Wind Energy: Turbine Diameter and wind Speed

http://en.wikipedia.org/wiki/Propeller#Forces_acting_on_an_aerofoil

Besides all the math...

Generally the maximum speed of the windmill is directly proportional to the average wind speed X the efficiency of the blades.

If you have two blades with the same efficiency but different length, the speed at the tip would be close to identical. This means the longer blade will have fewer RPMs but more torque or power

For blades with poor efficiency, the tip will travel slower then the wind speed. For higher efficiency blades, the tip will travel faster then the wind. The best way to rate the efficiency is to look for the minimum speed. The lower the minimum speed, the more efficient is the blade.

More surface catches more wind to make more difefrential pressure across the blade and more movement at lower wind speeds. Bigger = power at low wind speeds. At high wind speeds and gusts and shifting wind these big boys blow up . . . it's just too much force on the 30 - 45 m long blades (yes . . . 45 m long). I just attended a wing energy relaibility workshop and the big ones can't take high or shifting winds. They can make power at 6 mph winds with those big blades.

So the "simple" solution would seem to be automatically telescoping blades, which would be computer controled to extend to their maximum surface area and pitch, depending on the wind direction and speed as measured near the blades. Strong wind and gusts, minimize surface area, etc. Combine length extension and "fan" opening of the blade tips to give greater surface area for less wind. Hurricane winds, feather the blades and have a speed governor on the shaft.

There are pitching systems in place (complex and they don't work well), and even some fixed pitch blades that deflect at high wind and auto-pitch by deformation (that only cover a few scenarios).

Wind turbines are notorious for being unreliable. The simple fact is no one can predict the wind forces.

I'm a machinery engineer, not a wind guy.

At the wind turbine reliability conference I stood up and said "These failures can be solved by a good machinery engineer. You guys are 20 years behind the industry"

Most people attending who were not 100% wind people agreed.

This is simply incorrect. All fixed speed wind turbines 750KW to 5MW and up feather there blades to maintain a constant RPM. almost all of these machines don't need to start feathering there blades until around 28 mph (12.5 meters per second) they can continue to produce at 100% power or close to, up until approximately 60 mph (27 meters per second)

6 mph is there cut in wind speed. When they start to produce power

Turbine diameter and wind speed are not related directly yet both are contributing towards power generation. higher the wind speed, higher is the pressure on blades and so more force to run the turbine. again larger the blade dia more area it will capture and again more force to run the turbine for a given wind speed. Even this can be adjusted by adjusting the pitch & design of the blade upto some extent.

The available (raw) wind power is a function of wind speed (and humidity, temperature, air density). It is expressed in W/m². For example, at 6.4-7m/s, the available wind power is 300-400W/m². The efficiency of wind turbines is around 35-45% and cannot exceed the theoretical Betz limit of 59.6%.

To determine what power you can get from a wind turbine, you have to know several parameters like: efficiency, cut-in speed, cut-out speed, swept area. The larger the swept area, the more power can be obtained. But every assessment of energy production/year starts from the evaluation of the site. There are companies doing only that, specialized instrumentation and software. There are also maps showing the regional wind potential.

If you do not design a wind turbine, than browse manufacturers who are providing curves showing power/wind speed for each turbine style, diameter, etc.

I read somewhere (CR4?) that a new type of "rotary coil"
is more efficient than the normal blades?

It is (was) a helix type of "DNA" spiral that is more efficient;
does anyone know of this? I ask because it could be used
horizontally, to be less intrusive on the landscape.

jt.

Free web page in 30 secs. - http://www.mfnb.at

What is the relation of wind turbine diameter and wind speed?

haw do we make a wind turbines?

How do we break wind (turbines)?

Dear Sir

In Wind mills Wind Turbine output is mainly depend on the Swept area of the Rotor if we increase the swept area we can get high output .

But if we are going on increasing the length of the rotor blade ( swept area = 22/7 *D*D /4 ) the stability will go down .

Wind speed is More important in Wind Mills If wind speed increases the power out put will be more . To get more wind speed we can increase the Height of Tower

Increasing the tower height at the same place we will get more wind speed

we are having limitation in increasing the height of tower to get stability .

Regards

I.DHANARAJ LAZARUS