Wind Turbines

[Tarman]

There are more and more Wind Turbines appearing on our hilltops and out at sea. (In the UK anyway) I was always led to believe that they would face into the wind ( prop first, then the turbine)and are a great aid to identifying the wind direction. But I’ve recently seen a few that rearward facing with the turbine facing the wind in front of the prop. Does anyone have any comments ?

[Need money]

I believe they can be either, Upwind being the most common (extract below taken from a wiki) :

Since a tower produces turbulence (http://en.wikipedia.org/wiki/Turbulence) behind it, the turbine is usually pointed upwind of the tower. Turbine blades are made stiff to prevent the blades from being pushed into the tower by high winds. Additionally, the blades are placed a considerable distance in front of the tower and are sometimes tilted up a small amount.

Downwind machines have been built, despite the problem of turbulence, because they don't need an additional mechanism for keeping them in line with the wind, and because in high winds, the blades can be allowed to bend which reduces their swept area and thus their wind resistance. Since turbulence leads to fatigue failures, and reliability is so important, most HAWTs are upwind machines.

Hope that helps !

[Helinut]

Fancy trying to track and balance those..........:confused:

[500e]

Tack & balance How did the Transit get stuck up there

[Flying Bull]

Hi Tarman,

the things are not allways pointing direkt into wind.
Had one occasion, when the whiry things around me turned and all faced in a different direction - but the wind wasn´t strong that day.
One way they show the actual wind is, when they are on fire:E.
Black smoke shows the direction, clearly visible for miles (if your upwind or crosswind - otherwise you may see nothing at all :} )

Not a windmill - but to understand the idea :}
http://www.fotocommunity.de/pc/pc/extra/egallery/pcat/367917/display/4503128Winddrehung - fotocommunity.de (http://www.fotocommunity.de/pc/pc/extra/egallery/pcat/367917/display/4503128)

Greetings Flying Bull

[Tarman]

Thanks Guys, I think that I'll stick to smoke and water for wind indications. These turbines are less reliable than I was led to believe !:ok:

[RotorDompteur]

I have often used wind turbines for wind reference. The vast majority of them are “facing” into the wind. And even if I should stumble upon one of those with the blades one the back of the nacelle – I don’t think that it will lead me to believe that there has been a 180 degrees change of wind.
That said, in low winds (>5kts) they tend to get confused and end up facing in random directions.

Speechless Two; I know that you wrote it tongue-in-cheek, but I have to comment that when hoisting to a wind turbine the blades are locked in position and cannot suddenly spin themselves to destruction.
By the way, I took that first picture of yours – funny to see it appear here. Not that I mind at all. :ok:

Regarding track and balance: They are balanced by adding weights at the blade root – not flimsy weights like in the helicopter business but weights of many kilos. They are not adjusted for tracking as such.

One way they show the actual wind is, when they are on fire :E .
When thinking about it – you can say the same about helicopters… :bored:


RD http://www.uni-fly.dk/images/diverse/propeller_125.gif

[petit plateau]

There are both upwind and downwind designs.

A substantial number of the small wind turbines are downwind with all Proven models and the SouthWestWindpower Systream being downwind designs. These are of 2.5m dia to 7m dia and cost £10k to £50k. In jthe upwind style you can see the Fortis, Iskra and Bergey machines. They are almost all passive yaw devices irrespective of whether they are upwind or downwind.

These days there are no large wind turbines which are down wind layout. The UK government killed off the UK large wind manufacturers about 20 years ago and they were the only serious downwind large wind models. The large wind turbines are active yaw devices and are turned out of wind (side on) for maintenance, very high wind episodes, etc. by motors. Downwind is being reconsidered for particular large wind layouts especially for very large ones a long way offshore. A French company called Vergnet is looking seriously at a downwind layout. These are all about 50-70m diameter and £1-4m.

Ordinarily the shaft brakes are not supposed to be used to stop the blades rotating when running. They are intended to keep the blades stopped once they have stopped. Engaging them too quickly can result in serious damage as you have illustrated.

This is a fast-growing industry and the operators are going up a very steep learning curve. Mistakes do happen.

Hope that helps you decide whether to use them as a wind direction guide.