A windmill is a machine which converts the kinetic energy of the wind, i.e., wind energy into mechanical energy or electrical energy.
A windmill resembles a large electric fan which is erected at some height on the rigid support.
The number of blades and their shape and the height of the windmill depend on the average wind velocity and other related factors at a given place.

Principle and working of windmill

The design of the blades of windmill is such that a pressure difference is created between its different regions when wind strikes them.
This pressure difference produces a turning effect and makes the blades rotate about a horizontal axis.
The rotational motion of the blades is then utilized to perform useful mechanical work or to generate electricity.

A windmill is used to

  • Pump water where the rotational motion of the windmill is utilized to do the mechanical work to operate a water lifting pump.
  • Generate electricity where the rotational motion of the windmill is used to rotate the armature of the electric generator. Such an arrangement is called wind turbine generator.

  • Wind energy farm.

    The electric power output of a single windmill is quite small and cannot be used for commercial purpose. Therefore, a large number of windmills are erected over a large area. A cluster of windmills is called a wind energy farm.
    The combined energy output of all the windmills generates electricity which is used on commercial scale.
    The main requirements for a wind farm are a site where a wind blows constantly and from a consistent direction, such as on mountain passes, offshore locations and island. Leading users of wind energy includes the Germany, USA, Denmark and India.

    Merits of wind energy

  • It is a non- polluting and environmental friendly source of energy.
  • It is an important renewable and sustainable source of energy.
  • The gestation period is low and the power generation starts immediately after commissioning of the windmill.
  • Power generation is cheaper as there is no shortage of input (i.e., wind). The recurring expenses are almost nil.

  • Limitations of wind energy

  • Wind energy farms can be located only in vast open areas located in favorable wind conditions as the minimum velocity for a windmill to function is 15km/h.
  • The cost of construction of a wind energy farm is high.
  • The appearance of windmills on the landscape and their continuous whirling is irritation.
  • The location of wind energy farms should not be on the routes of migratory birds otherwise it will play havoc with the birds.

  • Wind power potential of India

    India is rated high (ranked fourth in the world) for wind resource availability. The total wind power potential in India is estimated at 45,000MW, out of which about 6000MW is located in Tamil Nadu and 5000MW in Gujrat.
    A total capacity is more than 1700MW has already been installed which will increase further with the coming up of new facilities.
    India`s largest wind energy farm established near Kanyakumari in Tamil Nadu can generate 380 MW of electricity.

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