Aerodynamics Guide.pdf

Wind turbine blades are designed to maximize power from the wind at minimal cost, with a compromise between aerodynamic and structural efficiency. The blade shape is influenced by materials and manufacturing processes, and its design starts with a "best guess" compromise between aerodynamic and structural efficiency. The wind's power varies with the cube of its speed, and sites are selected based on steady winds. Turbines affect the wind, slowing it down, and there's an optimum amount of power to extract. The number of blades is limited by available power, with most large machines having three blades due to aerodynamic efficiency and aesthetics. Blades capture wind power by generating lift, and their shape is similar to airplane wings, with a curved side creating low air pressure and high pressure pushing on the other side. The lift force increases with angle of attack, but drag also increases, and there's an optimum angle for maximum lift. Blades are twisted to account for apparent wind angles, and their cross-sections are based on aerofoil shapes with good lift/drag characteristics. Structural requirements mean the aerofoil needs to be thicker than the aerodynamic optimum.