The effect of environmental factors and dust accumulation on photovoltaic modules and dust-accumulation mitigation strategies

Renewable and Sustainable Energy Reviews 82 (2018) 743–760 Contents lists available at ScienceDirect Renewable and Sustainable Energy Reviews journa...

Download PDF

2MB Sizes 492 Downloads 1109 Views

Report

PDF Reader
Full Text

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

Contents lists available at ScienceDirect

Renewable and Sustainable Energy Reviews journal homepage: www.elsevier.com/locate/rser

The eﬀect of environmental factors and dust accumulation on photovoltaic modules and dust-accumulation mitigation strategies

MARK

⁎

Syed A.M. Saida,b, , Ghassan Hassana,b, Husam M. Walwila, N. Al-Aqeelia a b

Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals (KFUPM), Dhahran 31261, Saudi Arabia Center of Research Excellence in Renewable Energy (CoRE-RE), King Fahd University of Petroleum and Minerals (KFUPM), Dhahran 31261, Saudi Arabia

A R T I C L E I N F O

A B S T R A C T

Keywords: PV performance Dust accumulation Dust mitigation

The mitigation of environmental eﬀects on clean-energy technology is an area of increasing interest. Photovoltaic (PV) modules have been widely used in small and large-scale applications for many years. However, they are not yet competitive with other electrical energy-generation technologies, especially in environments that suﬀer from dust, airborne particles, humidity and high ambient temperatures. This paper presents a review of the eﬀect of climatic conditions on PV module performance, in particular, the eﬀect of dust fouling. Research to date indicates that dust deposition has a considerable eﬀect on PV module performance as it reduces the light transmissivity of the PV module surface cover. Studies on the ways in which dust is deposited on PV module surfaces are reviewed, as understanding this process is essential to develop eﬀective mitigation approaches. Module performance is also adversely aﬀected by high ambient temperature, humidity and lack of rainfall. The current review summarizes the past, current and promising future approaches towards mitigating environmental eﬀects, in particular dust fouling. Electrostatic cleaning methods and micro/nanoscale surface functionalization methods both have the potential to counteract the negative eﬀects of dust deposition, with the combination of the two methods showing special eﬃcacy, particularly in arid regions.

1. Introduction The use of, and interest in, renewable sources of energy is growing rapidly. This trend has been driven by increases in the price of fossil fuels, concerns about air quality and human health and the eﬀect of fossil-fuel dependence on the environment. Photovoltaic technology could oﬀer a promising and clean alternative to fossil-fuel-based energy generation. The Kingdom of Saudi Arabia (KSA) planned to install PV systems capable of producing 1481 MW of power over a four year period as it scales up production of renewable energy [1]. Renewable energy reliability had always been a huge question mark, as we have no control on natural parameters like solar radiation, Wind etc. Also, the maintenance required for a renewable energy is more than most of the conventional forms of energy, Advantages of the renewable energy is that they are eco-friendly which makes them "not harmful" to our environment. It is abundant and is a natural form of resource. Despite the development of new higher-performance materials, the greatest disadvantage of photovoltaic systems remains their limited eﬃciency in converting solar to electrical energy, which ranges between 12% and 20% [2]. The degradation of PV system performance is mainly due to several

⁎

factors such as climate and environmental conditions, mishandling of PV modules which happens in the transport and installation, the site at which is installed and the maintenance. Although signiﬁcant advances have been made in PV systems within the last few decades, designers still face challenges related to the eﬀects of climate conditions on PV system performance. In practice, PV module performance is much lower when operating outdoors than under controlled laboratory conditions [3,4]. Key climatic conditions that strongly aﬀect PV module performance include solar radiation, temperature, wind speed and direction, relative humidity, and dust [5–8]. Ordinarily, solar irradiation and air temperature have more signiﬁcant impact on PV output power than wind speed and humidity [9,10]. Dust is a unique problem that signiﬁcantly aﬀects the performance of PV modules in the Gulf Region. Studies have been conducted on the eﬀects of diﬀerent climatic conditions on PV system performance. In general, the environmental factors have diﬀerent impact on the PV systems performance. For example, the PV power outcomes reduced with elevated relative humidity, air temperature and dust deposition while it increased with increasing in wind speed [11]. Mekhilef et al. [12] reviewed the eﬀects of dust accumulation, humidity level and air velocity surrounding the PV system. They concluded that each condition inﬂuences the other,

Corresponding author at: Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals (KFUPM), Dhahran 31261, Saudi Arabia. E-mail address: [email protected] (S.A.M. Said).

http://dx.doi.org/10.1016/j.rser.2017.09.042 Received 4 May 2017; Received in revised form 4 September 2017; Accepted 14 September 2017 1364-0321/ © 2017 Elsevier Ltd. All rights reserved.

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

and therefore they should be considered together. Mani and Pillai [13] reviewed the dust eﬀect on PV module performance during two time periods, 1940–1990 and 1990–2010. They developed and used an appropriate cleaning/maintenance cycle for their PV systems that considered the prevalent climatic and environmental conditions. However, such studies focused only on changing parameters that signiﬁcantly aﬀect PV module performance without investigating eﬀective ways of mitigating their impact. This study presents a review of recently published studies on factors inﬂuencing PV module performance, particularly dust fouling, and diﬀerent methods of mitigation. The ﬁrst part focuses on how performance is impaired due to a variety of environmental conditions. An overview of studies describing the mechanisms that cause these eﬀects and how they aﬀect each other is also given. In the second part we look at some of the past, current, and promising future approaches for mitigating dust-fouling eﬀects and summarize how the eﬀectiveness of these mitigation techniques is aﬀected by other environmental factors.

Fig. 1. Impact of wind speed on temperature diﬀerence between PV modules and the environment-case study in Greece [28].

particles (> 75 µm) and that caused by small particles (30 µm) [20]. That results was conﬁrmed by who observed that the surface mass density of the dust deposition was negligible at a high wind velocity which is greater than 24 m/s [21].

2. Eﬀect of climatic and environmental conditions on PV module performance The variation of climatic conditions from location to location around the world has a corresponding eﬀect on PV module performance in diﬀerent regions [7]. The parameters that may impact PV module performance include solar radiation, wind velocity, rainfall, temperature, humidity and the probability of dust presence. The following subsections summarize the eﬀects of each of these conditions on PV module performance, as reported in the literature.

2.1.2. Wind speed and direction impact The wind enhances dissipative convective heat transfer from the module, thereby reducing its temperature, which helps maintain its conversion eﬃciency [5,22–25]. For example in Dhahran, KSA increasing the wind speed from 2.8 to 5.3 m/s resulted in reduction in module temperature within a range of 10 °C [26]. In Slovenia, the diﬀerence between the module temperature and the ambient temperature for any non-zero conversion eﬃciency (regardless of the mounting conditions) reduce to half the value, if the wind speed increases from zero to 12 m/s [27]. In Greece, the ﬁndings of an outdoor measurement clearly indicated that the diﬀerence between modular and ambient temperature (Tc-Ta) decreases with increasing wind speed, as shown in Fig. 1 [28]. It is also observed that the diﬀerence between the cell and ambient temperatures is between 10 and 20 °C during calm spells, then demonstrating a gradual shift to zero for high wind speed cases [28]. However, under series of artiﬁcial tests for wind speed and direction eﬀects on PV performance, it was found that the PV cell temperature rise over the ambient one is extremely sensitive to wind speed, less so to wind direction [29].

2.1. Eﬀect of wind velocity Wind velocity can have both positive and negative eﬀects on PV module performance. The impact of wind velocity on PV module performance is mainly a function of wind speed and direction, PV module surface structure, and dust deposition. In an outdoor environment, wind velocity, ambient temperature, surface structure, and sun irradiance inﬂuence module temperature. 2.1.1. Dust deposition impact Wind blows away dust particles from the PV module surface, which can reduce dust deposition [14]. In Egypt, it is observed, a decrease in the rate of dust deposition occurs on a module at a particular tilt angle due to wind blowing after 2 weeks of exposure to weather conditions [15]. However, the wind can also add to the negative eﬀect of dust by transferring and spreading dust and sand particles within the atmosphere, which may lead to increased deposition layers. As the wind speed increases more dust deposition will occur, which results in deterioration of solar cell's ﬁll factor [12]. In the Greatest Desert-Libya, Clarke et al. [16] reported that increase in dust deposition generally coincides with increase in mean monthly wind speed. For example wind velocities of 6.5 m/s represent the minimum threshold velocity for dust entraining winds in Libya [17]. To simulate the eﬀect of wind speed and direction on dust deposition and accumulation and resulting PV module performance, Goossens et al. [18] performed a wind tunnel simulation and ﬁeld experiments. Their results indicated that wind direction affects dust deposition and distribution more than wind speed does. However, it is concluded that the reﬂected eﬀect of wind on dust deposition depends on the wind speed. The wind speed was tested in range between 0.63 m/s and 2.59 m/s. High wind speeds (2.59 m/s) lead to high dust accumulation on a cell, resulting in sharp performance drops. In cases of low wind, dust accumulation is smaller, and the drop in cell performance is less [19]. Additionally, it is observed that the eﬀects of Martian dust particle size on PV performance vary with wind velocity. When the wind velocity was very high (89–116 m/s) there was no signiﬁcant diﬀerence between the degradation caused by large

2.1.3. PV surface structure impact It has been reported that the surface structure has a signiﬁcant cooling eﬀect, increasingly pronounced at higher wind speed [30]. At higher wind speeds, the module temperature decreased due to the increased convective module cooling. Experiments carried out in a wind tunnel in USA showed that at high wind speed, structured glass modules operate at lower temperature than ﬂat glass modules. Fig. 2 shows that at a wind speed of 10 m/s, a module fabricated with grooved glass

Fig. 2. Eﬀect of wind speed on module temperature (temperature diﬀerence compared with ﬂat glass module) in USA [30].

744

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

Fig. 5. Solar panel temperature and Eﬃciency [38]. Fig. 3. Average temperature increases of anti-reﬂective coated and textured modules with respect to ﬂat glass modules – Dhahran, KSA [26].

cover was found to be 3.5 °C cooler than a ﬂat glass cover [30]. Duell et al. [30] indicates that at low wind speed (i.e. when the wind speed is less than 3 m/s) the structured glass modules temperature was relatively higher than that of ﬂat glass modules. This behavior is attributed to increasing in light transmission to the cells. Interestingly, as the wind speed increased, the structured glass modules were observed to be progressively cooler than the ﬂat glass modules. Up to a 2.5 °C temperature diﬀerence was observed at 12 m/s winds speed for the grooved glass module. This is attributed to increase in convective cooling of the structured glass [30]. Whereas in Dhahran, KSA, four glass surface structures were tested at outdoor conditions, with the wind ranging between 0 and 10.5 m/s during the testing period. The modules included a ﬂat surface with anti-reﬂection coating, a ﬂat glass surface with no anti-reﬂection coating, a micro-textured surface coated with anti-reﬂection coating, a micro-textured surface with no anti-reﬂection coating, and a mm-scale textured surface. All tested modules except mm-scale texture showed an increase in their temperature regardless of the wind speed. The average ranges of increase in modules temperature was 1–2 °C as shown in Figs. 3 and 4 [26].

Fig. 6. Solar cell eﬃciency variation with cell temperature [43].

performance has been observed during high-temperature periods (as shown in Fig. 5) [38–42]. Katkar et al. [43] used an environmental chamber to test the eﬀect of temperature on the performance of industrial solar cells. The eﬃciency of the solar cells was seen to increase from 9.7% at 31 °C to 12.0% at 36 °C, beyond which the eﬃciency started to decrease, as shown in Fig. 6. Hence, the output power reduction mainly depends on panel mounting and weather conditions [1,44]. Some studies showed that power output of a PV module decreases by about 0.5% per degree (°C) of cell temperature rise [28]. Preliminary results with respect to module eﬃciency demonstrated that the single crystal silicon solar cell eﬃciency highly depends on cell operating temperature. It was observed that at 64 °C operating temperature, the eﬃciency of the solar cell decreased by 69% compared with that measured at STC [45]. At outdoor conditions of 1000 W/m2 irradiation level without cooling, the cell temperature increased to 56 °C this increase lead to 3.13% decrease in module electrical eﬃciency [46]. Another study indicated that for an increase in module temperature from 43 to 47 °C, the module eﬃciency decreased by around 5% which indicated the eﬀect of wind speed variation on the rate of temperature increase [40]. Literature reports the maximum PV eﬃciency at 25 °C ambient temperature. In contrast, Garg [47] reported that the DC output obtained at 40 °C ambient temperature in Western Rajasthan, India. On the other hand, it was noticed that mounting the module on a tracker system makes the hourly backside temperatures of the solar PV module higher than the temperature of modules mounted on ﬁxed stand. This is due to the fact that modules with tracking systems receive more solar radiation and hence their back temperature is higher as shown in Fig. 7 [40]. Hence, the simpliﬁed proposed linear correlations between both module electrical eﬃciency and its power output with its operating temperature is considered to be doubtable; as the relations

2.2. Eﬀect of temperature The PV modules transform only a small portion of solar radiation into electricity and the rest into heat. Therefore, the modules temperature increased and their electrical eﬃciency is reduced [31]. The PV cell performance is sharply sensitive to cell temperature which is function of weather variables (ambient temperature) solar irradiance [32–35] cell material and module encapsulation absorption [12]. However, the expected temperature coeﬃcient and PV performance given by the manufacturers, did not always ﬁt the real modules performance [36]. As module temperature increases, the band gap of the cells usually decreases, resulting in the absorption of longer wavelength photons, and the minority carrier lifetime generally increases. These factors slightly increase the light-generated current (Isc) but lead to a reduction in the cell's open circuit voltage (Voc), which results in the cell's ﬁll factor overall reduction. The ﬁll factor determines the module's overall power and hence its eﬃciency [37]. An obvious drop in PV

Fig. 4. Eﬀect of wind speed on modules temperature – KSA [26].

