Environmental dust particles repelling from a hydrophobic surface under the electrostatic influence are considered and the dynamics of the dust particles are analyzed incorporating the high speed camera. The velocity of the repelled dust particles are formulated using the force balance incorporating the forces associated with the electrostatic repulsion, particle adhesion, particle drag, and the inflight particles interaction under the charge influence. The functionalized silica particles are deposited on the glass surface towards achieving a hydrophobic wetting state on the surface. An electronic circuitry is designed and built while generating the electrostatic effect, in the pulse form, on the dust particles located on the surface of the hydrophobic plate. Findings revealed that functionalized silica particles deposited surface results in hydrophobic wetting state with contact angle in the order of 158° ± 2° and contact angle hysteresis of 2° ± 1°. The electrostatic impulsive force generated on the plate surface enables to repel most of the sizes of the dust particles; however, some of the small dust particles remain as the residues on the surface after the electrostatic influence. The dust particle velocity predicted from the analytical formulation agrees with that obtained from the high speed camera data. The pinning force of the small size particles (0.6 µm≤), due to adhesion on the surface, is found to be larger than the average size particles (∼1.2 µm), which in turn, suppresses these particles repelling from the surface under the electrostatic influence. The residues of the dust particles on the as received glass surface after dust repelling are more than those residues on the hydrophobic surface. This behavior is associated with the dust particles adhesion on the surface. Consequently, hydrophobic wetting state on the plate surface improves the dust particle repelling from the surface.

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Environmental Dust Particles Repelling from A Hydrophobic Surface under Electrostatic Influence.

Soiling, the accumulation of dust, is a detrimental influencing factor for solar energy generation in desert climates, as it blocks the sun light and therefore reduces the energy yield of photovoltaic (PV) modules. Accordingly, soiling requires mitigation by frequent cleaning. However, regular cleaning of PV modules can damage glass surfaces and commonly used anti-reflective coatings (ARCs), which typically enable 2–3% or even higher increases in the power output. Within this study, the damage potential of dry manual cleaning on uncoated solar glass and two different commercial ARCs is examined. For this, a cleaning test apparatus and methodology applicable to full size PV modules were developed. The changes in the optical behavior of coated and uncoated glass samples were investigated both theoretically and experimentally, including the analysis of spectroscopic reflectance and microstructural damage patterns. It is found that dry brushing on dusty surfaces causes only minor damage to uncoated glass surfaces with no changes in hemispherical reflectance, even at high numbers of brush cycles. In contrast, both the tested coatings indicate significant reductions of the AR performance, already after 100 brush cycles with increasing reflectance up to 2.3% at 600 nm. Furthermore, the coatings indicated different stabilities during extended abrasion testing, but still retained the AR properties after 500 cycles of testing, reflecting harsh and bi-weekly cleaning over 20 years of operation. Localized coating removal and—to a less extent—coating thinning were identified as ARC degradation mechanisms, which were supported by spectroscopy experimental and simulation results for microstructural analysis of the samples.

Resilience of industrial PV module glass coatings to cleaning processes

Enhancing the efficiency of rooftop solar photovoltaic panel with simple cleaning mechanism

Two dust samples were collected from the same solar panels on June, 2017 in Dakar. The first was sent to Ithemba Labs (South Africa) and the second to Lincon Nebraska University (USA) for structural and physical properties study. This work aims to evaluate the dust impact on PV efficiency. The study shows that these particles have a non-spherical shape with sizes between 0 and 50 μm. However, most of them have a size about 2 μm. Elemental composition based on Energy Dispersive X-ray microanalysis indicates that dust is dominated by elements such as O, Na, Mg, Al, Si, Cl, K, Ca, Ti, Mn and Fe. Some elements such as P, S, Zn, Sr, Zr and Cr are minority or in traces form. The analysis shows that this African dust is a mixture of different chemical compounds with a predominant phase consisting of SiO2 type quartz about 73.8% of the total and the second phase is certainly calcite(CaCO3) representing 13.6% of the collected particles. The rest (12.6%) is presumably a mixture of Iron Oxide Chloride (FeOCl), Mantienneite (Al2FeH33K0.5Mg3O34P4Ti) and Kaersutite (Al2Ca2Mg6NaO24Si6). Finally, the diffuse reflectance spectroscopy (DRS) shows that these particles reflect more than 70% of the irradiation reaching the PV panels surface.

Structural and physicochemical properties of dust collected on PV panels surfaces and their potential influence on these solar modules efficiency in Dakar, Senegal, West Africa

This study was carried out at the International Center for Training and Research in Solar Energy (CIFRES) and its main purpose was to study the performance of a solar module cleaning system. To handle this work, a measuring platform consisting of two polycrystalline (pc-Si) PV modules was designed. The modules were connected to a waterless cleaning system on the surface of the solar panels. The platform also contained a temperature sensor on the surface of the module, a pyranometer, shunt resistors (for current measurement), and an acquisition unit. This platform was exposed under real conditions and measurements of the parameters were taken in increments of ten seconds. Only one of the two modules was cleaned daily, and an evaluation of the degradation rate of the short-circuit current (Isc) of the dust module with respect to the cleaned module was carried out. After one month of exposure, the analysis of the results showed a degradation rate of 17.13% of the short circuit current (Isc) of the dirty module compared to the clean module. Compared to the initial conditions under the standard test conditions, a degradation of 10.16 and 24.09%, respectively for the clean module and the dirty module was obtained. This work also showed that a polynomial relation exists between the degradation rate and the dust deposition density with a coefficient of determination of 0.9933.

