Sand accumulation can pose significant problems to wind turbines operating in the dusty Saharan environments of the Middle East and North Africa. Despite its difficulty, sand particles can be to a great extent avoided using sealed power drive trains; however, surface contamination of the blades is certainly unavoidable. As a result, aerodynamic losses and even premature separation can be incurred. To mitigate such advert consequences and avoid significant power losses, the choice of properly designed airfoil sections with low contamination sensitivity is a must. Alternatively, mitigation techniques for premature separation may also be considered. In this paper the contamination sensitivity of a number of airfoil sections widely used in the wind turbine industry is compared. Additionally, the possibility of deploying a leading edge slat to mitigate the contamination-driven performance degradation of wind turbine airfoils is explored. A two dimensional CFD model of the particle laden flow over an airfoil section is developed by solving Navier-Stokes equations along with the SST k-ω turbulence model. Additionally, a particle deposition model has been deployed via FLUENT’s discrete phase modeling capability to simulate dust particles trajectories and hence predict their accumulation rate. The preliminary results obtained indicate that airfoil sections with low surface contamination sensitivity specifically designed for wind turbines perform better under dusty conditions. Furthermore installing a leading edge slat affects the aerodynamics of the particle laden flow and may therefore be used to mitigate the adverse effects of surface contamination that otherwise would require frequent cleaning which can be expensive.

Dust may be challenging to the blades of wind turbines deployed in the harsh environment of the Sahara. In this paper, the airfoil sections of a wind turbine have been customized for low sensitivity to surface roughness at the wind conditions prevailing in Hurghada—Egypt to avoid serious power degradation. To this end, a two-dimensional a computational model is developed using ANSYS-FLUENT 15.0 to understand the distinguishing features that govern the specific behavior of NACA-63-215 (root section) and NACA-63-415 airfoils (midspan and tip sections) with respect to dust deposition and sand erosion. Subsequently, a two-objective genetic algorithm is developed in MATLAB 16.0 and used to customize the airfoil geometry, enhancing the lift-to-drag ratio while simultaneously minimizing the deposition and erosion rates. The whole optimization process is realized through coupling MATLAB 16.0 with ANSYS-FLUENT 15.0 via the ICEM meshing tool to predict the optimum blade shape based on its aerodynamic performance in a dust-loaded environment. The optimization process enhanced the aerodynamic performance for the aforementioned airfoils under particle laden conditions with up to 38.34% higher lift-to-drag coefficients ratio in addition to 70 % and 99.267 % drop in dust deposition and sand erosion, repectively.

The process of surface erosion due to particle collision has been the focus of a number of investigations with regards to gas turbine engines, aircraft, reentry missiles, pipelines carrying coal slurry, etc. Recently, increased interest in wind energy by countries in the Saharan regions of the Middle East and North Africa (MENA) brings about some concern about leading edge erosion of wind turbines operating under such dusty conditions. Leading edge erosion can have a detrimental impact on the extracted energy as it changes the blade surface roughness causing premature/unpredictable separation. Though erosion may not be easily avoided; it may be mitigated via using airfoil families characterized by low roughness sensitivity. In this paper, a model of an airfoil erosion subjected to sand blasting is developed using the discrete phase modeling capability in ANSYS-FLUENT along with the DNV erosion model. The effect of various flow parameters, such as angle of attack, and particle size, on the extent of erosion is investigated for a number of airfoil designs. The developed model is used as a predictive tool to assess the power deterioration of eroded wind blades.

Sand erosion and dust deposition may induce surface irregularities of the blades of a wind turbine deployed in the Sahara, causing performance deterioration. In the current work a multi-objective optimization algorithm is developed to upgrade the aerodynamic blade profile of wind turbines operating in a Saharan environment. As a case study, the rotor of the Nordtank 300 kW horizontal axis wind turbine operating in Hurghada, Egypt is customized for lower sensitivity to surface roughness. The goal is to achieve a high lift-to-drag ratio while simultaneously maintain high resistance to dust deposition and sand erosion. The optimization algorithm is developed in MATLAB using C-language and coupled via ANSYS-ICEM to ANSYS-FLUENT computational fluid dynamics software for a particle-laden flow simulation until the optimization objectives are iteratively met. The optimization process yields a blade with lower sensitivity to surface roughness issues not only offsetting the 10.58% loss in Annual Energy Production (AEP) using the original profile, but actually boosting the AEP by 10.87% for the optimized blade. It is believed that this research may draw attention to the need for site-specific blade design to avoid environmental surface degradation as a result of dust deposition and sand erosion that may be unavoidable in the Saharan environment of countries in the MENA region.