Solar Photovoltaic Energy as a Promising Enhanced Share of Clean Energy Sources in the Future—A Comprehensive Review

Abstract

The use of solar energy is now a common and modern alternative that many countries throughout the world have adopted. Different studies on PV systems have been documented in the literature; however, several reviews focus excessively on particular facets of solar modules. In this paper, the literature on PV systems published between 2000 and 2023 was reviewed thoroughly. This review is structured in three main parts. Primarily, the main factors impacting dust deposition on solar modules are discussed. These include temperature, wind speed, inclination angle, location, climatic conditions, photovoltaic module surface characteristics, and dust characteristics. Many methods for mitigating and reducing dust as well as approaches to cleaning PV modules are also reviewed in this study. The many types of solar modules, together with their most important characteristics and operational effectiveness, are presented. As more solar photovoltaic panels expand their end of life (EOL), solutions are required to recycle and dispose of solar photovoltaic panels at the lowest economic cost and with the least environmental damage through reduced carbon emissions and greenhouse gases. Subsequently, this paper further reviews solar PV energy for a green environment and PV waste recycling and its costs. Moreover, integrating solar energy with other clean energy constituting an energy source for hard-to-reach areas and an alternative to fuel are discussed. Therefore, this comprehensive review of the use of photovoltaic systems for green energy production is helpful in an increased share of clean energy for various energy sectors in the future.

1. Introduction

Recently, relying solely on fossil fuels, as well as the increasing population and industrial areas in cities, pose challenges to energy security and the environment [1,2]. Subsequently, the production of renewable energy has increased, with solar energy taking a bigger share. Photovoltaics is considered a major source of electricity generation through solar radiation, and its use to generate electricity reached 32% in 2016 [3,4]. Around the globe, many governments have made investments in clean energy sources, including solar and wind energy [5]. It is now viable that renewable energies help reduce reliance on fossil fuels, adding economic value to and benefits for the environment as a whole. In many regions of the world, solar photovoltaics have surpassed substitutes in terms of the cost to produce power.

In 2020, solar photovoltaic energy production grew by 22%, exceeding 1000 TWh and setting a record growth rate of 179 TWh. In addition, solar photovoltaics, which is currently the second-largest renewable electricity technology after hydropower, produced 3.6% of the world’s electricity in 2016. However, to reach net zero emissions by 2050, an average annual generation growth of 25% is required in 2022–2030 [6]. About 38% of the increase in solar PV generation in 2021 was achieved by China. Solar PV showed its resilience and set a new record for annual growth capacity of almost 190 GW, further increasing power output growth in 2022 [7]. In addition, in 2022, over 200 GW of solar installations were installed globally, with global installed solar capacity increasing by 203 GW [8]. By 2027, solar PV is expected to have the greatest global installed electricity capacity, surpassing coal. The amount of solar radiation that reaches the surface of solar panels and is subsequently transformed into energy is a measure of the efficiency of the panels.

The power rating of a typical-size panel has grown from 250 W to over 420 W as a result of the average panel conversion efficiency increasing from 15% to more than 22% in recent years. Cell design, silicon type, cell layout, configuration, and panel size all affect the efficiency of solar modules. Efficiency can also be increased by expanding the panel. IBC panels are the most efficient, reaching 23.8% due to the high-purity silicon layer and the lack of losses from bar shading, but in contrast, advanced heterogeneous cells (HJTs) achieve efficiency levels much higher than 22%, and high-efficiency tandem perovskite cells can reach 28% [9]. Furthermore, efficiency decreases with high temperatures because semiconductor materials in solar cells become more conductive at high temperatures, increasing the flow of charge carriers and lowering the produced voltage and efficiency [10]. Photovoltaic cells in regions classified as high-temperature environments with dust accumulation experience a power reduction during electricity generation [11]. It was reported that photovoltaic system performance could decrease significantly by 81% under temperature and dust restrictions [12].

Even though the use of solar energy is increasing globally, end-of-life solar panels might end up as a source of hazardous trash. The installed PV capacity worldwide was over 400 GW at the end of 2017; by 2050, it will have reached 4500 GW. Given the typical panel lifespan of 25 years, global solar PV waste is predicted to increase to more than 80% by 2050 and from 4% to 14% of total generation capacity by 2030 [13]. This requires a research focus to enhance solar photovoltaic energy while keeping the environment clean. Though there are reviews available on solar photovoltaic technologies and methods of enhancing energy conversion, the majority focus excessively on particular facets of solar modules. Therefore, this review aims to highlight the progress made on the solar photovoltaic systems in the last few decades. The main factors affecting solar PV energy conversion, PV cleaning methods, technological advances, solar PV recycling, and enhancing the share of solar PV are reviewed thoroughly and the future perspectives are highlighted.

2. Solar Photovoltaic Potential

Solar energy would be a strategic solution for providing electrical energy for different sectors. Solar PV has been projected to be the main source of clean energy in the coming decades [14]. Figure 1 compares energy supplies between conventional energy sources and clean energy sources. The energy produced from renewable sources is expected to reach more than 400 EJ, among which solar PV would take a bigger share while the energy sources from conventional fuels would be minimal. The difference in total energy supplies from fossil fuels would see a drastic drop due to the challenges faced by the environment [15]. Subsequently, energy investment in clean sources would rise by more than threefold. For instance, energy production from solar PV in the USA is expected to rise threefold from 22 GW in 2021 to 58 GW in 2030, and this is huge difference when compared with energy sources from wind power. As a result of renewable energy sources, the emissions from different sectors are expected to decrease significantly from over 12 Gt CO₂ to below 1 Gt CO₂ by 2050. The significant global solar PV installation has been attributed to the lower cost of solar cells in the last few decades. The cost of solar modules has decreased by 88% during the past ten years [16]. Figure 2 depicts the annual solar photovoltaic cell production between 2010 and 2021, where China contributed 78% of solar module production worldwide [17,18].

3. Dust Accumulation and Cleaning Method

3.1. Dust Deposition Rate and Factors Affecting Dust Deposition on Photovoltaics Modules

The dust particle deposition rate is higher closer to desert areas and factories. Dust deposition is one of the processes that most impacts electricity production. It is especially severe in desert areas because of the exposure to solar radiation [19]. Based on the transport mechanism, dust deposition on a PV is classified into three mechanisms. At first, in the dry deposition process and in the absence of water content, airborne particles are transported to the PV surface [20]. Secondly, due to adhesive forces, dust particles adhere to the PV module’s surface in dry conditions [21]. Thirdly, during wet deposition, many forms of precipitation, mainly rain and snow, contaminate airborne dust [22]. There are different factors affecting the performance of photovoltaic modules.

3.2. Effects of Temperature on the Performance of PV Systems

The variation in temperature between ambient and solar cells impacts dust accumulation. The proportion of humidity surrounding the solar cell decreases at high temperatures, and this makes it simple for the dust percentage to increase. For instance, the North African Saharan desert during the dry season and the soot produced by oil exploration have high temperatures that result in a lot of dust [23]. Moreover, because of the sea’s low temperature, a higher percentage of steam rises and condenses on solar cells, making them stickier and more viscous and drawing in more dust [24]. An increase in temperature affects the panel’s electrical parameters, where the PV panel’s open circuit voltage, short circuit current, and efficiency are all decreased by 2–6%, 15–21%, and 15–35%, respectively, when 20 g/m² of dust accumulates [25].

Divya et al. (2022) [26] studied the effectiveness of using a phase-change material (PCM) to reduce the increase in surface temperature of the photovoltaic cell, as this material maintains the temperature for a long time. Amino acids were used as a PCM. The results showed that the use of the PCM reduced the heat on the surface of the cell, leading to improved efficiency of the photovoltaic cell. Figure 3 shows temperature profiles with and without PCM. According to the eco-economic investigation, using hybrid nano-PCM, hybrid PCM, and hybrid PCM–water was more effective at reducing the environmental cost of carbon dioxide (CO₂) released in the atmosphere than using each technology separately [27]. Katkar et al. (2011) [28] found a relationship between the temperature and the efficiency of solar panels, where the efficiency increased from 9.7% at 31 °C to 12.0% at 36 °C.

A PV module’s electrical production can decrease due to overheating caused by the heat produced by absorbed solar radiation that has still not completely been converted into energy. The PV panel’s operating temperature may increase due to the stored thermal energy, causing the system voltage to decrease [29]. Kazem et al. (2022) [30] investigated the effect of dust heating on a photovoltaic/thermal (PVT) module for two PVT water-cooling systems employing a spiral coil. One of the two systems in the research was cleaned on a regular basis, whereas the other was left to gather dust. After 30 days, the results showed that the average energy output by the polluted PVT, clean PVT, and conventional PV systems was 46.96%, 61.17%, and 42.73%, respectively. This demonstrates the power output reduction of both the contaminated PVT and the conventional PVT as the time exposed to environmental conditions increased [30]. Cell temperature is directly affected by humidity, wind speed, and the amount of accumulated dust on the surface, in addition to becoming directly dependent on solar radiation and the surrounding temperature [31]. Kumari et al. (2023) [32] investigated the potential application of heat collectors (HHDs) to increase power production and improve the performance of a solar panel. The results indicated that electricity efficiency increased by 1.2 to 1.5 times when PV panels were operational. The study also demonstrated how PV-cooling solutions keep the operational surface temperature of a commercially available PV panel at a low and steady level by removing thermal heat. This, in turn, increases the panel’s total conversion efficiency. According to Preet et al. (2017) [33], the temperature of the PV module, in the absence of any cooling mechanism, may reach up to 85 °C, which is greater than the daily ambient temperature. Additionally, it has been observed that using PVT and PVT-PCM layouts reduces temperature by 47% and 53%, respectively. A photovoltaic air thermal collector (PVT) is a collector that is used as a heat transfer medium instead of water or to convert solar energy into thermal energy. Many studies have been conducted on PVT.

An effective, dynamic, and cost-effective PVT combination using phase-changing materials based on dynamics was proposed by Tariq et al. (2020) [34]. For each of the three climatic zones, an annual equivalent analysis was carried out to determine the best phase-change material. It was found that the best phase-change materials could achieve a temperature reduction of about 20%, according to the results of fifteen multidimensional performance indicators that were analyzed based on energy, sustainability, and carbon dioxide emissions in the life cycle. There was a range of around 8 to 11% for electrical, 25~33% for thermal, and 13~17% for power efficiency. In Lyon, France, Gaur et al. (2017) [35] conducted a numerical study of the electrical and thermal performance of a PVT collector for the winter and summer months. The PCM worked as a heat source during the night and produced hot water that could be used another day. Three varieties of photovoltaic (PV) modules were designed by Joo et al. (2023) [36]: glazed PVT panels with clear film covering the PV cells, glazed PVT panels with glass covering the PV cells, and unglazed PVT panels with glass covering the PV cells. According to the results, the photovoltaic panels in the glazed PVT panels with a clear film covering them achieved a maximum total efficiency of around 71.1%. This could have been due to less heat loss from the glazing and decreased reflection from the film that covered the solar panels. The better electricity efficiency of the unglazed PVT panels was made possible by less reflection and more cooling. In an experimental study on the water spray-cooling method for solar panels, Nižetić et al. (2016) [37] discovered a 16.3% increase in the panels’ electrical efficiency and a drop in temperature to 24 °C from 54 °C for non-cooled convectional PV panels.

