Describe the various components of wind energy conversion system

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Q. Describe the various components of wind energy conversion system.

Ans. The power available in wind is due to its velocity, i.e., kinetic energy This kinetic energy of wind can be utilized to run a turbine, which in turs drives an electric generator and produces electricity. The main components of a wind energy conversion system (WECS) are shown in fig. 1.1 in block diagram form.

Aero turbines convert kinetic energy of wind to rotary mechanical energy. A mechanical interface consisting of a step up gear and a suitable coupling transmits this rotary mechanical energy to an electric generator, which generates electricity. Aero turbines requires a pitch control and yaw control for proper operation. Yaw control is fitted to rotate the turbine about vertical (or yaw) axis, so that the blades always faces the wind. The physical embodiment of such an aero-generator is shown in fig.1.2 and its components are discussed below-

(i) Wind Turbine or Rotor - They intercepts the flowing wind and uses its energy to run them. The rotor is fixed in a orientation having swept area perpendicular to the predominant wind direction, so that area of wind stream swept is maximum. Rotor may be of two types - horizontal axis rotor and vertical axis rotor.

(ii) Windmill Head-It supports the rotor, houses the rotor bearings

and control mechanisms for changing the pitch of the blades and for changing orientation of blades. It is mounted on top of the supporting structure of suitable bearings.

(iii) Supporting Structure - The supporting structure or tower supports all the other components and prevents them from heavy wind load during gusts, and other ground related effects. Supporting towers may be of following four types -

(a) Reinforced concrete tower (b) Pole tower (c) Built-up shell-tube tower

(d) Truss tower.

Among these truss tower is mostly preferred because of its low cost, easy availability and easiness to transport.

(iv) Transmission System- The rate of rotation of large wind turbines is low about 40 to 50 r.p.m. But in order to have optimum output from the generator, the rates of revolution should be around 1800 r.p.m. Thus, it is necessary to greatly increase the low rotor rate of turning. This is achieved by a step up gear transmission system.

(v) Electric Generator - Both constant or variable speed electrical generator can be used, however variable speed units are expensive and/or unproved. A synchronous induction type constant speed generator is mainly used in WECS.

(vi) Controls - The purpose of a controller in WECS is to sense wind speed, wind direction, shaft speeds and torques, output power, generator temperature, etc. It also protects the system from extreme conditions brought upon by strong winds, electrical faults, malfunctioning of components, etc. The of a control system includes

(a) Sensors - Mechanical, electrical or pneumatic.

(b) Decision elements-Relays, logic modules, analog circuits, a microprocessor, a fluidics unit or a mechanical unit.

(c) Actuators-Hydraulic, electric or pneumatic.