Abstract
This work presents a novel framework for the aerodynamic design and optimization of blades for small horizontal axis wind turbines (WT). The framework is based on a state-of-the-art blade element momentum model, which is complemented with the XFOIL 6.96 software in order to provide an estimate of the sectional blade aerodynamics. The framework considers an innovative nested-hybrid solution procedure based on two metaheuristics, the virtual gene genetic algorithm and the simulated annealing algorithm, to provide a near-optimal solution to the problem. The objective of the study is to maximize the aerodynamic efficiency of small WT (SWT) rotors for a wide range of operational conditions. The design variables are (1) the airfoil shape at the different blade span positions and the radial variation of the geometrical variables of (2) chord length, (3) twist angle, and (4) thickness along the blade span. A wind tunnel validation study of optimized rotors based on the NACA 4-digit airfoil series is presented. Based on the experimental data, improvements in terms of the aerodynamic efficiency, the cut-in wind speed, and the amount of material used during the manufacturing process were achieved. Recommendations for the aerodynamic design of SWT rotors are provided based on field experience.
Highlights
There has been an increased necessity for the development of small grid-independent energy applications [1] in which wind energy plays an important role
This paper presented a novel and comprehensive framework for the aerodynamic design of small hybrid wind turbine rotors and proposed a hybrid solution procedure based on two metaheuristics to solve this complex problem
The rotor performance was quantified through the implementation of a state-of-the-art blade element momentum model, which was coupled with the XFOIL 6.96 software and the Viterna-Corrigan extrapolation procedure for the determination of the local blade aerodynamics
Summary
There has been an increased necessity for the development of small grid-independent energy applications [1] (e.g., domestic, street lighting, and rural electrification) in which wind energy plays an important role. For SWT, requirements may be altered if the SWT safety is not compromised as stated by the International Electrotechnical Commission (IEC) standards [15], which is often the case given the highly constrained scenarios where SWT operate In this regard, SWT must be as flexible as possible in order meet the energy demand; any other relevant secondary objectives, such as noise generation, may be relaxed in order to maximize the cost-effectiveness of SWT. Secondary objectives related to the minimization of acoustic, structural, mechanical, and electrical issues were not explicitly considered in the proposed framework with the aim of studying the key geometrical factors influencing the aerodynamic efficiency of SWT rotors.
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