3.3. Impact of Wind Speed on the Performance of PV Systems

Wind has an impact on the natural convection phenomena that lowers the photovoltaic temperature and affects the efficiency of solar photovoltaics. The amount to which the wind removes the dust accumulated on the surface of photovoltaic cells was examined using the theory of particle resuspension. The theory considers torque, adhesion force, and wind speed. As a result, at a specific wind speed, particles with sizes ranging from 0.1 to 100 micrometers were suspended. The idea that the theory can be realized using just large particles has also been confirmed. Due to the high shear speed needed for separation, the theory is ineffective for small particles [21]. The simulation model developed using an energy-based particle adhesion mechanism was validated via experiments. The results showed an upward relationship between humidity and particle size and an opposite relationship between wind speed and tilt angle for the particle kinetic energy loss in the impact, which demonstrated a total of 10^−13 J. In addition, with increasing wind speed and particle size, the number of particles deposited first decreased and then increased. Nevertheless, it decreased with increasing tilt angle and increased with increasing humidity [38].

The wind is also a mechanism that transports dust from one place to another. Wind affects the accumulation of dust and, at the same time, its removal from surfaces. As a result, it was demonstrated that dust collection increased as wind speed increased [23]. The PV module’s performance was significantly reduced by wind speed, with the decrease being more pronounced at higher velocities. Wind also had an impact on the sedimentary structure of the dust layers that were created on the cell, which caused the layers created during strong or high winds to have higher light transmittance. Goossen et al. (1999) [39] investigated the effect of wind speed and dust on the performance of the cells during four hours of wind and at four concentrations of dust. Performance reduction due to dust accumulation was more significant with an increase in wind speed.

Lu et al. (2019) [40] investigated the effects of wind speed on the deposition of different-sized particles. Similar results were seen at various wind speeds, and as dust diameter increased, it also increased the deposition rate. The maximum dust deposition diameter was 100 µm at 1.3 m/s wind speed and 150 µm at 2.6 m/s wind speed, as depicted in Figure 4. This is because there was an interaction between the various wind speeds and particle masses. In Qatar, Figges et al. (2016) [41] studied the relationship between dust accumulation rate and wind speed on an oil-rich collector placed on a building. The study highlighted that, for a wind speed of less than 3 m/s, dust deposition became significant on the surface of the collector. Yao et al. (2022) [42] conducted research in Tianjin, China, where they measured weight and transmittance to investigate the effects of dust on solar panels. The research relied on a platform with four typical orientations and seven inclinations designed to measure the transmission of PV panels in an outdoor environment. The study theoretically supports the design and development of the photovoltaic system since the results indicated a link between the loss of transmittance of the glass plate and dust density. The southward PV panels were more greatly affected by wind speed and direction than other panels. When it started to rain, the dust on the southward PV panels increased quickly. With no rain, the dust on the southward PV panels was 1.90% lower for 45 days than the eastward PV panels, 7.32% higher than that westward PV panels, and 11.95% higher than that northward PV panels [42].

The effect of wind speed, relative humidity, and module location on dust deposition on the surfaces of solar modules was studied by Ndeto et al. (2022) [43]. It was indicated that lower deposition rates were observed at locations with higher wind speeds and module tilt angles, which had a smaller impact on the variables affecting current and voltage reduction. The average wind velocities at the location were not high enough to completely resuspend small-sized particles (less than 500 µm) adhering to the PV module surface. As a result, dust accumulation on the surface of the PV panels adversely affected the voltage and current properties [43]. The density of the dust gathered on the surface may have been affected by the wind in two different ways. Those facing the wind had part of their surface dust cleared by the mild wind; however, those facing the opposite direction had more dust condensed on the surface due to the development of the vertex [44].

Figure 4. Rate of dust deposition and particle size at various wind speeds [45].

Figure 4. Rate of dust deposition and particle size at various wind speeds [45].

3.4. Impact of Relative Humidity on the Performance of PV Systems

It has been reported that humidity does have an influence on the performance of photovoltaic systems. Different studies have shown that an increase in humidity during the day leads to an increase in the humidity of the photovoltaic surface. This results in the accumulation of mud and, thus, a reduction in the efficiency of the solar panels [46]. Over more than a two-year period in Qatar, Touati et al. (2016) [47] investigated the impact of dust on PV module performance while considering relative humidity and temperature as variables influencing dust deposition on a PV. Their results showed that an eight-month period without cleaning resulted in a 50% reduction in power production.

Humidity has an impact on solar panels as a consequence of the parameters of PV performance changing as a result of the humidity variable. It was found that high humidity reduced solar saturation and panel energy because it caused the panel temperature to decrease by 11.40% and resulted in a 34% reduction in energy output when the humidity reached 50.15% [48]. Dust accumulation was negatively correlated with particle size under 30% humidity. Dust accumulation decreased with an increase in particle size from 10 µm to 30 µm, leading to an energy efficiency reduction to 3.89% and a decrease in permeability to 8.38% [49]. According to Said et al. (2018) [49], relative humidity increased up to 80% when the adhesion was between 40% and 80%. This reveals that relative humidity promotes dust particle cementation, which can be classified as a secondary factor affecting dust accumulation. On the other hand, water droplets that condensed from vapor could also hold dust [50]. Figure 5 shows a comparatively higher efficiency at lower relative humidity.

3.5. Impact of Dust Properties on the Performance of PV Systems

Al Siyabi et al. (2021) [46] studied the effects of dust accumulation on the photovoltaic cells in Muscat. Dust accumulation reduces solar radiation and works as partial shading of the cells, significantly reducing the output power of photovoltaic systems (see Figure 6). This study observed a 30% decrease in electricity generation for all solar radiation. Some studies found that dust classification included sand, ash, red soil, limestone, carbon, manganese dioxide, calcium oxide, iron oxide, and natural dust. They investigated the preceding types and discovered a more significant impact on PV performance. It was also discovered that red soil had the greatest impact on lowering pollutant mass output power, which exceeded 0.3 g/m³. It was reported that carbon had the strongest effect on decreasing the performance of photovoltaic panels by about 99.76% at a mass density of 0–20.27 g/m². Unlike natural dust, it was better than carbon, as the performance of photovoltaic modules decreased by 98.92% in mass density from 0–164.38 g/m² [52].

A study by Chen et al. (2020) [53] reported that the average dust density on PV modules was 0.644 g/m² per week and that dust reduced PV output power by 7.4% in one week. Moreover, it was found that the short-circuit current and maximum power exponentially decreased with the density of the dust mass deposited. The photoelectric conversion efficiency also decreased by almost 7% with an increase in mass density [54]. A dust concentration and energy conversion efficiency (DC-ECE) model was developed to evaluate dust accumulation’s influence on power production performance using a CFD and the k-e model. In addition, a wind tunnel experiment was conducted to evaluate the efficacy of CFD simulation. A sedimentation rate expression was also developed to investigate the effects of particle diameter and wind speed on dust concentration. The spiral vortex of dust particles gradually expanded and became clearer as the fixation angle increased. The peak conversion efficiency loss for solar panels was 72.9% when conversion efficiency loss increased with increasing wind speed and dust particle diameter [55].

Even for particles bigger than 10 µm, dust concentration alone is thought to be a poor indication of PV contamination and the efficiency of PV modules. Therefore, a nonlinear relationship was observed between aerosol mass, relative humidity losses, and PV. A dynamically resolved three-dimensional aerosol dispersion model and real-time meteorology were used to simulate the emission and movement of dust particles in the environment. One advantage of the model is that it simplified nearly every aspect of the deposition process into a single particle deposition velocity parameter. An average deposition velocity for the different sizes of coarse dust particles ranged from 1.1 cm s⁻¹ to 3.3 cm s⁻¹ in the summer to 1.6 cm s⁻¹ to 3.7 cm s⁻¹ in the winter [56]. For larger dust particles, gravity had an essential effect on the rate at which dust was deposited. The gravity-induced accumulation rate decrease for 50 micrometer dust particles was as much as 75%. However, the impact of gravity was less than 5% for tiny dust particles. The rate of dust deposition on PV panels was not clearly affected by variations in the number of discharged dust particles [57]. The microstructure of the super-hydrophobic coating increased the effect of dust particles. Consequently, the self-cleaning layer kept particles—especially big ones—from piling up [58]. Liu et al. (2022) [54] analyzed the amount, condition, formation, and development of dust particles on solar PV panels. Furthermore, the characteristics of dust development and the impact of contamination from dust on the PV panels were investigated. The results showed that pores and nano-, micro-, and coarse particulates erratically dispersed on the PV panels. The dust particles on the PV panels were comprised the components Fe₂O₃, SiO₂, CaMg (CO₃)₂, Al₂O₃, CaCO₃, and Ca(OH)₂. Additionally, the main sources of dust particles on the panels were the lime, sandstone, and dolomite contaminants carried from the ground to the PV panel flow field by wind and movements caused by traffic [59].

The interactions between dust and a solar panel were simulated using the soft sphere model and the CFD-EDM technique in the work by Zhang et al. (2022) [60]. The simulation results for dust deposition showed that most of the dust particles avoided the solar panel with the airflow and that only a small percentage of dust particles could deposit on the solar panel’s surface. Hence, the deposition rate was 4.6%. Fine sand deposition, on the other hand, occurred at a much greater rate—up to 32% [60]. Fan et al. (2021) [61] created the DC-PCE, indicating photoelectric conversion efficiency and dust concentration, after researching the effects of dust deposition on photovoltaic (PV) panels. A PV power production examination with six typical dust pollutants was conducted to determine the selection, range, and impact coefficient of dust accumulation in the model. The results showed the suggested model’s remaining generality and 83.18% accuracy. The DC-PCE is considered an easy and reliable tool for determining how much dust has accumulated at a location [61].

Shi et al. (2020) examined the impact of high-velocity dust- and sand-testing equipment. A total of 330 PV panels from 53 various makers were subjected to sand and dust testing. The results indicated that the unqualified percentage of PV panels operated in the last five years was about 5.76%. According to the test results, the VOC and fill factor were also slightly impacted. Further, the sand and dust test caused the current to decrease, which lowered the production of power [62]. The ability of the dust particles to stick to the solar panel surfaces was investigated along with the nature of these pollutants through various studies. The results of dust characterization indicated that the dust that was deposited on the solar panels had a heterogeneous size and shape that was less than or equal to about 18 microns. As a result, energy degradation was significantly impacted. Controlled laboratory tests showed a linear association with a slope of 1.269% per g/m² between the absolute difference in power output and the amount of dust deposited on the plate’s surface [63]. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to investigate the dust’s composition. The solar panel’s maximum output, Pmax, decreased to about 20 W with an amount of dust of around 20 g/m² [64].

Figure 6. I–V graph with respect to dust deposition [65].

Figure 6. I–V graph with respect to dust deposition [65].

