I plan to remake this video at some point. It's a really shallow explanation. I simply did not have the skill and experience to make a longer video when this was released. I could crank this video out in a single day now. The subject definitely deserves a more in-depth explanation.

hey, engineering student of renewable energies here, the centrifugal force is not a major reason why the turbines usually have 3 instead of 2 blades. It is due to the fact that in different heights you have different wind speeds and having an even number of blades gives you periodic stress on the system, when the upper blade encouters the highest wind speeds the lower blade is receiving relatively slow winds additional to passing in front of the tower which disturbs additionally. this periodic torque stress will wear down the machine pretty quickly, thus we use 3. plus your notion about the the wrenches is entirely wrong, doubling the blades wont double the torque, adding more blades will decrease the speed needed to extract the energy from the wind. unbelievable you didn't caught that contradiction, those principal are mutually exclusive. be a good man of science and remake the video instead of just putting a half-arsed remark in the notes about it being just the "basics". It's not that you left out additional information it's that you are factually wrong about your explaination. your channel looks pretty promising if you are able to take constructive critizism seriously. pm me if you want some references or advice , cheers

quite shallow explaination why not 4 blades. did not explain why the additional power is small, you just stated it. but thats the important part no?

Ok, here's some real info for you - note I live in one of the world's largest wind turbine producing cities in China and do consultancy engineering for a few of the companies associated. A one bladed WT is actually the most efficient, this is due to the air having time to recover by the time the next sweep comes around, having done some aircraft wing turbulence stories you may be able to visualize that. Problem for one blade is balance and harmonics, but that's another story. 2 blade is still more efficient than 3 for exactly the same reason, But in the real world, 2 blades are also hard to balance and align exactly opposing each other and a big harmonic problem when they "shade" - shading is when the lower blade sweeps past the tower where there is no air flow. The loss of pressure when shading makes the blade flick forwards as the wind pressure on the blade stops momentarily. So simply put, one more blade, 3, is the minimal suitable for these factors. They are less disturbed by balance and shading issues which also helps to control harmonics. Note that 4 would suffer shading issues like 2 does, so 5 would be the next choice, and note that many car radiator cooling fans have 5 so they can mass produce thousands with larger tolerances.

I like your channel a lot, but this video misses the spot way too far. I have the strong impression sure you just read the english wikipedia page, which, for whatever reason, does not cover the root of the problem in comparsion to other wikipedia languages and masses of other articles on the web about the topic. Do you remember how three-phase electricity works and why it's magic? If the load is identical on all phases the fourth wire has zero current the other three equal out completely. The same principle applies to a three-blade turbine similarly: There is zero unbalance and much less vibration. The forces on the central axis are always straight and therefore three-blade turbines last longer both in the gearing as well as in the tower construction, are less noisy and have a smaller tendency to soar into big fatal movements like in the crash you show in the video (they're not fully resistant either as you video shows :-) ) PS: Initial construction cost-wise a two-blade design seems to be the real sweet spot and if you research a bit int cheap turbines for underdeveloped rural regions you will find a lot of two-blade designs. But in the long run three-blade designs are more cost-efficient due to the fundamental mathematical priciple (and not because of the sheer cost structure)

Great video. Looking forward to the next!

I would have preferred to have a more Technical Explanation of what the Advantages would be on 4 or even 6 Blade Turbine rather than just writing it off with Cost... i know Costs count, but the Technical aspect should be the primary aspect of the video. That said: will you be doing a Video on the "Vertical Axis Wind Turbines" soon? because in theory, they are a lot more efficient and cost effective than the classic Horizontal Axis Turbines, yet you don't see too many around yet... WHY???

More blades mean more "Solidity" (a factor of wind turbines). It is the area of the inscribed circle of the blades length divided by the frontal area of the blades as experienced from the axis of rotation. More blades would mean more solidity and this would block a large part of the airflow, lowering the effectiveness of the next turbine in the row. Also the effectiveness is more affected by the length of each wing as there is little to no torque at the base of each wing, while adding an extra wing would increase the rotational mass, the cost of the construction when a similar increase in weight and cost invested in wing length would have better performance! PS: Two blades have balancing issues as the height of the turbine oscillates, so will the torque from the wind and to make matter worst when one blade of a two blade turbine is at the top position the other blade is in front of the mast having no air flow at all, so both the rotating assembly would have a knock like imbalance when a blade passes the mast, AND the whole turbine would have a great oscillation from the oscillation of the torque transmitted to the mast! You're welcome!

