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Wind Power Generation | Operation of Wind Turbines

Updated on December 17, 2014

Wind energy is a form of renewable energy. No doubt, wind energy has been used by the human beings millennia before the invention of electricity. Earlier, wind energy was used in shipping, grinding, pumping water etc. Today wind energy is used for the generation of electricity. The utilization of wind energy for power generation is increasing day by day due to the increase in the coast of oil, gas and coal. Also these resources are depleting fast and will exhaust in few years. One of the serious issues with these conventional energy resources is their impact over the environment. But on the other hand, wind energy is plentiful, inexhaustible and pollution free. These advantages encourage the developing as well as developed countries to trust wind energy for the production of electricity.

What is wind energy?

Wind energy can be considered as a form of solar energy. It is caused due to the uneven heating of Earth’s atmosphere by the Sun. The air near the earth surface gets heated up and moves upwards and the cold air replaces it. The motion of wind is affected by the rotation of the Earth and its geographical variations. The kinetic energy of the wind can be utilized in power production.

Wind Turbine

Over view of operation

Wind turbines are now primarily used for Electric power generation. The simplified operating principle of a wind turbine is as follows:

The fast moving wind strikes the turbine blades of the wind mill and rotates it. The turbine is coupled with the generator shaft through coupling gears. These gears are used to multiply the rpm of the shaft in order to match the rated rpm of the generator. The rated rpm of the generator can be calculated using the following formula:

Ns = 120f/p

Where

P = number of stator poles.

Ns = Speed of the rotor in rpm.

F = frequency of the output power.


The output of the generator may be AC or DC depending on the type of generator used. If the generator used is an AC generator (alternator or induction generator then the output of the generator is directly supplied to the grid provided the output frequency and voltage of the generator remaining the same as that of the gird or the output of the generator is again rectified, stored in batteries, inverted and supplied to the grid. In case if DC generator is used then the output of the generator is inverted and fed to the grid.

Output power

The speed of wind generally increases with height. It is calculated that the wind at a speed of 26 mph contains 1 kW per square meter of cross-section. That is more than 1.3 horsepower. The output power of a wind mill depends upon the following factors:

The area swept by the blades of the turbine.

The Speed of wind

The wind density of air

The output power of a windmill can be given by the following formula:

Developed power P = 2.14 x Adv3 watts

Where,

A - The area swept by the blades of the turbine.

d - The wind density of air.

v – Velocity of wind.

Parts of a wind power plant

Parts of a wind power plant

A wind power plant consists of the following parts:

  1. Turbine
  2. Gear box
  3. Generator
  4. Nacelle
  5. Tower

Wind turbine

Wind turbines are classified based on their axis of rotation into two general types: horizontal axis and vertical axis. In a horizontal axis machine, the blades rotate on an axis parallel to the ground. In a vertical axis machine, the blades rotate on an axis perpendicular to the ground. Horizontal axis turbines are more commonly used than the vertical axis turbines.

HAWT

Horizontal axis wind turbines

In a Horizontal-axis wind turbine (HAWT), the main rotor shaft and electrical generator are mounted at the top of a tower. Most of the turbines have two or three blades rotating around a horizontal axis. Horizontal axis turbine is provided with yaw control in order to keep the turbine always pointing towards the direction of wind.

Advantages of horizontal axis turbines.

  1. Horizontal-axis wind turbines are capable of collecting the maximum amount of wind energy, since the area swept by the turbine is more.
  2. Horizontal-axis wind turbines can withstand strong winds
  3. Horizontal-axis wind turbines can be more effectively controlled.
  4. High efficiency since the turbine always moves perpendicular to the direction of wind.

VAWT

Vertical axis wind turbines

The vertical axis turbine (VAWT) has its blade rotating in an axis perpendicular to the ground. These turbines are mounded near the ground. Vertical axis turbines are not affected by the change in wind directing. But it is less stable than the horizontal axis wind turbines.

  1. Advantages of vertical axis wind turbines
  2. Since this type of turbines is placed at less height from the ground, it is easy to maintain.
  3. Yaw control is not necessary.
  4. Electricity can be generated at lower wind speeds as low as 6 m.p.h. (10 km/h).
  5. They may have a lower noise signature.

Asia's Largest wind farm

A markerMuppandal Wind Farm Windmill Rd Aralvaimozhi, Tamil Nadu 627105 -
Windmill Road, Muppandal Wind Farm, Aralvaimozhi, Tamil Nadu 627105, India
get directions

The largest wind farm in Asia is Muppandal wind farm in Kanyakumari, India. It has the total generating capacity of more than 1500MW.

2. Gear box

The turbine is coupled with the generator shaft through coupling gears. These gears are used to multiply the rpm of the shaft in order to match the rated rpm of the generator.

3. Generator

Generator is a device used to convert mechanical energy into electrical energy. The turbine is coupled with the generator through coupling gears. When the turbine is rotated by the wind the generator shaft is rotated and electricity is generator due to electro magnetic induction. The generators used for power generation can be classified into three categories. They are:

  1. Induction generator
  2. Permanent magnet Synchronous Alternators
  3. DC generator (Brushed)

1. Induction Generator

It is an ordinary three phase induction machine operating at generating mode. When the shaft of an induction moor is rotated at a speed greater that its synchronous/ rated sped, it acts as an induction generator. In the wind turbines where induction generators are used, initially the turbine is driven using the same induction machine, by drawing power from the grid. When the velocity of wind is sufficient enough to drive the shaft at a speed higher than its rated speed, the machine starts operating in generating mode and supplies the excess power back to the grid. While operating in generating mode, induction machine requires reactive power for magnetization that is drawn from the grid. Hence once it starts generating power, capacitor banks can be connected across the supply terminals in order to supply reactive power.