3.6. Impact of Tilt Angle, Location, and Installation on the Performance of PV Systems

The effectiveness of a photovoltaic cell varies from one location to another, with some locations experiencing rainfall and others experiencing high levels of dust accumulation. It was reported that the efficiency of a dusty solar cell subjected to dust deposition decreased by 29.76% compared to a frequently cleaned cell. Additionally, the solar module suffered permanent damage from the concentration of dust that had accumulated at its bottom. On the other hand, deposition is a factor that not only affects the open circuit and current voltage but also has a 30–40% impact on the short-circuit current [66]. One of the elements that influences dust deposition is the tilt angle. Due to the force of gravity, dust particles are deposited at an extremely fast rate on level surfaces where the inclination angle is zero. As for the vertical surface, where the angle is 90°, gravity’s weakness indicates that the rate of deposition is low, making it easier to remove dust over time, as it was found that dust deposition decreases with the inclination angle from the horizontal axis [24].

Adinoyi et al. (2019) [67] conducted a study in Saudi Arabia on the relationship between dust accumulation and the tilt angle of PV cells. They observed that the deposited dust decreased as the PV cell tilt angle increased. There was a linear relationship between dust density and PV energy, with a decrease of 1.7% per g/m². The morphology accumulation increased for the inclined cells (0-45–25). Hachicha et al. (2019) [68] discussed that, when the dust density increased by 5.44 g, the loss of pollution increased by 12.7%, indicating that a linear relationship may be used to estimate the loss of pollution for solar PV systems. The study by Cattani et al. (2023) [69] investigated the effect of environmental factors on the efficiency of solar PV panels. The efficiency of 91 solar PV panels situated in Australia was estimated using data envelope analysis (DEA). The reduced regression model was used to measure the impact of environmental factors on the estimated efficiencies. The results make it possible to identify Australia’s best solar PV energy-producing areas and locations [69].

In an open rooftop site in Lahore, Ullah et al. (2020) [69] investigated the impact of the tilt angle of solar panels. According to the results, Lahore consistently had a soiling rate of 0.8% per day for 30° tilted panels, among the highest soiling rates recorded for various urban areas around the Gulf and South Asia. Among the greatest soiling rates recorded for Middle Eastern and South Asian cities, monoficial PV panels’ average daily output power loss due to soiling at a tilt of 0° reached 1.11%, at a tilt of 90° reached 0.11%, and at a tilt of 30° reached around 0.8% per day [70]. The sedimentation rate decreased when the particle size exceeded 50 µm, as gravity made it difficult for big particles to reach the PV. Additionally, independent of the effect of gravity, the sedimentation rate increased as the size of the dirty particles grew, regardless of the difference in tilt angle. The number of particles that reached the plate surface for the minimal plate tilt angle was fewer than that of the tilt angle perpendicular to the direction of the particle [71].

Babatunde et al. (2018) [72] studied how PV systems performed when exposed to dust, various tilt angles, and different instructions. Three different mounting methods were investigated for five different photovoltaic (PV) systems. After the cleaning method, a specific yield variation of 2.5% on average was observed. Additionally, the impact of each system on the various behaviors was recorded. Arazi’s mean specific output was 1732.44 kW/kWp, 17.3% and 5.6% more than Stonite’s and Arena’s, at 6° and 25° tilts, respectively. Whereas the energy output at the Arazi, Carpark, and Arena PV plants exceeded the simulated results by 7%, 3%, and 7%, respectively, it decreased by 3% at the Stonite and B-Block PV plants [72].

Lu et al. (2018) [73] examined the effects of various tilt angles and dust particle sizes on dust deposition. The results showed that the various tilt angles had a significant effect on the dust accumulation rates of a PV panel. Relative to the downward PV installations, the upward PV installations had significantly higher rates of dust accumulation. Additionally, when the solar PV screen was more horizontal to the surface of the ground, the rates of dust deposition were higher. The PV panels were soiled for about 100 days in Pakistan, and the power output and short-circuit current measurements versus the clean panel showed a proportional decrease in output power of 26.2%, 18.4%, and 13.5% for the tilt angles of 0°, 35°, and 90°, respectively [74].

Since monocrystalline and polycrystalline PV modules are commonly used in Southern Europe, diffuse radiation from the northern parts of the world, such as Germany and Belgium (Europe), is essential for monocrystalline and polycrystalline PV modules. After many thousands of years, the deposition crystallizes, making it extremely hard to remove since the coating of dust and pollutants takes on the consistency of caramel. Consequently, after six years of exposure to pollutants, there was a decrease from 75 W to 20 W [75]. The output power and efficiency indicated a significant fall in both measurements when no light was visible on the plate’s surface. The results showed that the clean, dirty, and muddy plates had the highest efficiency rates of 15.69%, 10.29%, and 5.67%, respectively. For the clean, dirty, and muddy plates, the average measured efficiency of the various patterns during the test was 14.60%, 9.74%, and 5.44%, respectively [76]. The energy from the panels in the winter decreased by 6.72% and 20.09% for the inclined and horizontal panels, respectively, compared to the summer, according to the changing seasons and the angle of the sun’s incidence. The installation angle was essential in the case of a horizontal board. Because of the gravitational force’s effect on the accumulation of dust, it reduced solar energy absorption [77]. Figure 7 also shows the highest dust deposition rate at a reduced tilt angle.

3.7. Impact of Photovoltaic Surface Properties on the Performance of PV Systems

The rate of dust accumulation varies according to the type of surface, as the rate is very high with surfaces made of plastic and epoxy compared to surfaces made of glass [78]. The morphological properties of the surface and its cleaning effectiveness are related, as it is possible for the design of the surface to influence its cleaning efficiency in either a decreasing or increasing way [79]. This study examined the variables that affect dust, including wind speed, dust buildup, ambient temperature, and cleaning frequency, for four PV types—crystalline, monocrystalline, microcrystalline, and thin films. According to the results, the isotropic model predicted a 1.5% higher energy output in the summer than the anisotropic model, as seen in Figure 8. With thin-film solar panels, the working cell temperature decreased by up to 7.05% when the cooling impact of reduced wind speed was considered. When the panels were cleaned every two months, the energy produced each year decreased by 24%. In all cases studied, when the rate of dust accumulation doubled, energy production decreased by 10% [80]. The influence of dust collection on the performance of the SPV panels and the low-iron glass surface was studied. Additionally, the mineralogy analysis of dust particles on the horizon determined the transmittance loss from the PV solar panels’ glass surface owing to local pollution loss. Furthermore, the electrical power production of the SPV panels was monitored at various dust deposition levels. The electricity generated by photovoltaic panels was significantly reduced when natural dust accumulated in certain areas [81].

3.8. Impact of Weather Conditions on the Performance of PV Systems

Partial shading poses problems for photovoltaic systems (See Figure 9). Solar cells receive varying levels of solar radiation, but in the case of partial shading, it leads to a reduction in the photovoltaic output energy [82]. To reduce partial shading, some researchers are applying artificial intelligence techniques. Usually, artificial neural networks are frequently used to analyze partially shaded PV systems [83]. Increased dust deposition caused by rainfall impacts the process of dust deposition. A study conducted in California, USA, found that rainfall of at least 20 mm was required to remove dust from the surface of a solar cell. As a lack of rain causes the dust to turn to clay, a mechanical cleaning method is required [24]. Climatic conditions affect the performance of photovoltaic modules via the accumulation of dust.

Weber et al. (2014) [84] found that the performance of a PV system dropped by 15% after 60 days of dust deposition on the modules without rain. In contrast, the performance rate decreased in the event of rain by 0.24% [84]. Gholami et al. (2018) [85] conducted an experiment to identify how dust accumulation affects PV performance. A total of 6.0986 g/m² of dust had accumulated on the surface after 70 days without rain, resulting in a 21.47% reduction in power output. Dust activity was found to decrease in the summer. Particle size, organic carbon, elemental carbon, and ions in the dust were all found to have an impact on dust strength [86].

Sandstorms have a role in decreasing total daily solar radiation. Severe sandstorms of 2700 rad or higher throughout the day reduce daily radiation by 57% [87]. Another study by Mejia et al. (2014) [88] measured changes in a large commercial site’s efficiency over the summer months in relation to rain events recorded at a nearby weather station. The efficiency decreased over a 108-day dry summer period from 7.2% to 5.6%, but then a rain event restored most of the lost efficiency to 7.1%. Sadat et al. (2022) [89] reviewed the impacts of haze on PV performance. The solar spectrum was reported to be affected by the haze. Moreover, pollution-related haze costs PV operators a substantial amount of money every year in many locations worldwide. Haze significantly affects PV systems, with a negative impact on direct irradiance. When there are severe weather situations, factors such as the aging impact, seasonal temperature variation, the solar radiation heating effect, and the dust and soiling effect are all affected. Therefore, they need to be taken into consideration while building the system to avoid any power demand shortages. Cooling and cleaning are two methods to increase system performance [90]. The impact of dust varies based on the season, with the summer experiencing a more detrimental impact than the winter. Energy losses due to pollution were 8.7% greater in the summer than in the winter. Different environmental variables have been identified as the cause of the variation, with high humidity and slow wind speeds being the primary aggravating factors for dust throughout the summer [91].

Figure 9. I-V and P-V curves for shaded, partially shaded, and not-shaded panels [92].

Figure 9. I-V and P-V curves for shaded, partially shaded, and not-shaded panels [92].

4. Materials and Photovoltaic Technologies

Photovoltaic solar cells can be categorized as either wafer-based or thin film (see Figure 10). Wafer-based cells can be produced on semiconductor wafers without the need for an additional substrate and are coated strategically with special glass for mechanical stability and protection. The three wafer-based technologies existing today include crystalline silicon (c-Si), gallium arsenide (GaAs), and III-V multijunction (MJ). Crystalline silicon (c-Si) solar cells are classified into single-crystalline (sc-Si) and multicrystalline (mc-Si) [93]. The efficiency of charge extraction and power conversion in sc-Si cells increases as crystal quality increases, although wafers that are 20% to 30% more expensive are needed [94]. Photovoltaic crystalline silicon (c-Si) is considered the first generation and has reached a market share of 95% of the total photovoltaic production worldwide. Traditional and advanced silicon solar PV technologies are two categories of crystalline silicon technology. The traditional silicon solar photovoltaic technology is superior for a variety of reasons, including its abundance in nature and its non-toxic nature. Crystalline silicon solar photovoltaic panels tend to have long-term stability in climatic conditions and better energy conversion as the efficiency reaches 20%.

Monocrystalline and polycrystalline PV are two separate varieties of typical crystalline silicon. Due to different production procedures that affect cost and efficiency, single-crystalline and polycrystalline solar panels have different physical and chemical characteristics. Whereas polycrystalline silicon PV is formed of multiple components using an alloy-casting process, monocrystalline silicon is produced by chipping from a single crystal, producing high-quality solar cells with a uniform black appearance. Therefore, monocrystalline silicon is more expensive due to the manufacturing process and is produced using single-crystalline silicon, making it more efficient in contrast to polycrystalline silicon cells, which are produced using crystalline granules and are therefore less efficient than monocrystalline PV [95]. Multicrystalline wafers are frequently formed by pieces thrown from fluid silicon and contain crystalline grains with a size of around 1 cm² that are distributed arbitrarily. The presence of grain limitations in mc-Si cells reduces performance compared to sc-Si cells, as they hinder charge extraction [96].

