1. Rotor – three blades, mounted on a hub – typical rotor diameters are 80 90m for today’s larger machines. Blades are usually made from Glass Reinforced Plastic (GRP) and incorporate lightning protection measures. The picture below shows a single blade being transported to a wind farm site.

2. Nacelle – the “box” within which the main components are housed and home to the gearbox, generator and transformer as well as some of the control electronics. The picture below shows a nacelle being lifted onto the wind turbine tower (if you look closely you can see the construction team at the top of the tower waiting to fix the nacelle in to place)

3. Gearbox – converts the rotational speed of the rotor (typically 10-20rpm) to 1500rpm for the generator

4. Generator – converts rotational movement to electrical energy

1 Spinner
2 Spinner bracket
3 Blade
4 Pitch bearing
5 Rotor hub
6 Main bearing
7 Main shaft
8 Gearbox
9 Service crane
10 Brake disc
11 Coupling
12 Generator
13 Yaw Gear
14 Tower
15 Yaw Ring
16 Oil Filter
17 Generator Fan
18 Canopy

http://www.powergeneration.siemens.com

5. Transformer – converts electricity from 415V or 690V to 11,000V for transmission down the tower. The picture below shows transformer housing. The transformer can also be housed inside the wind turbine tower itself.

6. Tower – usually steel, a cylinder supporting the nacelle and rotor. Typical tower heights are 60-80m. Cables run down the tower taking the electricity from the generator at the top, into the ground and then onto a connection point to the grid. Lifts or ladders allow maintenance crew to access the nacelle. The picture below shows a 60m wind turbine tower.

7. Base – a concrete base, typically 15m x 15m x 1m which acts as the foundation for the structure.

1. Rotor
2. Nacelle
3. Gearbox
4. Generator
5. Transformer
6. Tower
7. Base
8. Nasty polluting 4×4 (not mine for clarification purposes)

Operation

When the wind blows the turbine hub turns into the wind. When the wind passes over the blade, the shape of the blade means that the air flows more quickly over one side of the blade than the other. This results in the turning of the rotor.

Wind turbines operate when the windspeed is within certain limits. There has to be enough wind for the blades to turn – typically 3-4m/s (or 7-9mph, 6-8 knots). When the windspeeds get to 25m/s (56mph, 49 knots), turbines typically shut down to protect the structure from excessive loads. Wind turbines are certified to specified levels and designed to the highest of these.

Instruments at the top of the nacelle (wind vane and anemometer) measure the wind speed and direction.

Control of the turbine

As windspeeds increase, so the energy generated by the turbine does as well. At some point where windspeeds are around 15m/s (34mph, 29 knots), the maximum (or rated) capacity of the turbine is reached. A limit has to be set to define the sizes of the various components – gearbox, generator, cables, rotor blades).

To control production of wind energy above the rated windspeed, the turbine can use various methods:

• Variable pitch – the blades of the wind turbine are feathered to limit the energy produced as windspeeds increase
• Variable speed – on some wind turbines, the rotor is allowed to speed up and slow down as the windspeed varies

In both cases, changes to the pitch or speed can happen several times a second so the wind turbine is always running in an optimised state for the wind conditions it sees, providing the most efficient extraction of energy from the wind and therefore maximising renewable energy production.

All of the information about the wind turbines are recorded by computers and transmitted to an off-site control centre. Wind turbines are for the majority of the time self sufficient although periodic mechanical checks are usually carried out every few months.