The Physics of Windmill Design

[@JohnSmith-kj2od]

I'm not gonna lie, This hasn't ever occured to me and don't think it would ever have without this video

[@Kapin05]

@@dontreadprofile1834 OK

[@drGigg]

You lie a lot?

[@mattmarzula]

Are you working or do you plan on working in an engineer field dealing with the construction of wind turbines? Because unless you are, this information is superfluous. Additionally, if you are planning to join that field, this concept didn't occur to you, and you're over the age of 12... Cash your chips in kid. You're only losing at this game.

[@sponge1234ify]

@@mattmarzula but what if he wants to know because... he's just curious? Can't a man question their world, no matter how irrelevant it is in their path of life?

[@michaelduffy3866]

@@sponge1234ify Amen

[@Squantle]

I’m scared for that bass player, forever trapped in the recording studio playing the same riff.

[@stevenutter3614]

I'm scared for your fingers, forever trapped in your mom's basement typing the same comment.

[@Synthetica9]

I fear not the bass player who has practiced 10,000 riffs once, but I fear the bass player who has practiced one riff 10,000 times.

[@joeyhardin5903]

@@stevenutter3614 im bouta end this mans whole career

[@Squantle]

@@stevenutter3614 bad day?

[@DC-cx9ye]

These chats are getting wholesome now

[@jorndielen1568]

Fun fact: now a days a lot of wind mills come with serrations. Which are tinny triangle like shapes put in rows on the back side of the blade to reduce the noise the blade creates from cutting true the wind. The idea is based of the wings of an owl. I work as a techician on these things so further questions are welcome :)

[@KanishkaWijesekara]

In Texas we saw windmills freeze a few weeks ago. Was it the electrical equipment inside the hub that malfunctioned or did the spokes just stopped spinning after freezing? How can windmills be freeze proofed in future?

[@tylerdurden3722]

Aircraft wings damage signicantly faster when flying low. In my mind, wind turbine blades are like aircraft wings flying very low, 24/7. What witchcraft goes into those blades to make them withstand that kind of abuse?

[@jorndielen1568]

@@KanishkaWijesekara normally temperatures like that don't occure there so the turbines build are, let's say, "normal" models. Usually when turbines are build in areas where such low temperatures are present they use "Cold climate" types. They have heating everywhere (including in the blades), use special metal alloys that can withstand temperatures up to - 40°C and special grease types as wel.

[@RhodokTribesman]

@@KanishkaWijesekara A ton of places winterproof their wind turbines (turbines are used in arctic research bases). Texas' energy problem was NOT wind's fault lmao, gas lines froze and so did turbines; Texas did not listen to suggestions after 2011 and so the non-winterized energy grid was cripples

[@jorndielen1568]

@@tylerdurden3722 I don't know for aircraft but wind turbine blades are usually made to be very resiliant. Especially for bending since the force on the "wings" are spread over a bigger surface. I don't know for other companies, but at ours the blades are made by taking glass Fibre mats in a mold and vacuum impregnation them with resin to make them strong but still very bendable.

[@EEVblog]

In theory and simulations there are designs that use ducting around the blades and other mechanisms that claim to have beat Betz's Law. But in practice none of them have worked. Many wind turbine startups have tried and wasted a lot of investor dollars. Commercial wind turbines usually cap out at around 80% of Betz's law due to the hubs and other design factors.

[@SovereignStatesman]

That's because they're focused on mechanical efficiency, and not ECONOMIC.

[@Terra_Lopez]

Interesting, thanks!

[@Rotaretilbo]

@@jimbob1353 I guess it would be more accurate to say that they focused on the pursuit of greater mechanical efficiency to the exclusion of considering economic efficiency. Rather than settling for a suitably efficient design that already exists, they continued pouring money into reaching for an even more mechanically efficient design that ultimately proved out of reach. Not to say that is a bad thing. That's basically how innovation works: pursuit of of new, better things that might not turn out, even if it is more immediately and securely profitable to settle for existing designs.

[@DarkJokingDragonSP]

@@jimbob1353 Let's say you have a design that is 100% efficient, with a core build out of gold that need replacement every three months. Let's say the alternative is made from steel and aluminium, is 75% efficient and needs replacement every two years. Three mills of the first design provide as much energy as four of the second design. In the first option you need to replace replace a core on average every month, while in the second case every six months. Ignoring the fact that gold is way more expensive compared to steel/aluminium, it would still be six times more expensive to go for three of the first design compared to four of the second.

[@bronzedivision]

@EEVblog I do wish you'd actually apply the baloney detection kit, rather then get swept away by the marketing hype. Fact is, everything that's true about the small energy schemes you debunk is also true of renewable energy in general. Just on a bigger more traumatic scale. It's the modern day alchemy, a hopeless idea that has no hope of fruition. That's why the only future for energy is nuclear power, the only thing we're 'debating' on this issue is how much everyone suffers before doing what was always the one scientifically valid option anyway.

[@filippoorologio6777]

watched these guys since middle school, and they haven't changed much.

[@l1mbo69]

Except that they upload a lot less now

[@SantoLucasST]

Seems like you're getting younger, that or you went to high school when you were 4 or something

[@aresorum]

I watched these guys when I was an adult, and I still am, thus I may or may not have watched them for a long time.

[@gaeb-hd4lf]

guys?

[@familyguydominicdiesel4839]

There is only ONE guy

[@ImKibitz]

Never thought about this, cool video!

[@trustedjoy4960]

woah didn't expect your comment to be the first i see

[@deveshsingh4214]

Kibitz learning this for Satisfactory and Dyson sphere.

[@trustedjoy4960]

@@deveshsingh4214 Ye lol

[@anirbanchatterjee4794]

Hi, I'm Kibitz, and welcome to Satisfactory. Today we learn about windmills. Goes on to create 100 bejileon watts of nuclear power.

