The Geometric Modelling and Linearization of Small-Scale Wind Turbine Blades for Optimized Renewable Energy

The modelling of blade geometry is the first step to be taken before the boundary element momentum theory (BEMT) analysis can be conducted on the wind turbine (WT). Yet it is a crucial step in establishing the best aerodynamic achievement the WT can give. In this paper, the power coefficient of a WT utilizing different blade geometries are determined and compared using the BEMT method. The blade geometries are obtained from the proposed formulas in literature and from the recommended polynomials that are based on experimental works. All blades are analyzed using the extended BEMT that includes the tip loss effect, the axial induction correction factor, \(a\) and the stall effect. At the same time, the obtained tapered blade usually varies in its chord length and twist angle in a nonlinear manner with respect to radius of the blade. As this may cause manufacturing difficulty of the blade and increasing the wind turbine manufacturing cost, the best nonlinear distribution based on the BEMT analysis conducted has been linearized through a process of linearization. A comparison is made on the aerodynamic performances of the WT for the linearized and nonlinear blades. The study shows that the geometry of the blade is better with the use of the empirical formula that gives high power at higher tip speed ratio (TSR) while having lower axial thrust. Furthermore, comparing the linear and nonlinear blade, it can be concluded that linearizing the chord length and twist angle is a good practice because with its simpler construction, the maximum power of 200 W that was produced is at par with the nonlinear one, while the axial thrust is much lower at 125N when compared with 225N in the case of nonlinear blade.