745

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

Fig. 8. Hourly backside temperature of PV modules [40].

radiation. Therefore, the PV modules stores heat and the module backside temperature is greater than the ambient temperature. The results indicated that the polycrystalline module generally stores more heat than monocrystalline modules subjected to similar outdoor condition [40].

Fig. 7. Eﬃciency vs. temperature [40].

were extracted at a speciﬁc mounting geometry or building integration level. Thus, one must be careful in applying a particular relation for a certain conditions [48–50].

2.2.2. Material encapsulating impact Temperature eﬀects on PV performance strongly depend on the material used to encapsulate the PV module. The thermal dissipation and absorption properties of the materials encapsulating the module dictate the eﬀects of temperature. Highly dissipative materials can mitigate the heating eﬀects of climate factors. On the other hand, highly absorptive properties can exacerbate heating eﬀects from climate factors [54,55]. The correlations for the PV operating temperature are either explicit in form, thus giving Tc directly, or they are implicit. The temperature of the cells within a PV module, i.e. Tc, may be higher than the back-side temperature, Tb, by a few degrees, their diﬀerence depends on the module substrate materials and on the solar radiation ﬂux levels [49]. Historically, the encapsulant copolymer ethylene vinyl acetate (EVA) which is shown in Fig. 9 was commonly used in nearly all PV modules [56]. Over the years, in addition to ethylene-vinyl-acetate encapsulant (EVA), diﬀerent encapsulant materials have been used in PV modules such as Polyvinyl Butyral (PVB) and silicone rubber. A number of studies have shown the relative advantage of silicone encapsulant over EVA [57]. It has been demonstrated that silicone encapsulated modules outperform EVA encapsulated modules at levels higher than 2% kWhr/kWp relative eﬃciency gain after exposing modules to all seasons, experiencing temperatures from approximately 95°F to − 10°F, and sun, rain and snow conditions [58]. Walwil et al. [59] Compared the temperature impact on commercial glass cover and three diﬀerent commercial PV module encapsulates (EVA, silicone and Ionomere encapsulate). It was found that the temperature in all coated and textured modules increased by 0.5–3 °C compared to ﬂat surface

2.2.1. Solar based material impact Temperature coeﬃcients of modules are speciﬁed by heating the PV module to a predetermined temperature (commonly 80 °C). The I-V characteristics measured under a sun simulator as the module was allowed to cool down uniformly to ambient temperature (25 °C). Indeed, the eﬀect of module temperature on module performance varies with its cell material based. For example, At 1000 W/m2 irradiance, The maximum powers of all three modules have relatively low temperature dependence as compared to mono-crystalline and multi-crystalline modules [41]. Also, it was found that the a-Si:H/aSiGe:H tandem solar cell maintained a higher output power than the others even after longtime operation during which a temperature range of 25 °C to 80 °C [51]. Monocrystalline maximum eﬃciency (78%) was achieved at high temperature 49.9 °C at 12:45 p.m. But the maximum eﬃciency for amorphous PV is 61.6% corresponding to lowest temperature 40.9 °C at 15:45 p.m., where Δ Eﬃciency/1 °C for monocrystalline is −0.010 and for amorphous equals −0.030) [30]. Hashim [52] compared the PV performance (mono-crystalline Silicon (mc-Si), poly-crystalline Silicon (pc-Si), amorphous Silicon (a-Si) and Cupper Indium Gallium di-selenide (CIGS) under climate temperature of Baghdad city. The results revealed that the output power dropped with temperature by −0.0114, −0.0915, and −0.0276 W/°C for a-Si, pc-Si and CIGS, respectively while the maximum reported drop was −0.1353 W/°C for mc-Si. Based on ﬁeld studies, Table 1 compares the eﬀect of diﬀerent solar cell materials on the overall eﬃciency. The hourly backside temperature proﬁle of the polycrystalline module (HDS130P), mounted on the ﬁxed stand, is compared in Fig. 8. The modules were mounted in sun tracker that focused directly to solar Table 1 Shows the overall eﬃciency drop of diﬀerent solar cells with their testing temperature reported from diﬀerent ﬁelds. Study & location

Solar cell based

Testing temperature

Eﬃciency Drop

Greece [28] Saudi Arabia [1] Saudi Arabia [1] Japan [53] Japan [51]

mono-crystalline multi-crystalline thin ﬁlm amorphous hydrogenated amorphous silicon hydrogenated amorphous silicon germanium

20 °C 25 °C 25 °C 20 °C 25 °C

0.5% /C 16.5% 0.48%/C 15% 8.5%

25 °C

8.0%

Japan [51]

Fig. 9. Schematic view of a PV module with ethylene vinyl acetate (EVA) encapsulant [60].

746

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

cover. However, the performance of encapsulation will depend strongly on the location of the modules and the weather temperature to which they are subjected [57]. 2.3. Eﬀect of humidity An increase in solar panel eﬃciency is observed at low relative humidity. Suspended water vapor droplets in the atmosphere during humid days, particularly those that have a size larger than the wavelength of the solar beam, can scatter, refract, or diﬀract incident solar light. Hence, the humid conditions can reduce the power produced by the solar module [12,61]. Conversely, Omubo-Pepple [38] studied the eﬀect of relative humidity and solar ﬂux on the PV module eﬃciency using a B-K Precision Model 615. The conversion eﬃciency of solar panel was calculated using the following formula:

Efficiency =

Power of solar panel × 100% Area of solar panel × 100

W m2

The result indicate that a direct proportionality between, output current, solar ﬂux and PV module eﬃciency. Also the authors reported that a current of 1.842 A produced 82% conversion eﬃciency. Therefore, it has been reported that at low relative humidity the solar ﬂux increases, and thus, the solar panel eﬃciency becomes higher (as seen by Fig. 10) [35,38,39] and Fig. 11 [62]. The eﬀect of relative humidity on eﬃciency of solar panel is also reported by Ettah et al. [35] (Fig. 12). The eﬃciency of solar cell increases from 9.7% at 60% humidity to 12.04% at 48% humidity [43]. In terms of the output power, it has been reported that the power decreased by about 3.16 W with a 20% increase in relative humidity [36]. Also, in MENA region, Ramli et al. [63] studied the reduction of PV output power under rainy and cloudy conditions. The experimental results revealed that, under rainy conditions, the PV output power decreased by 40% at relative humidity of 76.3%, and a decrease in output power during cloudy conditions by 45% at 60.5% relative humidity. On the other hand, in India, Nair et al. [64] elucidated that humidity might have a positive impact on PV output power. This can be attributed to the other environmental factors inﬂuencing the dust accumulation. It was observed that, near saturation humidity (above 60%), the PV output power increased by 6–12%.

Fig. 11. Correlation between humidity and PV output [62].

Fig. 12. Eﬃcency vs. relative humidity [35].

2.3.1. Humidity and dust adhesion It is observed that dust sticks to modules glass covers due to humidity which thus requires vigorous but careful cleaning action to restore modules to their initial power outputs [40]. For example, the countries close to the Mediterranean Sea such as Spain, the registered values of humidity are high, as a result the adherence of dust particles on the surface of the modules is also high [65]. Quantitatively, it has been found that an increase in relative humidity from 40% to 80% lead to increase in the adhesion of around 80% as shown in Fig. 13 [66]. In addition to promote the adhesion of dust, high relative humidity (RH) create formation of sticky and cementing dust layers on PV surfaces

Fig. 13. Relation between humidity and adhesion [66].

Fig. 14. Optical performance vs. relative humidity, during exposure to dust, for uncoated glass and glass with an anti-soiling hydrophilic coating [67].

Fig. 10. Eﬃcency vs. relative humidity [38].

747

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

optimum tilt angles of PV panels installed in Saudi Arabia. MATLAB software was used in the simulation part to optimize the appropriate orientation. It was found that the tilt angles should be adjusted six times yearly in order to harvest 99.5% of the incoming solar radiation in the tested region. Rhythm and Rangan [75] compared the performance of large scale rooftop solar PV scenario under diﬀerent panel orientations in Mumbai. Diﬀerent orientations were compared and analysed (ﬁxed tilt orientation, horizontal E-W axis N-S tracking and two-point system orientation). The analyses revealed that the optimum tilt angle for the best performance is same as the region latitude (19°). Moreover, the horizontal E-W axis N-S tracking orientation provided 10.2% higher plane of array while the two-point system orientation produced 2.2% higher plane of array as compared with ﬁxed tilt. As discussed earlier, the environmental parameters (e.g. temperature) aﬀecting signiﬁcantly the PV module performance. It was reported that overheating because of high ambient temperature and excessive solar radiation will signiﬁcantly reduce the PV panel eﬃciency. Sharaf et al. [76] study the feasibility of using PV solar tracking system in cold and hot regions. They developed a mathematical model that validated experimentally under diﬀerent operating conditions (hot and cold). The result revealed that 8% gain in electrical energy in the hot city (Aswan, Egypt) while the gain can reach up to 39% in the cold region (Berlin, Germany). The variation of electrical energy gain can be attributed to PV overheating eﬀect. Therefore, if the required energy to run the tracking system reached 10% then using tracking system in the got region will not be feasible. It can conclude that the energy cost produced from PV ﬁxed system is lower than the energy cost generated from tracking PV system due to the initial and running cost of the tracking system. Rustu and Ali [77] studied and compared the performance of wo double axis sun tracking PV system after one year of operation. The analysis were carried out using both, experimental measurement and simulation with diﬀerence less than 5%. It was found that PV electricity obtained in the double axis sun-tracking system was greater by 30.79% compared with the latitude tilt ﬁxed system. The performance investigation done by Bashar et al. [77] revealed that the annual production of the tracking system was 31.3% which higher than that of the ﬁxed system. In addition, the annual conversion eﬃciency of the tracking system was 13.85%, while it was 13.83% for the ﬁxed system. It can be clearly observed that using of solar tracking system is better than the ﬁxed system from eﬃciency and electricity generation point of view. However, the economic feasibility of using tracking system will be analysed in the following section.

Fig. 15. Humidity eﬀect on PV module power output [68].

[21,62]. Fig. 14 compared the optical performance (transmittance percentage) of dusty coated glass samples with respect to clean glass substrate. The optical performance decreased with increasing the dust amount on the surface. However, the humidity eﬀect on dusty glass cover surface is signiﬁcant measured as below 50%RH as shown in Fig. 14. It is also observed that applying a hydrophilic anti-soiling coating to the glass lead to reduction in the amount of soiling on the surface, although there is still a measureable eﬀect of %RH as shown in Fig. 14 [67]. 2.3.2. Moisture ingression impact and encapsulation Exposing the PV module to humidity for long time causes degradation in the module performance due humidity ingression to solar cell enclosure [12]. Studies of PV module performance in a humid environment (produced by a humidity chamber) demonstrated an adverse eﬀect due to water vapor, moisture and oxygen ingress into the solar cell enclosure. The presence of these substances lead to corrosion and power degradation, as shown in Fig. 15 [68–70]. Water condensing at the interface between the encapsulant and the solar cell materials create areas of increased corrosion rate and the risk of encapsulant delamination [54,70]. Signiﬁcant reduction of the moisture ingress requires a true hermetic seal, the use of an encapsulant loaded with a desiccant, or the use of an encapsulant with a very low diﬀusivity [70]. Therefore, some proposed techniques were used to assess and monitor the moisture ingression rate in PV modules for long term out door PV system. This monitoring techniques provide the manufactures with detailed information about encapsulate diﬀusion coeﬃcient and water vapor transmission rate [71]

2.4.1. Economic feasibility of PV tracking systems Few countries around the world produce solar trackers (e.g. Spain, US, Germany and China). Various prices of solar trackers were observed based on and the manufacturer and the implemented method. Bahrami et al. [78] studied the techno-economic feasibility for using single and dual-axis solar tracking PV panels in 21 low latitude countries (from 0 to 15° N) located at Sub-Sahara Africa, Latin America and Southeast Asia. They used Perez and Koronakis sky diﬀuse radiation models to predict the electrical output energy from PV panels. The observed maximum annual electrical energy from 1 kWP PV panel was 2024 kWh which contribute signiﬁcantly to alleviating the chronic energy

2.4. Orientation eﬀect A perfect tilt angle of the PV module aﬀecting signiﬁcantly the amount of solar radiation that falls on the PV panel surface. The maximum PV generation is greatly aﬀected by optimal tilt angle which depend on several condition such as the geographic latitude, utilization period, surroundings, climate, dust, pollution and other atmospheric factors. It was reported that the optimum tilt angle with respect to local latitude can be considered as (latitude ± 15°) [72]. Based on a series of experiments, the authors proposed a more accurate formula that is (latitude ± 8°), while others suggested that latitude ± 2.8 according to speciﬁc coastal radiation data. However, the accuracy of the proposed formulas is not always guaranteed because of the geographical condition limitations [72]. Navid et al. [73] proposed a method to identify the optimum orientation and location of the PV system based on the generated output data. Their model provide an accurate estimation for azimuth, tilt and PV panel location. The result conclude that, for typical PV system, latitude, longitude, azimuth and tilt can be estimated as 4.08°, 0.2°, 5.85° and 2.75° respectively. Tarek et al. [74] investigated experimentally the

Table 2 Prices of diﬀerent solar tracing system.

