A wind turbine converts the kinetic energy from moving air into usable electrical energy. Modern turbines are sophisticated mechanical structures designed for efficiency and durability. They consist of three primary physical sections: the rotating component that captures the wind, the housing that converts motion into electricity, and the structure that supports the entire system.
The Rotor Assembly
The rotor assembly captures the wind’s energy and initiates rotation. It consists of the blades and the hub, which together collect kinetic energy. The blades are designed aerodynamically, using an airfoil shape to create lift as the wind passes over them, causing the rotor to spin.
The blades are typically constructed from composite materials such as fiberglass, carbon fiber, or wood composites, offering strength, stiffness, and low weight. The blades attach to the central hub, which functions as the pivot point and transfers the rotational force to the main shaft. The hub also houses components of the pitch system, which allows the angle of the blades to be precisely adjusted.
The Nacelle
The nacelle is the enclosure at the top of the tower, housing the machinery that converts the rotor’s slow rotation into high-speed electricity generation. The nacelle is a compact arrangement of mechanical, electrical, and control systems shielded from the elements. The main shaft extends from the hub into the nacelle, transferring the rotational torque from the blades to the internal drive train components.
A gearbox is a central component in most nacelles, serving to step up the slow rotational speed of the main shaft. The rotor might turn slowly, often between 10 and 20 revolutions per minute (RPM), but the gearbox increases this speed dramatically for the generator. This conversion ratio can be as high as 100:1, allowing the output shaft to spin at speeds between 1,000 and 1,800 RPM.
The high-speed shaft connects directly to the generator, which uses electromagnetic induction to transform mechanical energy into electrical energy. The electricity generated, usually alternating current (AC), is then prepared for transmission. The generator’s rotational speed must be controlled precisely to ensure the electrical output is compatible with the power grid.
The yaw system ensures the entire nacelle and rotor assembly constantly faces directly into the wind, maximizing energy capture. Sensors, including an anemometer and a wind vane, measure wind speed and direction, feeding data to the control system. Yaw drive motors then rotate the nacelle horizontally on top of the tower to maintain optimal alignment.
The pitch system controls the angle, or pitch, of the rotor blades. This mechanism adjusts the blade angle to optimize the amount of wind captured for a given speed, ensuring efficient energy production. During high-wind events, the pitch system can “feather” the blades, turning them out of the wind to reduce the rotational speed and protect the turbine from damage.
The Tower and Foundation
The tower provides the necessary height to position the rotor assembly and nacelle where wind speeds are stronger and more consistent. Constructed from conical tubular steel or concrete sections, the tower must support the substantial weight of the machinery and withstand bending forces from the wind. The total height is often selected to be roughly equal to the diameter of the rotor to maximize energy capture.
The foundation anchors the structure to the ground, providing stability against overturning moments caused by wind loads. Onshore turbines commonly utilize a gravity-base foundation, a large, reinforced concrete slab that relies on its own weight and the weight of the soil to resist forces. High-strength steel anchor bolts or an anchor cage secure the tower base to this foundation.
The electricity generated in the nacelle travels down through cables housed inside the tower. Near the base, the voltage is stepped up by a transformer to a higher level suitable for efficient transfer across long distances. This ensures the power is ready to be integrated into the electrical grid for distribution.