How can we classify Wind energy conversion systems, give advantages of wind energy

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Q. How can we classify Wind energy conversion systems, give advantages of wind energy? (R.GP.V., June 2014)

Ans. Wind energy conversion systems can be classified according to the

following criteria-

(i) According to the Axis of Rotation -

(a) Horizontal Axis Machines - The axis of rotation is horizontal and the aeroturbine plane is vertical facing the wind. is vertical.

(b) Vertical Axis Machines - The axis of rotation The sails or blades may also be vertical, or nearly so.

(ii) According to the Size - (a) Small scale machines, power output upto 2 kW. They can be used on farms, remote applications and places requiring relatively low power.

(b) Medium scale machines, power output between 2-100 kW. They are used to supply power to several residences of a small society. (c) Large scale machines, power output above 100 kW. They are used to generate power for distribution in central power grids.

(iii) According to the Type of Output Power -

(a) D.C. output
    (1) D.C. generator (2) Alternator rectifier

(b) A.C. output

    (1) Variable frequency, variable or constant voltage A.C.
    (2) Constant frequency, variable or constant voltage A.C.

(iv) According to the Rotational Speed -

    (a) Constant speed with variable pitch blades. This system uses a synchronous generator of constant frequency output.

    (b) Nearly constant speed with fixed pitch blades. This system uses an induction generator.
    (c) Variable speed with fixed pitch blades. This system could imply, for constant frequency output. It can be further classified as

(1) Field modulated system

(2) A.C.-D.C.-A.C. link

(3) Double output induction generator

(4) A.C. commutator generators

(5) Other variable speed constant frequency generating systems.
(v) According to the Utilization of Output-

(a) Battery storage

(b) Direct connection to an electromagnetic energy converter
(c) Other forms (thermal potential etc.) of storage
(d) Interconnection with conventional electric utility grids.

Advantages of Wind Energy - The advantages of wind energy are

as follows -

(i) Wind energy is a clean and pollution free source of energy.

(ii) It is an important renewable and inexhaustible source of energy, available at free of cost.

(iii) The power generated by wind energy is cheaper when produced at small scale.

(iv) There is no need of any kind of fuel.

(v) The generation period is low and power generation starts from commissioning.

(vi) It can be made available in many off-shore, on-shore and remote areas, thus helpful in supplying electrical power to remote and rural areas.