748

Axis type

Solar tracking system for 1 Kwp

Cost US$

Reference

Dual-axis Single axis

Dual-axis tracking system V axis tracking system IEW tracking system EW/NS tracking system

600–1900 350–930 205–840 135–700

[79,80]

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

shortage. Table 2 compares the installation cost (minimum and maximum prices) of diﬀerent tracking technology based on the levelized cost of electricity (LCOE) for 1Kwp. It was concluded that for the single axis tracker, EW/NS tracker was the most cost eﬀective tracker system due to the simple rotation formulation of the PV panel around the single axis while the vertical axis tracker (V) was the most expensive option that must follow the sun azimuth angle that varies during the year. However, the dual-axis tracker is more expensive option than the single-axis trackers. Fewer studies compared tracking to ﬁxed PV systems from economic point of view. Generally, the economic related study was based on some parameter such as Payback Period, Net Present Value, Levelized Cost of Energy, Net Present Beneﬁts and Internal Rate of Return. Bianchini et al. [81] reported that the feasibility of tracking systems is greatly dependent on tariﬀ policies, tax and system initial cost. Bashar et al. [82] compared the economic parameters of ﬁxed and double-axis tracking PV grid-connected systems installed in Jordan over 20 year. The economic analysis was conducted based on the electricity cost, payback period and internal rate of return. The payback period revealed that the ﬁxed system was 7 months shorter than the 35 months for the tracking system. In addition, internal rate of return for the tracking system was 8.7% lower than that of ﬁxed system. Finally, the electricity cost that calculated as the annual installments divided by the annual energy production (US$/kWh). The results have been summarized in Fig. 16. It was observed that the electricity cost increased with the time due to the annual degradation modules. for the tracking system was 20% more expensive than that of the ﬁxed system (0.08 US $/kWh) for the ﬁrst year and the diﬀerence grew over years. Although the energy prduced by ﬁxed system was lower than the energy prduced by tracking system, the economic analysis did not support the installation of double–axis tracking system in Jordan or in countries of similar geographical location.

Fig. 17. Self-shading caused by the preceding row of PV modules [86].

empirical formula that relate only the self-shading losses with spacing factor (F). The relative annual energy losses (RAEL) can be represented by:

RAEL = A. e−2.3F –0.00 1 F + 0.01; 1.5 < F < 5 d

Where A is an energy loss parameter and F is the spacing factor = b . This formula is derived only for 30° inclination angle in Slovenia and it can be valid for all other places with some modiﬁcation in terms of diﬀuse part fractions. Fatih et al. [87] studied the electrical performance of PV panels under partial shading conditions. A thermodynamics analysis and experimental tests were carried out for three diﬀerent shading scenario (cell, vertical and horizontal shading) at several shading ratio percentage. The result revealed that shading has a signiﬁcant eﬀect on exergy and energy eﬃciencies. The maximum power loss was 69.9% in cellular, 99.9% in horizontal and 66.9% in vertical shading.

2.5. Shading eﬀect

2.5.1. Modelling of partial shading The multiple peaks on the power–voltage characteristics curve were due to the Partial shading PV arrays. The common global searching techniques (e.g. perturb and observe) might fail in global maximum searching in terms of implementation complexity and speed. Therefore, a fast global tracking method should be proposed. Tsang and Chan [88] proposed current based method instead of the conventional voltage based method. This technique provided a good estimation of the global maximum power point under partial shading conditions. Advanced models are highly important in order to track and evaluate the PV system performance under shading condition. Many models reported in the literature to investigate partial shading condition such as by-pass diode, Lambert W function, voltage band, two stages

The PV module output power is greatly aﬀected by partial or complete shading that depend on module position, array conﬁguration and shading scenario [83]. Shadowing scenario plays a major role in the PV module performance that aﬀects the current ﬂow in the shaded cells. The cells can be shaded by trees, poles, bird droppings, buildings and dust accumulation [84,85]. Another type of partial shading is called self-shading that caused by the preceding row of PV modules. A careful planning will minimize the eﬀect of self-shading but it is impossible to avoid. Self-shading in mainly depend on solar elevation angle, minimal distance (d) and inclination angle (Ɓ), as shown in Fig. 17 [86]. Etal [86] developed an

Fig. 16. The electricity cost for tracking and ﬁxed PV system in US$/kWh [82].

749

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

successive estimation, predictive Model and Bishop model etc. [89]. Belhachat and Larbes [90] studied and analysed the performance of diﬀerent PV array conﬁguration (series, parallel, series–parallel, totalcross-tied, bridge-linked and honey-comb) under diﬀerent partial shading conditions. Bishop model was used and implemented by Simulink Power software. The analyses of these conﬁgurations revealed that the optimal conﬁguration strongly depended on shading type (uniform or not), shading pattern and location and the intensity of shading. It was reported that according to their analysis, the total-crosstied conﬁguration provide the best performances under all partial shading conditions. Similarly, Mahmoud et al. [91] compared and analysed the same multiple PV array conﬁgurations under faulty PV conditions and diﬀerent partial shading conditions. MATLAB/Simulink software was used to study diﬀerent indicators such as open circuit voltage, short circuit current, current-voltage at maximum power point, thermal voltage and ﬁll factor. This study provide a useful data to predict the partial shading conditions and detect the faulty PV module in the tested PV array conﬁgurations.

Table 4 Observed onsite module power output degradation for locations known to suﬀer a lack of rainfall in MENA region (hot and humid environment). Location

Yearly rainfall (ml)

Decrease in power output on site

Period of exposure

KSA [40,95] UAE [100] Qatar [39] Palestine [98] Egypt [15,97]

6–10 80–90 70–75 30–40 18–50

50% 10% 10% 5–6% 60–70%

26 weeks 5 weeks 14 weeks 1 week 26 weeks

rainfall is again also scarce, a 60–70% power reduction has been reported over a period of six months with a corresponding glass transmissivity reduction of approximately 20% after one month of outdoor exposure [15,97]. The magnitude of the eﬀect of dust on PV cover transmissivity and module performance are primarily aﬀected by dust deposition rate, as shown in Table 5. Generally, an increase in dust deposition leads to a drop in PV module performance [104–108], due to a decrease in its cover's spectral and overall transmissivity [109,110]. This relationship is not exactly linear due to the nature of the distribution of dust particles on the PV cover [111,112]. Diﬀerent studies have quantiﬁed the magnitude of PV performance reduction for various dust deposition rates, as shown in Fig. 18. Reductions in conversion eﬃciency of 10%, 16% and 20% were observed for dust densities of 12.5 g/m2, 25 g/m2 and 37.5 g/m2, respectively [113]. Moreover, another study observed that PV module eﬃciency was reduced by up to 26% when dust was deposited at a density of 22 g/m2 [69]. However, many models have been developed to simulate the PV overall transmissivity drop due to dust deposition rate. Based on NASA model, Wang and Gong [114] developed an improved tilt and incident angle model to provide complete analysis. These models can be applied to evaluate the eﬀect of dust deposition rate in the parametric PV systems design. Dust density does not increase linearly with exposure time, but strongly depends on climatic conditions during the exposure period [120]. For instance, the transmittance amount reduction is not uniform and depends on climatic conditions and sand storms frequency. Hence, the relation between dust deposition rates and glass transmittance reduction is nonlinear, as shown in Fig. 19. In some regions, dust density may drop due to rainfall and wind [121]. Greater exposure times generally lead to greater dust accumulation, and hence more signiﬁcant PV degradation [15,97,122,123]. For this reason, it is recommended to employ an appropriate cleaning cycle to recover maximum PV module output [13,40,98], and counter the adverse impact of environmental conditions. The optimal cleaning frequency depends mainly on the region environmental conditions.

2.6. Eﬀect of dust Eﬃciency of PV modules is governed by alterable and unalterable factors, thus dust is an unalterable factor which falls under the classiﬁcation location-dependent environmental factors [92]. Dust has two possible eﬀects on the energy output of PV modules. First, suspended dust particles in the atmosphere that have a size larger than the wavelength of the incoming solar beam can scatter the sunlight, reducing the amount of solar radiation that reaches the surface of the module. This eﬀect becomes worse when combined with the eﬀect of air pollutants [93]. A reduction in PV module energy output of over 60% has been attributed to the presence of dust and air pollutants (i.e. toxic gases and suspended particles) in the atmosphere [94]. The second eﬀect relates to the formation of a thick layer of dust on the PV module surface. This layer can change the surface optical properties to promote light reﬂection and absorption and reduce surface transmissivity, and hence PV module output. Table 3 summarizes some of published literature in relation to the eﬀect of dust on PV performance. There are variation in dust accumulation eﬀects from one region to another. These can be attributed to site conditions such as wind velocity, humidity and rainfall, PV module technology used, source of dust particles, particle type, and the material of PV module surface cover. Signiﬁcant reductions in power output were reported in regions that suﬀer from a lack of rainfall, and are thereby prone to high levels of dust, such as countries in the Middle East and North Africa (hot and humid environment), as shown in Table 4. In Dhahran, KSA, where rainfall is very scarce, after six months of outdoor exposure, a 50% reduction in PV power output has been reported by [26,40,66,95], and a 2.78% reduction in short-circuit current per day has been reported in Arar, KSA [96], where rainfall conditions are similar. In Egypt, where Table 3 Observed dust eﬀects on PV performance in diﬀerent countries. Study & location

Duration

Dust eﬀect

KSA [95] KSA [66] KSA [26] KSA [40] Qatar [42] Palestine [98] Egypt [99] Egypt [97] UAE [100] Spain [101] USA [102]

One Month Five weeks Six weeks Six months 100 days One week 21 days One month Five weeks Two months Two months

Athens [103]

Eight weeks

The average degradation rate of the eﬃciency was 7% per month The average power reduction without any cleaning action was around 6% The average power reduction was 13% for a plain glass module The output power decrease by as much as 50% without cleaning The eﬃciency decreased by around 10% because of dust accumulation 5 to 6% decrease in the solar panel eﬃciency 5% reduction of the output for 15° tilt angle The output power decreased about 17.4% per month The output power reduction after 5 weeks was about 10% After 15 days without rain the losses were greater than the 4%. The losses reach up to 15% after 2 months without raining With soiling rates of less than 1.0% per month in the low desert and peak rates of 11.5% per month in heavy agricultural regions of the Central Valley, California. 6.5% power output reduction

750

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

Table 5 Observed dust eﬀect on PV glass cover transmissivity. Study & location

Period of exposure

Transmittance reduction

KSA [26] KSA [66] Belgium [115] Egypt [15] Algeria [116] Thailand [117] UK [62] USA [67] South Africa [118] China [119]

45 days 40 days 5 weeks 30 days Indoor (2 h) 30 days Not reported 4 months one week 8 days

The overall transmittance of glass cover was reduced by 20% The spectral transmittance reduction was 37% The transmittance decrease between 3% and 4% after 5 weeks of exposure The glass loss 20% of its transmittance for an inclination of 30° The optical transmission drop is 16% The global transmittance reduced from about 87.9–75.8% The transmittance reduced by 5% with particle sizes typically in the range 1–500 µm, 25% reduction of glass transmittance Transmittance reduced by 1–2% The relative PV module transmittance declined by 20%

been determined using both optical techniques (including commercial particle analyzers), scanning electron microscopy (SEM), and recently, scanning probe microscopies. These important studies involved evaluating particle-size distributions (Fig. 20) using various microscopy techniques. Table 7 shows the dust particle sizing and distribution morphology characteristics for dust collected from diﬀerent cities in diﬀerent countries. The literature indicates that the deposition of ﬁner particles has a more signiﬁcant eﬀect on PV module performance than that of coarser particles. El-Shobokshy and Hussein [111] studied carbon, cement, and three types of limestone particles having median diameters of 5, 10, 50, 60, and 80 m. The dust particles were deposited on a PV surface at a controlled surface-mass density, and the power output was measured. Depositing equal densities (surface mass density of 25 g/m2) of limestone particles of diﬀerent sizes on a PV module surface showed that the ﬁner particles caused a greater power reduction. Their results also showed that normalized power output in the case of cement and carbon particles dropped by 40% and 90%, respectively. This was attributed to the greater uniformity of distribution of the ﬁne particles on the surface causing more scattering losses [111]. Moreover, high wind speeds remove coarser particles more eﬀectively than ﬁne ones [112]. On the other hand, gravity inﬂuenced signiﬁcantly the dust deposition rate. The deposition rate due to gravity for small dust particles (Dp < 5 µm) was 5% and increased to 75% for large dust particles (Dp > 5 µm) [132].

Fig. 18. Module eﬃciency reduction vs. dust density reported by diﬀerent studies. [69,113].

