Megawatt Wind Turbine

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Huge Wind Turbines Note from an intellectual basketcase We get many questions from individuals who are interested in having their own wind turbines. This web site has an equation (see Wind Equation ) that tells people how much power can be expected from a wind turbine of a given radius at a given wind speed. There is an example that is apporpriate to the case, of a wind turbine of 7m diameter in a 5 m/s wind. A (nameless) lout has evidently never seen textbooks, for he complains about the choice of numbers in the example problem. EGAD! I should have used numbers for giant wind turbines! I quote: "Similarly, no serious industrial windpower producer would build a wind generator with rotors only 7 meters long in a location where the wind speed averaged just 5 meters per second ... We would seriously question Dr. Hayden's choice of numbers." (I search in vain for where I said that this was meant to represent (A) average wind speed or (B) the power available from industrialgrade turbines.) OK, let's do it. For a wind turbine of diameter 80 meters cenetered at 100 meters (328 feet) off the ground. Let the wind speed be 10 m/s (22 miles per hour). The power would be 1.0* (40^2)*10^3 = 1,600,000 watts, or 1.6 MW. At a wind speed of 20 m/s, the power in the wind would be 1.0*(40^2)*20^3 = 12,800,000 W, or 12.8 MW. But

description

technical info regarding the wind turbine and its basic cost per MW

Transcript of Megawatt Wind Turbine

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Huge Wind Turbines

             

 Note from anintellectualbasket­case          

 

We get many questions fromindividuals who are interested inhaving their own wind turbines.  Thisweb site has an equation (see  WindEquation) that tells people how muchpower can be expected from a windturbine of a given radius at a givenwind speed.  There is an example thatis apporpriate to the case, of a windturbine of 7­m diameter in a 5 m/swind.

A (nameless) lout  has evidently neverseen textbooks, for he complains aboutthe choice of numbers in the exampleproblem.  EGAD!  I should have usednumbers for giant wind turbines!  Iquote:  "Similarly, no serious industrialwind­power producer would build awind generator with rotors only 7meters long in a location where thewind speed averaged just 5 meters persecond ... We would seriously questionDr. Hayden's choice of numbers."  (Isearch in vain for where I said that thiswas meant to represent (A) averagewind speed or (B) the power availablefrom industrial­grade turbines.)

OK, let's do it.  For a wind turbine ofdiameter 80 meters cenetered at 100meters (328 feet) off the ground.  Letthe wind speed be 10 m/s (22 miles perhour).  The power would be 1.0*(40^2)*10^3 = 1,600,000 watts, or 1.6MW. 

At a wind speed of 20 m/s, the powerin the wind would be 1.0*(40^2)*20^3= 12,800,000 W, or 12.8 MW.  But

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wind speed is rarely that high, so onewould normally use a 2­MW turbinethat would produce constant power at 2MW from about 11 m/s until shut­offat 25 m/s.

If the turbine rotated at 15 RPM, thetips would move at about 63 meters persecond (136 miles per hour).

A wind farm of these machines would havethem spaced at about 10 diameters in everydirection, that is,  800 meters (about a half­mile) apart.

Note:  When wind turbines are replaced byones of double the diameter, the power perwind turbine quadruples.  But so does theland area.  Well, that's not quite the wholestory.  Larger wind turbines are put on tallerpillars, and the wind speed up there isusually somewhat higher.  Nevertheless, thepower production per unit area of land is notparticularly impressive.

Wind farms in the US produce power at theaverage rate of about 1.2 watts per squaremeter (about 5000 watts per acre).  In orderto produce an average of 1000 MW ­­­ thepower produced by any large conventional(coal, oil nuclear, gas) power plant ­­­would require about 833 square kilometers(300 square miles) of wind turbines.  That'sthe area of a mile­wide swath of landextending from San Francisco to LosAngeles.  Multiply that by about 30 and youhave California's electricity.

In 1998, wind turbines in the US produced3.5 billion kWh.  The US produced a totalof 3,367 billion kWh, so the fraction fromwind was 0.10 percent ­­­ one part out of athousand.  

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