Wind turbines: why they only have three blades (6 photos)

No more and no less - the designers settled on just such an option.





Here you can draw a parallel with helicopters: they have on the carrier screw from two to eight blades. It depends on the weight and size of the machine - the lighter it is, the fewer blades are needed in order to lift it into air.

For example, the Robinson 44 has two blades, while the heavy "Mi-26" - eight. The more blades, the lower the specific load on each. It is they who account for the entire weight of the helicopter.



Robinson 44 and Mi-26

And with wind turbines, the weight is on the support, so if increase the number of blades, and the severity of the entire structure will increase. TO For example, this is what the transportation of one of the largest wind generators.





This colossus was taken to the installation site for several days



Although the blades are made of fiberglass, it still costs a lot of money. The engineers came to the conclusion that if you add a fourth blade, the efficiency will increase by only 3%, and the cost of construction - by 12%. There is no point.

Then why not make "windmills" with 1-2 blades?



Such wind turbines are also used, but there are much fewer of them.

They should be cheaper to manufacture and maintain - This means that the cost of electricity could also be reduced. But in reality everything not this way. If two blades are left on the windmill rotor, then how orient it to the wind? While the rotor is still spinning.

If the blades are vertical, then the inertia is small. A if they are in a horizontal position, then the moment of inertia increases dramatically. The wind guidance mechanism will experience sharp and constant loads at a frequency of two seconds.

Although designs with 1-2 blades were also made: they quickly electric motors overheated, gearboxes broke down and wore out bearings.

And for a system with three blades, the moment of inertia is unchanged and such a “windmill” has been working for years. Nothing better has come up yet.



Assess the scale of a man and a wind turbine

It also has features: it buzzes like a small helicopter, can become covered with ice and stop, it is periodically struck by lightning, expensive to maintain and repair. This is the reason why the whole of Europe not yet crammed with wind turbines - despite sworn assurances politicians and fans of green energy. It may come, but this is still far away.