[@tunatutuncu2221]

Hey Kibz!

[@physicsfun]

I love a video that answers questions I only know I had as I watch the video- noticing lately smaller turbines along the highway being replaced by larger ones.

[@Freakwave26]

That is why I love this channel. There are always these little things in life where I ask myself "why is it that way" or "how does it work" but the thought doesn't stick long enough to actually do some research. And then a video like this pops up and enlightens me on one of those things i've always wondered about.

[@trumanhw]

WINDMILLS .... make sense..?? Even though NUCLEAR exists..? We'll just use the energy from reeaaaallly really far nuclear reactions at 513 light seconds away ... ey? Hmmmk.

[@theboulder942]

I read it as "Why don't windmills have snails" at first and I was granted a glimpse into a much brighter timeline

[@mattwhaley1865]

One where you aren't beat by a blind girl?

[@Rosa-cr7qc]

@@mattwhaley1865 bad day?

[@mattwhaley1865]

@@Rosa-cr7qc have you never watched avatar the last airbender?

[@saali6860]

“What kind of music do you like?” “I’m a huge metal fan”

[@LuaanTi]

Actually, not made out of metal :P

[@saali6860]

What is? Metal? Of course not it's a genre of music...

[@hananas2]

​@@LuaanTi and not a fan 😆

[@MotoCat91]

I'd love to see a follow up to this comparing the 3 bladed direction windmill to those smaller profile helical ones which work in all directions

[@dlahouss]

Don't the 3-blade ones turn, thus working in "all directions"?

[@TimLF]

There are major difficulties in protecting the Darrieus turbine from extreme wind conditions and in making it self-starting. en.wikipedia.org/wiki/Darrieus_wind_turbine

[@groundzero_-lm4md]

Don't those helical ones work less well due to the blades needing to fight the wind on their way back? The 3 bladed ones can also turn like the turret of a tank, letting them adapt to wind direction.

[@HJSDGCE]

I actually did some research about this. Long story short; helical wind turbines aren't that efficient. It has a slower rotational speed, thus producing less power per square meter. It does come with advantages however such as being able to work at any direction of wind without needing to turn, taking up less space and have a lower minimum wind speed to work.

[@SovereignStatesman]

Motocat: Yeah at about 3% efficiency. There's no problem with putting a turbine on a rotating shaft; just mount the turbine on a tire-rim and axle from a junk car, and mount the generator on the front as a counterweight.

[@isaach1447]

Not to mention the shear force being applied to the tower. If you replaced the blades with sails, The tower would have to be massive to support the horizontal force being applied to the nacelle.🌬

[@MrBlaBlaCook]

Isnt the force equal to energy made? From the video it seemed to me as if the force is still the same (or even bigger with small, fast turning blades). Is it? The sails would be also turning and letting wind through.

[@isaach1447]

@@MrBlaBlaCook you would still have to limit the speed of the sails due to centripetal forces. Therefore you would be relying on the sails to push harder, not faster, and then take advantage of the additional force through internal gearing.

[@TimurIskhodzhanov]

@@MrBlaBlaCook No. In the extreme example of big sales that stop the wind entirely, the energy made will be zero while force applied will be high. Power = Force x Velocity.

[@CensoredUsername_]

That force really doesn't change. For the same amount of energy extracted from the same area, the wind will need to be slowed down an equal amount. Which requires a net force of equal magnitude.

[@Canadian_Ry]

Isn't it supposed to be a 'wind turbine' as opposed to a wind mill? I suppose 'rotating bladed wind energy capture device' isn't very relatable.

[@Khaim.m]

No it's a wind mill. By law, anything that captures wind must have a tiny millstone and a supply of grain to grind. (This is a joke.)

[@craigwall9536]

Consistency is the hobgoblin of small minds.

[@zarehs]

@@craigwall9536 In general yeah! But in this case - its an educational video needs be correct. Fortunately its mentionrd in this comment section

[@hedgehog3180]

In Denmark they're called wind mills and I feel like we have the final word in this.

[@Lefers94]

@@hedgehog3180 do you? As a german, i would relegate all windmill related duties to the dutch. But maybe im wrong.

[@flupoop]

I have a master's in energy engineering but the fact about the rotation speed was new to me. You never run out of learning. Thanks.

[@phantomhck]

300 ft turbines have larger blades, 400ft turbines have smaller. It depends how close to water they are. The upper third is the main wind generator but puts an enormous stress on the supporting tower.

[@pablogriswold421]

Another way to think of it without the ball and sliding wedge analogy is just that faster wind has a higher reynolds number as it passes over the blades, meaning that its inertia is comparatively more dominant over the viscous forces. Very inertial flow wouldn't pick up any rotation, and minimizing the viscous effect also reduces loss. One last thing is that, considering the blades to be airfoils, they have a coefficient of lift and coefficient of drag in the radial direction, the ratio of which determines the steady-state angle of attack. With low Cd, you get a low angle of attack, which means that the turbine has to spin quickly at a given wind speed to be in equilibrium. So low-drag, high-efficiency turbines are designed to spin fast!

[@utetopia1620]

This is something you learn only when you do a PhD in energy engineering

[@IFearlessINinja]

It's just a fancy way to show the work done on air, so it feels like something I should have seen before too. I like the explanation a lot!

[@rosepinkskyblue]

Maybe this is why they made fun of Howard No offence I’m just building on the phd joke

[@yeyo101]

Teacher: there are no stupid questions Student: why don’t windmills have sails? Teacher : bill please don’t ask stupid questions

[@schmidt403]

Last semester I had a month-long freshman engineering project where we investigated all kinds of aspects of windmill design. My team struggled to understand some of the results of our measurements, and this video was a major epiphany moment for me. For instance, we found that power generation didn't necessarily scale with blade count - a medium number of blades generated the most power, and also allowed for a faster windspeed through them. We figured this had something to do with turbulence, but this video really put it all together for me. I wish I had seen this last semester!