2. Permanent magnet Synchronous Alternator

Permanent magnet Synchronous alternators are widely used in wind power generation. This type of alternators has permanent magnet in its rotor. They have a very high efficiency (up to 90%). When the shaft of the alternator is rotated, due to electromagnetic induction, emf is induced in the stator of the machine. The output of this type of machines is alternating in nature, having its frequency varying with the speed of rotation of its shaft. Therefore the output of the alternator is rectified and either stored in batteries or again inverted and supplied to the grid.

3. DC generator (Brushed)

Brushed DC generators are used only in home wind turbines. It has very poor efficiency. Output is DC and it is stored in batteries.

4. Nacelle

Nacelle covers the key components such as generator, gear box etc. It protects them from external environment.

5. Tower

The whole set up of turbine, generator, gear box, control equipments are supported by huge towers. As the speed of wind increases with height, the heights of the tower are usually more than 30 meters.

Advantages and disadvantages of wind power

Advantages

  1. Wind is energy is “free”. Hence the fuel cost for the production electricity from wind is “zero”.
  2. No environmental pollution.
  3. Wind turbines have low operating costs.
  4. Wind energy is a renewable form of energy and is inexhaustible.

Disadvantages

  1. Very high initial cost.
  2. Causes noise pollution.
  3. It is difficult to predict their energy production in advance that reduces its reliability.
  4. Covers a vast area of land.

Comments

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    • KawikaChann profile image

      KawikaChann 3 years ago from Northwest, Hawaii, Anykine place

      Nicely done. I wonder if there comes a time when expenses for repair outweigh just abandoning them. In Hawaii on the island of Oahu, we have hillsides full of turbines that no longer spin, yet, remain after months. Upvoted/interest/follow. Peace. Kawi.

    • goodnews11 profile image
      Author

      OSBERT JOEL C 3 years ago from CHENNAI

      Thank you Kawi..

    • LauraVerderber profile image

      Power Ball Pythons 3 years ago from Mobile, AL

      Great hub, I didn't even know vertical axis wind turbines existed. I'd love to get one to help power my homestead one day. Voted up and interesting!

    • goodnews11 profile image
      Author

      OSBERT JOEL C 3 years ago from CHENNAI

      Thank you..

      Vertical axis wind turbines are not much preferred due to stability reasons.

    • WestelCS profile image

      Tim Anthony 3 years ago

      Nice article, pretty informative. The only thing I'm wondering about is how reliable are these wind turbines, and how stable they can be if someday in the future we decide to rely on them for generating electricity. I guess they might not prove themselves as good as dams.

    • Larry Rankin profile image

      Larry Rankin 3 years ago from Oklahoma

      You do a wonderful job of incorporating technical information while still allowing your article to be understood by a layman.

      I am a big fan of wind power. Something I heard recently is that wind power is hazardous to birds because of the turning blades. In your experience, is there much truth to that?

    • goodnews11 profile image
      Author

      OSBERT JOEL C 3 years ago from CHENNAI

      WestelCS, Even though wind turbines are environmental friendly, it is not so reliable as the non conventional resources. The reason is that the velocity of the wind wont be same throughout the year. It cannot generate power if the wind has sufficient velocity.

    • goodnews11 profile image
      Author

      OSBERT JOEL C 3 years ago from CHENNAI

      Larry Rankin, Thank you

      What you have heard is true. Wind turbines are hazardous to birds.

    • ClaytonDaily profile image

      ClaytonDaily 2 years ago

      One other con - the big 1 megawatt windmills are a pain when it comes to maintenance.

    • goodnews11 profile image
      Author

      OSBERT JOEL C 2 years ago from CHENNAI

      Thats true my friends. Maintaining windmills, either big or small is really a pain.

    • shivanipatel profile image

      Shivani Patel 2 years ago from Pune

      Highly informative page. Got to know something new. Following you.

    • Lionrhod profile image

      Lionrhod 2 years ago from Orlando, FL

      Useful hub, thanks much! Hubby and I are presently studying vertical wind turbines and planning to build some as soon as we move to a place where we can. Presently we're living in a Homeowners Assn. that prevents us from anything useful like this. So for the moment we'll have to focus on testing scale models to learn what works best. In our understanding, vertical turbines are better because they catch wind from any direction, take up less space and can even look pretty.

    • goodnews11 profile image
      Author

      OSBERT JOEL C 2 years ago from CHENNAI

      @Lionrhod

      Compared to HAWT, VAWT are less stable.

    • Lionrhod profile image

      Lionrhod 2 years ago from Orlando, FL

      Thank you Goodnews, that's important information to consider and/or find a work around for.

    • goodnews11 profile image
      Author

      OSBERT JOEL C 2 years ago from CHENNAI

      Even though VAWTs are less stable they are more efficient than HAWTs.

    • J - R - Fr13m9n profile image

      Jane Ramona Rynkiewicz Frieman 2 years ago from Morris County, New Jersey

      I found your hub to be very technically informative. This is a must needed alternative, along with solar, to the other energies which cause environmental disaster. Solar and Wind Power will also steer the consumer more to 'decentralized energy sources' instead of relying on 'centralized power' which results in cost raising energy bills for them.

    • Blackspaniel1 profile image

      Blackspaniel1 2 years ago

      I already have solar power. But, this could be an interesting addition. I would have to go through a specialist. I am a phsicist, but still getting the phase regulated requires too much precision for me.

    • AudreyHowitt profile image

      Audrey Howitt 22 months ago from California

      Very informative! We have wind farms nearby and while they are somewhat noisy, I love to see them in the distance.

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