Of the advanced silicon solar PV technologies, disrupted emitter back cell technology, a revolutionary silicon design that offers enhanced solar cell performance, is the most appealing and intriguing advanced silicon cell technology and is focused on enhancing efficiency. Back passivation film deposition is the primary characteristic of PERC solar PV. Aluminum oxide has taken the place of the silicon nitride oxide that was used before as a passivation material. However, the mass production of PERC technology increased in 2016, resulting in a 20–22% increase in efficiency [97].

Modern gallium arsenide (GaAs) cells use wafers as crystal growth templates despite using thin insulating films. The compound semiconductor gallium arsenide (GaAs) is ideally suited for converting solar energy. With 28.8% for lab cells and 24.1% for modules, GaAs achieved the most remarkable force change efficiencies of any material framework [98,99]. In order to efficiently absorb light over the sunlight-based range while limiting thermalization (heat) misfortunes, III–V multijunction (MJ) sun-powered cells stack at least two single-intersection cells with different bandgaps. Semiconductors of group III and group V elements can shape great crystalline films with variable bandgaps [98,100]. Wafer holding, grid-bungled (variable) methods, and weaker nitride materials (such as GaInNAs) are the main topics of current research and development (R&D) projects. Improving long-term dependability and vast area uniformity, reducing the amount of material required, and simplifying cell designs for various working conditions are major challenges for creating III–V MJ improvements [101,102,103].

Figure 10. Solar PV device structures—film formation [104].

Figure 10. Solar PV device structures—film formation [104].

Alternative developments may be able to reduce costs in the long run, but crystalline silicon now dominates the global PV market. This may result in reduced material use, manufacturing capital requirements, and lifecycle emissions of ozone-depleting substances. This category includes technological advancements in the form of nanostructure materials as well as business advancements in the form of conventional inorganic semiconductors [105].

Silicon wafers have a thickness ranging from 150 to 180 microns (µm), almost exactly the same as the width of a human hair (see Figure 11). Since silicon does not absorb light vigorously, thick wafers are generally needed. Other materials, such as CdTe, CIGS, and quantum dots (QD), have significantly better absorption properties and enable thin PV dynamic film layers to be as thin as 0.1 and 10 µm. When the right substrates are used, thin dynamic layers enable the creation of flexible and lightweight cells while conserving material. Layer opacities are displayed to scale.

4.1. Thin-Film PV Technologies

Thin-film PV technologies can also be divided into commercial and emerging low-cost film developments. Commercial thin film, constituting 10% of the global PV module production, includes cadmium telluride (CdTe), hydrogenated amorphous silicon (a-Si:H), and copper indium gallium diselenide (CuInGaSe₂, or CIGS) [107]. The technique involves the low-deposition production of semiconductor materials no thicker than a few micrometers. The technique is used on a commercial scale with lower efficiency since it is thought of as a less expensive substitute. These technologies can be divided into two types: thin-film photovoltaics (PV) that use silicon in the manufacturing process, including amorphous solar photovoltaics, and thin-film PV that use materials other than silicon, such as cadmium telluride, copper, and indium gallium selenide [108]. Comparing these solar cells to traditional crystalline silicon solar cells, they have a lower temperature coefficient.

Amorphous silicon is created by depositing the active material on a substrate between 150 and 300 °C using the plasma-enhanced chemical vapor deposition process. The use of fewer semiconductor materials during manufacturing, which brings up the possibility of lowering the cost and energy required for production, is an important feature of thin-film technologies [109]. Cadmium telluride (CdTe) and copper indium gallium selenide (CIGS) are two elements that form the basis of the non-silicon-based PV thin-film technology called CdTe. Because CdTe solar cells are produced using low-temperature techniques, they are extremely flexible and cheap. In the PV industry, CdTe has a sizable share of the market. Contrarily, CdTe has some drawbacks. Cadmium is a hazardous element that causes concern for the environment, although the toxicity of CdTe solar modules may be decreased by recycling them once they reach the end of their useful lives [110].

4.2. Emerging Thin-Film PV Technologies

Currently, there are vital emerging thin-film PV technologies, such as copper zinc tin sulfide (Cu₂ZnSnS₄, or CZTS), organic photovoltaics (OPV), perovskite solar cells, dye-sensitized solar cells (DSCs), and colloidal quantum speck photovoltaics.

4.2.1. Copper Zinc Tin Sulfide (Cu₂ZnSnS₄, or CZTS)

Copper zinc tin sulfide (Cu₂ZnSnS₄, or CZTS), with comparative handling approaches and problems, can be thought of as an alternative to CIGS that is bounteous on Earth [111,112]. However, one key test involves addressing a subset of flaws known as the cation issue, resulting from the uncontrolled substitution of copper (Cu) and zinc (Zn) cations, resulting in point abandonments and reduced open-circuit voltage. Lab-cell efficiencies reached 12.6% [113].

4.2.2. Perovskite Solar Cells

Perovskite solar cells were created from strong-state color-sharpened cells, and they have quickly emerged as one of the most potent new thin-film PV developments. Additionally, driving efficiencies increased from 10.9% to more than 20.1% [98,114]. “Perovskite” refers to the crystal structure of the light-retaining film. In addition, the hybrid natural and inorganic lead halide CH₃NH₃PbI_3−xCl_x is the perovskite component that has recently been the subject of most research. Vapor deposition or its solutions can be used to frame polycrystalline films at low temperatures [115,116]. Low material costs, the potential for bandgap adjustment by cation or anion substitution, low recombination misfortunes, and long charge carrier diffusion lengths are advantages of this sort of material [117,118]. However, there are some restrictions, such as high susceptibility to moisture, shape and material characteristics, questionable cell solidity, and the use of hazardous lead [119].

4.2.3. Organic Photovoltaics (OPV)

Organic photovoltaics (OPV), also known as natural photovoltaics, use organic small atoms or polymers to preserve light occurrence. Organic photovoltaics, or OPV, use organic materials or polymers to convert light into power. Donor and acceptor materials with carbon bases are used in OPV. There are no harmful materials like cadmium used in this photovoltaic technique. Consequently, it provides environmental advantages over competing technologies. Natural organic multijunction (MJ) cells may also be easier to build than conventional MJ cells due to their high deformation resistance and straightforward statements. These materials can be gathered into thin films with little effort and little expense using techniques like thermal dissipation and inkjet printing [120]. They typically consist of Earth-friendly components. Recent advances in nanoparticle and polymer OPV technologies have achieved 11.1% efficiency in the lab, but these efficiencies remain substantially lower for large-area cell and module applications. The primary issues relate to the wasteful transport of charged carriers and powered electron gap combinations. These cells have some drawbacks, including poor strength under light, poor long-term stability, and low large-area deposition yield [121,122,123,124]. Despite the poor performance, OPV may still be able to be made quickly and flexibly on a different substrate [125].

4.2.4. Dye-Sensitized Solar Cell (DSSC) Technology

Another advancement is dye-sensitized solar cell (DSSC) technology, which is one of the most advanced and well-known nanomaterial-based PV options [124]. These photoelectrochemical cells are made of a basic inorganic scaffold, often a nanoporous titanium dioxide sheet that has been sharpened with light-absorbing natural dye atoms, typically ruthenium structures. DSSCs generally use a fluid electrolyte to transport particles to a platinum counter cathode (electrode), in contrast to other developments that rely on strong-state semiconductors to transport electrons and generate a photocurrent. By using inexpensive materials and an easy assembly procedure, DSSCs may be beneficial. Additionally, efficiencies of up to 12.3% (11.9% guaranteed) and the potential for adjustable modules were both mentioned. The main challenges include limited long-term strength under high light intensity and high temperatures, low retention in the close infrared range, and low open-circuit voltages brought on by interfacial recombination [126].

4.2.5. Colloidal Quantum Speck Photovoltaics

Colloidal quantum speck photovoltaics, also known as quantum dabs (QDs) [127], are photovoltaic devices that use solution-handled nanocrystals to absorb light energy. Lead sulfide (PbS), a colloidal metal chalcogenide nanocrystal, can have its ingestion or absorption range tuned, which increases the possibility of MJ cells using a single material framework and enables efficient close-infrared photon collection [128]. With a record lab cell productivity of 9.2%, QDPV technological enhancements are improving dependably and promisingly simple manufacturing and air-stable operations [129].

There are many photovoltaic technologies on the market, and they are suitable for specific geographic locations [130]. Figure 12 shows different types of PV system with their efficiency.

Table 1. Types of photovoltaic technologies.

No	Type of Photovoltaic Technologies	Performance Efficiency	Max Power W	Description
1	N-type IBC	22.8%	440 W	A silicon heterojunction solar cell with interdigitated back contact (IBC) demonstrated exceptional performance under one-sun illumination or concentration. The lack of contact grid shadowing at the sunward side and perhaps inexpensive substrate cost due to the thin device design are two benefits of this design. The module assembly costs can also be reduced, as both connections are on the back. The lack of space between the solar cells allows for closer placement of the cells within the module. To increase cell efficiency and reduce manufacturing costs for solar cells, interdigitated back contact (IBC) solar cells are the only feasible choice (Anon, n.d.).
2	Half-cut mono PERC (Passivated Emitter and Rear Cell) HPBC	22.6%	440 W	Solar cells have better durability and performance. Half-cut cells can improve panel efficiencies by a few percentage points in terms of performance. In addition to having higher production rates, half-cut cells are also stronger physically than their conventional counterparts; their smaller size makes them more resistant to shattering. Furthermore, the technique for half-cut cells not only cuts the cells in half but also decreases the cost, guaranteeing a lower LCOE [131,132].
3	Half-cut mono PERC HJT (Heterojunction Technology)	22.3–22.5%	430–440 W	In a single-cell structure, HJT combines the benefits of crystalline silicon cells and thin-film technology. Efficiency levels of over 25% are implied by this. A heterojunction is a junction produced between two separate materials, crystalline and amorphous silicon, in an HJT cell, compared to a normal crystalline solar cell, which employs a single material, silicon. This results in several performance advantages over traditional cells [133].
4	Half-cut mono PERC TOPCon	21–22%	425–430 W	The solar cells receive an extra tunnelling oxide passivation layer from TOPCon. In terms of capital cost, this technology provides an unmatched mix of efficiency and reliability. With the TOPCon procedure, PERC cells (passivated emitter rear contact) become more powerful and effective. New TOPCon technology produces higher power under low irradiation and reaches up to 5 watts per panel above the minimum power rating, with 22% at peak efficiency. After 30 years, the panel would still produce 87.5% of the electricity, showing excellent investment with a longer lifespan (Anon, n.d.)
5	Shingled mono PERC	18–20%	440 W	The shingle cell solar panel uses the shingling method, which offers ultra-high efficiency and increases the performance of the panel in low-light situations, thereby increasing the duration of power generation by the solar PV system. Solar cells are separated into strips and placed inside shimmed modules. Intercell gaps are eliminated to increase power output and module efficiency, and more silicon cells may be packed into a given module [9].
6	Mono PERC	17–19%	440 W	Due to their purity and black appearance, monocrystals are easily identified. They also feature rounded edges and very high efficiency. In an ideal world, this could be about 20%. Such solar modules do not achieve a positive energy balance for several years (Anon, n.d.).
7	Poly PERC	16–17%	440 W	As a less complicated manufacturing alternative to monocrystalline solar cells, polycrystalline solar cells are available. This technique involves pouring liquid silicon into prepared blocks, which are subsequently cut into individual wafers. They become multi-crystalline at this point, accounting for their much greater brightness compared to monocrystalline ones. Although their efficiency is slightly lower at 15%, the streamlined production process improves the energy balance and manufacturing costs (Anon, n.d.).
8	Perovskite solar cells (PSCs)	25–26%	440 W	Recently, there has been a lot of interest in perovskite solar cells because of a number of factors, including their greater power conversion efficiency (PCE), simple fabrication process, flightiness, lightweight design, deplorability in extremely light space, and low cost of material components. The efficiency of perovskite solar cells has recently surpassed 25% [134] because of the superior quality of the perovskite membrane made using low-temperature synthesis techniques combined with the development of suitable interface and electrode materials.

shows the most efficient solar panels for 2023.