[@MindLaboratory]

Also, just basic engineering - the less material you can use to get the job done, the better. These blades are already enormous, difficult to move around, extremely heavy, and expensive.

[@romaindubray2325]

That is a terrible rule of thumb for anything that is built to last. Building more robust might mean higher upfront costs, but could also mean lower maintenance and risk of failure down the line.

[@jonathanodude6660]

@@romaindubray2325 ? there has been no issues with the longevity of windmills. their "difficult to move around" status and the fact that theyre designed to work in heavy wind means that they arent going to have many issues short of a natural disaster or coordinated effort to destroy them.

[@romaindubray2325]

@@jonathanodude6660 Didn't you just agree with me ?

[@jonathanodude6660]

@@romaindubray2325 you said building with less material is a terrible rule of thumb. i said that even though windmills were designed like that, it hasnt caused the issues you mentioned. also its good for reducing waste.

[@GeoffCostanza]

@@jonathanodude6660 windmills only last 20 years, and are extremely difficult and energy intensive to recycle, so they are quickly filling up landfills

[@MordecaiV]

I appreciate that you have to vastly simplify to get these across in a short time, but another design element that affects the design is the designed wind speed range. Lower cut-in and lower operating wind favors a higher blade count. This is why 'old west' homestead water pump windmills are multi-bladed with a 'solidity' of around 60-80%. They are optimized not for peak power, but low speed wind operation and better torque. Source: Graduate Level Wind power design course at the Technion in Haifa, Israel.

[@schipe]

Old west windmills also didn't have cfd optimized design. The low ar makes me curious, why was it ideal? Maybe just for durability and easier rotation to wind angle?

[@MordecaiV]

@@schipe I assume you mean low disk area by ar. I think the main thing keeping them smallish was a combination of cost, weight, and being only large enough to suit the purpose of moderate power needs (pumping a well) vs general purpose power generation. Larger would not only cost more, but in most cases would only result in wasted water. Also, keeping the solidity high while minimizing the starting inertia (both helpful for low cut-in speeds and intermittent wind) helps drive you toward smaller designs.

[@schipe]

@@MordecaiV Sorry, i meant aspect ratio. For the same force, you can use longer narrower blades. I think as you mentioned, it most definitely comes down to structural strength, longevity. The larger the radius, the more stress you put on the disc and the bearings.

[@stephenspackman5573]

@@MordecaiV I was told they were prefabricated and sold by mail order, which would limit size.

[@PaulPaulPaulson]

Beware: After watching this video, you might get spam mails with subject "enlarge your windmill"

[@Mike__B]

As long as it's all natural I'm fine with it

[@sponge1234ify]

@@Mike__B where may i find this coveted All-natural Windmill?

[@KangJangkrik]

Yeah confirmed exist, but with different subject. More like "Windmill installation discount"

[@jliller]

"After watching this video, you might get spam mails with subject 'enlarge your windmill'" That would blow.

[@ChadEichhorn]

As homework in my Computational Fluid Dynamics class, we had to determine what percentage of the wind's energy was extracted by a provided modern windmill design as we altered the number of blades. Everyone thought their results were wrong - 3 bladed windmills were notably less efficient than 4 bladed ones, which were a tiny bit less efficient than 5 bladed ones (efficiency started falling past 5 blades). If our results were correct, why did we only use 3 bladed windmills in practice? The answer, our professor explained, was cost-benefit analysis. Sure you could get more energy out of a 4 or 5 bladed windmill, but the blades cost a lot of money. Someone determined that for the lifetime of a windmill, the cost of the 4th blade wasn't recovered by the additional energy gained, and so we only see 3 bladed ones.

[@nachtegaelw5389]

Do you know how long modern blades tend to last? Just curious! They seem like they’d be hard to replace since the towers are so tall! Also, do you know how they figure out how to space windmills when a bunch are in the same area?

[@w0ttheh3ll]

@@nachtegaelw5389 the blades typically last as long as the rest of the installation, 20 to 30 years. if a blade needs to be replaced (e.g. due to unexpectedly high abrasion at the leading edge, failure of lightning protection or manufacturing defects) that's a major economic setback. Blades are inspected regularly by climbers or helis and can also receive (limited) maintenance.

[@oc-steve]

There another video, possibly by Real Engineering, that goes over number of blades

[@CensoredUsername_]

Yep, it's an amusing argument. Four-bladed turbines would be more efficient than three-blade turbines. But four 3-blade turbines significantly outperform three 4-blade turbines, enough to pay for the extra tower and nacelle/generator over their lifetime.

[@TheScienceBiome]

Its always hype when Minutephysics uploads

[@shashwatpandey1371]

I loved that block & ball illustration, very accurately captures the reason for specific shape of the blade! 💯

[@JAzzWoods-ik4vv]

Bass riff is in 5/4 and this is the first time I’ve seen someone talk about in the comments. Interesting

[@rfldss89]

Wait, but pelton turbines are most efficient when they capture all the kinetic energy of the fluid, why isn't it the same for wind mills?

[@feryth]

The fluid gets out of the way due to gravity, air can't do that

[@eolyas1664]

Because water will move out of the way of the newly incoming water thanks to gravity. Air doesn't. At first, wind will flow, but most of it will be stopped by the windmill, creating an area of still wind. This makes the incoming wind stop, not on the windmill, but on the air that stopped earlier. It is for the same reason parachutes need a hole at the top, to allow the air to flow through it.

