Effect of Dust Deposition on Performance of Thin Film ...

2nd International Conference on Renewable Energy Research and Applications

Madrid, Spain, 20-23 October 2013

Effect of Dust Deposition on Performance of Thin Film Photovoltaic Module in Harsh Humid Climate

Ahmed M.A.M. Serag ElDin1, Ahmed Hamza H. Ali1, Ali K. Abel-Rahman1 and S. Ookawara1,2 1 Energy Resources Engineering Department, Egypt- Japan University of Science and Technology E-JUST, New Borg Elarab, Alexandria 21934, Egypt 2 Department of Chemical Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology, Tokyo, Japan [email protected]

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Abstract This study investigated experimentally the effect of air born suspend matters deposition on PV module located in harsh climate close to the sea. The experimental measurements are carried out under outdoor conditions in Alexandria, Egypt to identify the module performance degradation as a function of time as well as the time schedule for module surface cleaning. However, as the sea is nearby it’s a source for nocturnal condensate on module surface. The experiments were conducted during period from 13 March to 17 April, 2013. The results indicated that the dust accumulation on the module surface has a significant impact on PV module output power. As the dust deposition density increased from 0 to 0.36 mg cm-2, the corresponding reduction of PV output efficiency as well as short circuit current Isc are degraded by 17.71%. Conversely, the reduction of open circuit voltage was insignificant where the maximum reduction of Voc from 100% to 97.86 of the clean module value. The average degradation of power and efficiency during the entire period of work (30 days) is 9.86%. Also the results show that the dust effect on thin film PV modules becomes most significant in cloudy weather day rather than clear day and the degradation in performance reaches about 16.01% in cloudy day. Keywords: Dust accumulation on PV; PV Performance; thin film PV module; PV efficiency degradation

I. INTRODUCTION Performance of a solar energy utilization systems whether using solar thermal collectors or Photovoltaic (PV) modules is influenced by the ability of the glass cover to transmit solar radiation into the collection surface, The dust particles in the ambient air carried by the wind can deposit on the solar photovoltaic devices external surface and obscure the solar radiation and therefore reduce their efficiency, especially in dry harsh environmental conditions. Dust is a term generally applying to minute solid particles with diameters less than 500µm known that dust promotes dust, the surface becomes more amenable to dust collection. Taking into account the effect of gravity, horizontal surfaces usually tend to accumulate more dust than inclined ones. This however is dependent on the prevalent wind movements. Generally a low-speed wind pattern promotes dust settlement. While a high-speed wind

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regime would, on the contrary, dispel dust settlement and have a cleaning. However, the geometry of the PV system in relation to the direction of wind movements can either increase/decrease the prospects of dust settlement at specific locations of the PV system. Dust is likely to settle in regions of low-pressure induced by high-speed wind movements over inclined/vertical surface. The dispersal of dust attributed to wind movements and geometry of PV system depends on the property of dust (weight, size, type) as reported in [1]. Moharram et al [2], investigate experimentally the influence of cleaning of PV panels using water as well as a surfactant using a non-pressurized water system on their performance. They found that the efficiency of the PV panels has decreased by 50% after 45 days of cleaning using non-pressurized water, while the efficiency remained constant when a mixture of anionic and cationic surfactants was used for cleaning. Kalogirou et al [3] studied the effects of soiling on performance of three types of PV panels: monocrystalline, poly-crystalline and amorphous silicon through on-site measurements. They performed two tests; the first is the degradation of PV’s performance under extreme soiling conditions caused by the artificial deposition of dust on the panels when their surface was dry. While, the second when the panels are wet before the dust deposition. Their results showed that the artificial soiling on the wet PV surface presents a serious degradation of the PV panels performance is about 13% for the affected PV panels. Mekhilef et al [4] studied the effect of various influential parameters on the efficiency and performance of photovoltaic cells, like impact of dust accumulation, humidity level and the air velocity elaborated separately and the impact of each on the other. They reported that each of these three factors affect the other two and they concluded that in order to have a profound insight of solar cell design, the effect of these factors should be taken into consideration in parallel. Hee et al [5] investigated the conditions affecting dust-fall in Singapore environment and its effect on the optical transmission through glass modules. They reported that after 33 days, the transmissivity of a plain glass slides reduced from 90.7% to 87.6%. Also, they investigated