2.6.2.2. Particle chemical analysis. The nature of the dust particles, including chemical composition and color, plays a major role in the degree of reduction in glass cover transmittance and hence PV performance. In Greece under cloudless sky, Kaldellis et al. [108] have deposited various speciﬁc red soils, limestone's and ash's deposition densities on the surface of PV-panels implying the deterioration of their performance when dust particles are deposited on their surface. The mean power reduction between the clean and the polluted PV pair, vary from approximately 3 W to 5 W for red soil particles’ accumulation ranging from 0.12 to 0.35 g/m2, 4 W to 7 W for red soil particles’ accumulation ranging from 0.28 to 1.51 g/m2 and 1–8 W for red soil particles’ accumulation ranging from 0.63 to 3.71 g/ m2 respectively. These results indicated that red soil deposition on PVs’ surfaces causes the most considerable impact on PVs’ performance and thus the highest reduction in generated energy, followed by the limestone and secondly by the carbon-based ash. An amount of 0.35 g/m2 of red soil deposition on PV-panels’ surfaces may reduce the generated energy by almost 7.5% while approximately the same deposition density for limestone (0.33 g/m2) causes almost 4% energy reduction. On the other hand, an indoor experimental study was conducted at Saudi Arabia to examine the degree of degradation due to diﬀerent deposits type [111]. The PV panel, the sun simulator and the experimental dust (carbon, limestone and cement) were the main components used in the experimental setup. It was concluded that the ﬁne dust

Fig. 19. Dust deposition with tilt angle for diﬀerent exposure periods in days [66].

2.6.1. Module glass covers impact Dust accumulation varies from surface to surface as shown in Table 6. Garg [124] studied the eﬀect of dust accumulation on the transmittance of light through glass and plastic plates for two months in India, with the plastic plate showing a greater reduction in transmittance. Similarly, Nahar and Gupta [125] observed that polyvinyl chloride (PVC) plates showed a greater reduction in transmittance than acrylic, which, in turn, suﬀered a greater reduction than glass. Similarly, Said et al. [26] indicated that texturing a module's surface and adding an anti-reﬂective coating boosts the power output of a clean PV module by an average of 4–8%. It is also shown that texturing and antireﬂective coating of PV modules glass cover can relatively reduce power reduction due to dust coverage [101,126,127]. 2.6.2. Field dust particles characterization Dust particles are characterized to better understand the cause of the eﬀect of dust deposition on PV module performance and to come up with eﬀective mitigation techniques. Dust particles characterization methods include particle sizing, morphology analysis and chemical composition analysis. 2.6.2.1. Particle sizing analysis. The particle sizes and morphology have 751

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

Table 6 Observed impact of cover surfaces on PV performance. Study

Glass surface

Region

Field Eﬀect

Said et al. [18], Said and Walwil [66] Piliougine et al. [65] Rocha et al. [81]

Anti-reﬂective coating and textured surfaces

Dhahran, KSA

The power output losses mitigated by 5% using anti-reﬂecting coating and texturing

Thin ﬁlm coated with Self-cleaning properties and antireﬂective coating Textured glasses are composed of little pyramids on the surface Coated glass samples (self-cleaning coating (SC), an anti-reﬂection coating and a multilayer coating) Structured glass (pyramids, grooves, inverted pyramids and a very light structured type and ﬂat) Glass and plastic plates

Malaga, Spain

The losses in output power due to uncoated modules was 3.3% while for coated was 2.5% There are no signiﬁcant power loss of the ﬂat glass modules and textured cover glass modules. The transmittance decreased by 1.75%, 1.3% and 0.85% for Anti-reﬂection coating, Self-cleaning and Multilayer coating, respectively. The Isc enhanced by 3% at normal incidence for structured glass cover.

Appels et al. [95] Duell et al. [22] Garg [104]

Malaga, Spain Heverlee, Belgium Golden CO., USA India

Nahar and Gupta [125]

PVC plates, acrylic, glass

India

Brown et al. [67]

Coated glass

Minnesota, USA

Brown et al. [67]

Coated acrylate polymer and acrylate polymer

Minnesota, USA

Kazmerski et al. [128]

superhydrophobic and superhydrophilic coatings

Lab work

Solar transmittance at normal incidence for plastic plates was 94% and for glass was 90% The maximum annual transmittance reduction was 7.15%, 5.16%, 2.35% for PVC plates, 5.27%, 3.98%, 1.78% for acrylic and 4.26%, 2.94%, 1.36% for glass with 0°, 45° and 90° tilt angle from the horizontal, respectively. 20% reduction of glass transmittance after 4 months compared with 25% for traditional glass 26% reduction of surface transmittance compared with 34% for uncoated acrylate The dust particles-glass cover adhesion force decreased from 90 to 12 nN due to SHP coating

of aluminum, iron, magnesium, potassium, and sodium. Similarly, Said and Walwil [66] reported that oxygen had the highest chemical concentration followed by calcium, silicon, sulfur, and iron as shown in Fig. 22. Also, it is found that quartz and calcite compounds occupied more than 60% of dust particle content (Fig. 23). Figs. 24 and 25 shows some SEM micrographs of dust particles. The Figures indicate that dust particles are composed of diﬀerent shapes and sizes. Large dust particles attach to the small dust particles, because of the electrostatic charges of small dust particles [136]. Small dust particles exposed to the solar irradiation for long durations and attaching of ionic compounds to the dust particles caused static charging of the particles [137].

Fig. 20. The fractions of the number, area, and volume of the particles distribution [66].

particles deteriorated the PV performance more than the coarser particles due to the ability of the ﬁne particles to spread and cover the PV surface. In addition, 28 g/m2 of carbon deposit caused a greater reduction in PV module power output than 73 g/m2 of cement or 250 g/ m2 of limestone. They attributed the reason for eﬀective solar radiation absorption by carbon and hence adversely aﬀects PV performance. Elminir et al. [97] conducted extensive mineralogical analysis using X-ray diﬀraction (XRD) to identify the chemical composition of the deposited layers of dust particles on PV module in Egypt. The dust particles were mostly composed of quartz and calcite, with smaller amounts of dolomite and clay minerals. Table 8 shows the observed dust chemical composition collected from diﬀerent locations. Fig. 21 presents the results of the XRF analysis. The major constituents were silicon from desert sand (quartz, or silicon dioxide, SiO2) calcium from the mineral calcite (calcium carbonate, CaCO3). The minor constituents consisted

2.6.3. Dust particle chemistry impact Dust particles absorb water vapor in humid air environments and form mud at the surfaces. Once the mud becomes dried at high temperature conditions under the solar radiation, it becomes diﬃcult to remove from the glass cover surfaces [138]. Water interaction with dust particles took place due to eﬀective adsorption of water molecules by dust particles surfaces [139]. The interaction between water molecules, dissolved ions and soil particles occurred because of the unbalanced force ﬁeld which depended on the particle size. It should be noted that the formed mud solution had chemically active characteristics [140,141]. The dissolution of dust particles such as calcite (CaCO3) and halite (NaCl), are expressed by Eqs. (1), (2) and (3) show below. In the ﬁrst example, halite reactions take place with molecules of polarized water which separate chloride and sodium into single ions which become surrounded by hydration sheaths and dissolved in the water

Table 7 Observed dust particle sizing and distribution morphology characteristics. Study

Area of Dust collection

Particle sizing

Additional

Qasem et al. [129]

Kuwait

4–8 μm

Said and Walwil [66] Appels et al. [95] Bouaouadja et al. [116] (Mastekbayeva and Kumar [117] Clarke et al. [25], Mohamed and Hasan [130] Hussein A. Kazem and Chaichan [131] Wang and Gong [114]

Dhahran, KSA KU Leuven, Belgium Algeria Bangkok, Thailand Libya (Sahara desert) Oman Qatar

0.5 −176 µm 2 – 10 μm 95 − 780 µm 53 − 75 µm 0.5 − 1000 µm 2 − 63 μm Average 2 µm

The major grain size was silt. The small silt grains were of slate, whereas the bigger grains were quartz Diﬀerent and irregular shapes, but generally, tend to be spherical shape. Other tested samples are: cement 10 µm, clay 68 µm and white sand 250 µm The shape of the grains is irregular but approximately spherical. Soft Bangkok clay used to prepare the artiﬁcial dust dust size variable from month to other dust deposition on PV was found to vary from one location to another Some non-uniform particles of few tens of micron

752

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

Table 8 The dust chemical composition collected from diﬀerent locations. Study

Area of dust collection

Dust composition

Qasem et al. [129,133] Said and Walwil [66] Elminir et al. [97] Adinoyi and Said [40] Clarke et al. [25] Modaihsh [134] Javed et al. [135]

Kuwait Dhahran, KSA Helwan, Cairo, Egypt Dhahran, KSA 24 sites across western Libya Riyadh, KSA Doha, Qatar

The dominating component of dust was quartz followed by calcite and albite 60% of dust particles were calcite and quartz. Quartz and calcite predominated with smaller amounts of dolomite and clay minerals. The dust was composed of oxygen (58%), calcium (13%), carbon (10%) and sulfur (6%). Quartz with lesser amounts of calcite, illite, and halite The dominant minerals were quartz, calcite, and heavy metals (Pb, Zn, Cd, Ni and Co) The dominant minerals were dolomite, calcite, quartz and gypsum.

Fig. 21. Organic components of the polluting material using XRF analysis [97]. Fig. 24. SEM micrograph of dust [40].

compounds. The alkaline and alkaline earth metallic compounds of dust particles dissolve in the water condensate on surfaces in humid environments, which gives rise to the formation of a chemically active mud solution that ﬂows around dust particles under the eﬀect of gravity and reaches the solid surface where the dust particles have settled. This chemically active mud solution layer has a major eﬀect on increasing the adhesion force between the formed mud and surface. Qasem et al. [133] investigated the air pollution impact on PVs’ performance for several amounts of carbon-based ash deposited on PV panel surfaces. They compared the power output decrease of the artiﬁcially polluted panel with the clean one control for the diﬀerent quantity of ash deposited on the PV panel surface. The results showed that for ash mass depositions of 0.63 g/m2, 1.89 g/m2, 3.15 g/m2, 3.78 g/m2; the panel power output dropped by 2.3%, 7.5%, 17%, and 27% respectively.

Fig. 22. XRF and EDS chemical element analysis [66].

2.6.4. Dust particle adhesion Another issue is the impact of humidity in dust fouling. Vapor condensation on the PV module surface forms capillary bridges in gaps between the particles and the surface, generating large meniscus forces that enhance adhesion between the particle and surface, which encourages dust build-up [145–147]. Table 9 reports the eﬀect of surface on the dust deposition amount. Generally, an increase in absolute humidity causes an increase in dust accumulation [68,100]. Mekhilef et al. [12] reported that adhesion force between dust particles and surfaces was highly inﬂuenced by the atmosphere humidity. As the relative humidity decreased, the eﬃciency of solar panel increased due to less dust particles adhered to the surface. In relation with particles size, Corn [148] studied the adhesion force between solid particles and demonstrated that their adhesion force increased signiﬁcantly with the particle size. Furthermore, the contact area between a particle and rough surface was found to have a major role in the adhesion between the particles and surface. The adhesion of dust and contact potentials were investigated by Penney [149]. It was reported that the adhesive forces of electrostatically deposited dust were much greater than a similar dust deposited mechanically. Each

Fig. 23. XRD qualitative and quantitative analysis [66].

molecules. The carbonation process takes place in calcite (CaCO3) dissolution, where the carbon dioxide attracted and dissolved in water producing carbonic acid [142]. NaCl + H2O→Na+1 + Cl−1 +H2O

(1)

H2O + CO2→H2CO3 H2CO3 + CaCO3→Ca

(2) +2

+ 2(HCO3)

−

(3)

During drying, the dissolved ions (Na+, K+, Ca+2, Cl-, SiO−) attract mud structure due to electrostatic and ionic bonding force. These ions become dissolved in the mud solution particles holding them together and forming crystals in between. The ions in the mud structure during water evaporation increasing the adhesion force. Yilbas et al. [143,144] demonstrated that dust particles consist of neutral and ionic 753

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

Fig. 25. SEM micrograph small dust particles adhering to the surface of large dust particles [136].

particle in an electric ﬁeld takes speciﬁc orientation by the dipole moment which is produced by the contact potential diﬀerences. The coulomb forces between the particles layers producing high adhesive forces by the dipoles orient electrostatically. In general, dust particle charge should be inﬂuenced by the adhesion force between the dust particles and PV glass cover and decrease the PV voltage output [137]. Mclean [150] presented the cohesion of dust layer and the cohesive force in electrostatic precipitators on the sediment layers of dust in particular. An electrostatic precipitator has a signiﬁcant cohesive force that inﬂuences the sediment layers because of the electric ﬁeld of particles in air inﬂuenced by the corona current across the layers. It was found that the electric ﬁeld which ﬂows through the layer had a linear proportional to the cohesive force approximately. Somasundaran et al. [151] reported using a cohesive force apparatus. It was improved to measure the various shapes, various sizes, and nature of the particles chemical structure under various conditions for very low cohesive force of around 1 nN. The cohesive force between glass surfaces and dust particles increased with the decreasing of PH and an additional amount of salt resulted in a signiﬁcant increase of the cohesive force. Also, the cohesion between dust particles and surfaces was reduced by the interaction of anionic surfactant with polyethylene oxide layer. Various models for adhesion force measurements are reported [152,153]. These models are the JRK model, Rabinovich model and Derjaguin, Muller and Toporov (DMT) models, all of which are used to characterize the adhesion force for surfaces and adhering dust particles. For similar particles, the adhesion force varied due to diﬀerent values of substrate roughness and the actual contact area which has an important role inﬂuencing particles adhesion. Kazmerski et al. [128] evaluated the basic interactions of dust particles adhesion to the PV module surfaces. Their main interest was to investigate morphology, and chemical

mechanisms of dust particles soiling. The measured adhesion forces of dust particles with surface chemistry were correlated using Cuddihy principles. The results revealed that relatively high adhesive forces are due to dust particles chemical bonding to the glass surface. One of the chemical solutions was suggested by Brown et.al [67] in 2012. They applied an anti-soiling hydrophilic coating to the glass cover which reduced the dust soiling amount on the surface. However, it is indicated that beads with large size do experience large adhesion force due to increase in the contact area between the bead and the surface [66]. In relation with adhesion forces measurements, Kazmerski et al. [128,154] reported that the inter-particle adhesion force is higher than particlemodule glass cover adhesion. On the other hand, Hassan et al. [136] measured the adhesion force of the dry mud formed from environmental dust particles on the PV glass cover. It was reported that the adhesion force increased due to formation of dry mud solution ﬁlm at the interface of the dry mud- glass surface. Fig. 26 shows variation of adhesion force due to dust particles size.