[@seraphina985]

@@eolyas1664 More simply it's the fact that when designing the system you don't release all of the potential energy of the water before using it to drive the turbine. You leave it with enough that releasing it is sufficient to do the work of accelerating the water out of the turbine hall and discharge it from the outlet. So you are still not really capturing its maximum potential but it's more efficient than the alternative which would require some other means to remove the energy-depleted water and discharge it. Trying to pump it out would be an inefficient potential>kinetic>electrical>kinetic conversion when you can just skip the last two and their associated losses if you simply save a fraction of the potential energy to release after the extraction process.

[@AlRoderick]

The fact that there's a downstream drain that lets the water flow away proves that it didn't gather all of the *potential* energy from the water. If it had, that would imply that the turbine was sitting in the reservoir at the bottom of the dam, and would therefore fill up with water and not be able to move anymore.

[@drawapretzel6003]

because real wind isnt compressed and shot out of a noozle.

[@jobta]

As a wind turbine design engineer, I understand why you call them windmills even though they are wind turbines, but it still bothers me a bit ;) Regarding size and speed, in practice and as a general rule, the bigger the rotor the slower it spins. Even though wind turbines are designed to maximise power they also have to follow strict rules such as noise limits. If you imagine 2 wind turbines, one big and one small, spinning at the same angular velocity, the tip speed of the bigger blade is going way faster that the small one. This can make a lot of noise and if you account that it ca also get in the range of supersonic speeds then a lot of other problems might come (ex: aerodynamics change, more vibrations inducing fatigue and lower component life etc). Great video as usual :)

[@mohammedjakhirhussain8699]

Where's the smart guy who explain complex videos like these in a single line with *BOLD* letters?

[@ジョンマーティン]

At last, something interesting that I did not even notice in normal life and not too complicated to become boring. A perfect minutephysics video

[@Dr.eminence]

I love your animation skills :)

[@drumna]

who doesnt :)

[@ubgqv]

@@drumna Any idea what app is used to make the animations?

[@SiMeGamer]

@@ubgqv no app. It's drawn by hand (at least they used to). There's a behind the scenes video on the matter from a few years back. If they moved to digital then they could technically just have finished drawings and use masking in any video software to reveal them and it creates the illusion of drawing.

[@ubgqv]

@@SiMeGamer thank you

[@Rock4everNRoll]

Other KZbinrs: This video brought to you by Raid Shadowlegends... Minutephysics: This video was created in partnership with BILL GATES

[@cacodemon_doom]

I prefer the former.

[@zebyurd9530]

@@cacodemon_doom Wtf is wrong with you

[@cacodemon_doom]

@@zebyurd9530 I don't support someone who hangs out with pedophiles and supports China's genocidal campaign and wants global authoritarianism.

[@zebyurd9530]

@@cacodemon_doom What the heck kind of propaganda have you been reading? Let me guess, you’re a huge trump supporter and probably believe that the election was faked.

[@hacheismo]

I been subscribed for years, but as soon as I heard that the Bill Gates sponsored this video... I dipped. Good luck with the channel.

[@ozonekidd]

Excellent use of simple animation to impart complex physical science to a reasonably intelligent lay person.

[@katherinelima7432]

Shame that you never discussed the reason for having odd numbered blades too! I always found it fascinating. If I remember correctly, it had to do with maintenance and stress on the blades due to asymmetrical air resistance.

[@joshmusic9766]

it is a shame but its hard to fit it all in. Interestingly enough, 1 blade would theoretically be the most efficient, but could never happen due to the intense forces of wobbling back and fourth. Two blades would have a similar issue with intense forces but from gyroscopic procession. Four blades would not be efficient due to what was mentioned in the video as stopping the air and not allowing enough to pass.

[@hookerno]

It is so because of the "tower shadow". If there were paired number of blades, the uppermost one would experience the most torque due to the faster air speed. The lowermost one is aligned with the tower and has low torque due to the effect of the tower to the airflow. This situation where unbalanced torques are present is bad for the mechanical strength of the nacelle. With odd number of blades the "tower shadow" effect is minimized.

[@TheRDBat5]

Notice how at 0:09 he just refuses to include nuclear energy when suggesting clean energy sources

[@ThisNameIsBanned]

Its paid by Gates, its partially propaganda for the book and agenda. Doesnt mean its bad, but it has quite some bias.

[@TheOwenMajor]

Notice how it's Bill Gates new world propaganda? This guy's always been a lefty, it's not about science, it's about control.

[@stickmanonastick6089]

Nuclear energy is cleaner than other energy sources, like fossil fuel, but not entirely clean like wind, water, and sun power, as there is still some nuclear waste to deal with. Thus, it’s a good stepping stone on the way to completely renewable energy, but not a permanent solution.

[@mattg8116]

@@stickmanonastick6089 There is no such thing as perfectly renewable energy. Everything creates waste to some degree. Nuclear has been proven comparable if not better than wind and solar in this regard. That said, wind and solar (especially solar) should be developed as much as possible where it makes sense geographically.

[@TheOwenMajor]

@@stickmanonastick6089 The idea that wind and solar is clean is ridiculous. It's a classic example of activists playing accounting games to justify there narrative. Wind and solar are horrendously polluting when you factor in their manufacture and after life waste. And that waste is large because wind and solar have significantly shorter infrastructure lifespans then other forms of production.

[@Sailorski75]

The fastest sailboats hardly even use sails anymore, they’ve largely switched to wings.(they also don’t float during racing). Check out the America’s Cup

[@strcmdrbookwyrm]

Technically, in certain configurations, a sail is functioning as a wing (mainly when going upwind).

[@jplmedley]

so satisfying to have something I never really thought about broken down so succinctly.