5. Multiple Techniques to Remove Dust Particles from the Surface of a Photovoltaic Module

Cleaning photovoltaic panels is an interactive method to improve their performance, which requires a high maintenance cost. PV facilities often have prearranged cleaning cycles that are determined by the projected pollutant losses at their locations and the local climate. PV panels may be cleaned manually or automatically. Depending on a number of factors, including the type and degree of dust deposition, cleaning can be carried out wet or dry [135].

5.1. Natural Removal

The surface of the photovoltaic module is cleaned of dust, either manually or mechanically, or by natural factors such as wind and rain. Dust and sand can naturally be decreased when rain washes them away, but moss would need to be properly cleaned [136]. Wind and rain were the only ways to clean the roofs. It was noted that the performance of solar modules decreased at the end of summer and spring and tended to increase at the end of autumn and winter [137]. On the other hand, the effect of dust on energy output was assumed. The output between the photovoltaic cells and the economic analysis indicated that the total cost of production losses is less than the cost of cleaning; therefore, it is not suggested to rely only on the wind and rain to clean solar panel surfaces [138].

Rainfall is considered to be the most efficient and environmentally friendly cleaning technique since it cleans PV module surfaces. In addition, light rain is detrimental because it collects airborne dust particles and deposits them on the surface, leaving sticky dirt patches that can suddenly reduce the performance of photovoltaic cells [139]. The amount of rain and the movement of wind at high speeds can affect the productivity of PV, as rain and wind are effective techniques for cleaning PV modules. However, they have the opposite effect when the relative humidity decreases simultaneously with wind speed. Using rain to clean PV panels would be both efficient and economical. However, in areas with light rain, dependence on the rain would deteriorate the performance of the PV, as the raindrops collect air molecules, forming a thin film on the surface of the PV system [140].

5.2. Manual Removal

Researchers examined cleaning efficiency, frequency, total cleaning cost, power consumption, and dust weight. A few cleaning techniques such as vacuum cleaners, brushes, cloth wipers, and certain combinations were examined. Each cleaning technique’s optimum cleaning time was investigated over periods of one day, one week, and one month. It was reported that, in desert climates, PV system efficiency was considerably reduced for monthly cleaning durations regardless of the cleaning method. The results showed that fiber-based fabric scanning was the most economical and performance-focused method. The best results were achieved at the lowest expense with regular, weekly cleaning [141]. Cleaning the solar module with brushes would have the potential to reduce the efficiency of the module. Yadav et al. (2021) [142] conducted a study in which the cell was cleaned with brushes and it was discovered that a slight deformation occurred in the cell, resulting in a decrease in power output.

The impact of dust on the electrical performance of PV modules cleaned by brush in Toujounine, Mauritania, weather conditions was examined by Lasfar et al. (2021) [143]. Dust lowered solar module output power by 21.57% compared to clean panels [143]. Tamadher et al. (2020) [144] found that cleaning the cells every evening daily was ineffective. However, efficient solutions reduced dust accumulation on the panels, such as rotating the cells in the evening to face the ground and covering them with a plastic cover from the evening until the morning. The effects of soiling on energy loss, along with the daily and monthly variations in energy production and soiling, were investigated. The results of the optimization showed that the manual cleaning method required cleaning once every three weeks. Further, it was noted that the cost of cleaning was higher than the cost of energy loss [145].

The best time to manually clean a tilt of 30° was found to be around once a week, whereas for a tilt of 90°, it was found to be once every three weeks [70]. The effects of sand and dust on the electrical performance of solar modules in the Adrar region were comprehensively examined. Subsequently, two similar solar PV systems with 7 kW of electricity each were compared. The first system received routine cleanings, whereas the second received irregular cleanings. The boards were manually cleaned with a high-pressure water-based cleanser to remove any remaining water droplets. It was observed that quickly cleaning solar PV systems following sandstorm days could significantly lower energy losses. Cleaning once every 20 days led to a 1.60% decrease in energy in the solar PV system due to the accumulation of dust [146].

5.3. Automated Removal

The surface temperature of the solar module plays an important role in power generation. A cell exposed to high temperatures may experience a reduction in energy production. Ghassan et al. (2023) [147] conducted a study in Al-Buraimi, Oman, and applied water spray technology to cool the surface temperature of the solar panels to maintain the surface temperature and reduce surface heating. The cooling system was very effective and enhanced the output power while maintaining the temperature of the solar panels. A technique based on compressed air was studied, in which a model of dust adhesion and separation mechanisms resulting from the air-blowing process was analyzed. The results showed that the technology was adopted as it increased the energy output of solar panels and could contribute to improving efficiency and decarbonization in the energy industry [148].

A study on the effect of weather variables on dust accumulation and techniques for cleaning solar panels was carried out in Oman by Kazem et al. (2022). Nine different cleaning techniques were adopted. It was discovered that in some cities where the dust accumulation is very low, water was sufficient to wash and clean the solar modules, compared to cities where dust is a problem and where factories and chemical compounds are near the area. For the latter case, a different cleaning technique was used to clean the panels, which included a sodium solution. However, dew made it useless in the winter or before sunrise because it reacted with sodium salts to form a layer that was difficult to remove [149]. Due to the low cleaning quality, high water consumption, and difficulty of achieving consistent cleaning with traditional manual cleaning methods, a water-free cleaning robot is therefore suggested to remove dust from photovoltaic panels of distributed photovoltaic systems in water-scarce areas. The structure, materials, and sealing device of the robot are optimized based on the photovoltaic system’s carrying capacity and operating efficiency. Moreover, to prevent dust during cleaning, a common dust removal system consisting of a rotating brush and negative pressure was developed to ensure the ability of the robot to clean the installed photovoltaic panels safely.

The advantage of the waterless cleaning robot is that it has a small weight and volume, which is more convenient than mechanical cleaning for removing dust from photovoltaic panels. The results showed that the waterless robot could effectively remove dust from the panels, with the rate of increase in the PV energy efficiency ranging from 11.06% to 49.53% and the average dust cleaning rate reaching 92.46%. By assessing the PV efficiency and light transmittance of the panels, the efficacy of the robot was confirmed [150]. The system is composed of a power supply unit, chassis mounts, a motor with a driving circuit, a wiper, and a light-dependent resistor (LDR). A direct current servo motor with a stall torque of 1.47 Nm at 6 V powers the wiper. Silicone rubber is used to manufacture the wiper blade. It can operate in a temperature range of 148 to 572° Fahrenheit and is extremely durable. Moreover, a microcontroller uses an LDR to control the wipers. The experiment was successful, and the results showed that the cleaning efficiency was 97.8% higher than the suggested cleaning technique [151]. For PV panels to operate at their best, contaminants should be removed from their surface using an auto-cleaning system. The location’s climate characteristics, the heating effect of solar radiation, and the seasonal ambient temperature all affect the cleaning method and timetable. Consequently, decreased system efficiency can require a cooling method [90].

In a study by Ekinci et al. (2022) [152], a solar PV panel cleaning robot developed with 3D printing technology was used to clean dirt and dust from solar PV panels. Three chemical solutions were produced in a lab and applied to the solar PV panels. The results showed the significance of using chemical solutions to improve solar PV panel efficiency. Moreover, the solar PV panel cleaning robot ensured that chemical solutions penetrated the surface of the PV panel. As a result, the PV panel cleaned using the recommended chemical solutions produced 15% more power compared to the panel that was not cleanedp. Juaidi et al. (2022) [153] examined the effect of dust deposition on photovoltaic performance by comparing the power output of manually and automatically cleaned panels. The cleaning technique employed in the experiment was an automated cleaning system that was set up to clean the facility every two days. After seven consecutive months, output power dropped by 9.99%, with an average monthly power decrease of 2.93%.

Automated BCS is regarded as the most effective degusting procedure for solar panels and an autonomous self-cleaning method. The primary reason for selecting this approach over others is to lower power costs, decrease dependence on fossil fuels, and help with measures to stop additional environmental harm. Within a month, BCS may increase panel efficiency by up to 9.2% [154]. A cleaning mechanism was developed using a drone to fly over solar panels to clear dust and increase the effectiveness of the panels. Most of the dust gathered on solar panels could be removed since it was at a particular height above the panels. Throughout several studies, various sizes of dust particles were put on the panel to demonstrate its efficacy. The drone pushback can effectively clear the solar panels of most dust while also enhancing their power output. For instance, it was discovered that the output power increased by more than 70% for 50 dust particles spread out across the panel [155]. Robots that clean up dust have different challenges. Slip, weight balancing, control, stability, materials utilized, energy management, energy harvesting, security concerns, online monitoring, data transfer, the cleaning method, and the cleaning medium are issued from the robot-handling point of view [156].

5.4. Preventive Removal

The self-coating technology for solar panels prevents the deposition of particles larger than 10 µm, improving energy efficiency while reducing dust buildup [38]. The effect and efficiency of using glass coated with superhydrophobic silicone and fluorine films were studied. Wang et al. (2018) indicated that the impact of dust on the energy generation efficiency of photovoltaic modules coated with a waterproof fluorine film was lower than its effect on photovoltaic modules coated with a hydrophobic silicon film and that it reduced dust accumulation on the surface of the modules and increased efficiency [157]. A study conducted in Guangzhou, China, on the reduction of dust deposition on the glass covering solar cells by a transparent, highly hydrophobic coating material under different inclined angles of the PV revealed that the hydrophobic super coating significantly reduced dust deposition on the surface of the glass due to its low adhesion energy. The superhydrophobic coating performed better in reducing dust precipitation than the hydrophobic coating. The deposition density on the water-repellent coated glass was only 44.4%, 28.6%, or 11.2% of the bare surface for tilt angles of 30°, 45°, and 60°, respectively [158]. Anti-pollution coatings (ASCs) are a solution to the problem of pollution on PV panels because they can significantly reduce dust buildup and pollution losses.

