Difference between revisions 558535800 and 593220878 on enwiki

{{AFC submission|d|exists|3=Wind turbine|declinets=20130606015258|decliner=Howicus|ts=20130529185033|u=Kunal991|ns=5}}
*{{afc comment|1=Needs check to see if the material has been merged   '''[[User:DGG| DGG]]''' ([[User talk:DGG| talk ]]) 03:09, 31 January 2014 (UTC)}}
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{{afc comment|1=The same as [[Wikipedia talk:Articles for creation/Wind Turbine Plants]], which was put into mainspace and then redirected to [[Wind turbine]] [[User:Howicus|Howicus]] ([[User talk:Howicus|talk]]) 01:52, 6 June 2013 (UTC)}}
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== Introduction ==

[[File:Flow diagram for wind turbine plant.jpg|thumb|Figure 1. Flow diagram for wind turbine plant]]
A '''wind turbine power plant''' uses the kinetic energy in wind for delivering the mechanical power. [[Wind power]] is a renewable source of energy. Since the prehistoric days wind is being used as a natural source of power and is being utilized for performing variety of mechanical work. It is one of the cleanest form of energy for producing power. There is no considerable waste materials from wind turbines after operations as compared to other energy source. The total annual [[wind energy]] available on earth is approximately about 13*10<sup>12</sup> kWh which is equivalent to 1500 power stations each delivering 1000 MW of energy.<ref>Turbines,Compressors and Fans|author= S M Yahya|edition= Fourth edition|isbn=0070707022|year= 2011|Publisher= Tata McGraw Hill Education Private Limited,New Delhi</ref>.

There are different classes of wind turbines ranging from small to large having corresponding suitable applications. The small one having power production less than 10 kW are used in homes, farms and remote applications whereas intermediate wind turbines (10-250kW ) are having their utilities in village power, [[hybrid systems]] and [[distributed power]].  The larger wind turbines (660kW – 2+MW) are used in central station wind farms, distributed power and community wind<ref>http://www.alternative-energy-news.info/what-factors-affect-the-output-of-wind-turbines/</ref>. ⏎
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[[File:Economic comparison of wind energy.jpg|thumb|Figure 2. Economic comparison of wind energy]]

== Resources ==

[[Wind]] is natural source for [[wind turbines]]. The moving air is known as [[wind]]. The wind energy is one of the earliest forms of energy which is used for delivering mechanical power from  a [[renewable]] source. The working fluid of wind turbine plants is flowing air or wind which is freely available and thus leading to the reduction of fuel costs whereas other expenditures may be  involved. As similar to other [[power plants]], the cost per unit energy generated decreases with the increase in size of wind turbines<ref>Turbines,Compressors and Fans|author= S M Yahya|edition= Fourth edition|isbn=0070707022|year= 2011|Publisher= Tata McGraw Hill Education Private Limited,New Delhi</ref>.  [[Energy storage system]] must be employed in wind turbine plants in order to compete with [[anisotropic]] or random nature of wind energy<ref>Fundamentals of turbomachinery|author= B.K. Venkanna|Third Printing|isbn= 9788120337756|year= 2009|Publisher= PHI Learning Private Limited, New Delhi</ref>. Wind turbines can be set up anywhere if sufficient wind velocities were available for an adequate time.

== Available energy calculation ==

It is obvious that wind contains some energy. Therefore, the available energy in wind during time T is given by  <ref>Turbines,Compressors and Fans|author= S M Yahya|edition= Fourth edition|isbn=0070707022|year= 2011|Publisher= Tata McGraw Hill Education Private Limited,New Delhi</ref>
:<math>E = k\int_{0}^{T} c^3\ dt.\,</math>, where;
k=constant (depends on the [[air density]], [[efficiency]], and size of wind turbine, c=instantaneous wind velocity

Now, maximum [[power]] that a wind turbine can develop is

'''''P<sub>max.</sub> = 0.593ρAv<sup>3</sup> /2''''', where; v = mean wind velocity, A = [[propeller]] diameter. 

Therefore, after considering efficiency factor (ἠ = 0.59)

'''''P = 0.000206Av<sup>3</sup>''''' kW

=== Calculations for different design of wind turbines ===

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==== [[Horizontal axis]] ====

Axial [[thrust]] due to [[static pressure]] difference across the disc,

'''''F<sub>x</sub>=A(P<sub>1</sub> - P<sub>2</sub>) = 1/2ρA(c<sub>u</sub><sup>2</sup>  - c<sub>d</sub><sup>2</sup>)''''' , 

where; P<sub>1</sub> - P<sub>2</sub> = Pressure difference across the [[blade]]

(contracted; show full)
# By incorporating a fan tail mechanism.This is relatively slower mechanism.