[@Savvy07]

After watching this video, my fan became windmill.

[@sundroid7562]

everyone: noooo, you can't make a windmill with small blades, it'll be ineffecient!! engineers: no, windmill go brrr

[@hacked2123]

I wanna see a city that uses windmills on the end of it, and buildings along the way channel the wind to a focused path.

[@SwedeOnRoad]

Wind turbines isn't efficient as a power source

[@whollypotatoes]

This was a beautifully concise video. Well done.

[@daemn42]

Who else found the most fascinating statement in the vid, that the moving wedge extracts more energy from the ball than the stationary one? It's thrown out there as an explanation for why faster moving blades are more efficient, but is not itself explained in any satisfying way.

[@ricoautosauve7849]

Have you had any luck figuring it out. Like in my opinion it’s not as intuitive as it seems

[@daemn42]

@@ricoautosauve7849 No, I haven't figured it out. As someone who plays ping pong, I can see (and perform) this experiment and verify the net result (ball bounces less far when paddle is receding at an angle, versus stationary or advancing), but I've never thought of it in terms of increased energy transfered to the paddle. Generally it feels more like linear kinetic energy translated into increased rotational energy of the ball, but maybe not. The only hypothesis I can think of is that the receding surface gives more time for the non-instantaneous elastic collision to occur thus more energy transfered over a greater time. That would suggest that ramp or no ramp, the ball should impart more energy into any receding surface for the same reason.

[@curseofgladstone4981]

@@daemn42 If you want the maths explanation it's to do with conserving both momentum And energy Say the slope is stationary. The ball bounces off it pushes it to the right moving left. The momentum of the ball and slope are the same. As the ball is lighter however it takes most of the energy since energy is proportional to Velocity squared. Now say the slope is moving. The ball hits it and barely rolls to the left. The slope is accelerated to the right by a smaller amount than when it was stationary. But because once again energy is proportional to velocity squared that small increase in speed is a larger amount of energy gained than it got when it was initially stationary. Or to put it another way, less energy went into the ball rolling left so more of it must of gone to the slope moving right.

[@daemn42]

@@curseofgladstone4981 Ya nah mate, that didn't clear it up. You're just describing the same symptom not the cause. Yes clearly if the ball bounces away with less energy then more went into the moving ramp. That doesn't tell me *why* more energy went into the moving ramp.

[@tylerbrown8808]

For those of you that don’t have a clue. The blades on a turbine have hydraulic motors to pitch. To control the speed and prevent them from pin wheeling and causing damage. The drivetrain inside with all of the gear reductions turns the shaft to the generator a lot faster than you think. Trust me I put them up.

[@vitasartemiev]

Man, the falling ball and slanted block thing took me way to much time to figure out

[@ricoautosauve7849]

Care to explain

[@joshmusic9766]

@@ricoautosauve7849 Like throwing a baseball off the back of a moving car versus off the back of a stationary car.

[@enderyu]

@@ricoautosauve7849 Work done on the object = Change in kinetic energy = Force x Distance traveled During the collision, the forces on both objects are the same, but with the slope moving in the direction of the force, the energy stored in the compression from the elastic collision is more quickly depleted, leaving very little time for the ball to accelerate back and regain speed. With the moving slope, the change (Δ) in speed and momentum are smaller for both objects, but the increase in kinetic energy of the slope is higher since it increases quadratically with speed

[@lazyman7505]

Re the energy imparted on the wind by the blades - would adding the 2nd wind turbine with reversed blades right after the 1st help in this case? Similar to how multi-rotor helicopters work.

[@ResandOuies]

It might cancel out the twisting of the wind stream, but it's not the fact that the wind is twisting that's the issue, it's the work done to make it so. Adding more work into the system to stop the twisting shouldn't help, I'd think. Multi-rotor helicopters cancel out the twisting of the helicopter, where it's mainly the twisting it self that's the issue, not the lost efficiency

[@tylerdurden3722]

Twisting wind behind the rotor blades equate to inefficiencies. Adding another rotor, behind the first, won't make the first rotor more efficient 🤷 And the idea is to extract the maximum energy out of the wind, with minimal material used.

[@kilianschabort6347]

I agree with the other replies but also your setup would only work in 1 wind direction and would prevent the turbines from turning to track the wind.

[@kazedcat]

@@ResandOuies Counter rotating fans are more efficient but not as efficient as just making the fan larger. The additional blades is a lot more mass that needs to be supported but it only gives you a small amount of additional efficiency. Adding a duct around the fan also increases efficiency but the mass of the duct makes it not worth it for the additional efficiency they provide.

[@arfyness]

You'd be better off just putting the 2nd windmill in the cleanest wind possible. Also, counter rotation would only work if the wind never changed direction, which it is quite famous for doing.

[@zeppie_]

This video tells me that a windmill with a single, extremely long blade would be most optimal

[@ronwesilen4536]

And you would be stupidly wrong. Luck us that you are not in charge. He has another video explaining that, so watch it, and think about what you will write before doing so

[@ElijsDima]

@@ronwesilen4536 Ron, relax. Not everything in life is a battle.

