Wind mill

Hello kamesh_dvk,

1) i want to know, how much time these machines will take to produce 500Kw, 600Kw, 1.25Mw etc. after they set to run ............?

"....how much time...."

Time relates to kWH = KiloWatt Hours, not simple output which fluctuates with the wind input.

The Stated Output of the machine quantifies the maximum instantaneous output, but only if enough energy input in the form of wind transmitted to turning motion by the propeller vanes, connects mechanically to the Alternator.

"........and do they have the capacity to produce the same even at low wind speeds(cutin speed)"

Of course you cannot get out more than is put in, less all losses on the way (heat, friction, noise etc) So the answer is NO.

"2) does their power output vary according to wind speed, height, etc.. if so what is the relation?"

Quite a complex series of calculations to explain the relationships, my friend.

Kind Regards....

Contact Todd at TFfins@aol.com for the answer.

Can you e-mail me information about the wind-turbines you're using ?

Yos at y.agmon@cbvista.com

Thanks and GOOD LUCK

The power in the wind is proportional to the cube of the wind speed and to the area over which it is being intercepted and the density of the air (which in turn depends on temperature and pressure). So at a particular site the power would vary with wind speed and temperature. But how much of this gets converted to mechanical shaft power and then to electrical power depends on the machine efficiencies. It is not likely to be over 35%.

Dear Friend, wish you happy new year..

first of all, the power is nothing but work done per unit time. So, it does not accumulate or goes on adding as time increases.

The power generated depends upon mainly on the wind speed, the area of blade (length of the blade and the chord length of the blade) which cuts the wind, and the rpm of the rotation of the blades.

the wind speed depends upon the geographical location of the site, the height, the location such as on-shore, off-shore....

the power generated is directly proportional to the cube of the relative speed of the wind.

regards

abhijit nalawade

I think you have some confusion regarding the area of interception of the wind. This is not the actual area of the blades. It is the swept area of the blades or the area of the circle described by the blade tips. The actual area of the blades can be much less than this. It is possible to harness the wind through the entire swept area either using a large number of broad blades rotating slowly or even just one thin blade going very fast.

<1) i want to know, how much time these machines will take to produce 500Kw, 600Kw, 1.25Mw etc. after they set to run....>

A 500Kw generator will take 1 hour to make 500KwH of electricity when it spins at its maximum speed continuously for that time.

<2) does their power output vary according to wind speed, height, etc.....>

Clearly, yes!

I'm not going to bother answering point 1 but with regards to point 2 "does their power output vary according to wind speed, height, etc.. if so what is the relation?" I think the other commentators are going about this answer from a too scientific stand point.

Generally speaking, wind turbines are controlled by hydraulics (in relation to output) in two distinct ways:-

1) Pitch control determines the power derived from the blade in relation to available wind speed and......

2) Brake control prevents overspeed (and blade lock) from erratic gusts of wind!

Of course, the hydraulics are, in turn, controlled by a PLC connected to wind speed and direction transducers mounted above the nacelle AND a direct data link to the remote control room.

Keep making 'em as there will be plenty of wind about while Heinz still produce baked beans!

Happy Y2.008K

The other answers are all fine -- although some may be a little more complicated than you were looking for... and others may be a little too brief. Of course my own take on it just another guess, re what you were looking for:

1. The power ratings of windmills are often (but not always) maximum ratings, and windmills will have some means of governing to prevent destruction of blades, bearings, wiring, gearboxes, etc. Power is rated in kW. Energy (Power x time) is rated in kilowatt hours (kWh). So a 500 kW unit, running at its rated output, will produce 500 kWh of energy in one hour.

2. The output of a given windmill depends most strongly on wind speed, with the output increasing (theoretically) with the cube of wind speed (until the output rating is reached). (In practice, the efficiencies of the various parts of the windmill will change this theoretical relationship.) Temperature, humidity, and barometric pressure effect the mass of a given volume of air, so that high temperatures and humidity and low pressures result in less power, for a given wind speed... but these effects are relatively small, compared to the huge differences made by wind speed. Wind speeds are greater further from ground, so taller windmills will produce more power, other things being equal.

The elemental torque produced is given by

dQ = B*(1/2)*ρ*W²*(Cl. sin θ-Cd.cosθ)*(c.r.dr)

where,

dQ= elemental torque developed (N-m)

B = no. of blades.

ρ = density of wind (Kg/m³)

W = relative wind speed (m/s)

Cl and Cd are the coefficient of lift and drag.

θ = flow angle (in degree)

c = chord length (m)

r = length of blade (m)

dr = elemental blade length (m)

Now the power developed is gievn by

dP = dQ * ω

where ω is the angular rotation of the wind turbine blade (RPM)

the total power is given as

P = ∫ dP = ∫ dQ * ω

the limits of integrations are 0 to r.

thanks and regards

abhijit nalawade

India.

Hi abhijit,

All this looks good, although I am stumbling over "r" as in

dQ = B*(1/2)*ρ*W²*(Cl. sin θ-Cd.cosθ)*(c.r.dr)

Wouldn't this need to be the radius of the particular element, rather than blade length?

Later the integration would be 0 through r, which would be the blade length.

So is r being used to mean two different things?

HI ken

yes definitely, r is nothing but the length of the blade. as in the design of wind turbine blade, the blade is treated as cantilever. The design is done as per Beam Element Theory.

regards

abhijit nalawade.

India

Hi Abhijit:

I'd intended to reply long ago, but got involved in other things. In the paper below, R is used for blade length and r is used for the radius at a particular element. That avoids the problem of using one variable to mean two different things.

http://digital.library.okstate.edu/OAS/oas_pdf/v56/p121_124.pdf

When looking for the Jischke paper I came across this, which is about it's author. http://en.wikipedia.org/wiki/Martin_C._Jischke

Regards, Ken

With what kind of vertical or horizontal wind turbines you get 500Kw, 1.25Mw ?

Big ones.

(from: http://www.windturbinecompany.com/ )

(In this picture, the wind turbine, and the water tower are the same distance from the camera.... only kidding )

Horizontal wind turbine are larger and hence, more useful in rural areas with open spaces. If you are living in an urban or suburban area, you will want to opt for the vertical wind turbine. In fact, vertical wind turbines were specifically designed to address the unique issues associated with electricity production in urban or suburban settings where horizontal winds become vertical when encountering the face of a building. The helical shaped blades of the vertical wind turbine can make use of horizontal or vertical wind bursts blowing in from any direction.

The world of wind turbines are about to change as we know it. I say this because currently the three blade monsters rule the day. These monster are very expensive for the energy recovered and require about 10 miles per hour of wind to produce any power. Recently I submitted a patent for a totally new wind turbine design that can produce considerable power at lower wind speeds. I believe that this new turbine is far superior to anything currently out there. But I must add that others are working on new ideas and something will change very soon.