Optimasi Sudut Twist dan Geometri Airfoil Sudu Turbin Angin Sumbu Horizontal Berbasis Kecepatan Angin Rendah Menggunakan Based-Gradient Method dan Algoritma Genetika

Abstract

Utilization of wind turbine technology as the electrical energy generation in Indonesia is still experiencing a lot of obstacles. Tropical climate throughout the year covering Indonesia cause the average wind speed is relatively low, ranging from 2.5 to 6 m/s. At the other side, wind turbine performance is strongly influenced by the airfoil geometry. Therefore, in order to obtain a wind turbine with optimum output power capacity, the need to design an airfoil of wind turbine blades is necessary in order to adjust to the available wind speed (cut-in speed). During this time, wind turbine blade design is conducted by selecting an airfoil arbitrarily. Until now it is still many problems when airfoil geometry engages in the process of optimization using computational fluid dynamic (CFD). In this final project the output power capacity of horizontal axis wind turbine was optimized with respect to twist angle distribution and airfoil geometry of the blades. To involve the airfoil geometry in the optimization process, the airfoil design is performed by the direct method which is based on artificial neural network (ANN). Using this method the airfoil geometry is generated by using Joukowski transformation in which a circular is transformed to be an airfoil shape and then its aerodynamic characteristics are determined utilizing CFD. Based on these results a database which contains relation between center points of the circle and these aerodynamic characteristics can be developed to perform ANN. In this final project the coordinates of the circle center (x,y) and the twist angle distribution were chosen as design variables The optimization was performed using the optimization toolbox of MATLAB solver, i.e. based-gradient method optimization and genetic algorithm. A computer code namely yawdyn is applied for determining the output power of the wind turbine. The results showed that for average wind speed of 5 m/s the optimization of reference wind turbine which apply NREL S834 as airfoil blade is able to produce power of 200 watts, meanwhile the present wind turbine is capable of generating output power of 1.3 kW in which the optimum airfoil blades are formed by a pair coordinates of the center of the circle of (-1009, 0.0951) and the optimum twist angle distribution is represented by the equation θ_i=-1.063-3.610.r_i, where ri indicates station distance from blade root. The results also showed that the influence of the angle of twist and the airfoil geometry on the output power of the wind turbine is significant.