3. Methods of mitigating negative impacts of dust deposition Reviews of dust-impact mitigation approaches, consider the techniques that address the eﬀect of dust, as dust is one of the most signiﬁcant environmental factors aﬀecting PV module performance. The methods are important in the Middle East and North Africa, two regions where solar power may become a particularly viable alternative to fossil fuels considering the high level of sunshine. To recover the PV module performance that is impaired because of dust, it is important to carry out periodic cleaning. However, the required frequency of cleaning depends on environmental conditions. There are a variety of methods that have been used or developed to mitigate the dust eﬀect on

Table 9 Eﬀect of cover surface on PV performance. Study & location

Surface

Testing

KSA [66]

Coated and uncoated

KSA [26]

Anti-reﬂecting coating

(NREL) [30]

Grooved, pyramid structured, lightly textured and ﬂat glasses

Belgium [115]

Three diﬀerent coated glass samples

KSA [26] Málaga [65]

Texturing and anti-reﬂecting coating Three diﬀerent types of glasses (textured with little pyramids follow an angle pattern and pyramids show an orthogonal pattern)

The transmittance reduce by 30% for coated glass and after 37% for uncoated glass after 40 days of exposure. The power output enhanced by 8% using anti-reﬂective coatings on PV glass cover surface. Module Voc was higher by 50 mV, 80 mV and 10 mV for grooved, pyramid structured and lightly textured glass module as compared to the reference module Transmittance decreased by (%): Multilayer (ml) (0.85), Self-cleaning (SC) (1.30), Anti-reﬂection (AR) ( 1.75) and Regular glass (2.63) Texturing and anti-reﬂecting coating reduced the dust accumulation by 5%. Energy losses due to soiling for coated modules was 10% and 12% for uncoated modules during summer months.

754

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

[15,97,110,124,125]. However, PV eﬃciency is aﬀected by the module's tilt angle due to the change in the amount of solar energy received at the module surface. Such angle will primarily depend on climatic conditions during the year, and the type of application [94,156]. High module temperature reduces signiﬁcantly the energy conversion. However, a high temperature variation between ambient air and the surface of the PV module is reported as contributing to in decreasing the dust deposition on glass cover of PV modules [157]. 3.2. Mechanical and electromechanical dust-removal methods Fig. 26. Eﬀect of particle size on adhesion force from diﬀerent studies [67,108,136].

Mechanical methods to remove dust from the surface of PV module covers include mechanical wiping, blowing, and the use of removable covers. Electromechanical methods encompass shaking or vibrating the PV module array and using subsonic or ultrasonic waves to break dust adhesion. Al Shehri et al. [158] reviewed diﬀerent dry cleaning mechanisms that use robotic systems. It was reported that dry cleaning methods using Nylon brushes did not aﬀect the optical characteristics of the PV glass surface after equivalent simulation of 20 years. Williams et al. [159] reported that the use of mechanical vibration to remove dust resulted in a restoration of 95% of the power-generating capacity of the photovoltaic module. Another electromechanical method consisting of a microprocessor and a programmable logic controller (PLC) was used to operate a mechanical wiper or brushing system, as shown in Fig. 27. Fernandez et al. [160] designed a robotic dust wiper supported by a high performance brush to clean surfaces from deposited Martian dust particles. The results showed that the cleaning eﬃciency was above 93%. Moreover, Lamont and El Chaar [144] presented cleaning approaches based on PLC and peripheral interface controllers (PIC) that are eﬀective in reducing the accumulation of dust and bird droppings on PV modules. PIC- and PLC-based combination cleaning systems have demonstrated promising results, with better cleaning efﬁciencies for the PLC-based systems. In relation to dust removal process from PV cover, Rifai et al. [162] studied the dynamic response of accumulated dust particles on rotating polycarbonate disk. Their result revealed that centrifugal force was higher than the friction, lift, drag and adhesion forces which aﬀect the dust particles removal. The cost of system oversizing or manual cleaning is approximately 1.5 times that of the PIC or PLC-based systems [161].

PV module performance. Some also contribute to mitigating other climate factors as well, such as temperature and humidity. The reported dust mitigation methods can be divided into four categories: spontaneous, mechanical and electromechanical, electrostatic shields, and micro- and nanoscale surface functionalization. These are discussed in the following sections. 3.1. Spontaneous dust-removal processes The natural means of cleaning dust from the surface of PV module covers are rainfall, wind, and gravity. Water is the most eﬀective cleaning agent and high rates of rainfall reduce the eﬀect of dust. In wet regions, such as Singapore, the eﬀect of dust accumulation is only a minor problem [121]. Although rainfall improves the power output of dusty solar modules, it cannot be relied upon for cleaning as it occurs occasionally and minimally in dry regions. Wind may partially improve PV performance as it works to pull dust particles oﬀ the PV surface. Mekhilef et al. [12] reported that increased wind velocity leads to greater heat dissipation from the PV cell surface and a reduction in the relative humidity of the surroundings that in turn, also lead to better eﬃciency. While wind can have a positive effect, it also cannot be depended upon completely. As well as being unreliable in less windy regions, wind may also increase dust accumulation. Wind speed and direction have a strong eﬀect on PV module performance [19,121,155]. The angle of inclination aﬀects dust deposition on the modules cover. Tilting the surface of PV modules can reduce dust deposition through the eﬀect of gravity, but it can also decrease the captured solar energy. It is important to determine the optimal tilt angle that will reduce dust deposition and at the same time maximize the captured amount of solar radiation. The eﬀect of inclination is dependent on climatic conditions. For example, in Singapore there was no obvious eﬀect on dust accumulation due to changing the angle of inclination of PV modules [121]. Elsewhere, in contrast, decreases in dust accumulation were observed as a result of increasing the angle of inclination

3.3. Electrostatic dust-removal methods NASA has proposed electrostatic approaches for mitigating the negative eﬀects of dust on lunar solar panels. An electrodynamic screen can be attached to the PV module surface. The screen is made of transparent plastic sheets, such as polyethylene terephthalate (PET) (which is UV- radiation resistant), and a parallel or spiral conﬁguration of conducting electrodes made of transparent indium tin oxide that are

Fig. 27. Mechanical and electromechanical dust-removal methods. Left: PIC-based cleaning approach. Right: PLC-based cleaning [161].

755

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

Fig. 28. Electric curtain: (a) Three-phase electric curtain [163]. (b) The electrical ﬁeld distribution between the electrodes of the shield [169].

embedded beneath a thin transparent ﬁlm. A single- or multiple-phase AC voltage supply connects to the electrodes to produce an electromagnetic ﬁeld on the surface, which repels the dust particles, as illustrated in Fig. 28 [163–166]. This approach, known as the “electric curtain method” is the best strategy for dust removal [167]. Electrodynamics screens showed approximately 80% dust removal eﬃciency from a PET surface [168] and an increase in solar cell performance of up to 90% [163]. However, the eﬃciency of the screen is dependent on many parameters, including dust deposition rate, type of dust particle, method of operation and the applied voltage. The dust-clearing ability of such an electric curtain depends on the type of accumulated particles. A Mars dust simulant was shown to be the easiest powder to be cleaned from the shields, with more than 90% being removed using high voltage, compared with lower values for acrylic polymer powder and lactose [169]. This is because the Mars dust simulant particles are smaller and the electric curtain [164,169,170] has overcome the van der Waal forces that are a function of particle size [170]. Under normal operating conditions there is the possibility of intermittent operation of electrodynamic screens. A comparative study between continuous and intermittent operation was conducted, and it was found that the average dust removal eﬃciency during continuous operation was over 95%, whereas it was approximately 90% when the screen was activated intermittently [165]. One concern that must be addressed is the power needed to operate the electrodynamic screen. The power required is dependent on dust deposition. The average power consumption of the screen varied between 1.0 and 2.9 mW when dust deposition varied from 0.4 mg/cm2 to 0.6 mg/cm2 [165]. For a dust load of 0.6 mg/cm2, the total power needed to operate the screen was approximately 10 W/m2, that is, 5 W/m2 for the supply operation and 5 W/m2 for removing the dust [166,168]. To reduce the power necessary for the supply operation, a low-power microcontroller can be used instead of a digital signal controller system [171]. The dust-clearing ability of a transparent electrodynamic shield is sensitive to changes in the amplitude, pulse (wave shape) and frequency of the applied voltage. Higher voltages lead to better dust removal eﬃciency, as do pulsed and triangular signals. Low frequencies improve removal eﬃciency by increasing the velocity across the shield surface [169,172]. Recently, a comparative study of various dust cleaning methods (manual cleaning, vacuum suction cleaning, automatic wiper based cleaning and electrostatic precipitator) was conducted by Hudedmani et al. [156]. The results recommended that using of Arduino-controller electro static precipitator (shown in Fig. 29) utilized the solar energy eﬀectively and enhanced the solar panel eﬃciency.

Fig. 29. Arduino Interface to Electro-Static Precipitator [173].

develop self-cleaning surfaces with optimal optical properties. This method enables the creation of a super-hydrophobic surface that has low wettability and high water droplet mobility. Such a surface can enhance the cleaning eﬃciency and thereby reduce the necessary cleaning frequency. Super-hydrophobic surfaces include micro- or nano-structure surfaces coated by a thin ﬁlm of low surface energy material or vice versa [174]. A number of recent eﬀorts have attempted to mitigate the eﬀect of dust in this manner. Park et al. [175] developed a super-hydrophobic surface with a contact angle greater than 150° and a hysteresis of less than 20°. However, developing a novel surface with the necessary properties of low adhesion, low wettability, high transmissivity, and high resistivity to aggressive environments (such as high humidity and temperature) has posed a diﬃcult challenge. Verma et al. [146] created a super-hydrophilic nano-structured glass with a contact angle less than 5°. This material caused an improvement in solar cell performance because of an increase in net optical transmission and the self-cleaning nature of the surface. Hee et al. [121] deposited diﬀerent thicknesses of a titanium dioxide ﬁlm on the glass surfaces and observed reduction in dust accumulation due to deposition, with the eﬀect becoming more signiﬁcant with increasing ﬁlm thickness. However, the accumulated dust particles increased the panel's temperature which inﬂuences the voltage losses. Therefore, using Nano-coated PV modules with self-cleaning nanomaterial will not only reduce the dust deposition rate but also have better temperature mitigation, especially in the hot climate of the MENA region [176].

3.4. Self-cleaning surface approaches 3.4.2. Wet hydrophobic surfaces Texturing hydrophobic surfaces enhances their non-wetting properties by increasing the surface area through changes in its geometry.

3.4.1. Dry hydrophobic surfaces The purpose of micro- and nanoscale surface fabrication is to 756

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

Table 10 Glass transmittance and self-cleaning properties enhancement due to several coating techniques. Study

The coating techniques

Glass Transmittance enhancement

Latthe et al. [183] Zhang et al. [184] Nostell et al. [185]

Metallic anti-corrosion and drag resistant coatings Self-cleaning coating with anti-reﬂection (AR) properties. Dip-coating method using a sol-gel

Verma et al. [129]

Anti-reﬂective coatings

Li et al. [186]

Anti-reﬂective Coatings

Park et al. [187]

Anti-reﬂection and anti-adhesion coatings

PV optical transmittance was greater than 80% Self-cleaning coatings improved and the maximum glass transmittance of the substrates to more than 99%. The solar transmittance increased by more than 5.4% to reach 96%. The peak transmittance observed was 99.5%. The maximum solar transmission improvements was observed for 200 nm heights nanostructures and was in the order of 90% The maximum transmittance measured as high as 94%, whereas the glass transmittance was 91%. The coating enhanced the absorption of light on the silicon surface and increased the transmission as well.

surface functionalization methods show great promise in mitigating dust deposit on PV modules and combining the two methods could prove fruitful in yielding PV module surfaces with low dust adhesion, particularly for use in dry regions of the world.