Actualy that isn't the case. Two bladed turbines have problems with vibrations when pivoting when wind is changing course.

a nice simple video, but you eliminated a 4-blade design based on "will only provide marginally more performance" any reference for that? also, if sound is the issue, does a 2-blade design make sense in off-shore wind farms?

because it looks like the Mercedes logo and it looks cool

I really like your channel but was rather disappointed about this particular video. When you change the number of blades many other variables can also be changed to compensate for a fixed say energy output. You only gave one argument each but didn't properly argue why everything else stays the same. For the four blade you say the cost increases at a marginal increase in the performance, but you could also make each blade smaller and in particular all your arguments for the two blade variant apply (less speed and less noise) which would even make the four blade variant look better.

Are you sure it wouldn't be better to have 3.14... blades ? How, I don't care...

I passed one of these blades on the highway once. It took a long time to pass it. These things are so huge; when you are right next to it, it is unbelievable.

I don't get why people complain so much about engineering videos on internet, taking everything down to the "wrong" details. This is not a college lesson, it's meant for people with no background to take some interest, and to actually learn something in an easy way. I think the way he explains the basics in 3 minutes is perfect.

This all makes sense but you could make the exact same argument comparing 3, 4, and 5 blade designs and conclude that 4 is the best.

At least the comment section was informative, so the video wasn't a complete waste of time.

Curiosity says:Theoretically, a one-bladed turbine is the most aerodynamically efficient configuration. However, it is not very practical because of stability problems. Turbines with two blades offer the next best design, but are affected by a wobbling phenomenon similar to gyroscopic precession. Since a wind turbine must always face into the wind, the blades will have to change their direction vertically when there is a shift in wind direction. This is referred to as yawing. In the case of a two-bladed system, when the blades are vertical (i.e., in line with the tower and the axis of rotation) there is very little resistance to the yawing motion. But when the two blades are in the horizontal position, the blades span a greater distance from the axis of rotation and so experience maximum resistance to yawing (notice how a spinning figure skater slows down when they bring their arms away from their body. As a result, the yawing motion starts and stops twice per revolution, and this leads to stress on the turbine due to blade chattering. On the other hand, a turbine with three blades has very little vibration or chatter. This is because when one blade is in the horizontal position, its resistance to the yaw force is counter-balanced by the two other blades. So, a three-bladed turbine represents the best combination of high rotational speed and minimum stress.

Q: Why Do Wind Turbines Have Three Blades ? A: They all love Mercedes Benz cars.

When was kid, I used to build blades (from wood) and get them in garden for fun. Was aiming for ~80 (early)-100 (later) cm long (4,5-5 cm x 1,5 cm dimension, used knife to cut wood from both sides to get better wind pick-up for front side and reduce weight for back side - felt fragile but was sturdy enough for many months) blade with some 105-110 g weight each + central wood piece to hold that all. 3-blade version was lightest but also not great at picking up slow wind (since at ground level difference between up and down can be big with all turbulence etc.). 5-blade version I found perfect combination (for that size) - it picked up speed quickly and turned smooth (and looked more cool when was not spinning, hahaha). And same time at strong winds auto-turned sideways to slow down (design by accident). (still had to take down when storms were coming). Good memories.

Wonderful, as always.

What is the marginal increase in performance by adding a 4th blade? How do you know it's marginal?

Why the hell there is a lot of hating comments on this channel? ,what is wrong with you people ? ,this guy tries to educate the public with an interesting and easy way if you don't like this kind of subjects just don't watch the videos it's that simple ,hey man don't listen to them and keep the good work ,best regards from Palestine