[@amritsingh4251]

There's another video of him explaining why that wouldn't be a good solution

[@luciqua2517]

There are such windmills. They use a counterweight on the opposite side of the blade. There are two-bladed winmills aswell. But the threebladed approach is better because the pole the windmill is sitting on blocks the wind. So the one- and twobladed mills can start to oscillate when the force of the wind is interrupted periodically

[@ronwesilen4536]

@@ElijsDima oh, shit, i never remember, thanks man, you so cool

[@JoeRose8]

A very concise video in just three minutes

[@ninjakille316]

I designed wind turbines for 4 years in college and I never realized reducing rotational kinetic energy the wake was part of the reason 3 blade designs are preferred. I always understood it as a just a material optimization. Beautiful video! Hmmm, the reasoning in this video seems to disagree with what is stated on Wikipedia: "Aerodynamic efficiency increases with number of blades but with diminishing return. Increasing the number of blades from one to two yields a six percent increase in aerodynamic efficiency, whereas increasing the blade count from two to three yields only an additional three percent in efficiency. Further increasing the blade count yields minimal improvements in aerodynamic efficiency and sacrifices too much in blade stiffness as the blades become thinner"

[@Psytronex]

They're actually called wind turbines. Windmill is a term more specifically used to describe a wind powered grain mill - hence wind-mill.

[@pancake_boi9891]

Me: It is impossible to get sponsored by Bill Ga- Minutephysics : 3:07

[@tylerdurden3722]

He's been sponsoring a lot of yt channels lately. Accompanied by the types of products his companies sell.

[@TheTubejunky]

@@tylerdurden3722 I notice this too. It's not an agenda thing is it?¿ Probably... History repeats itself.

[@tylerdurden3722]

@@TheTubejunky he's a businessan. Nothing wrong with that.

[@TheTubejunky]

@@tylerdurden3722 Yup nothing wrong with "Business as usual" , I'm sure his goal in the end is innocent and not about power or control. Google is also a business but they only want you to conform to their agenda also.

[@dante224real1]

"when shit hits the fan is you still a fan?" -Spindrik Llamarks

[@commieTerminator]

Another factor: More blades makes the structure heavy and shifts the CoG of the structure upwards which makes it less stable and increases construction cost

[@mathieuchangeux7840]

Wait! What if instead of losing out on capturing all that kinetic energy (2:10) from the windmill you created 1 windmill behind the first one to capture all that rotating wind?? Would that make it more efficient? And I’m imagining like a series of windmills behind each other rotating wind as it passes through them and utilizing it, almost like creating vents/currents in the open air.

[@FoxDog1080]

See the problem with this is that it doesn't work since the wind is now moving more parallel to the blade angle If we make contrarotating windmills We probably already do that The rule of thumb is that if I can think of it and it doesn't exist, there's probably a reason why it doesn't exist

[@ajax4887]

I thought they were called wind turbines. A wind mill grinds grain

[@Ddub1083]

true but people largely generalize them to wind mills... which doesnt really make much sense because a mill is something that grinds specifically.

[@Dayvit78]

Yet here's everyone calling it a windmill. So, who's right?

[@Ddub1083]

@@Dayvit78 you can be right but at the risk of being an asshole. I think thats the rule. lol

[@sundroid7562]

Love it! Thanks for answering a question that I've always had in the back of my mind

[@nerdlord2411]

Aren't modern windmills called wind turbines since they aren't milling anything?

[@laurencefraser]

Technically, in English... Though in casual speech where the distinction isn't relevant the terms are used interchangeably.

[@nerdlord2411]

@@laurencefraser So with that logic it is fine to call a windmill a wind turbine, even though a wind turbine doesn't mill anything?

[@calvinlee1127]

Finally first ever yt video talk about it

[@exactzero]

Is it just me or are anything about aerodynamics is always filled with paradoxes and counter-intuitive solutions? It's amazing.

[@Umski]

Windmills DO have sails (or sweeps as they're known in the South East of the UK!) at least ones that actually 'mill' - wind turbines on the other hand have blades ;)

[@sammy3212321]

It kinda upsets me that we call turbines "windmills" when they're not even milling anything

[@rashidisw]

Yeah, turbines are more appropriate term.

[@victortitov1740]

Tin foil, tin can and blackboard have entered the chat!

[@victortitov1740]

they mill magnetic fieds to produce electricity!

[@KarelKannel]

No, they are milling government support money for owners.

[@sammy3212321]

@@KarelKannel It's also kinda gross that so much investment is going into turbines when they have such terrible energy efficiency in convergence :/ They're not helping to give a good name to green energy.

[@prithwishguha309]

But Please explain why 3 blades, why not 2, not 4 or more?

[@justineberlein5916]

Because 3 is the number thou shalt count, and the number of the counting shall be 3

[@andrewwade1651]

In a two-bladed design the differing wind speed with height is trying to pitch the rotor up when the blades are vertical but not when they are horizontal. This contant variation is very hard on the rotor bearings. Going to a three-bladed design mostly evens out the loading on the rotor bearings, and the benefits of going above three blades does not justify the cost of the extra blades.

[@whosaidyoucandance]

Look into the difference between wind turbines and wind mills.

[@DrakiniteOfficial]

I'm glad Gates is sponsoring channels to spread climate conservation awareness.

[@adamkendall997]

Ya I'm sure it has more to do with a money making scheme. The guy has a carbon footprint of a small city.

[@t1kosuave]

Can you examine horizontal vs vertical wind generstors

[@carultch]

Search the terms HAWT wind turbine and VAWT wind turbine, to see some examples.

[@BEdwardStover]

Hmm, do mean wind turbines? You know wind mills mill grain.

[@WadcaWymiaru]

Here is HOW to spell it: *BORD CHOPPERS* good! Repeat!

[@Omnywrench]

Morbo: *WINDMILLS WORK THAT WAY! GOODNIGHT!*

[@mickelilltroll77]

Thanks! I have sometimes been thinking of this when trying to sleep, and then the next morning always forgot to google it. The brain of an engineer.

[@jerrydixon]

What I want to know is why is it when I see a field with 100 windmills, only 30 are moving?

[@bowiebrewster6266]

I don’t fully understand the area part, might need some formulas to get it.

[@joshmusic9766]

agreed. Im sure its hard for minutephysics to decide how much or how little detail to include.