	Key words: Photovoltaic modules, dust, short-circuit current, impact, automatic cleaning without water, degradation.

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Study of the performance of a system for dry cleaning dust deposited on the surface of solar photovoltaic panels

The dust accumulation on the photovoltaic solar panels surface is one of the phenomena that significantly affect the proper functioning of solar power plants by hiding the exposure to the sun. The depositing process of dust on the photovoltaic modules surface is highly dependent on the climatic parameters and is therefore specific to the installation site. In this study, both electrical and climatic parameters had been observed at the same time in the Dakar region in Senegal (17 ° 10 and 17 ° 32 west longitude and 14 ° 53 and 14 ° 35 north latitude) from June 2016 to July 2016. A correlation is made between the two types of climatic parameters and the daily variation of the cleanness index. We have noted that rain contributes to the recovery of solar panel performance and that wind speed and relative humidity are the main climatic factors that affect the dust deposition on the photovoltaic solar modules surface.

Correlation between Dirt on The Photovoltaic Module Surface and Climatic Parameters in the Dakar Region, Senegal

Abstract The accumulation of dust on the surface of solar panels reduces the amount of sunlight reaching the solar cells and results in a decrease in panel performance. To avoid this loss of production and thus, to improve the performance capacity, solar panels must be cleaned frequently. The West African region is well known for its high solar energy potential. However, this potential can be reduced by the high occurrence of dust storms during the year. This article aims to provide a contribution to the construction of a meteorological information service for solar panel cleaning operations at Diass solar plant in Senegal (Western Sahel). It is based on a full year in situ experiment comparing the power loss due to dust between solar panels cleaned at different frequencies and those not cleaned. The model to determine the cleaning frequencies is based on the deposition rate of airborne particles, the concentration of airborne particles, and the density of the dust that has a major impact on the power loss. Cleaning frequencies are presented at seasonal scale because in the study area, dust episodes differ according to the seasons. A cost–benefit analysis is also performed to demonstrate the advantage of using weather information service to support the dust cleaning operations at Diass plant. As results, it is found that cleaning every 3 weeks is required during the dry seasons, December–January–February and March–April–May. During the rainy season, cleaning every 5 weeks is recommended in June–July–August, while in September–October–November cleaning every 4 weeks is sufficient to maintain an optimal performance of the solar panel. The total costs of cleaning operations based on these results are reduced compared to the current costs of cleaning and the benefits are much higher than without cleaning action.

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Contribution to the building of a weather information service for solar panel cleaning operations at Diass plant (Senegal, Western Sahel)

The problems of power fluctuations, induced by the integration of wind turbines into a power grid, during changes in wind speed are manifested usually by variations in the voltage, current or frequency. Besides affecting the quality of energy, these problems can lead to the dysfunction of sensitive equipment. To solve these disturbances caused by the wind turbines, effective protection of the sensitive loads connected to the grid is required. The purpose of this paper is to improve the quality of the energy produced by a wind power plant. This new approach is then validated in the context of Mauritania. For that, a Dynamic Voltage Restorer (DVR) is proposed to compensate for the voltage drops and harmonic distortions of the voltage supplied by the wind turbine when the wind speed changes. In order to boost the performance of the proposed system without using its model, a fuzzy controller is adopted. In addition, to verify the efficiency of the proposed control, a simulation model using MATLAB/Simulink is developed and the behavior analysis of the restorer under different operating conditions is carried out. The obtained results show that the reactive power is reduced by 15% and the harmonic distortion rate of the voltage is limited to 1%. This is fully compatible with the IEEE-519 standard.

Power Quality Improvement of a Wind Turbine System in Mauritania Using a Fuzzy Logic Controlled Dynamic Voltage Restorer

Today, renewable energy projects connected to the interconnected network, with powers of the order of tens of megawatts, are more and more numerous in sub-Saharan Africa. And financing these investments requires a reliable amortization schedule. In the context of photovoltaic systems connected to the interconnected electricity grid, the quintessence of damping is the amount of energy injected into the grid. Thus it is fundamental to know the parameters of this network and their variation. This paper presents an evaluation of the impact of power grid disturbances on the performance of a solar PV plant under real conditions. The CICAD photovoltaic solar plant, connected to the Senelec distribution network, with an installed capacity of 2 MWp is the study setting. An energy audit of the plant is carried out. Then the percentage of each loss is determined: voltage drops, module degradation, inverter efficiency. The duration of each disconnection is measured and recorded daily. The corresponding quantity of lost energy is thus calculated from meteorological data (irradiation, temperature, wind speed, illumination) recorded by the measurement unit in one-minute steps. The observation period is three months. The total duration of disconnections related to the instability of the electrical network during the study period is 46.7 hours. The amount of energy lost is estimated at 22.6 MWh. This represents 2.4% of the actual calculated production. 

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Mohamed Cherif Aidara

Papers

Study of the performance of a system for dry cleaning dust deposited on the surface of solar photovoltaic panels

Correlation between Dirt on The Photovoltaic Module Surface and Climatic Parameters in the Dakar Region, Senegal

Contribution to the building of a weather information service for solar panel cleaning operations at Diass plant (Senegal, Western Sahel)

Power Quality Improvement of a Wind Turbine System in Mauritania Using a Fuzzy Logic Controlled Dynamic Voltage Restorer

Study of the Impact of Grid Disconnections on the Production of a Photovoltaic Solar Power Plant: Case of Diamniadio Power Plant