General Structure of Wind Electricity Generation

General Structure of Wind Electricity Generation Showing Main Components

Main components of such an aero-generator are physically shown in Figure. The sub components of the wind mill are :

1. Wind turbine or rotor
2. Wind mill head
3. Transmission and control
4. Supporting structure.

(i) Rotor : Rotors are mainly of two types :

(A) Horizontal axis rotor, and (B) Vertical axis rotor. 

• The vertical axis machines , have an advantage that they operate in all wind directions and need to yaw – adjustment. Rotor is one of the important components.

(ii) The wind-mill head : Wind-mill head supports the rotor, housing, the rotor bearings. It also houses any control mechanism incorporated like changing the ‘pitch’ of the blades for safety devices and tall vane to orient the rotor to face the wind. The latter is facilitated by mounting it on the top of the supporting structure.

(iii) Transmission : The rate of rotation of large wind turbine generators is operating at rated capacity or below, is conveniently controlled by varying the pitch of the rotor blades, but it is low about 40 to 50 rpm, as optimum generator output requires speed as high as 1800 rpm, it is necessary to increase greatly the low rotor rate of turning. Among the transmission options are mechanical systems involving fixed ratio gears, belts and chains, singly or in combination or hydraulic systems involving fluid pumps and motors. Fixed ratio gears are recommended for top be mounted equipment because of their high efficiency, known cost and minimum system risk.

Generator : Either the constant speed or variable speed generators can be used. Synchronous Induction and permanent magnet type constant speed generators are mainly used for constant speed system.

Controls : Modern large wind turbine generators require a versatile and reliable control system to perform the following functions :

1. Orientation of rotor Into the wind.
2. Start-up and cut – in of the equipment.
3. Power control for rotor by varying pitch of the blades.
4. Generator output monitoring.
5. Shutdown and cut-out, owing to malfunction or very high winds.
6. Protection of the generator.
7.  Auxiliary and/ or emergency power.
8. Maintenance mode.

(iv) Supporting Structure (Tower) : Four types of supporting towers deserve considerations, these are :

1. The reinforced concrete tower
2. The pole tower
3. The built-up shell- tube tower and
4. The truss tower. Among these, the truss tower is favourable, because it is proved and widely adaptable, cost is low, parts are readily available. It is readily transported and it is potentially stiff. Shell-tube towers also have attractive features and may prove to be competitive with truss towers.