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2nd International Conference on Renewable Energy Research and Applications bare glass substrates that were tilted at angles of 0, 10, 20, 30, 40, 50, 60, 70, 80 and 90 degrees during outdoor exposure. They reported that after 33 days, the average transmissivity of the upper part of slides was 88.7%, while through the lower part it was 87.9%. Kaldellis and Fragos [6] experimentally investigated side effect of the atmospheric air pollution on the degradation of photovoltaic (PV) cells’ performance, by using two identical pairs of PV-panels. The first tested cell is being clean and the second one being artificially polluted with ash, i.e. a by-product of incomplete hydrocarbons’ combustion mainly originating from thermal power stations and vehicular exhausts. They carried out series of systematic measurements of current intensity, voltage output and incident solar radiation that are executed simultaneously for the clean and the polluted PV-panels. They reported that the deterioration of the PVpanels’ performance is almost 30% energy reduction per hour or 1.5% efficiency decrease (in absolute terms) for the case when ash accumulation on the panels’ surface reaches up to 0.4 mg/cm2. Jiang et al [7] studied the dust accumulation onto different types of solar PV modules and the corresponding efficiency degradation under various conditions. Their experiment was designed and conducted inside the laboratory with a sun simulator and a test chamber. They reported that dust pollution has a significant impact on PV module output, as dust deposition density increasing from 0 to 22 g m-2, the corresponding reduction of PV output efficiency grew from 0 to 26%. The reduction of efficiency has a linear relationship with the dust deposition density, and the difference caused by cell types was not obvious. Elminir et al [8] studied experimentally the influence of dust on the performance of PV systems and their experimental set up involving 100 glass samples with different tilt and azimuth angles. The transmittance of the glass was evaluated at regular intervals over a period of about seven months and after every thunderstorm in the surrounding area. They found that the reduction in glass normal transmittance depends strongly on the dust deposition density in conjunction with plate tilt angle, as well as on the orientation of the surface with respect to the dominant wind direction. The dust deposition density goes from 15.84 g/m2 (for glass sample installed at a tilt angle of 00) to 4.48 g/m2 (for glass sample installed at a tilt angle of 900 and oriented with 1350 deviation from north), the corresponding transmittance diminishes by approximately 52.54 – 12.38%, respectively. They also reported that for the solar cell installed at a 450 angle facing south a decrease in the output power of about 17.4% per month is recorded. El-Shobokshy and Hussein [9, 10] carried out comprehensive experimental study on the impact of dust on the performance of PV cells as well as the physical properties of the dust accumulation and deposition density and their impact on parameters degrading PV system efficiency. The experiment was entirely simulated with artificial dust (including limestone, cement and carbon particulates) and halogen lamps. They kept the solar (light) intensity constant and varied the densities of dust and the test was repeated several times. Their study revealed that the impact of cement particles to be the most significant, with a 73 g/m2 deposition of cement dust resulting in an 80% drop in PV module short-circuit voltage. The atmospheric dust with mean diameter 80 mm at 250 g/m2 was found to reduce the shortcircuit current by 82% while fine carbon particulates (5 mm)

