Design and simulation of an optimized small wind turbine

Abstract

The volatility of fossil fuel's price, pollution, and emission associated with converting fos- sil fuel into a useful type of energy led man to search for more sustainable energy sources that are pollution-free and renewable. Today, renewable energy technologies, such as solar and large wind turbines, are developed to a stage of maturity, having the cost of produc- ing electricity dropping signi􏰀cantly in the last decade, therefore making these technologies competitive with the traditional counterpart. The cost of producing electricity through small wind turbines is still high compared to large wind turbines or photovoltaic technology. For small wind turbines to successfully compete with other technologies and contribute to the diversi􏰀cation of o􏰈-grid technology, further research is needed to reduce the levelised cost of energy (LCOE). Therefore, this study aims to reduce the levelised cost of energy (LCOE) of small wind turbines. To achieve the ob- jective, a 10 kW wind turbine operating at a site of an average wind speed of 7.5 m/s was designed, optimized, and simulated. With low LCOE in mind, the turbine components were designed as simple as possible to reduce manufacturing costs. The blades are made of uniform cross-sectional area, which made possible to use aluminum as the blade material, and the blade cross-sectional area is made out of a high lift airfoil. The hub is made of aluminum and modelled and designed as a disc with holes to bolt the blades and attach the main shaft. The mainframe is treated as a thick plate with a proper arrangement to connect the generator, the main and yaw bearings, the tail support, and any other ancillaries needed. An octal tapered tower with a height of 20 m made of steel was designed and optimized for low weight. The electrical power is to be produced by a direct drive variable speed permanent magnet synchronous generator. The control system is designed in such a way that allows the turbine to operate in maximum power e􏰊ciency for any speed below the rated speed, and to increase reliability, a sensorless control system is suggested. The research started with a broad review of the relevant literature on wind turbines in general and small wind turbines. The turbine blades design began by analysing the aero- dynamic performance of the blade. To accomplish that, XFoil was used to generate the aerodynamic parameters of the airfoil, the Blade Element Momentum (BEM) method was used to estimate the blades' aerodynamic performance, and Qblade was employed to com- pare the results, and Computational Fluid Dynamics (CFD) was used to verify the results. The preliminary design was done using standard IEC 61400-2 to obtain the load cases, and general engineering formulas, CFD and Finite Element Analysis (FEA) was used to analyse the load in the components according to IEC 61400-2, FAST-V7 was used to simulate the turbine's overall performance, standard formulas were used to evaluate the economic perfor- mance of the design, MatLab was used to perform all needed calculations. In this study, it is evident that using standard IEC 61400-2 to estimate the load, gyroscopic load components dominate the design, and the control system must be used to limit those loads. The designed turbine has relatively high e􏰊ciency and low LCOE.