The blades and the hub together are called the
rotor. It is the rotating component which converts kinetic energy available in
the wind to mechanical energy. The rotor hub connects the rotor blades to the
rotor shaft. It is also the place where the power of the turbine is controlled
physically by pitching (A method of controlling the speed of a wind turbine by
varying the orientation, or pitch, of the blades, and thereby altering its
aerodynamics and efficiency) the blades. Hub is one of the critical components
of the rotor requiring high strength qualities.
Blade is a rotating component designed aerodynamically to work on the principle of lift and drag to convert kinetic energy of wind into mechanical energy which is transferred through shaft then converted to electrical energy using generator. Most turbines have either two or three blades. Wind blowing over the blades causes the blades to "lift" and rotate. Mechanical applications like pumping water, grinding uses more number of blades as it requires more torque. Blade length is key factor determining power generation capacity of a wind turbine.
The nacelle is an enclosure that sits atop the tower and contains the gear box, low-speed shaft and high-speed shaft, generator, controller, and brake. Some nacelles are large enough for a helicopter to land on. The nacelle also protects turbine components from atmospheric weather conditions and reduces noise.
Low-speed shaft is the principle-rotating element which transfers torque from the rotor to the rest of drive train. It also supports the weight of the rotor. It is connected to the gearbox to increase the rpm.
Gear box steps up the speed according to the requirement of the electric generator. Gears connect the low-speed shaft to the high-speed shaft and increase the rotational speeds from about 30 to 60 rotations per minute (rpm) to about 1000 to 1800 rpm, the rotational speed required by most generators to produce electricity. The gear box is one of the costliest (and heavy) parts of the wind turbine and there are also "direct-drive" generators that operate at lower rotational speeds and don't need gear boxes.
Types: Planetary Gear Boxes, Parallel shaft gear.
Transmits the speed & torque from the gearbox and drives the generator.
During the periods of extremely high winds and maintenance, brakes are used to stop the wind turbine for its safety.
Types of Brakes: mechanical brake (Disc brake, clutch brake), Aerodynamic brake (Tip brake and spoilers)
Generator converts the rotational mechanical energy into electrical energy. Usually wind electric generator produces 50-cycle AC electricity.
Types: Synchronous generator (Electrically excited, permanent magnet), asynchronous generator (Squirrel cage, Slip ring)
The controller starts up the machine at cut-in wind speed (generally 3 m/s) and shuts off the machine at cut-out wind speed (generally 25 m/s) as per the design requirement. The controllers also operate the turbine to produce grid-quality electricity. The controller measures and controls parameters like Voltage, current, frequency, Temperature inside nacelle, Wind direction, Wind speed, The direction of yawing, shaft speed, Over-heating of the generator, Hydraulic pressure level, Correct valve function, Vibration level, Twisting of the power cable, Emergency brake circuit, Overheating of small electric motors for the yawing, hydraulic pumps, Brake-caliper adjustment etc.
Anemometer is a sensor used for measuring the wind speed. Other than using it for wind resource assessment, it is normally fixed on top of the wind turbine to provide input to the controller for power regulation and braking beyond the cut out & survival wind speed .
Blades are turned or pitched, out of the wind to control the rotor speed and keep the rotor from turning in winds that are too high or too low to produce electricity.
The tower enables wind energy utilization at sufficient heights above ground, to absorb and securely discharge static and dynamic stress exerted on the rotor, the power train and the nacelle into the ground.
Types: Lattice tower, tubular tower, Guyed tower, Hybrid Tower
Foundation (not shown in the picture)
Foundation is needed to support and absorb the loads from the wind turbine. The choice of foundation type is much dependent on the soil conditions and water table location prevailing at the planned site of a wind turbine.
Onshore Foundation Types: Slab Foundation (preferred when the top soil is strong), Pile Foundation (Preferred when the top soil is of a softer quality)
Offshore Foundation Types: Monopile, Gravity base, Tripod
Measures wind direction and communicate with the controller for orienting the turbine properly (yawing) with respect to the wind direction.
Yaw drive turns the nacelle with rotor according to the wind direction using a rotary actuator engaging on a gear ring beneath the nacelle. Yaw system keeps the turbine always facing the wind.
Yaw motor is to power the yaw drive.