Wind - novice question

[to do]

Hello everyone, I'm new to this forum

I am more and more interested in wind energy and I am in the phase where I try as best I can to understand how they work.

Except I wonder about certain points:

- why the output (in power I hear) of commercially available wind turbines generally drops there beyond a wind of 15 m / s, is it not technically possible to create wind turbines capable of producing current with winds of 80 or 120 km / h?

- small wind turbines (less than 2 m in diameter) have a low power, I understood that this was among other things due to the wind speed and the swept surface.
By imagining a duct with a diameter of 160 cm or air circulating at 90 km / h, would it not be possible to put a wind turbine of the same diameter but with a generator more powerful than those provided for winds of 12 m / s so to increase the power of this one?

Thank you in advance for your answers and again sorry for my naivety

[Obelix]

Hello,

And understand your questions ...

A wind turbine is a machine manufactured to extract the maximum power from a moving air stream.
We therefore calculate it for a specific wind speed and try to make compromises to see what it gives at other speeds.
A more telling example: aircraft wings, calculated for an optimal speed range. It’s not the same on a jumbo jet or a supersonic .....
This specific speed of calculation is therefore the most common found in the regions where we want to sell our product (in general we take 10m / s).
Another limitation of wind turbines is the speed at the end of the blades and technological limits are quickly reached. The speed taken into account in the calculations is 6 to 7 times the wind speed with a safety coefficient. If we take a coefficient of 1.5 a wind of 120 km / h and 7 speed at the end of the blade 120 * 7 * 1.5 => 1280 km / h at the end of the blade very close to the disintegration by the sound barrier !!
So in summary everything is a question of compromise for the exact point where we intend to install the machine.

For the second question, the power is a function of the area swept and the cube of the wind speed.
The idea of ​​putting the wind turbine in a tube at constant speed gives a certain power whatever the generator coupled to this wind turbine. It can be calculated with a swept area of ​​2 m² a "wind" of 25m / s => 19 150 Watts available in the air stream. It only remains to calculate a wind turbine with a good performance in general around 40% is a good 7500 Watts that will have to be transformed into electric .....
But we can never "shoot" more! The theoretical maximum possible is 16/27 of this power given by BETZ's law, i.e. approximately 11250 Watts. But we have not yet found a wind turbine approaching this yield.

Obelix

[Alain G]

Savalfaire

Welcome to Econologie!

- why the output (in power I hear) of commercially available wind turbines generally drops there beyond a wind of 15 m / s, is it not technically possible to create wind turbines capable of producing current with winds of 80 or 120 km / h?

-The wind turbines fall in power because they are voluntarily reduced to protect the blades which with centrifugal force would break them, either by a brake, by resistive load, by orientation of the blades or by feathering.
-Yes it is possible but not necessary because it happens very rarely and we would lose it on other operating ranges.
Note that there are some that produce and resist beyond 200 Kmh.

- small wind turbines (less than 2 m in diameter) have a low power, I understood that this was among other things due to the wind speed and the swept surface.
By imagining a duct with a diameter of 160 cm or air circulating at 90 km / h, would it not be possible to put a wind turbine of the same diameter but with a generator more powerful than those provided for winds of 12 m / s so to increase the power of this one?

-This already exists, it is the principle of concentration of the flow in a double funnel to accelerate the speed and increase its performance.
-The disappointing point of this system is the total size and the cost.

Here I hope to have enlightened you a little.

[bidouille23]

good evening, new too, but I can give a few more explanations.
First a small precision at 1280 km / h we exceeded the sound barrier which is 1224km / h or the disintegration of the blades has already taken place at 1280 km / h.

Then as well explained by Obelix have optimized generator and blades to have a nominal operation at a given wind speed, (average annual speed on site recovered by positioning of an anemometer!).
Knowing that in a region called sale as in Brittany the average winds are around 6 to 7m / s, that is to say that if the wind turbine produced has say 7 ms it will produce a large part of the year. Now take the case of a wind turbine to produce 80 km / h of wind (22.2 m / s) well we are not ready to see the slightest kilowatt except on very windy days.
We can make wind turbines which produce in very strong wind but in this case it will turn ONLY in very strong wind.
And the drop in production is voluntary we block the production before mechanical or electrical deterioration of the wind turbine, by a system either of blade orientation (variable pitch) by offset of the wind turbine laterally or vertically or then we load the engine to create a brake effect if not wall sound and more production because HS machine.

the larger the blades, the larger the visteese at the tip of the blade, so the less they will have to turn quickly
And you don't have to put a wind turbine at home as much as it produces a maximum not only on stormy days, knowing that wind is more often weak than strong ...

here is also hoping to have been a help for you savalfaire and a question is never naive believe that by not asking it will have the answer that is naive !!



see you soon and good luck

Bidouille23

[oli 80]

hello, here is an animation of a wind turbine with folding blade
http://www.youtube.com/watch?v=5r26CBIy ... re=related
http://www.youtube.com/watch?v=s3RINNrI ... re=related

there is also a topic on a robi plane wind turbine in them forums