Trapped air between the surface encourages super hydrophobic behavior, as the water drop sits partially on air [177]. One challenge is to keep these air pockets stable as, under humid conditions such as those in the KSA, the air pockets may collapse due to the condensation of dew or the evaporation of a water drop. These processes may occur at the nanoscale, rendering the textured surface highly wetting [177]. Attempts to produce super-hydrophobic surfaces that are eﬀective in humid conditions have led to the development of non-wetting surfaces with self-healing properties. The properties of the texture are maintained by creating pockets of liquid instead of air by impregnating the surface with lubricant, which is stabilized by capillary wicking which is resultant from the micro- or nanoscale texture [178]. Lubricant-impregnated surfaces show extremely low-contact-angle hysteresis within the droplet, which enhances the slippery nature of these surfaces, preventing droplets from being pinned and thereby oﬀering selfcleaning properties [179–181]. It has also been observed that lubricantimpregnated surfaces enhance condensation and maintains their nonwetting properties under conditions of high humidity [182]. Table 10 summarizes glass transmittance improvement due to coating methods.

Acknowledgments The authors would like to acknowledge the support of King Abdulaziz City for Science and Technology (KACST /NSTIP Project 11ADV2134-04) in conducting this study. References [1] Baras A, Bamhair W, Alkhoshi Y, Alodan M. Opportunities and challenges of solar energy in Saudi Arabia. World Renew Energy Forum 2012:4721. [2] Razykov TM, Ferekides CS, Morel D, Stefanakos E, Ullal HS, Upadhyaya HM. Solar photovoltaic electricity: current status and future prospects. Sol Energy 2011;85(8):1580–608. [3] Gaglia AG, Lykoudis S, Argiriou AA, Balaras CA, Dialynas E. Energy eﬃciency of PV panels under real outdoor conditions, an experimental assessment in Athens, Greece. Renew Energy 2017;101:236–43. [4] Onyegegbu SO. Performance of photovoltaic cells in an equatorial climate. Sol Wind Technol 1989;6(3):275–81. [5] Tian W, Wang Y, Ren J, Zhu L. Eﬀect of urban climate on building integrated photovoltaics performance. Energy Convers Manag 2007;48(1):1–8. [6] Gonzalez MC, Carroll JJ. Solar cells eﬃciency variations with varying atmosoheric conditions. Science 1994;80(5):395–402. [7] Jordan DC, Wohlgemuth JH, Kurtz SR. Technology and Climate Trends in PV Module Degradation Preprint. no. October, 2012. [8] Dabou R, Bouchafaa F, Arab AH, Bouraiou A, Draou MD, Neaibia A, Mostefaoui M. Monitoring and performance analysis of grid connected photovoltaic under different climatic conditions in south Algeria. Energy Convers Manag 2016;130:200–6. [9] Pradesh U. Eﬀect of Temperature, Irradiation, Humidity and Wind on Ideal Double Diode PV System Performance. pp. 1–5; 2016. [10] Chaichan MT, Kazem HA. Experimental analysis of solar intensity on photovoltaic in hot and humid weather conditions. vol. 7, no. 3, pp. 91–96, 2016. [11] Kazem HA, Chaichan MT. Eﬀect of Environmental Variables on Photovoltaic Performance-Based on Experimental Studies Eﬀect of Environmental Variables on Photovoltaic Performance-Based on Experimental Studies. no. October; 2016. [12] Mekhilef S, Saidur R, Kamalisarvestani M. Eﬀect of dust, humidity and air velocity on eﬃciency of photovoltaic cells. Renew Sustain Energy Rev 2012;16(5):2920–5. [13] Mani M, Pillai R. Impact of dust on solar photovoltaic (PV) performance: research status, challenges and recommendations. Renew Sustain Energy Rev 2010;14(9):3124–31. [14] Assi A, El Chaar L. Eﬀect of wind blown sand and dust on photovoltaic arrays. In: Proceedings of the 23rd European Photovoltaic Solar Energy Conference; 2008. [15] Hegazy AA. Eﬀect of dust accumulation on solar transmittance through glass covers of plate-type collectors. vol. 22, pp. 525–540; 2001. [16] Clarke L, Elatrash MS, L.Ã S. Field measurements of desert dust deposition in Libya. vol. 40, pp. 3881–3897; 2006. [17] Callot Y, Marticorena B, Bergametti G. Geomorphologic approach for modelling the surface features of arid environments in a model of dust emissions: application to the Sahara desert. Geodin Acta 2000;13(5):245–70. [18] Goossens D, Oﬀer ZY, Zangvil A. Wind tunnel experiments and ﬁeld investigations of eolian dust deposition on photovoltaic solar collectors. Sol Energy 1993;50(1):75–84. [19] Goossens D, Kerschaever EVAN. Aeolian dust deposition on photovoltaic solar cell: the eﬀects of wind velocity and airborne dust concentation on cell performance. vol. 66, no. 4, pp. 277–289; 1999. [20] Gaier JR, Perez-davis ME. Eﬀect of Particle Size of Martian Dust on the Degradation of Photovoltaic Cell Performance; 1992.

4. Conclusions PV module performance can be signiﬁcantly aﬀected by both environmental conditions, such as outside temperature, wind velocity, and humidity, as well as the accumulation of dust on the module surfaces. Climatic factors can also inﬂuence the amount of dust accumulation directly. This manuscript reviews the latest published literature on the subject of dust accumulation on PV module glass covers and diﬀerent mitigation techniques. Hence, it serves as a quick reference and guide for researchers and engineers interested in this subject. Reducing the amount of dust accumulation on PV glass cover surfaces is an important consideration in arid regions such as the Middle East and North Africa where dust build-up can signiﬁcantly aﬀect the performance of PV modules. The loss of performance due to dust accumulation depends on the chemical composition, size and density of the deposited dust particles. A number of approaches to reduce the eﬀect of dust on PV module performance have been explored, but there is no one clear optimum approach. The most eﬀective dust-removal method depends on climate conditions at the site of interest. There is no ﬁxed recommended frequency of module cleaning, as this strongly depends on the frequency of local dust storms. The published literature on this subject indicates a lack of studies on the eﬀect of dust type and module cover characteristics on dust deposition. There is also a lack of research on the adhesion forces between the dust particles and the surface. Further work is needed to devise glass covers for PV modules that oﬀer low dust adhesion properties for use in dry, dusty regions. The economic feasibility of the discussed mitigation methods also require further consideration. Microscale and nanoscale textured PV module surfaces impregnated with lubricants demonstrate superior non-wetting properties at all levels of ambient humidity. Electrostatic and microscale/nanoscale 757

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al. [21] AlBusairi HA, Hans Joachim Möller. Performance evaluation of CdTe PV modules under natyral outdoor conditions in Kuwait; 2010, no. September, pp. 3468–3470. [22] Mazón R, Káiser aS, Zamora B, García JR, Vera F. Analytical model and experimental validation of the heat transfer and the induced ﬂow in a PV cooling duct in environmental conditions. World Renew. Energy Congr. 2011(2011):2907–15. [23] Yahya SM, Anwer SF, Sanghi S. Enhanced Heat Transfer and Fluid Flow in a Channel Behind a Photovoltaic Panel in a Hybrid Photovoltaic / Thermal System; 2013. [24] Krauter S, Hanitsch R. Actual optical and thermal performance of PV-modules. Fuel Energy Abstr 1996;37(6):436. [25] Solanki CS, Sangani CS, Gunashekar D, Antony G. Enhanced heat dissipation of Vtrough PV modules for better performance. Sol Energy Mater Sol Cells 2008;92(12):1634–8. [26] Said SAM, Al-Aqeeli N, Walwil HM. The potential of using textured and anti-reﬂective coated glasses in minimizing dust fouling. Sol Energy 2015;113:295–302. [27] Kurnik J, Jankovec M, Brecl K, Topic M. Outdoor testing of PV module temperature and performance under diﬀerent mounting and operational conditions. Sol Energy Mater Sol Cells 2011;95(1):373–6. [28] Kaldellis JK, Kapsali M, Kavadias KA. Temperature and wind speed impact on the eﬃciency of PV installations. Experience obtained from outdoor measurements in Greece. Renew Energy 2014;66:612–24. [29] Griﬃth JS, Rathod MS, Paslaski J. Some Tests of Mod Temps_PVSC1981.pdf. In: Proceedings of the 15th IEEE Photovoltaic Specialists Conf. pp. 822–830; 1981. [30] Duell M, Ebert M, Muller M, Li B, Koch M, Christian T, Perdichizzi RF, Marion B, Kurtz S, Doble DMJ. Impact of Structured Glass on Light Transmission, Temperature and Power of PV Modules. In: Proceedings of the 25th Eur. Photovolt. Sol. Energy Conf. Exhib. / 5th World Conf. Photovolt. Energy Conversion, 6–10 Sept. 2010, Val. Spain, no. Figure 2, pp. 3867–3872; 2010. [31] Rahman MM, Hasanuzzaman M, Rahim NA. Eﬀects of operational conditions on the energy eﬃciency of photovoltaic modules operating in Malaysia. J Clean Prod 2016;143:912–24. [32] Kant K, Shukla A, Sharma A, Biwole PH. Thermal response of poly-crystalline silicon photovoltaic panels: numerical simulation and experimental study. Sol Energy 2016;134:147–55. [33] Raviraj KL, Purushothama HR, Manjunatha A, Mishra V Kumar. Thermal design and evaluation of cooling conﬁguration of solar photovoltaic panel. Indian J Sci Technol 2016;9(45). [34] Alonso Garca MC, Balenzategui JL. Estimation of photovoltaic module yearly temperature and performance based on nominal operation cell temperature calculations. Renew Energy 2004;29(12):1997–2010. [35] Ettah EB, Udoimuk AB, Obiefuna JN, Opara FE. The eﬀect of relative humidity on the eﬃciency of solar panels in Calabar, Nigeria. Univers J Manag Soc Sci 2012;2(3):8–11. [36] Tossa AK, Soro YM, Thiaw L, Azoumah Y, Sicot L, Yamegueu D, Lishou C, Coulibaly Y, Razongles G. Energy performance of diﬀerent silicon photovoltaic technologies under hot and harsh climate. Energy 2016;103:261–70. [37] Meyer EL, Dyk EE Van. Assessing the reliability and degradation of photovoltaic module performance parameters. IEEE Trans Reliab 2004;53(1):83–92. [38] Omubo-Pepple V. Eﬀects of temperature, solar ﬂux and relative humidity on the eﬃcient conversion of solar energy to electricity. J Sci Res 2009;35(2):173–80. [39] Touati F, Massoud A, Abu-Hamad J, Saeed S a. Eﬀects of environmental and climatic conditions on PV eﬃciency in Qatar. Renew Energy Power Qual J 2013;1(11):275. [40] Adinoyi MJ, Said S aM. Eﬀect of dust accumulation on the power outputs of solar photovoltaic modules. Renew Energy 2013;60:633–6. [41] Meyer EL, van Dyk EE. Characterization of degradation in thin-ﬁlm photovoltaic module performance parameters. Renew Energy 2003;28(9):1455–69. [42] Touati F, Al-Hitmi M, Bouchech H. Towards understanding the eﬀects of climatic and environmental factors on solar PV performance in arid desert regions (Qatar) for various PV technologies. In: Proceedings of the 2012 First Int. Conf. Renew. Energies Veh. Technol., pp. 78–83; 2012. [43] Katkar AA, Shinde NN, Patil PS. Performance & evaluation of industrial solar cell wrt temperature and humidity. Int J Res Mech Eng Technol 2011;1(1):69–73. [44] Rajput P, Sastry OS, Tiwari GN. Eﬀect of irradiance, temperature exposure and an Arrhenius approach to estimating weathering acceleration factor of Glass, EVA and Tedlar in a composite climate of India. Sol Energy 2017;144:267–77. [45] Malik AQ, Damit SJBH. Outdoor testing of single crystal silicon solar cells. Renew Energy 2003;28(9):1433–45. [46] Rahman MM, Hasanuzzaman M, Rahim NA. Eﬀects of various parameters on PVmodule power and eﬃciency. Energy Convers Manag 2015;103:348–58. [47] Garg S. High temperature eﬀect on multicrystalline photovoltaic module in Western Rajasthan, India. Commun Appl Electron 2016;4(2):44–8. [48] Skoplaki E, Palyvos JA. On the temperature dependence of photovoltaic module electrical performance: a review of eﬃciency/power correlations. Sol Energy 2009;83(5):614–24. [49] Skoplaki E, Palyvos JA. Operating temperature of photovoltaic modules: a survey of pertinent correlations. Renew Energy 2009;34(1):23–9. [50] Dubey S, Sarvaiya JN, Seshadri B. Temperature dependent photovoltaic ( PV) efﬁciency and its eﬀect on PV production in the world a review. Energy Procedia 2013;33:311–21. [51] Shima M, Isomura M, Wakisaka KI, Murata K, Tanaka M. The inﬂuence of operation temperature on the output properties of amorphous silicon-related solar cells. Sol Energy Mater Sol Cells 2005;85(2):167–75. [52] Hashim ET. Temperature Eﬀect on Power Drop of Diﬀerent Photovoltaic Modules. vol. 22, no. 5; 2016. [53] Zorrilla-Casanova J, Piliougine M, Carretero J, Bernaola P, Carpena P, Mora-Lopez

[54]

[55]

[56]

[57]

[58]

[59]

[60] [61] [62] [63]

[64] [65]

[66] [67]

[68] [69]

[70] [71]

[72] [73]

[74] [75]

[76] [77] [78]

[79] [80] [81]

[82]

[83]

[84]

[85] [86] [87]

