Farms: Why Do Wind Turbines Have Three Blades?

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1. It's centripetal for not centrifugal force
2. ....or, OR, we could go with sources of energy that are cost effective like coal, that are SO cost effective that they are profitable businesses that don't require government subsidies to hide their costs... Just a thought.
3. Why helicopter blades are not shaped like wind turbine blades? I mean, why aren't they thin at the tip, where the wind speed is higher, and widen up towards the center, to better cling to the slower wind speed?
4. 2:14-2:25 Oh My Jesus!! 😱
5. 0 mention of airflow around the blades with different numbers? Naw?
6. What about cyclorotors? What's their main drawback?
7. Why use horizontal wind turbines when you can use vertical ones?
   They have many advantages
8. Let's assume the three blade design is to kill more birds. Endangered species of birds. Now it all makes sense!
9. Hey Dumb-inic, It is centrifugal force. You "get it right" before trying to sound smart and make a fool of yourself. You can verify it in something called a dictionary.
10. This is even less accurate than some of their aeronautical stuff.
    
    Maybe a better question is 'Why does this crew come out with assertions like 'Why do Wind Turbines have three blades' when its a five second search to find WIndturbines with anything from 2 to multiple blades'?
11. 1) You say adding each blade adds torque, but you don't describe what makes a 4th blade marginal while a 3rd blade is not.
    2) Isn't the speed independent of the power generated? Can't we pick the speed of any turbine through gearing?
12. I guess he has never heard of feathering the blades.
    Single blade turbines or the fact that two bladed designs are cheaper and as fare as sound is concerned.... Fucking pussy!
    Too loud?!? Really!? (Sickening) :P
13. Centrifugal force doesn't exist. This is Inertia, a property of anything that has mass. If you're trying to turn in a car lets say, and you feel pushed to the outside of the turn, that's inertia resisting the change in direction.
14. Damn this guy is ignorant. Has nothing to do with weight of the blades. The tower forces are all due to the drag. Especially when the wind howls and the propeller effectively becomes a disk plane and why wind turbines are STOPPED at high wind speeds so they can reduce the forces on the tower. Otherwise when a tornado goes through the propeller effective area would blow over the tower. Has a lot to do with cost of the blades. Why 3? Has everything to do with natural frequencies causing fatigue. Why the competitors to the 3 blade design are the1 blade, 5 blade, and 7 blade designs, not the 2 or 4 blade designs. The problem with 5 and 7 blade designs is that the blades begin to interfere with each other. Gets back to the ~~ chord to gap ratio if you think about lifting efficiency. Decreases induced drag(yea), but decreases lift(boo), and increases drag(boo). If someone can figure out a balanced single blade design, three blade designs will vanish over night.
15. If Gillette got into the turbine business, would they use 8 blades?
16. Dude, you didn't explain anything. Saying "4 blades is less cost effective." just begs the question. Obviously, the answer to the original question is "other numbers are less cost effective". The REAL question is WHY N ≠ 3 (e.g. N = 4) is less cost effective than 3.
17. Well this was a shallow and useless video... I was expecting more details on turbulence or efficiency or something, but this just felt rushed.
18. If I don't reminder it wrong four blades and up aren't used because they cause too much turbulences which interfere with the other blades decreasing the energy extracted of the wind. So as you said it wouldn't be very cost/energy efficient.
19. More blades do not mean more power. Theoretically you can have the same power output with one or ten blades. The really relevant number is the sweep area of the blades (the area the blades cover in one rotation).
    Turbines with lesser blades have to spin faster for the same power output (you got that correct). However, spinning faster is usually considered a good thing. Firstly because a higher rotation speed means less torque (with constant power) and less torque means your generator and gear box becomes cheaper. Secondly imbalances e.g. due to wind shear become less dominant (with constant blade number).
    It is correct that faster means usually louder, but this is not the reason why turbines do not have two blades. Think about wind turbines offshore or in the desert. No one cares how loud they are, but they still have three blades most of the time.
    
    So turbines usually don't have four blades because you would need a fourth blades (they are expensive) for the same power output. Also the generator/gearbox would become more expensive.
    The two blades design is not preferred because of the imbalances it implies. Think e.g. of wind shear (wind speed increases the higher you get) and turbulence (fast local changes of wind speed). These imbalances do not cancel out with three blades, but become less of a problematic.
20. In the early 70's in the infantsy of large wind turbines: One of the factors that led to 3 bladed propellers was the fact the 2 and 4 bladed propellers were exceedingly hard on main shaft bearings. This was because the wind velocity differential between 100 feet (the propeller tip at the low end of the swing) and 300 feet (the propeller tip at the high end of the swing) would create enormous lateral stress on the main shaft bearing. The use of a three bladed propeller effectively neutralized this effect. All other factors aside, the three bladed propeller was the only configuration that would provide any degree of mechanical reliability in windmills that were large enough to be affected by (altitude) wind velocity differential.