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were found to have the most deteriorating effect on the PV efficiency. Mohamed and Hassan [11] investigated a framework of weekly cleaning on PV modules array throughout the period from February to May in the southern area of Libya. They Reported that a significant gradual decrease of the output power, while keeping a frequent weekly water washing lead to performance losses between 2 to 2.5%. Jiang and Sun [12] studied the dust accumulation onto different types of solar PV modules and the corresponding efficiency degradation. The experiment was designed and conducted inside the laboratory with a sun simulator and a test chamber. The degradation of PV module efficiency caused by dust deposition under various conditions was investigated. They reported that the dust pollution has a significant impact on PV module output. As the dust deposition density increases from 0 to 22 g/m2, the corresponding decrease in the PV module output efficiency are from 0 to 26%. Qasem et al [13] investigated the effect of in homogeneously deposited dust on the performance of Cadmium–Telluride photovoltaic (PV) thin film modules by developing a spatially-resolved 3 dimensional model utilizing the circuit analysis software PSPICE. They found that performance continuously deteriorates with increasing dust concentration, with operating efficiencies decreasing by 34% in only 90 days. Beattie et al [14] presented numerical and analytical models of sand and dust particle accumulation on photovoltaic modules in dry regions and supported their investigation by a laboratory investigation of sand particle accumulation on a glass surface. They reported that both models and the experimental data indicate that the reduction in the free fractional area can be described by an exponential decay resulting from the formation of clusters of particles. These results qualitatively describe existing field data beyond the linear regime and are developed to account for field conditions, including analysis of photovoltaic module tilt, humidity and wind speed. Kaldellis and Kapsali [15] develop a theoretical model to investigate the expected effect of regional air pollution on PVs’ performance. Furthermore, they carried experimental measurements to validate the proposed theoretical model. They reported that according to the results obtained a considerable deterioration of PVs’ energy yield and efficiency is observed when dust particles are deposited on the panels’ front sides (naturally or artificially).This is mainly depending on the type of the pollutant (i.e. composition, diameter, etc.) followed by the mass accumulated on the panel’s surface. AlHasan [16] analyzed theoretically the effect of sand dust deposition on the transmittance of light beam on a PV module. Their model output results predicted that the reductions in light transmittance up to 50% due to dust accumulation. Siddiqui and Bajpai [17] develop an equation with the given data for all seasons for a location (Lucknow, India) consisting of composite climate, which is further helpful in developing a relation between difference in efficiencies of module with respect to thicknesses of dust collected on the module. This equation that is developed mathematically is in good correlation with the measured data. They cited that this equation helps to evaluate the difference in efficiencies of module by knowing thicknesses of dust collected on its surface for any climatic conditions and is given by: ∆η=1:4128+345:9471t

(1)

2nd International Conference on Renewable Energy Research and Applications Where: t is thickness of dust layer, and ∆η ∆ is difference in efficiencies of module. Throughout the above and available literature, clearly shown that none has investigated the effect the deposition on PV module located in harsh climate close to t the sea through outdoor test to clarify the module performancce degradation and surface clearing schedule for the module. In I particular when the module installed nearby the sea, in whiich condensate on module surface at take place at late nighttimee. II. EXPERIMENTAL SETUP, PROCEDURE ES AND DATA REDUCTION 2.1 Experimental Setup To investigate the impact of dust accumuulation on thin film Photovoltaic panels’ performance, experimenntal measurements are carried out. The effect of the dust depoosition on the PV panels performance is the output from the measurements m and used to comparing the power output and connversion efficiency of two statistically checked identical paairs of PV-panels (located at the same area) both being soouth oriented and adjusted at the same inclination 300 with thhe horizontal. The experimental measurements is carried out at a the roof of the Laboratories of Energy Resources Engineeering Department located at the campus of the Egypt Japan University of Science and Technology (E-JUST) in New Borg Al--Arab, Alexandria, Egypt (Longitude/Latitude: E 029° 42' /N 30° 55'). The experimental setup is shown in Fig (1) annd consists of the following main components: Two identical thin film PVpanels, 30 glass slides, Variable load resistance, 4 Digital Ammeter, and, Weather station. 2.1.1 PV modules m) PV modules are Two CIS (copper, indium and selenium used in the measurements, one is used to invvestigate the effect of the dust accumulation on the output powerr while the other is always kept clean and its output power is ussed as a Reference Module. The main specifications and the mean m parameter of the panels are listed in Table (1). Althoughh CIS photovoltaic modules have low Efficiency reaches about 13%, a distinctive feature of CIS modules is their outstanding performance p in low light conditions. It has the highest spectral response r of among all photovoltaic technologies. Therefore, its performing better in bright sunlight and it’s the only modules thhat produce output power under cloudy skies. The semiconductoor layer made from copper (Cu), indium (In), selenium (Se), gallium (Ga) and sulphur (S) uses the broadest light specttrum of all solar technologies. This enables high yields eveen under diffused light conditions [18].