This is a great video. I think it adequately explains why a three-bladed wind turbine is preferable over a four-bladed one. The primary reason that two-bladed wind turbines are not common, however, is that the rotation of a two-bladed rotor is unstable.Any three-dimensional object, with three different moments of inertia, has one unstable axis of rotation. If you're not familiar with moments of inertia, think of it as mass distribution. A cube is identical in all dimensions, and therefore, has three identical mass distributions in all directions. As a result, a cube does not have an unstable axis of rotation.Your smartphone, however, has three different dimensions; the largest is the height, the shortest is the thickness, and the intermediate dimension is the width. Try throwing your phone into the air three times while giving it a spin. Each time, get it to rotate about a different axis. You will notice that it rotates without any surprises when spinning about its height axis and its thickness axis.However, you will also notice that it is impossible to actually spin your phone such that it will maintain its rotation about its width axis. No matter how precise your throw is, the phone will start out by rotating about its width axis, but the rotation will soon become unstable and the phone will begin rotating about the remaining two axes.This phenomenon is call the "intermediate axis theorem", and it is difficult to explain verbally. Those that are interested can lookup Euler's equations of motion for a mathematical explanation. See the following video for a visual explanation:kzfaq.info/get/bejne/Y7mZacyDsZuqmmx7.htmlow does this relate to a two-bladed wind turbine? The rotating components in a wind turbine are the rotor (which includes the blades and the hub) and the main driveshaft. If you draw a bounding box around a two-bladed rotor and its shaft, such that the box captures the outermost dimensions of this subsystem, you will notice that the shape of the bounding box is identical to the shape of your smartphone. It has a large height, a small thickness, and an intermediate width. In other words, the mass of the two-bladed subsystem is distributed differently in all three dimensions.Adding a third blade (or more) eliminates this instability problem, since the additional blades make the mass distribution identical in two out of three dimensions. Imagine taking your iPhone and reshaping it such that its width is now equal to its height. This change in geometry will eliminate the intermediate axis, and therefore, will eliminate the effect of the "intermediate axis theorem".

Aaaand another video where the question isn't answered.

0:19 Was one of those just photoshopped in? XD

The major explanation for this fact isn't shown in the video nor the comments here. The point is that three-bladed turbines may achieve the best power coefficient (Cp) which is above 0.5 and below the Betz Limit (maximum efficiency ANY device may reach when converting wind energy -- 59.3%). The thing about balance and mechanical stress is also true, although not the main reasons for the widespread use of three-bladed turbines. For further info just google: Curve Cp vs. blade number.

Fantastically interesting. My mum worked for the old wind energy group in the UK way back. They made 2 blade turbines. Mum left before they became obselete but the point abt long term stress on the structure from yawing is super interesting to note!

You forgot to mention that two blades results in mechanical fatigue ant the hub due to standing waves produced when one blade passes into the shadow of the tower. Three blades cancel any standing waves by splitting the energy to the opposite two blades thereby canceling any resonance.

How about which is better: a straight propeller design that has to turn to face into the wind OR a spiral design that always has a portion of it always facing into the wind?

Another aspect of the explanation is 3 blades counteract EACH OTHER during changes in yaw (yaw = directional aim for the entire rotor), whereas 2 blades transmit the forces resulting from changing directions to the bearings, tower, etc. A two-bladed rotor changes direction easily when vertical, and hard when horizontal. Old-timers call the resulting percussive hammering "yaw judders" or "chopping around the corner". That's why 3 blades run smooth, while 2 blades will shake the machine apart. And the reason you only need a few slender blades, rather than filling the whole circle with blades, is they go so fast that it doesn't take very much blade to extract all the available power from the airstream.. Many attempts at two-bladed turbines use teetering hubs with the rotor downwind of the tower, to decouple the yaw judders from the bearings, have been tried, but few, if any, have proven to be a good solution. As the video points out, two-bladers go just a bit too fast for effective noise control. Because two-bladers go too fast AND shake themselves apart, the extra speed makes the shaking that much worse. When you want machinery to last many years, smooth operation is key.

There's some important aerodynamic reasons missing from here. There's a tradeoff between maximum power that can be generated throughout a range of wind speeds. As the number of blades goes up, the max power increases, but the range of wind speeds over which you can achieve that drops. Three blades is ideal because a wind turbine needs to be efficient for a range of speeds.

So does having more blades mean the turbine will perform better? Ignoring costs for a moment, I just want to make sure I understood this properly.

What about no blades?

I just happened to stumble across this channel while looking at videos of the engine swap I'm doing in my car. I love it!!!! Very informational without being crazy long. You, sir, just got another subscriber!

Regardless of what you think about the video, it does raise the question of "why." That is always good!

Great video thank you. Always wondered why they did not have more blades.

This is the noise a wind turbine makes "Shows us a clip that shows how quiet they are*

I don't care at all why do they have three blades, but Real Engineering videos are so interesting so I will watch it anyway. There is always a lot of interesting peculiarities described in detail but very understandable.

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.

Just look and learn much more about it from Avasva .

every single argument you state that advantages 3-blade vs. 2-blade, can also be used *as is* for the 4-blade vs. 3-blade argument. Yet you discard the 4-blade design with a quick handwave blurb that contains NO quantitative data. i.e. You actually do NOT state why turbines have three blades.