[@dinodubroja7433]

"This video was created in partnership with Bill Gates" whaaa?

[@jonathanodude6660]

you must be new here. he sponsors all kinds of videos at certain times of the year across basically all science channels on youtube. people think he caused covid 19 because his last big speech was "we are unprepared for a pandemic." he was right, less intelligent people dont know how he could have predicted that the glaring holes in american pandemic resistance would lead to a pandemic, and now theyve fuelled conspiracy theories that already existed that hes evil or something.

[@crowforcast3583]

@@jonathanodude6660 He did convince oxford not to make their vaccine open source and instead sell it to astrazeneca. He's not innocent khn.org/news/rather-than-give-away-its-covid-vaccine-oxford-makes-a-deal-with-drugmaker/

[@Kislay11]

Don't mind me I am here only for the drama that will occur in this comments thread

[@SimGunther]

@@crowforcast3583 Using non renewable energy (coal and trees) to power things that are supposed to be "renewable" (electric cars and wind turbines) to accelerate the planet's destruction sounds good to me LOL

[@jollihotdog5196]

Oh so that was his purpose after all

[@Aldo_raines]

Anyone else annoyed that they called wind turbines “wind mills”?

[@FOVOutdoors]

Me too.

[@aidanlevy2841]

The thing a lot of people on the internet seem to forget about language is that when enough people use a word wrong it stops being wrong and simply becomes a new meaning for the word. Do you complain about the wind powered pumps in the Netherlands that pump water out of fields being called windmills?

[@TactileTherapy]

Been watching these guys since high school. Im still in high school. Hang on... I just started watching them in October

[@slimanus8m]

I was actually excited about the title but the most important thing I wanted to know is about the shape / profile of the blade which you didn't cover here

[@An.Individual]

Also they take energy from the grid to get the blades turning so they are never generating as much energy as you might think.

[@ProPowerMax]

Also the 3 blade design is still a compromise, ideal would be only one Blade but that isn't stable enough

[@Your_Paramour]

The structural mechanics probably dictate the design more since increasing the efficiency will have diminishing returns where as the power generation is squared on the blade length and cubed on the wind velocity.

[@Uhlbelk]

Material engineering, you need to limit the size and increase the number of blades to reduce the force to any one blade to the tolerance of the materials.

[@Keldor314]

This still doesn't explain why a 2 blade design isn't used.

[@justinhannan1713]

This single blade turbine seems ok: kzbin.info/www/bejne/mqHOfp54hZuirbM

[@Uhlbelk]

@@justinhannan1713 yes, but that is not the most energy efficient design.

[@NicholasKratzer]

Thank you for making this. I've low key wondered this for years.

[@MeisterHaar]

I recently listened to a podcast and they talked about how windmills are super optimized as individual mills but nowadays mills rarely stand alone and are often placed in windparks. It turns out windmills im the past have not been optimized to be used like that and all that is currently done is to optimize the placement of mills in the area. but for example a study they cited found that having some windmills spin the opposite direction could in perfect conditions increase the produced energy of a given area by 40% if I remember correctly. I found that super fascinating and wanted to shared it with you.

[@alessandrobertolotti8757]

Instructions unclear. My windmill took off and flew away

[@lukerab]

Why does a moving block absorb more energy from the ball? I feel like there should be a good explanation, but I cannot think of one for the life of me.

[@BL3446]

Not the only reason, but often starting friction is higher than kinetic friction. So it would take more energy from the ball dropping to get started than if it were already going.

[@docostler]

The 'reflecting' surface of they block is constantly moving away from the ball, thus lengthening the contact time between ball and surface. This allows more transfer of energy from the ball to the block, thus causing a smaller 'reflection'. The same principle for padded dashboards, air bags, crush zones in cars. Lengthen the contact time by moving with the colliding object to absorb some of the energy.

[@brauno3539]

That's a good question. I have an answer, but it is going to get a bit technical, despite a simplification. I'd love to hear more simple answers. Simplification: The ball is very light and doesn't push the block away. If the block is moving, you can change the inertial system to the moving block, and add the speed to the horizontal velocity of the ball (it is like when you are in a moving train, it looks like the landscape is moving by). And that makes it alot easier. With the simplification you can exactly calculate the angles of the incoming ball and the outcoming ball (incoming angle=angle, when it is reflected). Then when you subtract the horizontal velocity at the beginning from the horizontal velocity at the end, you get v(end)=v(start)*[sin(2a+b)-sin(b)] with a: angle of the object b: angle of the incoming ball and v*(end) is smaller, the bigger b gets. and b is dependent from the horizontal speed of the ball

[@lukerab]

@@BL3446 That is an interesting idea. But we should expect kinetic friction to be pretty much constant and wouldn't explain the difference between the second and third cases when the block is moving faster.

[@lukerab]

@@docostler I was thinking about that as I was watching. I was thinking in terms of impulse, that the extended time would decrease the force on the ball. But I wasn't sure if that was even true and it would also diminish the force on the block due to Newton's 3rd Law. I am still a little confused by the longer time allowing more transfer of energy in terms of equations or laws.

[@BL3446]

Also, lol at all the Dunning-Krugers in the comments. The sources are literally right there for you to read on your own.

[@seanforrest1106]

Not gonna lie yo, i dont think this would have ocurred to me if i didnt watch this video. My high school maff teacher called me smart once tho so maybe if i thunk hard enough😅

[@BL3446]

@@seanforrest1106 lmao what?

[@rupert7565]

And you can find out why windmills have 3 blades from the video of Real Engineering: kzbin.info/www/bejne/iH-zeoWcrbqHh5Y

[@mementomori5580]

Except that that video has several factual errors and thus should be remade and not shared in its current state.