A study by Hossain et al. (2022) focused on different anti-dust techniques used to minimize PV soiling, and one of the solutions to this issue is anti-soil coatings, which add hydrophilic or hydrophobic coatings to the PV glass’s outer layer and have spectral properties appropriate for PV applications. However, the efficacy of these coatings can be significantly affected by local and environmental factors. It was observed that the coatings’ anti-soiling efficacy varied greatly based on exposure location and time. Coatings showed both increased and reduced anti-soiling performances as opposed to typical uncoated glass [159]. As the 1D and 2D shields were tested, it was discovered that the 1D shield performed better, whereas the 2D shield contributed more to dust deposition on the photovoltaic surface than the non-shield panel. Furthermore, dust collection was greatly decreased by using a mechanical vibrator with a 1D shield. Thus, applying the anti-static coating with the 1D shield while the plate vibrated maintained the efficiency of the plate [160]. Often, coated panels exhibit greater efficiency in terms of energy savings than non-coated panels for certain site conditions. The results showed that the power difference between the coated and uncoated panels was 3.5 kilowatts at its peak when the installed capacity of each group of panels was about 39 kilowatts [161]. Du et al. (2022) [162] designed a new vacuum dust collector to collect the suspended dust particles generated by the MEC nozzle operation. The movement of dust particles was simulated under the operation of the new vacuum dust collector. High-speed imaging experiments were performed to assess the effectiveness of dust collectors and determine the optimum inclination suction angle. The dust-cleaning effect was greatly increased, proving that the dust collector and the MEC nozzle can successfully remove dust from PV panels.

5.5. Electrostatic Removal

An electrodynamic screen (EDS) transmitting particles by electrodynamic waves either up or to the side of concave solar modules is a widely used method to prevent dust from collecting on PV modules. After examination, it was discovered that more than half of the particles successfully moved up the cell, despite the fact that some particles also moved down the slope due to gravity. It is possible to produce an electrodynamic screen (EDS) under optimal and suitable parameters and conditions [79]. Kawamoto et al. (2019) [163] studied electrostatic cleaning equipment where a very high alternating current voltage is applied to the parallel screen electrodes on the solar panel, following which the resulting electrostatic force acts on the particles near the electrodes. A reciprocal movement of the particles arises between the electrodes. Hence, some particles pass through the holes of the upper electrode and then fall into the lower part of the panel due to gravity. In this technology, it is preferable to have a high inclination of the panel and a high voltage at a low frequency. The energy consumption is very low and can be used efficiently in solar power plants in the desert [163].

EDS efficiency was measured in a different situation in Qatar for six months by comparing the soiling loss of an EDS-PV module with EDS activation to that of an EDS-PV module without activation. The EDS exhibited no discernible soil mitigation impact when activated at a 6 kVpp activation voltage; however, it minimized soil loss by 16–33% when activated hourly at 9 kVpp. More research with bigger sample numbers and longer testing intervals is needed to fully comprehend the soiling mitigation capabilities of EDS in field environments [164]. A novel electron beam (e beam) mitigation method was used by Farr et al. [165] to clean dust from surfaces that were shielded. This novel method shows how large charges on dust particles can result from the release and re-absorption of e-beam-induced secondary electrons inside microcavities between dust particles, which can cause the particles to be released from the surface under the effect of strong repelling forces. As a result of the random angles of the microcavities, it was shown that more microcavities can be disclosed by transforming the sample surface to change the e-beam incident angle, increasing the cleaning efficiency.

In contrast to a single fixed beam and sample, it has been shown that a multiple electron beam source setup increases cleaning efficacy by 10–30%. After just 2–3 min of beam interaction, most insulating samples reach 80–90% cleanliness [165]. Said and Walwil (2014) [57] studied the effect of dust pollution on the transmittance of aggregate flat glass, the physical and chemical properties of dust particles, and the spectral transmittance of anti-reflective coated glass. The weak adhesive forces of dust particles on flat glass surfaces were involved. The findings showed that after 45 days, there was a 20% reduction in glass transmittance and a 5 g/m² dust buildup on the cover glass of the PV modules tilted at 26°. Compared to the uncoated glass, the transmittance of the anti-reflective-coated glass decreased less. Due to the increasing contact area between the particles and the surface, the adhesion forces of the particles on the flat surfaces increased as the particle size increased [57]. The effects of dust deposition on the reflectivity of a parabolic trough reflector were investigated in various places. In comparison to dust on the middle and higher edges, the results showed that dust deposition on the bottom edge of the reflector produced the greatest decrease in reflectivity. Dust particles also dominated the mineral feldspar (21.1%), which was followed by calcium oxide (25.4%) and quartz (53.5%) [166].

5.6. Self-Cleaning Removal

In a study by Elnozahy et al. (2022) [167] hydrophilic nano-coated material was investigated as a potential method for reducing the effect of dust on building-integrated PV (BIPV) panels. The results indicate that the nano-efficiency coating reached 11%. PV panels with nano-coating resulted in a targeted 11% reduction in BIPV carbon emissions [167]. Dust accumulation reduces the ability of glass to transmit visible light, which lowers a solar module’s efficiency in producing electricity. It has been proven that one of the solutions to clean dust is to use a superhydrophobic coating to reduce the surface adhesion of dust that results due to special nanostructures and low surface energy [166]. Regarding the issues of ice and dust buildup and the cleaning requirements for solar modules, the highly waterproof coating typically exhibits good light transmission of up to 98.7%; however, its application is restricted by the thickness and shape of the applicable object. Applying most coatings is challenging, with the exception of flat units [166].

An SMA wire actuator was proposed as a new method to reduce dust on PV panel surfaces. It uses waste heat energy at the PV panel’s back surface and converts it into usable mechanical energy using a special thermomechanical property of SMA materials. The test results conducted indoors using a sun-simulator tool demonstrated the possibility of using the reject heat at the PV panel’s back surface to prevent the activation of an SMA-based PV-cleaning system. At an applied solar irradiance power of 1200 W/m², experimental results showed that an SMA activation temperature of about 60 °C was successfully reached over a 40 min test period. This enabled the cleaning system to operate by producing a suitable mechanical displacement based on the collected rejected heat. The cleaning method and its efficacy were highlighted by analyzing and evaluating the overall performance of the constructed systems [168]. The power efficacy of PV panels can increase by up to 14.3% when they are coated with monolithic hydrophobic compounds, including dimethyl siloxane and paraffin.

Dimethyl siloxane-based hydrophobic coverings reduce the surface temperature of coated panels more than uncoated panels [169]. A novel PV/T bi-fluid hybrid system combining active cooling and self-cleaning technology via forced air circulation was used to actively cool this distinctive hybrid system from the backside of PV modules, and water flow was used to cool and clean the front. In accordance with the reference situation without cooling, the test results showed a decreasing linear connection between the electrical efficiency and the temperature increase of the PV modules. The PV module placed in the new hybrid system had an average temperature decrease of up to 15 °C compared to the reference situation. A 5.7% increase in electrical efficiency above the reference condition was achieved under the same operating conditions and at the maximum global solar radiation, or G = 650 W/m². Whereas the average individual energy efficiency was about 14.7%, the average overall energy efficiency was 85.3%. Comparing the new PV/T hybrid fluid system to the reference example thus showed how well this new hybrid system maintained the PV module’s electrical efficiency at its highest level [170]. The photovoltaic solar panels were coated with a water-resistant SiO₂ nanomaterial, which is considered a self-cleaning panel.

Alamri et al. (2020) [171] studied its efficiency and compared it with the clean and unclean panels. It was found that SiO₂ coating resulted in better performance of the PV panels. The overall efficiency of coated plates increased by 15%. Temperature variation has a substantial impact on PV panel cells in dusty conditions, and this can result in severe deterioration and ultimately permanent damage to PV materials. To reduce the surface tension produced between water and the coated face of the solar panels, a novel hydrophobic silicon dioxide (SiO₂)-based nanoparticle coating is recommended. To conduct parallel pilot testing that is equivalent, two identical PV panels were installed. SiO₂ nanoparticles were coated on the first panel, and the second was uncoated. The results showed a substantial improvement in the total energy produced over the study period. Additionally, the waterproof surface of the coated panel’s self-cleaning function allowed water droplets to move easily down its surface, removing dust particles [172].

Researchers highlighted one of the plans to develop a cleaning method and improve the security of the network connection of photovoltaic power stations by carefully evaluating the accumulation of dust on photovoltaic panels. Consequently, a new algorithm was proposed to improve the image to evaluate the accumulation of dust on photovoltaic panels. To investigate the differences in the visual characteristics of dusty and clean PV panels, an atmospheric scattering model was used. By reducing the pixel difference between dirty and clean PV panel images, a model was put forth to explain the relationship between the model coefficient and the dust level. A test setup was created to capture photos of clean and dirty PV panels with various degrees of dust. The parameters of the model were chosen based on how well the data fit, and the addition of a noise component increased the model’s capacity for generalization. The model could estimate the level of dust on photovoltaic panels with an accuracy of 83.78% [150]. PV-cleaning methods are summarized in

Table 2. Summary of PV-cleaning methods.

Reference	Location	Study Period	PV-Cleaning Method	Results
Al-Housani et al. [141]	Qatar	6 months	Manual cleaning: - Mechanical brush - Microfiber-based cloth wiper	PV system efficiency is considerably reduced for monthly cleaning durations regardless of cleaning method in desert climates. Moreover, fiber-based fabric scanning is the most economical and performance-focused method. The best results were achieved at the lowest expense with regular, weekly cleaning.
Yadav et al., 2021 [142]	United Arab Emirates	-	Manual cleaning: - Brushes	After using a cleaning brush to clean the solar cell, it was discovered that the brush caused surface scratches. The output current (A) and voltage (V) were measured together with the electrical characteristics, and they were found to be 7.2 mA and 3.171 volts, respectively. This translates into a voltage loss of 23% and a current loss of 8%, respectively.
Lasfar et al. [143]	Toujounine, Nouakchott, Mauritania	2 months	Manual cleaning: - Brushes	Using a cleaning brush, a power increment of 21.57% was observed.
Tanesab et al., 2017 [137]	Perth, Western Australia, and Nusa Tenggara Timur (NTT), Indonesia	1 year	Natural cleaning	The end of summer and spring saw a decline in solar module performance, whereas the end of autumn and winter saw an increase.
Kimber et al., [139]	California and the Southwest region of the United States	1 year	Natural cleaning	Rainfall is considered to be the most efficient and environmentally friendly technique for cleaning a PV module’s surface. However, light rain is detrimental, as it collects airborne dust particles and sediments them on the surface, leaving sticky dirt patches that can suddenly reduce the performance of photovoltaic cells.
Juaidi et al., 2022 [153]	Palestine	7 months	Automated cleaning	The results showed a power loss of 9.99% and an average monthly power decrease of 2.93% after seven consecutive months.
Fan et al., 2022 [150]	Northeast China	5 months	Automated cleaning: - Water-free cleaning robot	The findings demonstrated that the waterless robot was capable of removing dust from panels, with an average dust cleaning rate of 92.46% and an increase in PV energy efficiency ranging from 11.06% to 49.53%. The usefulness of the robot was confirmed by assessing the PV efficiency and light transmittance of the panels.
Yadav et al., 2021 [151]	India	1 year	Automated cleaning: - Light-dependent resistor (LDR)	The cleaning efficiency was 97.8% higher than the suggested cleaning technique.
Wang et al. [157]	Qinghai, China	-	Preventive cleaning: - Hydrophobic silicon film	Dust has a smaller impact on the energy generation efficiency of photovoltaic modules coated with a waterproof fluorine film than it does on those coated with a hydrophobic silicon film, although both types of modules can benefit from reduced dust accumulation on the surface and higher efficiency.
Zhang et al., 2019 [158]	Guangzhou, China	1 month	Preventive cleaning: - Hydrophobic super coating	The findings showed that the hydrophobic super coating’s low adhesion energy could greatly reduce dust deposition on the surface of the glass. The super hydrophobic coating performed better than the hydrophobic coating at reducing the precipitation of dust. For tilt angles of 30°, 45°, and 60°, the deposition density on the water-repellent coated glass was only 44.4%, 28.6%, or 11.2% of the bare surface.
Joshi et al. [161]	India	1 month	Preventive cleaning: - Anti-soiling coating	The installed capacity of each set of panels reached around 39 kilowatts, and the power difference between the coated and uncoated panels peaked at 3.5 kilowatts.
Elnozahy et al. [167]	Egypt	5 months	Self-cleaning: - Nano-efficiency coating	The nano-efficiency coating reached 11%. Also, according to the economic results, using PV panels with nano-coating resulted in a targeted 11% reduction in BIPV carbon emissions.
Alamri et al. [171]	Egypt	6 months	Self-cleaning: - SiO2 coating	SiO2 coating improved the performance of PV panels. Coated plates’ general efficiency rose by 15%.
Chen et al., 2019 [173]	Doha, Qatar	-	Electrostatic cleaning: - Electrodynamic screen (EDS)	It was discovered that more than half of the particles successfully moved up the cell, despite some particles also moving down the slope due to gravity. It is possible to produce an electrodynamic screen (EDC) under optimal and suitable parameters and conditions.
Farr et al. [165]	USA	-	Electrostatic cleaning: - Electron beam (e beam) mitigation	It has been shown that, by transforming the sample surface to change the e-beam incident angle, more microcavities can be disclosed, increasing the cleaning efficiency. In contrast to a single fixed beam and sample, a multifaceted electron beam source arrangement was demonstrated to improve cleaning performance by 10%–30%. Upon only 2–3 min of beam contact, 80–90% cleanliness was achieved by the majority of the insulating samples.