758

L, Sidrach-de-Cardona M. Analysis of dust losses in photovoltaic modules. World Renew. Energy Congr. 2011 - Sweden, pp. 2985–2992; 2011. Sala Sa, Campaniello M, Bailini A. Experimental study of polymers as encapsulating materials for photovoltaic modules. 2009 Eur. Microelectron. Packag. Conf., pp. 1–7; 2009. Kempe M, Reese M, Dameron A, Moricone T. Types of encapsulant materials and physical diﬀerences between them. In: Proceedings of the NREL PV Module Reliability Workshop, Denver West Marriott, Golden, Colorado; 2010. King DL, Quintana MA, Kratochvil JA, Ellibee DE, Hansen BR. Photovoltaic module performance and durability following long-term ﬁeld exposure. Prog Photovolt Res Appl 2000;8(2):241–56. Mclntosh KR, Cotsell JN, Norris AW, Powell NE, Ketola BM. An optical comparison of silicone and EVA encapsulants under various spectra. In: Proceeding sof the Conf. Rec. IEEE Photovolt. Spec. Conf., pp. 269–274; 2010. Ketola B, S C, Griﬃth P, Bunea G. Demonstration of the Beneﬁts of Silicone Encapsulation of PV Modules in a Large Scale Outdoor Array. In: Proceedings of the 25th EUPVSEC, vol. 2, no. 1, pp. 4060–4063; 2010. Walwil HM, Mukhaimer A, Al-Sulaiman FA, Said SAM. Comparative studies of encapsulation and glass surface modiﬁcation impacts on PV performance in a desert climate. Sol Energy 2017;142:288–98. Yang HY, Zhou X-D, Yang L-Z, Zhang T-L. Experimental studies on the ﬂammability and ﬁre hazards of photovoltaic modules. Materials 2015;8(7):4210–25. Gwandu BAL, Creasey DJ. Humidity: a factor in the appropriate positioning of a photovoltaic power station. Renew Energy 1995;6(3):313–6. Ghazi S, Ip K. The eﬀect of weather conditions on the eﬃciency of PV panels in the southeast of UK. Renew Energy 2014;69:50–9. Ramli MAM, Prasetyono E, Wicaksana RW, Windarko NA, Sedraoui K, Al-Turki YA. On the investigation of photovoltaic output power reduction due to dust accumulation and weather conditions. Renew Energy 2016;99:836–44. Nair AK, Chantrabose Arunraj, Murugan. Increasing solar PV output by controlling environmental parameters. IEEE 2016;6:251–6. Piliougine M, Cañete C, Moreno R, Carretero J, Hirose J, Ogawa S, Sidrach-decardona M. Comparative analysis of energy produced by photovoltaic modules with anti-soiling coated surface in arid climates. Appl Energy 2013;112:626–34. Said S AM, Walwil HM. Fundamental studies on dust fouling eﬀects on PV module performance. Sol Energy 2014;107:328–37. Brown K, Narum T, Jing N. Soiling test methods and their use in predicting performance of photovoltaic modules in soiling environments. In: Proceedings of the 2012 38th IEEE Photovoltaic Specialists Conference (PVSC); 2012, pp. 1881–1885. Ming C, Khai B, Chen E, Peng K. Microelectronics reliability humidity study of a-Si PV cell. Microelectron Reliab 2010;50(9–11):1871–4. Jiang H, Lu L, Sun K. Experimental investigation of the impact of airborne dust deposition on the performance of solar photovoltaic (PV) modules. Atmos Environ 2011;45(25):4299–304. Michael D. Kempe. Modeling of rates of moisture ingress into photovoltaic modules. vol. 90; 2006. pp. 2720–2738. Topic M, Ballif C, Sculati-Meillaud F, Perret-Aebi L-E, Li H-Y, Galliano F, Annigoni E, Matic G, Jankovec M. In-Situ Monitoring of Moisture Ingress in PV Modules with Diﬀerent Encapsulants. In: Proceedings of the 32nd Eur. Photovolt. Sol. Energy Conf. Exhib., vol. 6, no. 5; 2016. pp. 2260–2264. Xu R, Ni K, Hu Y, Si J, Wen H, Yu D. Analysis of the optimum tilt angle for a soiled PV panel. Energy Convers Manag 2017;148:100–9. Haghdadi N, Copper J, Bruce A, Macgill I. A method to estimate the location and orientation of distributed photovoltaic systems from their generation output data. Renew Energy 2017;108:390–400. Kaddoura TO, Ramli MAM, Al-turki YA. On the estimation of the optimum tilt angle of PV panel in Saudi Arabia. Renew Sustain Energy Rev 2016;65:626–34. Singh R, Banerjee R. Impact of solar panel orientation on large scale rooftop solar photovoltaic scenario for Mumbai [no. December 2015]. Energy Procedia 2016;90:401–11. Eldin SAS, Abd-elhady MS, Kandil HA. Feasibility of solar tracking systems for PV panels in hot and cold regions. Renew Energy 2016;85:228–33. Eke R, Senturk A. Performance comparison of a double-axis sun tracking versus ﬁxed PV system. Sol Energy 2012;86(9):2665–72. Bahrami A, Okoye CO, Atikol U. Technical and economic assessment of ﬁxed, single and dual-axis tracking PV panels in low latitude countries. Renew Energy 2017. 〈http://www.xinpeng-solar.com〉. 〈http://www.enfsolar.com/directory/component/tracker〉. Bianchini A, Gambuti M, Pellegrini M, Saccani C. Performance analysis and economic assessment of diﬀerent photovoltaic technologies based on experimental measurements. Renew Energy 2016;85:1–11. Hammad B, Al-sardeah A, Al-abed M, Nijmeh S. Performance and economic comparison of ﬁ xed and tracking photovoltaic systems in Jordan [no. September 2016]. Renew Sustain Energy Rev 2017;80:827–39. Bana S, Saini RP. Experimental investigation on power output of diﬀerent photovoltaic array con ﬁ gurations under uniform and partial shading scenarios. Energy 2017;127:438–53. Fouad MM, Shihata LA, Morgan EI. An integrated review of factors in ﬂ uencing the performance of photovoltaic panels. Renew Sustain Energy Rev 2017;80:1499–511. Zhang W, Lu L, Peng J. Evaluation of potential beneﬁts of solar photovoltaic shadings in Hong Kong. Energy 2017. Brecl K, Topi M. Self-shading losses of ﬁ xed free-standing PV arrays, vol. 36; 2011. Bayrak F, Ertürk G, Oztop HF. Eﬀects of partial shading on energy and exergy eﬃciencies for photovoltaic panels. J Clean Prod 2017.

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

[120] Paudyal BR, Shakya SR. Dust accumulation eﬀects on eﬃciency of solar PV modules for oﬀ grid purpose: a case study of Kathmandu. Sol Energy 2016;135:103–10. [121] Hee JY, Kumar LV, Danner AJ, Yang H, Bhatia CS. The eﬀect of dust on transmission and self-cleaning property of solar panels. Energy Procedia 2012;15(2011):421–7. [122] Jiang Y, Lu L, Lu H. A novel model to estimate the cleaning frequency for dirty solar photovoltaic (PV) modules in desert environment. Sol Energy 2016;140:236–40. [123] Bajaj M. Comprehensive Analysis of Eﬀect of Accumulation of Dust on a Solar Panel. vol. 4, no. 1; 2016. p. 224–227. [124] Garg HP. Eﬀect of dirt on transparent covers in ﬂat-plate solar energy collectors. Sol Energy 1974;15(4):299–302. [125] Nahar NM, Gupta JP. Eﬀect of dust on transmittance of glazing materials for solar collectors under arid zone conditions of India. Sol Wind Technol 1990;7(2–3):237–43. [126] Cabanillas RE, Munguía H. Dust accumulation eﬀect on eﬃciency of Si photovoltaic modules. J Renew Sustain Energy 2011;3(4). [127] Grunow P, Sauter D, Hoﬀmann V. The inﬂuence of textured surfaces of solar cells and modules on the energy rating of PV systems, 20th EPVSEC, …, vol. 1, no. 2003; 2005. [128] Kazmerski LL, Diniz ASAC, Maia CB, Viana MM, Costa SC, Brito PP, Campos CD, Neto LVM, Hanriot S De Morais, Cruz LR De Oliveira. Fundamental studies of adhesion of dust to PV module surfaces: chemical and physical relationships at the microscale. IEEE J Photovolt 2016;6(3):719–29. [129] Qasem H, Betts TR, Mullejans H, AlBusairi H, Gottschalg R. Eﬀect of dust shading on photovoltaic modules; 2011. [130] Mohamed AO, Hasan A. Eﬀect of dust accumulation on performance of photovoltaic solar modules in Sahara environment. J Basic Appl Sci Res 2012;2(11):11030–6. [131] Kazem HA, Chaichan MT. Experimental analysis of the eﬀect of dust's physical properties on photovoltaic modules in Northern Oman. Sol Energy 2016;139:68–80. [132] Lu H, Lu L, Wang Y. Numerical investigation of dust pollution on a solar photovoltaic (PV) system mounted on an isolated building. Appl Energy 2016;180:27–36. [133] Qasem H, Betts TR, Müllejans H, AlBusairi H, Gottschalg R. Dust-induced shading on photovoltaic modules. Prog Photovolt Res Appl 2014;22(2):218–26. [134] Modaihsh A. Characteristics and composition of the falling dust sediments on Riyadh city, Saudi Arabia. J Arid Environ 1997;36(2):211–23. [135] Javed W, Wubulikasimu Y, Figgis B, Guo B. Characterization of dust accumulated on photovoltaic panels in Doha, Qatar. Sol Energy 2017;142:123–35. [136] Hassan G, Yilbas BS, Said SAM, Matin A. Chemo-Mechanical Characteristics of Mud Formed from Environmental Dust Particles in Humid Ambient Air. Nat. Publ. Gr., no. May; 2016. p. 1–14. [137] Dastoori K, Al-Shabaan G, Kolhe M, Thompson D, Makin B. Impact of accumulated dust particles' charge on the photovoltaic module performance. J Electrostat 2016;79:20–4. [138] Yilbas BS, Ali H, Al-Aqeeli N, Khaled MM, Said S, Abu-Dheir N, Merah N, YoucefToumi K, Varanasi KK. Characterization of environmental dust in the Dammam area and Mud after-eﬀects on bisphenol-a polycarbonate sheets. Sci Rep 2016;6:24308. [139] FitzPatrick EA, Fitzpatrick EA. Soil microscopy and micromorphology. Chichester: John Wiley & Sons; 1993. [140] Zhang H, Li X, Du C, Qi H. Corrosion behavior and mechanism of the automotive hot-dip galvanized steel with alkaline mud adhesion. Int J Miner Metall Mater 2009;16(4):414–21. [141] Yilbas BS, Hassan G, Ali H, Al-Aqeeli N. Environmental dust eﬀects on aluminum surfaces in humid air ambient. Sci Rep 2017;7. [142] Giovanoli R, Schnoor JL, Sigg L, Stumm W, Zobrist J. Chemical weathering of crystalline rocks in the catchment area of acidic Ticino lakes, Switzerland. Clays Clay Miner 1988;36(6):521–9. [143] Yilbas BS. Eﬀect of mud drying temperature on surface characteristics of a polycarbonate PV protective cover. Sol Energy 2017;143:63–72. [144] Yilbas BS, Ali H, Khaled MM, Al-Aqeeli N, Abu-Dheir N, Varanasi KK. “Inﬂuence of dust and mud on the optical, chemical, and mechanical properties of a pv protective glass. Sci Rep 2015;5:15833. [145] Zhang X, Shi F, Niu J, Jiang Y, Wang Z. Superhydrophobic surfaces: from structural control to functional application. J Mater Chem 2008;18(6):621–33. [146] Verma LK, Sakhuja M, Son J, Danner aJ, Yang H, Zeng HC, Bhatia CS. Self-cleaning and antireﬂective packaging glass for solar modules. Renew Energy 2011;36(9):2489–93. [147] Jing L, Zhi-Jun Z, Ji-Lin Y, Yi-Long B. A thin liquid ﬁlm and its eﬀects in an atomic force microscopy measurement. Chin Phys Lett 2009;26(8):86802. [148] Corn M. The adhesion of solid particles to solid surfaces, I. A review. J Air Pollut Control Assoc 1961;11(11):523–8. [149] Penney EW. Contact Potentials and the Adhesion of Dust; 1962. p. 200–204. [150] Mclean KJ. Cohesion of precipitated dust layer in electrostatic precipitators. J Air Pollut Control Assoc 1977;27(11):1100–3. [151] Somasundaran P, Lee HK, Shchukin ED, Wang J. Cohesive force apparatus for interactions between particles in surfactant and polymer solutions. Colloids Surf A Physicochem Eng Asp 2005;266(1–3):32–7. [152] Kumar A, Staedler T, Jiang X. Journal of Colloid and Interface Science Role of relative size of asperities and adhering particles on the adhesion force. J Colloid Interface Sci 2013;409:211–8. [153] Petean PGC, Aguiar ML. Determining the adhesion force between particles and