2.1.3 Meteorological Data Meaasurements The environmental conditioons such as Wind Speed, Wind Direction, ambient day bulb Temperature, T Relative Humidity, Horizontal Solar Radiation Intensity and Rain Fall are measured by Met one Portable Weather Station (Model Number 466A) installed in thhe same location which is side beside with the experimental seetup that is shown in Fig(3). 2.1.4. Performance data measu urements The outputs of Photovoltaicc Panels DC Volt and Ampere (I, V) are measured through the foollowing techniques: A variable load system is built and used too characterize the output power.

Fig. (1) Two (SF80-A) CIS phhotovoltaic modules with slide glaasses Table (1) PV thin film m module specification Model

SF80-A

Power-generating elem ment

CIS (thin-film)

(Pm) nominal maximum m output

80W

Nominal operating volta age Maximum output (V VPm)

41.0V

Nominal maximum pow wer current (Ipm)

1.95A

Nominal open-circuit vo oltage (Voc)

56.5V

Nominal short-circuit current (Isc)

2.26A

Gross weight

12.4kg

Overall Dimensions, in mm m

641 × 1,235 × 35

(W × L × D)

2.1.2 Dust Accumulation Measurements To measure the rate of dust accumulation on the solar cell surface as a function of time, 75x22 mm glaass slides are fixed side beside with the cell with the same level and inclination as shown in Fig (2). Therefore, as the dust deeposit on the solar cell PV surface is almost the same deposit on the glass slide surface under same environmental conditionss.

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Fig. (2) A photograph show ws the location of the glass slides



2.3 Data Reduction The hourly measurements during period of 30 Days from March 14 to April 13, 2013 for f Current, Voltage of the two panels simultaneously are recorded as well as the Meteorological data readinngs. Therefore, from these measurements the panels outtput Power and Efficiency is determined. For data redduction, the average daily measurements were determineed. The normalized efficiency reduction was obtained by Fig. (3) A Photograph of the Portable Meteorological M Weather Station The concept is, instead of measuring the output current as a function of voltage, followed by converting them t to power as a function of load, in this study the power is measured as a function of load directly as shown in Fig. (44). the test system presents a variable resistive load to the PV Paanels. The variable load includes the short circuit and open circcuit conditions and steps through many intermediate resistance values. v It provides measures for the voltage and current acrosss the load at each value of load resistance. The collected inform mation is plotted as the characteristic curves and the extracted data d is used in the listed performance parameters. 2.2 Experimental Procedure After installing the measuring instrumennts, the two panels are cleaned therefore they are at same initial conditions at beginning of the experimental measurements on March 13 2103. The glass slide are numbered and faastened in parallel with the PV panels after measuring their weight individually. The time step for measuring samples of glass slides with deposited dust was four days. The glass slide s is picked up carefully and weighted, followed by coatiing them by gold coating in order to be to be photographhed by Scanning Electronic Microscope (SEM) (Model JS SM-6010LV) with x100 magnification to determine the dust coverage c area and mean particle size in µm. The dust compoosition analysis is performed by X-Ray Fluorescein (Model X-RF NEXCG made by Rigaku, Japan). While, a particle siize analyzer type Mastersizer 2000 made in England is used u for Imaging (version1.46r) with the software to meaasure the average particle size in and the average coverage arrea fraction of the dust at each glass slide after certain periodd of time. The PV modules performances are measured for foour hours from 10 AM to 2 PM. The measured data are output current c and voltage (I,V) as well as the metrological data (W Wind Speed, Wind Direction, Atmospheric Temperature, Relativve Humidity, Solar Radiation, and Rain Fall)

Fig. (4) Current and Voltage (I, V) meaasurement circuit

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η

⁄η

η

ηD

⁄η

)

(2)

,η are Dusty and Clean Modules Where η efficiencies respectively. In thhis work, the module efficiency estimated by: η

P IA

(3)

Where Pmax (W) is maximum power p output from the module, I incident solar radiation intenssity (W/m2) and A is Module surface Area (m2). A DISCUSION III. RESULTS AND To check the validity of bothh PV panel for comparing their output power throughout the experimental work procedure, both PV panels are tested side by b side in order to be proved that they are totally have the same and equal characteristics under the same operational conditioon. This has been done before carrying out the experiments to investigate the effect of the dust accumulation on one PV P panel outer surface. The measured characteristics that compare the two panels are carried out under a sunny cleaar sky day with both panels are cleaned just before the measuurements at 11AM, of April 3, 2013. The measured data for the relation of I, V and P are presented in Fig. (5), and, from m the presented data in the figure it can be seen that there are very v small difference in Isc, Voc with maximum deviation of 0.1 0 % and 0.03 % respectively. However, this deviation is verry small and throughout the rest of this study it can be consideered that both panels are almost identical and any of them can be b used as a reference panel.