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6. Solar Photovoltaic Fabrication Methods, Waste Recycling, and Costs

At this time, attempts are being made to find methods to manufacture solar cells so that they are highly efficient, light in weight, and low in cost and have a very long life. Previously, development began with the manufacture of cells using relatively simple and inexpensive techniques such as rotational coating and thermal evaporation; however, it was found that the general manufacturing methods of rotational coating and high-vacuum thermal evaporation were not compatible with the high productivity of cells. Therefore, new methods were used to manufacture solar cells, including the manufacture of polymer solar cells using several methods. This uses the roll-to-roll (R2R) system, and it has been found that the system is considered an efficient processor, requires effective control of the process during manufacturing, and needs to supply new materials and processes to reach organic photovoltaic (OPV) devices that provide operational stability of more than 10 years [174].

In an effort to overcome problems associated with the production of solar cells, there is now 3D-printing technology. Hunde and Woldeyohannes (2023) [175] tested this technology and discovered that 3D-printing technology might be an appropriate option for producing large areas of solution-based solar cells, like perovskite solar cells (PSCs), which are the most promising solar cell materials currently available, with excellent material utilization, low waste, and good elasticity. Moreover, the next generation of photovoltaic devices has an appealing prospect due to their processability and compatibility with large-scale deposition methods. Additionally, even though 3D-printing technology offers many advantages over traditional solar cell-making methods, more effort is required to make it widely accepted by companies and academic institutions [175].

Because of environmental and economic factors, the course of solar hypnotics at the end of life is a concern. Subsequently, some studies focused on recycling technology and environmental impacts but, in return, ignored the policies and regulations for recycling and managing solar photovoltaic waste modules. Using the theoretical approach, Zhang et al. (2023) [176] created a reverse supply chain for a photovoltaic module. A reverse supply chain with two rival collectors and a formal processor under government involvement is the subject of the model framework. The collectors are followers, and the formal processor is the leader. Waste PV modules are collected by collectors from PV power stations at unit collection price P_i and sold. Two avenues for sales are accessible: A module can be purchased through (1) an unofficial channel for unit price c_w, although a unit penalty charge f needs to be paid to the government, or (2) a formal processor for transfer price w. The collector’s prospective revenue determines the channel to be used. The formal processor purchases a PV module from a collector and proceeds to disassemble, grind, remove glass, and treat the module with heat and chemicals to extract recyclable components. The government provides unit subsidy s, which is based on utilization rate τ, and those materials can be sold at unit price P_r (See Figure 13). The effects of cost standards on optimal decisions and the mechanism of government intervention have been analyzed. The results showed that assistance is more effective than penalties for low-cost investments. Still, either of the two policies is effective for high-cost investments in terms of the official processing rate of the solar unit waste in order to select a more appropriate technique for recycling PV in actual recycling procedures. Moreover, the interactive decision model helps the formal processor of waste PV modules achieve the best conversion price and processing capacity at various capacity investment prices. The model also shows the ideal redemption pricing strategy and sales channel plan for collectors. The formal processor selects a low-capacity state at various investment prices. In contrast, the competitive assembler selects a mixed-channel approach only when the investment cost is higher than the threshold. Both the official processor and other collectors would establish a strong relationship in capacity matching when the investment cost is low [177].

Researchers are looking for solutions for recycling solar photovoltaic panels since an increasing number of end-of-life (EOL) solar photovoltaic panels are in use nowadays. An efficient, economical, and environmentally friendly recycling technology system has been established, divided into three steps: unit dismantling, material recycling, and reuse [13]. When EoL PVMs are landfilled, valuable metals are lost and environmental risks arise [178]. The procedure is considered open loop if retired solar panels are stored or landfilled. When solar cells are burned, they damage the air, water, and soil. The production of photovoltaic (PV) modules or other materials using recycled resources is regarded as a closed-loop process [179]. Photovoltaic module recycling is now a wise investment due to improvements in solar module manufacturing. Before recycling, machining is important because it shows how much useful material is recovered and lowers the energy payback time of photovoltaic modules and CO₂ emissions. Studies have concentrated on the utilization of physical, chemical, and thermal processes to recycle photovoltaic modules. Metal content is incredibly low compared to glass and frames. Recycled metals may seem to be worth very little, but when the amount is estimated for 60–78 million tons of PVM waste, the economic advantage combined with the energy generation is huge. Concerns about the economy, energy, and ecology would all greatly benefit from it. The most important materials and metals are frequently used to create wafers or thin films for solar cells—for example, Pb, Ag, Se, Mo, Al, Fe, Zn, Cu, and Ti [180,181]. Improvements in operations and operational conditions can increase the degree of recovery [179,182]. The major variables impacting recycling are the overall PV concentration and the silver (Ag) content in the PV. Recycling volumes and Ag yields are important variables in determining the economic viability of PV recycling. Recycling EoL PV panels without using any PV charges is feasible as long as the Ag concentration is between 0.1% and 0.2%. In this case, the sustainability capacity would be dependent on the actual Ag concentration in the PV waste as the Ag concentration in the PVs decreases. In order to achieve sustainability in PV recycling generally, it is necessary to increase material recovery, establish a smaller number of larger recycling facilities, and reward early investments [183]. Over 80% of materials may be recovered with the Advanced Photolife Process, which integrates a combination of chemical, thermal, and physical processes [184,185,186]. The Advanced Photolife Process was shown to be economically feasible in early research [187]. However, the evaluation was carried out as the last phase of process development, based on predetermined assumptions (such as recycling quantities and concentrations), which have no bearing in the context of waste management as a whole. Many variables that may impact sustainability are unknown, and others—like the materials used to make PVs—are predicted to change over time [188].

One of the top renewable energy technologies that has attained widespread recognition is silicon-based photovoltaics. During the high-value recycling process, a variety of materials are recovered, including aluminum (Al), lead (Pb), silver (Ag), copper (Cu), tin (Sn), silicon, and glass. To enable the separation of raw materials, vacuuming is employed. The main targets of this degassing procedure are the EVA and other polymer-based encapsulations that keep the various PV panel components together. The method used to separate the materials is determined by their density, particle size, and magnetic, optical, or electrostatic characteristics. Compared to conventional EoL Si PV waste treatment solutions, including landfilling, pavilion recycling procedures are also more ecologically beneficial. Additionally, energy use, chemical use, and transportation are important hotspots for PV recycling. It has been noted that using recycled materials generally provides greater economic and environmental benefits [189].

Future approaches for PV recycling have been referred to as chemical recycling (CR), mechanical recycling (MR), and thermal recycling (TR). Using life cycle assessment (LCA), the costs and advantages of various technologies have been thoroughly investigated and contrasted. The results indicate that MR, CR, and TR, have the smallest amounts of life cycle energy usage, industrial water use, and global warming potential, respectively. Cost–benefit analyses also revealed that PV recycling was expensive, despite the fact that all three methods outperformed landfilling in terms of economy and the environment. Additionally, pyrolysis, one of the three recycling technologies, had an edge over the other two, producing more environmental gains since it recovered more metals to replace virgin manufacturing and produced fewer pollutant emissions during recycling [190].

In research conducted in China, electrostatic separation was used to recover silicon from the mechanical cracking products of c-Si solar panels in a non-costly way. A mass fraction of 82.8 wt% of Si in crushed c-Si PV waste was dispersed into the mixed powder that was recycled by electrostatic separation. Waste c-Si PV panels were processed by mechanical crushing, and the products contained two parts: lumps and mixed powder. Investigations were conducted into how Si recovery was affected by powder particle size, DC power supply voltage, and drum rotation speed. The best separation result was reached at a spin speed of 30 rpm and a voltage of 15 kV at this particle size, with a Si percentage of 91.0% and a Si recovery rate of 48.9%. The ideal particle size for Si recycling by electrostatic separation was 0.30–0.45 mm. This work offers a novel approach for recovering silicon from used c-Si solar panels with more industrial recycling potential [191].

The method of recycling solar waste has certain significant challenges. First, five points of view—technology, economics, laws, rules and standards, and industrial environment—were used to categorize the challenges facing the recycling of solar module waste. Second, a suggestion for the methodology and framework of the study of the challenges of recycling PV module waste was made, and third, the interrelationships between the challenges and variables were sorted out. The difficulty of conducting recycling operations in batches for an extended period of time, the costly initial investment, the lengthy payback period, the lack of incentives, the limited size of the industry, and the institutions’ lack of excitement are the key barriers at this time. The findings indicated that the primary constraints on recycling used PV modules are the difficulties of recycling in batches over an extended period of time, the high initial investment costs, the lack of incentives, and the limited market size. Therefore, after ten years, the negative effects of the high initial investment and the small market size would decrease, whereas the negative effects of the inadequate infrastructure would increase. The government should execute work in four areas—recycling standards, incentive programs, technological research and development, and the installation of demonstration sites—in order to remove significant barriers and encourage the positive development of solar-recycling companies [192].