[88] Tsang KM, Chan WL. Maximum power point tracking for PV systems under partial shading conditions using current sweeping. Energy Convers Manag 2015;93:249–58. [89] Belhachat F, Larbes C. Global maximum power point tracking based on ANFIS approach for PV array conﬁgurations under partial shading conditions. Renew Sustain Energy Rev 2017;77:875–89. [90] Belhachat F, Larbes C. ScienceDirect modeling, analysis and comparison of solar photovoltaic array conﬁgurations under partial shading conditions. Sol Energy 2015;120:399–418. [91] Dhimish M, Holmes V, Mehrdadi B, Dales M, Chong B, Zhang L. Seven indicators variations for multiple PV array con ﬁ gurations under partial shading and faulty PV conditions. Renew Energy 2017;113:438–60. [92] Zaihidee FM, Mekhilef S, Seyedmahmoudian M, Horan B. Dust as an unalterable deteriorative factor aﬀecting PV panel's eﬃciency: why and how. Renew Sustain Energy Rev 2016;65:1267–78. [93] Pang H, Close J, Lam K. Study on eﬀect of urban pollution to performance of commercial copper indium diselenide modules. In: Proceedings of the Conference Record of the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion, vol. 2; 2006, p. 2195–2198. [94] Asl-Soleimani E, Farhangi S, Zabihi MS. The eﬀect of tilt angle, air pollution on performance of photovoltaic systems in Tehran. Renew Energy 2001;24(3–4):459–68. [95] Said SAM. Eﬀects of dust accumulation on performances of thermal and photovoltaic ﬂat-plate collectors. Appl Energy 1990;37(1):73–84. [96] Ibrahim A. Eﬀect of shadow and dust on the performance of silicon solar cell. J Basic Appl Sci Res 2011;1(3):222–30. [97] Elminir HK, Ghitas AE, Hamid RH, El-Hussainy F, Beheary MM, Abdel-Moneim KM. Eﬀect of dust on the transparent cover of solar collectors. Energy Convers Manag 2006;47(18–19):3192–203. [98] Boykiw E. The Eﬀect of Settling Dust in the Arava Valley on the Performance of Solar Photovoltaic Panels; 2011. pp. 1–36. [99] and Eltaib Abdeen MO, El-Sayed Hasaneen. Real Study for Photovoltaic System Performance in Desert Environment – Upper Egypt – Case Study; 2016. [100] Mohandes BMA, Lamont LA. Application Study of 500 W Photovoltaic (PV) System in the UAE 1. vol. 45, no. 4; 2009. p. 242–247. [101] Rocha MP, Rubio JEC, Sidrach-de-Cardona M, Montiel D, Sánchez-Friera P, Carretero Rubio JE, Piliougine Rocha M. Comparative Analysis of the Dust Losses in Photovoltaic Modules With Diﬀerent Cover Glasses. In: Proceedigs of the 23rd Eur. Photovolt. Sol. Energy Conf., no. September; 2008. p. 2698–2700. [102] Caron JR, Littmann B. Direct monitoring of energy lost due to soiling on ﬁrst solar modules in California. IEEE J Photovolt 2013;3(1):336–40. [103] Kaldellis JK, Kokala A. Quantifying the decrease of the photovoltaic panels' energy yield due to phenomena of natural air pollution disposal. Energy 2010;35(12):4862–9. [104] Abderrezek M, Fathi M. Experimental study of the dust eﬀect on photovoltaic panels' energy yield. Sol Energy 2017;142:308–20. [105] Saidan M, Albaali AG, Alasis E, Kaldellis JK. Experimental study on the eﬀect of dust deposition on solar photovoltaic panels in desert environment. Renew Energy 2016;92:499–505. [106] Maghami MR, Hizam H, Gomes C, Radzi MA, Rezadad MI, Hajighorbani S. Power loss due to soiling on solar panel: a review. Renew Sustain Energy Rev 2016;59:1307–16. [107] Rajput DS, Sudhakar K. Eﬀect of dust on the performance of solar PV panel. Int J ChemTech Res 2013;5(2):1083–6. [108] Kaldellis JK, Fragos P, Kapsali M. Systematic experimental study of the pollution deposition impact on the energy yield of photovoltaic installations. Renew Energy 2011;36(10):2717–24. [109] Mehmood U. Characterization of dust collected from PV modules in the area of Dhahran, Kingdom of Saudi Arabia, and its impact on protective transparent covers for photovoltaic applications. Sol Energy 2016;141:203–9. [110] Qasem H, Betts TR, Mullejans H, AlBusairi H, Gottschalg R. Dust eﬀect on PV modules; 2011. [111] El-Shobokshy MS, Hussein FM. Eﬀect of dust with diﬀerent physical properties on the performance of photovoltaic cells. Sol Energy 1993;51(6). [112] El-Shobokshy MSS, Mujahid A, Zakzouk AKMKM. Eﬀects of dust on the performance of concentrator photovoltaic cells. IEE Proc I Solid State Electron Devices 1985;132(1):5. [113] Kumar ES, Sarkar B, Behera DK. Soiling and dust impact on the eﬃciency and the maximum power point in the photovoltaic modules. Int J Eng Res Technol, 2013 -2013;2(2). [114] Wang ZZJingshu, Gong Hengxiang. Modeling of Dust Deposition Aﬀecting Transmittance of PV Modules - Volume 5 Number 3 (May 2017) - JOCET, Jocet, vol. 5, no. 3; 2017, pp. 217–221. [115] Appels R, Lefevre B, Herteleer B, Goverde H, Beerten A, Paesen R, De Medts K, Driesen J, Poortmans J. Eﬀect of soiling on photovoltaic modules. Sol Energy 2013;96:283–91. [116] Bouaouadja N, Bouzid S, Hamidouche M, Bousbaa C, Madjoubi M. Eﬀects of sandblasting on the eﬃciencies of solar panels. Appl Energy 2000;65(1–4):99–105. [117] Mastekbayeva GA, Kumar S. Eﬀect of dust on the transmittance of low density polyethylene glazing in a tropical climate. Sol Energy 2000;68(2):135–41. [118] Pedersen H, Strauss J, Selj J. Eﬀect of soiling on photovoltaic modules in Norway. Energy Procedia 2016;92(1876):585–9. [119] Guan Y, Zhang H, Xiao B, Zhou Z, Yan X. In-situ investigation of the eﬀect of dust deposition on the performance of polycrystalline silicon photovoltaic modules. Renew Energy 2017;101:1273–84.

759

Renewable and Sustainable Energy Reviews 82 (2018) 743–760

S.A.M. Said et al.

Proceedings of the ESA-IEEE joint meeting on electrostatics; 2003, vol. 814. [170] Atten P, Pang HL, Reboud JL. Study of dust removal by standing-wave electric curtain for application to solar cells on Mars. IEEE Trans Ind Appl 2009;45(1):75–86. [171] Bock JP, Robinson JR, Sharma R. and others, An Eﬃcient Power Management Approach for Self–Cleaning Solar Panels with Integrated Electrodynamics Screens. In: Proceedings of the ESA Annual Meeting on Electrostatics; 2008. [172] Biris AS, Saini D, Srirama PK, Mazumder MK, Sims RA, Calle CI, Buhler CR. Electrodynamic removal of contaminant particles and its applications. In: Proceedings of the 39th IAS Annu. Meet. Conf. Rec. 2004 IEEE Ind. Appl. Conf. 2004, vol. 2; 2004. p. 1283–1286. [173] Hudedmani MG, Joshi G, Umayal RM, Revankar A. A comparative study of dust cleaning methods for the solar PV panels. Adv J Grad Res 2017;1(1):24–9. [174] Cao L. Superhydrophobic surface design fabrication and application. Engineering 2010:111. [175] Park Y-B, Im H, Im M, Choi Y-K. Self-cleaning eﬀect of highly water-repellent microshell structures for solar cell applications. J Mater Chem 2011;21:633. [176] Fathi M, Abderrezek M, Friedrich M. Reducing dust eﬀects on photovoltaic panels by hydrophobic coating. Clean Technol Environ Policy 2016;19(2):1–9. [177] Lafuma A, Quéré D. Superhydrophobic states. Nat Mater 2003;2(7):457–60. [178] Smith JD, Dhiman R, Anand S, Reza-Garduno E, Cohen RE, McKinley GH, Varanasi KK. Droplet mobility on lubricant-impregnated surfaces. Soft Matter 2013;9(6):1772–80. [179] Lafuma A, Quéré D. Slippery pre-suﬀused surfaces. EPL (Europhys Lett 2011;96(5):56001. [180] Liu H, Zhang P, Liu M, Wang S, Jiang L. Organogel-based thin ﬁlms for selfcleaning on various surfaces. Adv Mater 2013;25(32):4477–81. [181] Wong TS, Kang SH, Tang SKY, Smythe EJ, Hatton BD, Grinthal A, Aizenberg J. Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity. Nature 2011;477(7365):443–7. [182] Anand S, Paxson AT, Dhiman R, Smith JD, Varanasi KK. Enhanced condensation on lubricant- impregnated nanotextured surfaces. ACS Nano 2012;6(11):10122–9. [183] Latthe SS, Imai H, Ganesan V, Kappenstein C, Rao AV. Optically transparent superhydrophobic TEOS-derived silica ﬁlms by surface silylation method. J Sol-Gel Sci Technol 2010;53(2):208–15. [184] Zhang XT, Sato O, Taguchi M, Einaga Y, Murakami T, Fujishima A. Self-cleaning particle coating with antireﬂection properties. Chem Mater 2005;17(3):696–700. [185] Nostell P, Roos A, Karlsson B. Optical and mechanical properties of sol-gel antireﬂective ﬁlms for solar energy applications. Thin Solid Films 1999;351(1):170–5. [186] Li X, Du X, He J. Self-cleaning antireﬂective coatings assembled from peculiar mesoporous silica nanoparticles. Langmuir 2010;26(16):13528–34. [187] Park Y-B, Im H, Im M, Choi Y-K. Self-cleaning eﬀect of highly water-repellent microshell structures for solar cell applications. J Mater Chem 2011;21(3):633–6.

rough surfaces. Powder Technol 2015;274:67–76. [154] Kazmerski LL, Sonia A, Diniz AC, Brasil C, Machado M, Costa SC, Brito PP, Dias C, De Morais S, Oliveira LR De. Soiling particle interactions on PV modules: surface and inter - particle adhesion and chemistry eﬀects. Pvsc 2016:2–4. [155] Goossens D, Oﬀer ZY, Zangvil A. Wind tunnel experiments and ﬁeld investigations of Eolian dust deposition on photovoltaic solar collectors. vol. 50, no. 1; 1993. p. 75–84. [156] Pavlović T, Pavlović Z, Pantić L, Kostić L. Determining optimum tilt angles and orientations of photovoltaic panels in Niš, Serbia. Contemp Mater 2010;1(2):151–6. [157] Jiang Y, Lu L. Experimentally investigating the eﬀect of temperature diﬀerences in the particle deposition process on solar photovoltaic (PV) modules. Sustainability 2016;8(11):1091. [158] Al Shehri A, Parrott B, Carrasco P, Al Saiari H, Taie I. Impact of dust deposition and brush-based dry cleaning on glass transmittance for PV modules applications. Sol Energy 2016;135:317–24. [159] Williams RB, Tanimoto R, Simonyan A, Fuerstenau S. Vibration characterization of self-cleaning solar panels with piezoceramic actuation. In: Proceedings of the Collect. Tech. Pap. Struct. Dyn. Mater. Conf., vol. 1, no. April; 2007. p. 512–520. [160] Fernandez D, Cabas R, Moreno L. Dust wiper mechanism for operation in Mars. Eur. Sp. Agency, Special Publ. ESA SP, no. SP-653; 2007. [161] Lamont LA, Chaar L El. Enhancement of a stand-alone photovoltaic system's performance: reduction of soft and hard shading. Renew Energy 2011;36(4):1306–10. [162] Rifai A, Abu Dheir N, Yilbas BS, Khaled M. Mechanics of dust removal from rotating disk in relation to self-cleaning applications of PV protective cover. Sol Energy 2016;130:193–206. [163] Calle CI, Buhler CR, McFall JL, Snyder SJ. Particle removal by electrostatic and dielectrophoretic forces for dust control during lunar exploration missions. J Electrostat 2009;67(2–3):89–92. [164] Sun QX, Yang NN, Cai XB, Hu GK. Mechanism of dust removal by a standing wave electric curtain. Sci China Phys Mech Astron 2012;55(6):1018–25. [165] Sharma R, Wyatt CA, Zhang J, Calle CI, Mardesich N, Mazumder MK. Experimental evaluation and analysis of electrodynamic screen as dust mitigation technology for future Mars missions. IEEE Trans Ind Appl 2009;45(2):591–6. [166] Sharma R, Wyatt C, Zhang J, Mazumder MK, Mardesich N. Performance Analysis of Electrodynamic Self- cleaning Transparent Films for its Applications to Mars and Lunar Missions. vol. 1, no. 1263202; 2007. p. 434–437. [167] He G, Zhou C, Li Z. Review of self-cleaning method for solar cell array. Procedia Eng 2011;16:640–5. [168] Mazumder MK, Sharma R, Biris AS, Zhang J, Calle C, Zahn M. Self-cleaning transparent dust shields for protecting solar panels and other devices. Part Sci Technol 2007;25(1):5–20. [169] Sims RA, Biris AS, Wilson JD, Yurteri CU, Mazumder MK, Calle CI, Buhler CR. Development of a transparent self-cleaning dust shield for solar panels. In:

760

The effect of environmental factors and dust accumulation on photovoltaic modules and dust-accumulation mitigation strategies

The effect of environmental factors and dust accumulation on photovoltaic modules and dust-accumulation mitigation strategies

Recommend Documents