Andrew Gerrad the president of the European Wind Energy Association, said in one conference speech that 3 bladed wind turbines are the result of human preference. 2 blade wind turbine would be way cheaper to move from one place to another. You could put it together in a factory and ship it to the site in one piece. When with 3 blade system you need to install the blades on site and that is really hard and expensive. But for some strange reason people hate how 2 blade turbine look like. Gerrad also said that now that offshore wind turbines are getting more common, wind turbine engineers don't need to think so much about the looks of the turbine. Sorry for my english I'm from Finland.

The example used to show what happens when there is a brake failure, is actually from my country, I lived not far from that turbine when it exploded.

BUT WHAT ABOUT 100 BLADES AT 500 METERS LONG EACH BLADE

This one is very incomplete.

Very good video. Will use this in future projects.

I teach economics, and am thinking of using this video in class. You stumble on a bunch of economic concepts that I can point to and say "Here it is in real life." The economic question I have (that perhaps engineering can answer) is: Once the initial manufacturing cost is sunk (irretrievable), won't the 4-bladed turbine last longer due to less wear-and-tear? (The reverse of your argument against the 2-blade) Downside: The total cost to build 4-blade will be "hundreds of thousands of dollars" more. There will be additional costs to make the structure sturdy enough to carry the additional weight load. There will also be the cost to re-design, re-engineer, and build the 4-blade unit. Upside: There is an increase in efficiency... small, but measurable. There will be a longer product life due to less wear-and-tear. There will be reduced maintenance costs due to slower moving mechanical parts. So, there will be a greater initial (sunk) cost. However, there will be a greater long-term output, lower maintenance costs, and a longer overall life... leading to potentially greater profit. Longer term to be sure, but Turbines are not get-rich-quick operations. All this assumes that the 4-blade will have a longer productive life than a 3 blade. With this in mind, does the engineering match the economics? Will the 4-blade unit as I describe it last significantly longer? Or am I mis-stating the assumption about "wear-and-tear?" Thanks mucho!!

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.

not happy with this explanation

Marcellus Jacobs is the engineer who figured out the three bladed propeller system for wind generators back in the 1930s. Look it up. His successful basic design is the still the one that exists today in the many patented improvements. No one needs to reinvent the wheel. It's still the gold standard for ANYTHING wind generated.

I am glad you feel the need to talk about renewables, but PLEASE know your subject before telling the world how it is. I hope you can learn more about the subject and come back with better reasoning. All the best

Q: Why Do Wind Turbines Have Three Blades? A: It's better than other numbers of blades, thanks for watching

3 blades look better. That's why. the end.

It's also about reducing vibration. With an even number of blades, as in the 2-bladed design, when the lower blade passes by the tower it is masked from the wind. This is at the exact time that the upper blade is receiving its full amount of wind. This effect will set up vibration in the tower. With an odd number of blades, as with the 3-bladed design, there is not the same vibration effect as when the lower blade is masked by the tower there are still 2 more in the airflow to smooth out the effect.

Very awesome to see that the first scene of this video is at the Zaanse Schans in the Netherlands, an area where I grew up nearby. I biked past this view daily for nearly 6 years.

Wasn't very informative, I expected some physics of airflows and such

it felt as if I should be getting smarter, and yet i haven't learned a thing... =/

I learned a lot about this interesting subject from your video and from the many technical comments it spawned. Thanks.

Cool we have dozens of these in a small island off the coast of Anchorage and they are beautiful!

There are also one-bladed designs available!

please make a video explaining why centrifugal force doesn't actually exist. Interesting topic.

I don't mind the noise, it's kind of metronomic and soothing. The speed regulation also helps maintain the cycles of power generated to comply with the national grid. Good video dude, keep up the great work. Loved your Eddystone light house video.