* [[Tower]] - Rotor is to be mounted at high altitude because of high wind velocity and for this purpose a tower is used. Economic and vibration problem are the major factor in designing the tower.<ref>Turbines,Compressors and Fans|author= S M Yahya|edition= Fourth edition|isbn=0070707022|year= 2011|Publisher= Tata McGraw Hill Education Private Limited,New Delhi</ref>

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== Analysis of Suitable Place ==

[[File:Fluctuations in hourly wind velocities.jpg|thumb|Figure 4.Fluctuations in hourly wind velocities]]

It should be noted that the wind cannot be stored elsewhere or in a way it should be pointed out that wind is available in a highly diluted form.The prediction of characteristic of wind due to the wide variations with time during the year and location is quite difficult and thus proper study of both the long and short range behavior of wind of a given location are requ(contracted; show full)Major considerations for selecting the site are :-
* High mean wind velocity.
* Open area, not surrounded by mountain, buildings, forest etc. as presence of these retard the wind.
* Good land quality for such a huge foundation.
* Climatic conditions or [[topography]]. 
* Should be located at a distance from the site of application.
* Local labor and building materials should be easily available.
* Low temperature problem
.<ref>Turbines,Compressors and Fans|author= S M Yahya|edition= Fourth edition|isbn=0070707022|year= 2011|Publisher= Tata McGraw Hill Education Private Limited,New Delhi</ref>.

== Efficiency of wind turbines ==

A wind turbine is an exclusive form of [[turbo machine]] which often operates at relatively lower speeds. Efficiency of wind power plant is maximum at its rated (design) wind velocity and thus efficiency decreases with the fluctuations in wind. The lowest velocity at which the turbine develops its full power is known as rated wind velocity. 8 kmph is the minimum wind velocity below which no useful power output can be produced from wind turbine. There is limitation on both minimum and maximum wind velocity for the efficient operation of wind turbines and 56 kmph is the upper limit on wind velocity above which wind power plants are uneconomical. Therefore, they should work in these velocity ranges.<ref>Large wind turbines|author=  Hau, E.--(Erich),Snel, Herman|edition=|isbn= 0471494569|year=2000|[[Wiley]],Chichester,New York</ref>.

=== Factors affecting efficiency ===

The efficiency of wind turbines are mostly dependent on five important factors:

* [[Wind power]]- The amount of power generated by a wind turbine would be greater if the wind blows faster and thus applying stronger force. Wind speed vary with the variation in locations and thus relationship between wind velocity with power production should be properly understood<ref>http://www.solarpowerwindenergy.org/2010/03/04/what-factors-affect-the-output-of-wind-turbines/</ref>.         P=Kvf, where  P= wind power, V= wind speed, F=wind force and k is a constant

* [[Altitude]]- Due to various atmospheric factors, wind speeds are higher at higher altitudes there would be lesser obstructions from the surrounding hills, trees and buildings. Adequate study of relationship between wind velocity and altitude shows that if the distance between turbine and ground is doubled then there would be approximately 12% increase in wind speed.
* [[Obstructions]]- The various factors such as trees, buildings, hills etc. restrict the free air flow by creation some form of friction which eventually slows down the wind and thus reduces the efficiency.
* Blade aerodynamics- The angle of airfoil with the direction of relative wind which is known as angle of attack has a significant effect on amount of lift. Turbulence develops and drag increases when angle of attack becomes too large which results in loss of lift.
Thus in order to get maximum efficiency the shape of blades should be accurately selected.<ref>Aerodynamics of Wind Turbines|author= Martin O.L. Hansen|edition= Second edition|isbn= 9781844074389|year= 2008|Publisher= [[Earthscan]] in the UK and USA</ref>.
* [[Air temperature]]- The cold air has higher [[density]] and thus increase power output. It has been observed that power output from a wind turbines increases by approximately 16 % when the temperature of air is lowered from +20 deg celsius to  -20 deg celsius  for any given wind speed.

== Advantages and Disadvantages ==

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=== Advantages of Wind turbines ===

* Wind is a renewable source of power and thus available in plenty.
* It is eco friendly therefore, no carbon-dioxide emission thus no [[greenhouse effect]].
* Wind turbine plants are easier to set-up with easily available materials in a very short time.
* Installation of wind turbine is labour intensive so also good for employment.
* Fuel expenditure vanishes and thus saves [[fossil fuels]].
* After installation no cost for producing electricity except maintenance.
(contracted; show full)
*http://www.articlesbase.com/environment-articles/wind-turbine-physics-factors-affecting-performance-1450642.html
*http://www.alternative-energy-news.info/what-factors-affect-the-output-of-wind-turbines/
*http://www.solarpowerwindenergy.org/2010/03/04/what-factors-affect-the-output-of-wind-turbines/
*http://www.istockphoto.com/file_thumbview_approve/49112563/2/istockphoto_4912563-design-elememts-wind.jpg


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== Wind turbine plants ==

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