3.1 Characterization of the Depposited Dust The main factor affecting dust accumulation a rate on a surface is the weather data and conditionns such as Wind speed, Relative Humidity and Dew Point. In this study, the dust deposition density was determined by measuring m the weight of a glass slide before and after dust accuumulation. The picked glass slide is prepared to be scannedd under Scanning Electronic Microscope (SEM) by coating it with golden film as shown in Fig. (6). this figure shows SEM M pictures of glass slide picked up every four days. While the dust accumulation density as a function of the time is shown in i Fig. (7). This figure illustrate the relation between weather conditions (Ambient Air Dry Bulb Temperature, Dew point, Relative Humidity (RH %) and Wind Speed) with both dust coverage c area fraction and dust deposition density. From Figurres (6 and 7) its can be seen that during period from 3/14/2013 to t 3/22/2013 (after 8 days) there are a significant increase in dusst coverage area fraction. It



Fig. (5). Comparison of the paneels output under for a sunny clear sky day with both pannels’ surfaces are clean.

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18 March (aafter 4 days)

22 March (after 8 days)




3 April (aftter 20 days)


9 April (after 26 days)

13 April (affter 30 days) Fig. (6) SEM picture for deposition rate of the dust as function of the time on PV moddule outer surface.

Fig. (7) Effectt of weather condition on dust deposition characteristiccs

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Volume(%)

reaches up to 20.45% of the total photovoltaiic surface area and dust deposition density of 0.15 mg/cm2. This T is due to the remarkable activity in the movement of dust--laden wind during this period as the wind speed reaches to 8.27 8 m/s, Relative Humidity (RH) reaches 74%, and averagee horizontal solar radiation intensity is 604.84 W/m2. This resullt based on the fact that dust promotes dust and the higher Relative R Humidity (Close to the sea conditions) leads to facile the dust coagulation. After that date the dust coveragge area fraction is decreased to reach about 10.27% while thhe dust deposition density increased to 0.27 mg/cm2 (after 12 days) d due to lower Relative Humidity that reaches to 57.29% and a moderate high wind speed that reaches to 5.38m/s. As tim me passes, the dust coverage area fraction is increased again too reach to 24.40% and 0.37 mg/cm2 dust deposition density (aafter 16 days) with the weather condition of high RH that reaach to 72.15% at relatively low wind speed reach that to 3.14m/s. With time progress, the dust coverage area fraction increeased with slightly and reaches to 25.23% (after 20 days) whiile dust deposition density decreased to 0.33 mg/cm2. The particcle size distribution of the accumulated dust on the PV panel haas various average


diameter sizes ranged from 1 µm to 44µm as shown in Fig. (8). The elemental analysis of dust collected sample it’s found that the main ingredients of accumuulated dust are oxides of metals (SiO, Al2O3, FeO, Fe2O3, CaO) and carbonate (CaCO3, MgCO) which are components of the earth’s crust as shown in Table (2) with some vegetationn contaminants as shown on Fig. (6) after 12 days. As this dustt is originated from the nearest desert it contains heavy meetals like lead, iron, arsenic, manganese, vanadium, nickel, chromium, c etc. and the transport of dust from the desert is a natural n source of trans-boundary pollution. 3.2 Effect of Deposed Dust on the Panel Performance Sample results clarifying the effect e of dust settlement on the PV module outer surface on the module performance parameters compared with the clean outer surface PV module are shown in Fig. (9). The figuure shows the time variation of power and efficiency of the tw wo modules on April 3, 2013. As seen from the figure, the perfformance characteristics for the reference module output powerr and efficiency are higher than that of the dusty module withouut cleaning for 20 days.

8 6 4 2 0 0

50

100

150

200

Size (µm)

Fig. (8) Meassured dust particle size volume percentage distributionn.

