV surface as well as the power output.

The SEM analysis showed that the size and shape of the particles varied considerably among the sites in the range of 0.01–300 µm, and the shapes were irregular with a high proportion having spherical, square and rectangular particles. Such variability in size and shape can lead to significant differences in the behaviour of dust on the PV modules, with some particles having a more profound shading impact and, consequently, the power output. In another study [12], SEM image analyses showed that the dust particles varied in the range of 10–50 µm, and the smallest particle blocked more sunlight and ultimately reduced the efficiency of solar panels. Several factors could influence these characteristics such as local soil, traffic and industrial pollution, construction around sites, wind speed and relative humidity.

3.4. Elemental Composition Analysis (Energy Dispersive Spectrometry, EDS)

Table 2. Elemental composition analysis of dust particles from five PV installation sites.

Sample Element	GS-10 (%) Mass Atom		GT-10 (%) Mass Atom		R-10 (%) Mass Atom		S-10 (%) Mass Atom		T-10 (%) Mass Atom
Ca	9.32	3.8	7.52	3	15.59	7.55	12.59	5.91	13.61	6.3
Si	10	5.95	8.57	4.88	10.64	7.35	11.35	7.6	9.73	6.43
Mg	2.11	1.45	2.01	1.32	4.11	3.28	5.54	4.29	6.59	5.03
Al	1.74	1.08	1.51	0.89	2.79	2.01	2.75	1.91	1.81	1.25
Fe	1.2	0.36	0.96	0.27	3.67	1.27	3.21	1.08	2.83	0.94
Na	0.48	0.35	0.4	0.28	0.72	0.61	0.48	0.42	0.39	0.32
K	0.46	0.2	0.43	0.17	0.85	0.42	0.7	0.34	0.46	0.22
S	0.14	0.07	0.13	0.06	1.92	1.16	0.39	0.23	0.34	0.19
C	25.33	35.2	32.5	43.2	10.32	16.68	10.79	16.89	11.78	18.19
O	49.23	51.4	46.0	45.9	49.02	59.46	52.19	61.38	53.1	61.57
Cl	-	-	-	-	0.37	0.2	0.3	0.22	0.21	0.11

presents the relative elemental composition of the samples collected from the Solar Park.

The analysis conducted on these samples revealed an intriguing combination of uniformity and variation. However, the EDS analysis confirms the XRD findings.

Table 3. Origin of elements in EDS from the XRD analysis.

Element in EDS	XRD Peak	Source
Ca, C, O	A, C, and E	Calcite, Dolomite, and Gypsum
Si, O	B, F	Silica and K-Feldspar
Ca, Mg, C, O	C	Dolomite
Al, Si, O	D, F	Kaolinite and K-Feldspar
S, O	E	Gypsum
Cl		Sodium Chloride
Na		Aluminum Calcium Sodium Silicate *

* Shown in Figure 3 for GS-10 and GT-10 dust samples.

below explains the origin of the elements present in the dust particles.

Across all the samples, there was a certain degree of consistency in the presence of elements, suggesting common sources or mechanisms contributing to the dust accumulation on the PV panel surfaces. However, upon closer examination, it became evident that the compositional contribution of each element exhibited significant deviations across the samples. This phenomenon raises important questions about the underlying factors that influence the formation of distinct compositions on the PV panels.

Interestingly, among the observed elements, one element, namely chlorine (Cl) was found to be additionally present in certain samples. The detection of this element in specific samples further underscores the notion of pronounced variation across the different sites within the PV facility. The presence of Cl could be attributed to diverse environmental factors, such as air pollution, industrial emissions, and local geological characteristics, influencing the dust composition in specific areas. The elements appearing in EDS are also being detected in XRD peaks as shown above in Table 3. It is crucial to note that the non-detection of certain elements, such as Cl and Na, by XRD can be attributed to their low concentration. This phenomenon results in a diminished intensity of the detected peaks associated with chlorine components, thereby underscoring the analytical sensitivity of the XRD method in discerning elements at lower concentrations. In the study by [22] conducted in South Africa, the EDS analysis showed oxygen and silicon as predominant elements in dust collected from the PV panel surface, which shows the diversity in the dust elements based on the geographical location.

Understanding the implications of these variations in elemental composition is of paramount importance as it can have a significant impact on the performance and maintenance of PV panels. Some elements may interact with the surface coatings or framing of PV panels, potentially affecting their durability or efficiency. Moreover, the variations in composition may also influence the adherence of dust particles to the panel surfaces and, consequently, deter certain cleaning/self-cleaning mechanisms.

4. Conclusions

The study attempted to understand the morphology and composition of dust particles collected from five sites characterised by Optical Microscopy, Scanning Electron Microscopy (SEM), X-ray Powder Diffraction (XRD), and Elemental Composition Analysis (Energy Dispersive Spectrometry, EDS) were employed in this study. Dust samples were collected from the sites in the month of October.

The optical images of the dust samples over PV surface reveal different colours compared to the ground sand at the same site, indicating potential interaction between dust particle and the PV surface. The SEM analysis of the dust particles revealed irregularly shaped particles with sizes ranging from 0.01 to 300 µm, the presence of small cavities and densely packed particles indicative of cohesive behaviour and possible aggregation due to electrostatic forces potentially impacting PV shading. The particle sizes vary across different sites, showcasing notable variations within each sample. For instance, in the case of sample T-10-22, a diverse particle size distribution was observed, ranging from 0.01 to 30 µm. The distribution displayed a Gaussian curve centred around 15 µm, highlighting a concentration of medium-sized particles. Conversely, the dust particles in sample R-10-22 exhibited a broad range of sizes and morphologies, with a predominant size falling within the 0.01 to 30 µm range. The Gaussian distribution for this sample centred around 10 µm. Sample S-10-22 revealed a particle size distribution ranging from 0.01 to 30 µm, with the Gaussian curve centred around 10 µm, indicating a higher prevalence of small-sized particles. In the case of sample GS-10-22, particle sizes ranged from 30 to 300 µm, with the Gaussian distribution centred around 100 µm. Lastly, sample GT-10-22 displayed a particle size distribution spanning from 20 to 100 µm, with a Gaussian curve centred around 50 µm. These variations in particle sizes underscore the diverse nature of dust particles at different locations, providing valuable insights into their morphological characteristics.

The XRD analysis showed variations in the chemical composition among the dust samples, with calcium carbonate and silicon oxide being predominant in all samples. The presence of Cl in certain samples indicated significant variations across different sites within the PV facility, which could be influenced by environmental factors and local conditions. Elemental Composition Analysis via EDS revealed uniformity and variation in dust samples’ element presence. Notably, unique elements like Cl found in specific samples highlight diverse environmental influences.

Overall, the study provided valuable insights, highlighting the differences among ground dust and PV surface dust of same origin and across the samples of different locations. The findings provide a deeper understanding of dust-related issues and lay the foundation for further research to optimise PV cleaning methods specific to site of PV deployment within the UAE context.