The lower carbon emission of solar photovoltaic (PV) energy has prompted the construction of PV installations worldwide. This has consequences on biodiversity and the climate, resource use, and the removal of enormous solar panels that have reached their end of life. The development of a network that carries out long-term monitoring and evaluation of many facets of the setting, such as the soil microenvironment, biological community, radiation balance, and energy balance, has been studied as one of the proposals for and solutions to this problem. Additionally, thorough planning and site selection, full disclosure of construction conditions, avoidance of installation in environmentally sensitive areas and sites with historical significance, and careful planning in construction are proposed. It was recommended that PV companies be instructed to create greener, lower-carbon technologies as well as information management and certification systems that index the full PV industry life cycle [177].

Significant progress in renewable energy sources is expected to lead to decarbonization and a reduction in greenhouse gas emissions worldwide. Evaluating energy integration is crucial in light of climate change in order to boost the stability of the energy supply. A set of global climate models from the CMIP6 project was used to investigate the integration of solar and wind PV generating in North America using the SSP2-4.5 scenario. Two metrics were employed to assess this integration: the temporal integration index (Ci) and the similarity index (Si). These variables were grouped and integrated into an index to determine the best places to integrate solar photovoltaic and wind energy sources. The results indicated that a high degree of similarity (SI) between two renewable resources was found in the Caribbean Sea, Gulf of Mexico, the coastal margin of the South Pacific Ocean, and most of the interior of North America, whereas a high degree of temporal synchronization (CI) was obtained in most of North America, with the exception of several regions of Mexico, the eastern Caribbean, Hawaii, and the coastal edge around California [193]. In another study, on a few islands in the Philippines, the integration of solar photovoltaic (PV) and wind energy was modeled. The results showed that solar and wind energy grids accomplished 58.58% of off-grid renewable energy in the Philippine Islands, saving 34.03% in electricity spending compared to diesel systems [194]. A hybrid renewable energy system integrating solar, wind, and hydroelectricity into one compact grid was implemented and investigated. The results showed that hybrid renewable energy is a practical alternative to costly national utility networks, making it appropriate for isolated places that require power. Additionally, by reducing the requirement for fossil fuels and wood, the use and hybridization of energy supplies would improve environmental sustainability and promote active and healthy lifestyles [195]. Daniela-Abigail et al. (2022) [196] worked to develop sustainable PV waste rules for a vulnerable area in Yucatan, Mexico, by combining the environmental, economic, and social components of PV waste. It was reported that these effects could be mitigated by recycling PV energy, with a noteworthy 78% reduction in human toxicity and freshwater ecotoxicity. According to life cycle cost analysis, recycling solar panels can result in an isoelectric cost that is around 2% less than it would be otherwise. According to the sociological study, recycling photovoltaic panels may be permissible if public awareness campaigns and group training programs are offered to promote the process of enforcing regulations.

7. Market Value of Photovoltaic Installation

Solar energy is the most widely used and developed renewable resource in the world. However, a discrepancy between market demand and related production profiles prevents it from reaching its full capacity. Winkler et al. (2016) [197] highlighted that some of the primary drivers of changes in market value include fuel costs, conventional capacity, and CO₂ pricing. Furthermore, the significance of these factors varies with the rate of penetration: For smaller percentages of renewable energy, fuel costs, conventional capacity, and CO₂ pricing are the most significant, but flexibility choices become more significant as the rate of penetration increases. The Swiss electrical system was designed using two models. The first model makes use of Swissmod, a load flow and transmission model for electricity, and the second model, OREES, is a system model for electricity that employs an evolutionary strategy to enhance the PV situation. Borenstein quantified the cost–benefit market value comparison of a 10 kW solar PV system in California using simulated and historical wholesale market pricing that accounts for typical transmission losses and investment expenses. They concluded that PV did not have a compelling financial case in California by comparing the time-varying value of solar to its constant counterfactual and considering the costs of investment and maintenance. Moreover, different panel orientations in California indicate that load–response investments might raise the market value of solar energy [198]. Using historical data, Zipp et al. (2015) [199] investigated demand-oriented designs as opposed to orientations that maximize gross productivity. They discovered that rules that disregard market value are mostly responsible for Germany’s solar orientation. The study modeled market prices for upgraded PV installations by examining meteorological data from many years, various CO₂ costs, and upcoming advancements in Europe’s electrical infrastructure. As a result, it was discovered that mountain installations need less land and have a greater market value than low-altitude PV placement options. Better demand alignment has contributed to market appreciation, especially during the winter months, when demand is at its highest. Consequently, it was discovered that the returns from panel capacity from optimum placements in the Alps are typically 20% higher than those from PV installations in cities. Furthermore, the Swiss Alps have even higher yields (33%), allowing for a capacity of over 1 GW. Alpine photovoltaic systems may be extremely profitable investments, in addition to being beneficial from a system viewpoint, because of their high market prices and increasing value elements [200]. Moreover, the cost of silicon photovoltaics fell from USD 76.67 in 1977 to less than USD 0.36 in 2014 as competition in technology improved efficiency and lowered costs [201]. This dropped further to an even lower price in recent years, making solar PV more popular.

Gómez-Calvet et al. [202] emphasized the need for flexible technology development in research to transmit suitable market signals for investment and create a flexible network similar to that of European countries. Demand-side responses would also be very important. Additionally, it is critical that market design strengthen system resilience by equating responsibility for all VRES generators with a cost-reflective imbalance-pricing design that encourages resilience in a practical way. For instance, the construction of a solar photovoltaic capacity of 5 megawatts in different locations in Oman is under discussion. The solar power plant produces renewable energy on an annual basis in 25 different places, ranging from 9000 MWh in Marmul to 6200 MWh in Sur. In the best location and in the least appealing site, the solar plant’s capacity factor varies between 20% and 14%, and the cost of energy varies between USD 210/MWh and USD 304/MWh. Without considering the external expenses of fuel, the analysis demonstrated that PV at the optimal site is comparable to diesel production [203].

8. Conclusions and Future Perspective

Solar energy is an appealing option that can satisfy the need to expand energy sources and assist with economic variety. Many regions have great prospects for solar energy development and expansion. This paper reviews the performance and efficiency of photovoltaic modules, which are greatly affected by temperature variations, wind speed, humidity, dust properties, and installation factors such as the inclination angle, the installation location of photovoltaic modules, and the surface properties of photovoltaic modules. Additionally, a variety of technologies and methods have been discovered to reduce the amount of dust that settles on the surface of the PV module. This paper also highlights the types of photovoltaic modules and compares them in terms of the efficiency ratio, maximum power, and most important characteristics of the modules. Moreover, the materials used to manufacture PV modules are presented. This comprehensive review of the usage of photovoltaic systems can be helpful for researchers. For example, it was identified that a combination of high temperatures and low humidity could lead to an increase in the deposition of dust. As for wind speed, with the increase in wind speed and particle size, the number of sediment particles decreases first and then increases. Differences in the amounts of dust particles do not clearly impact the rate of dust deposition on PV panels, but some types of dust cause partial shading, which leads to a decrease in the efficiency of the modules. In terms of the tilt angle, the amount of sediment dust decreases with the increase in the tilt angle of photovoltaic modules. Climatic conditions affect the performance of photovoltaic modules by accumulating dust. Rainfall has an impact on the process of dust deposition. Rainfall of at least 20 mm is required to remove dust from the surface of solar cell, and a lack of rain may cause the dust to turn to clay, leading to the modules being shaded. The N-type IBC is the best type in terms of efficiency and may reach 23%. In addition, IBC solar cells have demonstrated exceptional performance under one-sun illumination or concentration. Perovskite solar cells have received much attention due to their higher power conversion efficiency, reaching more than 25% recently. In terms of mitigating and reducing dust from photovoltaic modules, there is no fixed effective technology for photovoltaic cleaning, so it depends entirely on environmental conditions such as sandstorms and rain. Cleaning techniques include manual removal, natural removal, self-cleaning removal, automatic removal, preventive removal, and electrostatic removal, all of which have different effects on removing dust accumulation.

The most common solar cells are crystalline silicon (C-Si) cells, which are considered rather expensive but have excellent properties. They are environmentally friendly, have a long life, and can withstand harsh climate conditions. Over the previous 40 years, first-generation crystalline silicon (c-Si) modules have amassed a market share of 80–90% and would account for most of the upcoming PV waste stream. This is followed by thin-film technology, which is more flexible, less expensive, and has lower efficiency. On the other hand, the amount of power depends on material composition and cell size, radiation, and surrounding conditions. Currently, solar PV experiences lower efficiency mainly due to the conversion of much of the solar radiation into thermal energy, increasing the temperature of solar PV modules and reducing electrical power production. Photovoltaic thermal (PVT) technology has received much attention in recent research in terms of producing both electrical and thermal energy. The latter has been proposed to improve further with the use of phase-change materials (PCMs). Phase-change materials absorb and store the surplus heat from solar panels for different energy utilization. Nevertheless, after being charged, the PCMs return the thermal heat to the assembly. By heating a working fluid, the extra heat generated during the entire process may be used to meet the thermal energy needs of a household or commercial setting. Due to the recent extensive research on solar PV, it is projected that solar PV will become the first largest renewable electricity technology and take on a bigger energy share in the future while rendering the energy sources from conventional fuels minimal.

The end of life of solar energy is a concern because of environmental and economic factors. Between 60 and 78 million tons of PV waste are predicted to be in circulation by 2050. The most effective techniques for recycling modules are being investigated. Researchers are looking for solutions to recycle solar photovoltaic panels since an increasing number of end-of-life (EOL) solar photovoltaic panels are in use nowadays. One of the solutions is to dismantle the modules, recycle the materials, and reuse them to be effective, economical, and environmentally friendly. The presentation of challenges, possibilities, models, and circular arguments allows for careful evaluation of both open-loop cascade alternatives and closed-loop recycling. Adopting circular economy concepts can improve recycling and recovery rates and help balance environmental variables such as emissions from manufacturing.

There are many methods and techniques of photovoltaic recycling, including mechanical recycling, thermal recycling, and chemical recycling. Using the life cycle technique, each technology was verified, and it was found that thermal recycling technology is the best due to the fact that it achieves more environmental gains and results in fewer emissions during recycling. Several methods have been investigated to recover silicon from c-Si solar panels, and electrostatic separation has been found to be an effective and inexpensive method, where the ideal particle size for Si recycling by electrostatic separation is 0.30–0.45 mm and the Si recovery rate is 48.9%. The negative impacts of a large initial investment and a limited market size would decrease after 10 years of recycling PV modules, whereas the negative effects of inadequate infrastructure would increase. The government should focus on recycling standards, incentive programs, technical research and development, and demonstration locations to remove these obstacles and promote the growth of solar energy-recycling companies.

Through research and studies in the future, integrating wind energy, solar energy, and hydroelectric energy into a single network is a viable option. This would be a practical alternative to the costly national utility networks and suitable for isolated places requiring energy. In addition, it improves environmental sustainability and promotes active lifestyles. When photovoltaic panels reach the end of their lifespan, there are consequences for biodiversity and the climate. PV companies are guided to create greener and lower-carbon technologies as well as information management and certification systems that catalog the full PV industry life cycle. More attention is required to enhance the performance of solar PV, and this review can play a role in the effort to elevate green energy production from solar PVs in the future.