Fig. (9) Moodules performance time variation as of April 3, 2013

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250


Table (2) Dust Chemical Composition Chemical

% of Mass

Si

21.4

Al

5.60

Fe2

14.4

Ca

51.2

K

2.9

S

1.9

Ti

2.6

The time variation of measured experimental values for the panels efficiency, output daily energy, daily solar energy intensity and the normalized short circuit current (Isc dusty/Isc clean) of the two modules and variation of normalized open circuit voltage (Voc dusty/Voc) clean are shown in figures (10 and 11) respectively. The presented data in the figures clearly shows that the dust has significant effect on the PV module short circuit current and the output power. As can be seen from the figure, as the dust deposition density increased from 0 to 0.28 mg/cm2 on 9th of April (after 26 days without cleaning) the value of Isc is decreased from 100% to 83.39 % compared with clean module value and the power degradation value reaches to 12.11 %. This degradation is the effect of to the Dust Coverage Area Fraction that reaches to 26 % during this period. Moreover, the voltage degradation due to this settled dust is also clear in the results presented in the figure. However, the reduction in the voltage values is slight


compared with the current and the decrease in Voc is dropped from 100% to 99.7% compared with the clean module value. IV.

CONCLUSIONS

Deposition and accumulation of dust pollution significantly reduce the output performance of PV modules. In this study, field experimental measurements are conducted to study the impact of dust deposition on thin film PV modules performance. Two thin film PV modules were used one is kept clean through all experiments while the other is left under the atmospheric natural dust deposition. The effects of dust deposition density and the meteorological conditions were investigated. From the experimental results, the following can be concluded: • The average dust deposition density after 30 days in the experiments site reach 0.27 mg.cm-2 and the average coverage area fraction reach to 19.22% of the module effective area. • The dusty module Isc became 90.3 % of the reference value clean module value and the Voc became 99.7% from the reference module value • The average degradation of output dusty module power and efficiency during the entire measurements period of 30 days is 10.33%. • Dust effect on thin film PV modules becomes more significant in cloudy weather day rather than clear day and the degradation in performance reaches about 15.2% in cloudy day. • To maximize the output of PV module and reduce the degradation caused by dust accumulation, frequently

Fig. (10) Comparison of Module performance with Date variation

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Fig. (11) Time variation of experimental values for the panels’ efficiency cleaning of the module is strongly recommended. The cleaning time schedule should be based the geographical location and strongly recommend during cloudy day for those drought areas and polluted urban areas. Acknowledgment The first author would like to acknowledge Ministry of Higher Education (MoHE) of Egypt for providing a scholarship to conduct this study as well as the Egypt Japan University of Science and Technology (E-JUST) for offering the facility, tools and equipment needed to conduct this research work. REFERENCES [1]

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2nd International Conference on Renewable Energy Research and Applications experimental measurements. Energy, 36(8), 5154–5161. doi:10.1016/j.energy.2011.06.018 [16] Al-Hasan AY. A new correlation for direct beam solar radiation received by photovoltaic panel with sand dust accumulated on its surface. Solar Energy 1998;63(5):323–33. [17] Siddiqui, R., & Bajpai, U. (2012). Correlation between thicknesses of dust collected on photovoltaic module and difference in efficiencies in composite climate. International Journal of Energy and Environmental Engineering, 3(1), 26. doi:10.1186/2251-6832-3-26 [18] CIS technology, CIGS photovoltaics, CIGS solar cell - AVANCIS. (n.d.). Retrieved April 13, 2013, from http://www.avancis.de/en/cistechnology/cis-photovoltaics/

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[19] Kalogirou, S. a., Agathokleous, R., and Panayiotou, G. (2013). On-site PV characterization and the effect of soiling on their performance. Energy, 51, 439–446. doi:10.1016/j.energy.2012.12.018 [20] El-Shobokshy MS, Hussein FM. Effect of the dust with different physical properties on the performance of photovoltaic cells. Solar Energy 1993;51(6):505–11K. Elissa, “Title of paper if known,” unpublished. [21] El-Shobokshy MS, Hussein FM. Degradation of photovoltaic cell performance due to dust deposition on to its surface. Renew Energy 1993;3(6/7):58