It just occurred to me, that there is something distinctly off with that theory that 3 blades would help reduce the stresses that occur from one blade getting no wind when it passes the pole, or mast or tower or whatever it is and its name is, at the lowest point of the circle these blades describe, and that the idea that a 3-bladed design would involve a reduction in the distortion of balance (and with that extra vibrations and extra stresses that play onto several parts) simply can't be right. When you think about it, with a 3-blade setup, there are TWO blades getting full wind whilst one gets none each time, so now 2 put up full force against that one blade that produces less our none for a short while, instead of the one active blade that is oriented oppositive of the one that momentarily is inacive each time as it happens in the 2-blade design. The relative stresses are theoretically up to twice as big! I think it would be fair to conclude: 1 it may have got more to do with other variations and effects that might cause vibration, trembling and lack of balance, such as the fact that even over a distance of dozens of meters the force/speed of the wind might vary; 2 it might have got more to do with the actual surface of the blades (seems that although too long blades come with the problem of too high tip speed in up to several hundred kilometers/hour, blades that are constructed in a wider fashion like was done with the old (old-fashioned) wooden windmills, for some reason ALSO again is not favored by designers); 3 to overcome or at least significantly reduce the stress caused by the unbalance coming from one blade putting up no counter force for a short while each time, you would at least need 5 blades, and preferably even seven. In a setup that sports 5 blades, the blade that momentarily stops producing force (and therewith counterweight relative to the other blade or blades) is always accompanied by TWO other blades that ARE ACTIVE AT ITS OWN SIDE (halve if you will) of the axis so a construction like this puts up most of the oppositive forces that out takes to balance the two remaining active blades that are on the other side of the central point of rotation. As opposed to there being two active blades OPPOSITE to it on the axis and NONE on its own side in the 3-blade setup. This however gradually becomes much more difficult to mount to the central axis of the thing, supposedly might be pricier as there is some loss simply related to the scaling difference versus the effective surface created. And, ALL blades have a small part, near where they are mounted, where they catch little or no wind anyway, as the generator housing also blocks the wind

your info is far too generalist and you are throwing in your own assumptions. this my friend is what you call a token effort.

Those dont sound too noisy.

Nice presentation. Right to the point.

Curtiss-Wright figured this out late in the war, when incredibly large high performance piston engines were being built, just before the Jet Age. Too many blades, and you have a flywheel, with blades getting in the way...this isn't too bad for a low RPM water pumping mill. But at the other end? Even very small differences in weight will cause a two bladed design to tear itself right out of its motor mounts. This is why they went to three blades. And the old "Jacobs" windmills that were common in Rural USA before the grid also used the far superior three blade design.

0:22 When you get lost as a white boy in da hood.

Awesome, subscribed!

Good video, straight to the point

Here's the real explanation, from noted expert Mick Sagrillo: "When the blades of a two blade rotor are lined up vertically, they offer little resistance to yawing motion. However, when the blades move one quarter of a turn and are in a horizontal position, they exert maximum resistance to yawing. This continuous shifting of resistance to yaw jerks the wind generator as it hunts the wind. These vibrations eventually degrade the entire system. The inherent imbalance of a two blade rotor is totally eliminated by adding a third blade."

And that is how the wind destroys a wind turbine.

Your explanation of the problem with a 4 blade design 'adding a 4th blade provides such a marginal increase in performance' completely fudges the point. the answer to the question you pose about why turbines have 3 blades hangs on the question of why the increase is marginal and how marginal. Why does such as a steam turbine have 100's of blades. why is the goldilocks zone completely different in that scenario? The graph at 1:18 shows absolutely nothing. The turbine you showed failing, failed because the blade hit the stand. which is probably the most important factor, together with height in limiting the blade length, which in turn is why we use 3 blades not 2. Your videos are normally quite informative. But this is just, well nice looking garbage.

Fantastic insight. and in under 3min. brilliant!

Thx for this video cos I love wind turbines

There is no such thing as centrifugal force - there is only a centripetal force. Get it right "real" engineering.

we gonna talk about how centrifugal force is not a real thing or?

I really appreciate your videos, very interesting stuff! Currently studying for my bachelor's in mechanical engineering.

A video that explains Good Engineering ... The best solution considering time and cost

I liked this video, until he wished us happy earth day.

Come on. You can do better than this video

A girl once asked me this question now I can answer her. Thanks man. Keep up the great work.

Two blades wind turbines typically require a 'teetering hub' which is more of an engineering challenge. There's a shadow effect each time the blade passes the tower that creates eccentric forces that are much more prominent in a two blade design than a three blade. Larger two bladed concepts with more mass have tried to eliminate the need for a teetering hub, but they're still essentially concepts, with nothing in serial manufacture. Two bladed designs are also perceived as being more visually intrusive to the human eye. The reason for three blades is down to the aerodynamics of rotor solidity. The modern three bladed wind turbine is very aerodynamically efficient, it's mathematically the most optimum design for a horizontal axis wind turbine that needs to create high speed and relatively low torque and the design that will come closest to the Betz limit. Read up on Rotor Solidity and Betz.