[@rupert7565]

@@mementomori5580 Really? well it's not the only time he made a video with factual errors, see his latest one.

[@daniel_960_]

@@mementomori5580 I mean the dude made a video about how awesome Nikola is 😂 And went totally nuts because he got criticized for it. I liked the channel but can’t trust any his stuff at this point

[@davidequattrocchi5083]

Finally an explanation that made sense, and answered a question I had in my head for nearly a decade. Thank you

[@PeterShipley1]

you forgot to mention how these effects make windmills inefficient if they're too close to each other.

[@norbertfleck812]

Not to mention how ineffective they become on a day or night without wind. In winter 2020-2021 there were altogether more than 30 days in Germany without any wind (wind energy production less than 5% of the installed power capacity)

[@decorn2542]

Wow minuteEngineering, I like it

[@Big007Boss]

Was waiting for the birds flying around part

[@JustInTime0525]

Wish you could go more in-depth on numbers of the blades!

[@nineball039]

Thank you. I never thought about the physics of windmill design.

[@bilalhamid7728]

I think there is one more factor to consider,: thinner blades have a much smaller material cost as well, shifting the equation towards favoring them a lot more.

[@christophergerety1263]

What’s Bill’s carbon footprint? I.e. does Bill walk it or just talk it.

[@SwedeOnRoad]

Probably a lot more than the normal human being. Probably owns oversized buildings, many cars, boats and everything. And does that just because he can not that he must have all of it. My guess is that he doesn't care at all about any of this, just says and does stuff so it sounds good and that he is trying to save the planet.

[@ultimatedude5686]

@@SwedeOnRoad He also uses private jets. I think the most important thing is really to get corporations to lower their emissions though

[@thelegalsystem]

Does Bills book cover his efforts and lobbying to keep the COVID vaccine from being open sourced?

[@samtahir863]

I feel like I have to be that guy it's not a windmill it's a wind turbine

[@zwink37]

Does it not have anything to do with possible damage if the wing is blowing too fast? I would imagine larger blades would be more susceptible to deforming the stand or the blades themselves if they were bigger.

[@MrUtak]

I keep imagining weird sail/blade shapes with randomly allotted wholes in them so that they don’t resonate in any particular frequency (after reading Humble Pi), great video!

[@aguskate95]

As a wind turbine design engineer I would really appreciate if you didn't call them windmills lol

[@LuukvdHoogen]

being Dutch I am glad that we can still talk about our mills in the landscape

[@TheHanskov]

when i thing green energy i thing nuclear, change my mind

[@joshmusic9766]

I think many of minutephysics viewers would agree!

[@niccolopaganini1782]

Me: **Misreads the titles* Me: They have bad marketing skills.

[@ottertvmtg6229]

what did you read it as?

[@niccolopaganini1782]

@@ottertvmtg6229 Sales not sails

[@pnwmeditations]

An interesting limiting factor I learned in college: you don't want the tip of the blade to break the speed of sound.

[@doryiii]

I never thought about windmill blades until I took flying lessons. Then I realize how windmill blades and airplane wings are basically the same thing and have the same limitations.

[@GeoffCostanza]

Windmill blades have a fairly short life expectancy (about 20 years), and are contributing to a significant amount of landfill waste because they are extremely difficult and energy intensive to recycle. This doesn't include the costly and specialized equipment to manufacture, transport, assemble, and tear down these massive structures every couple decades, and all the carbon emissions produced by these processes. There's also no mention of the birds of prey and high altitude migrating birds killed by the spinning blades, which would otherwise be relatively unaffected by manmade objects. Windmills are a gimmick that do a lot of harm to the environment, and I wish pages like this wouldn't promote them as an environmentally-friendly alternative when there are better options.

[@infinitelyexplosive4131]

Yeah that's BS. There are 60,000 wind turbines in the USWTDB. Average power is about 1.5MW, which corresponds to about a 70M rotor diameter and had blades that weigh about 22 tons. That means the total blade waste would be 1.3 million tons. Municipal solid waste in 2018 was 300 million tons, of which 50% went to a landfill. That means that the combined waste from blades from _every wind turbine in the US_ is less than 1% of the amount of waste made each year by US citizens, and that's ignoring the enormous amount of waste from manufacturing. As if you weren't already disingenuous enough, you also don't talk about the waste from any other forms of electricity generation. It's almost like you're just trolling and don't actually care about landfill waste or any of the other so called issues with wind turbines.

[@peter4210]

Fun facts, wind farms slows down wind down wind of it, resulting in a temperature increase for the immediate area , they also destroy natural habitats due to their sound and large footprint required to install and maintain them, as well as the psychological impact of their presence on animals. With out a battery to store the energy, a lot of the energy they could capture is lost as well. P.S. I am not saying we should burn coal like there are no tomorrow but we can't shop down more forest in the name a "green energy". we should force corporation on being energy efficient and stop waste. We should force product to be energy efficient, no more incandescence light bulbs or LED's bulbs that are over powered so they burn out( the LED lights you buy can be made to give the same light with a longer lighting life and less power but the companies make them badly so they fail early).

[@JaapvanderVelde]

Excellent, concise, accurate. Nice.

[@FlintTD]

A few years ago I heard of a project to make a 6(?)-bladed windmill, with shorter blades to enable cheap shipping via the extra-long standardized shipping containers. The person behind it had supposedly worked out the math such that their design could achieve similar efficiency. The idea was to make more windmills, offsetting that cost with cheaper shipping and mass production. I only sort of grasped the numbers at the time, but I'm glad I found this video so I could get a slightly better grasp on said numbers. I suppose the reason I've never heard of that project since is because of the energy losses from deflecting the air!

[@AlexJohnson-be3tj]

Definitely wondered about windmills and their design before