CENTRIFUGAL FORCE ISN'T A REAL FORCE, pickup a physics book mr "Real Engineering".

Perhaps look at balancing issues so as to minimize vibration. Cost-effective manufacturing likes modular construction. Consider blades: Building with matched weights and centers of mass along the long axes of individual blades is relatively straightforward. Locating the CoM offset from the nominal axis consistently is less easy. Thus, two blade props are normally manufactured as a single unit so that balancing can be done in the shop in controlled conditions. Three blade configuration does not require such careful avoidance of induced torsional vibrations. Thus, shipping lengths are half.

The biggest benefit to the three blades is the reduction in vibrations when the wind quickly changes direction (as it usually does). When the two blade design is vertical it can change direction very quickly and easily. When both blades are horizontal it changes direction very reluctantly. Thus you have a vibration problem when the blades quickly go from the horizontal position to the vertical position. With the three blade system the blades are never exactly opposite each other and this helps to minimize the vibrations. I have had a 3 blade wind generator up for almost 18 years now and I watch it in high wind conditions. I also fly smaller aircrafts with only one or two seats and there again the three blade system is better.

I have just seen your (airplane) videos and now I can't stop to see your videos. They are very good researched!

you are legitimately my favorite channel.

In addition the effects of wind shear and tower Shadow further reenforce the three blade designs, impact of wind speed extracted by the blades varies along its axis, (azimuthal angle), then a blade is horizontal about its hub axis, it extracts little to no wind speed, but its compensated by the combination of the angles of the other blades, when the blade is facing downwards, the effect of the tower is much evident, redirecting the angles of wind speed thereby reducing the amount of wind energy extracted by the blades, again, the position of the other blades compensate for this in creating enough centrifugal force. Longer blades do provide more extraction of wind energy but also increases the effects of tower Shadow and wind shear in the wind turbine. Two blade system would also increase variation or flickers in the total energy extracted. In four different positions, the blades would require 3 times the wind speed to maintain rotation which would also increase flickers in power output. Three blade systems are the best because at each blades azimuthal angle, the other two blades compensate effectively for the ineffective extraction of wind energy of the blade... You can check in here for more details: www.ijsgce.com/index.php?m=content&c=index&a=show&catid=86&id=547

One little thing is forgotten: The more blades the lower the induced drag. Ref.: Prandtl, Betz. 1926. It's "hidden" in the tip loss. But mainly- absolute correct, it's a cost and optimization issue.

That was a good video. It was short and informal.

I live near the SoCal beach rail. At night there is a freight train that transports a lot of these blades. They are huge and are set onto special rigs that cover 2 train cars.

This is gives a complete answer without any questions left behind. ☺️

Hi, i took a class in modern wind turbine physics for a semester (about five years ago) and a another factor for three wings vs. two wings I remember is, that the tower is messing with the down stream wind speed. Basically, on a two winged wind turbine, the load forced on the upper wing will be much* higher compared to the lower wing when that one is in front of the tower. It is also higher compared to the sum of the two upper wings of a three winged turbine The effect of this would be a higher rocking of the turbine for a two winged turbine than a three winged turbine. Which can cause higher wear and tear for a two winged wind turbine.

Thanks for sharing this...it really continues the great universal phenomenon, "less is more''!

I looked into this a few years ago, and the mathematics was clear; the most efficient design is a single blade with a counterweight. I still find this counter-intuitive. For me the wind-pump multiple blades design makes sense. And why do turbines, which perform the exact-same function in reverse (i.e. they pull wind instead of being pushed) have hundreds of blades?

Really authentic content. This is just the kind of channel I will want to browse. Can you guys make a quick video of how does a quadcopter works? The physics behind the stabilization, turns etc.

No matter the number of blades, if you spin a given generator at a given speed, it will generate the same amount of energy. Spinning said given generator faster generates more energy. Speed matters. Also, the blades can be 'feathered' during high wind speeds, so that the windmill isn't damaged or destroyed. Simple physics folks. You don't need to be an electrical engineer or a genius to understand this. The speed of a windmill blade is like a propeller. The tip is moving much faster that the hub mount. Sound is a main reason that they aren't usually constructed near where people live.

Wonderful..keep up the good work .. and the video of the turbine brake failure was really cool