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How Wind Turbines Really Work: The Hidden Secrets — Transcript

by The Engineering Mindset · 3,633 words · 516 segments · language en · Watch on YouTube

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0:00sponsored by brilliant why are there
0:02three blades why are they so high why
0:05are they so slow and how does it even
0:08generate electricity grab a pad and
0:11paper to make notes and sip from your
0:13engineering mindset mug let's find out
0:16this basic wind turbine can power a
0:18small LED this larger one can power a
0:21small home but these Mega turbines can
0:24power entire towns a wind turbine simply
0:28converts the kinetic energy of of the
0:30wind into mechanical energy and that is
0:33converted into electrical energy we can
0:35feel the energy of the Wind on our hand
0:38we know that it can turn a windmill we
0:41can turn that into motion like this
0:43strange wind powerered
0:45walking thing or we can attach a
0:48generator to it and it will produce
0:50electricity try it yourself take a
0:53simple DC motor spin the shaft and
0:56you'll notice it produces a voltage so
0:59just attach a blade to it and it will
1:01spin in the wind and generate
1:04electricity the speed of the wind
1:06increases the higher we go and it's also
1:09less turbulent the larger the blades the
1:12more wind energy we can capture large
1:14blades need to be higher off of the
1:16ground but the speed of the wind is the
1:18largest influencer in power generation
1:21large turbines are difficult to
1:23transport so we often find the largest
1:26turbines out at Sea where space isn't a
1:29problem although it is a lot cheaper and
1:32easier to install them on land but they
1:34do Mark the landscape they cast long
1:37flickering shadows and they can also
1:39create Some Noise the wind turbines need
1:42a deep strong Foundation we can extend
1:45down into the seabed but some waters are
1:48so deep it's easier to just float the
1:50wind turbines on a platform you might
1:52notice that smaller wind turbines have a
1:55towel fin at the back but large ones
1:57don't I'll explain why later in the
1:59video video the wind turbine needs to
2:01face the wind and the wind changes
2:04direction we could use a vertical wind
2:06turbine and that will work in any wind
2:08direction there are many designs but
2:11they are usually less efficient in
2:13comparison and they don't scale up very
2:16well the wind turbine can be upwind or
2:19downwind upwind is more efficient
2:22because the wind hits the blades before
2:24the tower and then the cell but the
2:26blades need to be stronger so that they
2:28don't bend in the Wind and hit the tower
2:31how do you feel about wind turbines
2:33would you live next to one tell me in
2:35the comment section down below when we
2:38look at a large wind turbine we notice
2:41the Ste tubular Tower rising up out of
2:44the ground we see it reduces in diameter
2:47as it reaches the top it rises high up
2:49into the sky to reach the strongest wind
2:52inside the tower we have an access
2:54ladder for engineers there's some power
2:56cables and we often find a Transformer
2:59at the the base on the top of the tower
3:02we find a large bearing and a ring gear
3:04attached to this bearing is the bed
3:06plate and this is the main support a set
3:09of Y Motors are bolted onto the bed
3:11plate and their gears into lock with the
3:14large bearing gear this will control the
3:16direction of the turbine a small encoder
3:20counts how far the turbine has rotated
3:22I'll explain this part later on in the
3:24video we also find a set of hydraulic
3:27brakes and a large disc brake which will
3:29hold the turbine in position at the back
3:32of the bed plate we find the electrical
3:34generator there will usually be an
3:36electrical and a controls panel here too
3:39the generator connects to a gearbox via
3:42the high-speed shaft attached to the
3:44shaft is a disc brake which is
3:46hydraulically controlled this will be
3:48powered from the hydraulic control set
3:51the gearbox then connects to the main
3:53low speed shaft this is supported by the
3:56main bearing this connects to the Hub at
3:58the very front of the tur turbine the
4:00blades will then bolt onto the Hub via
4:03some geared bearings the metal Hub is
4:05covered with a nose cone to protect it
4:08and also improve the aerodynamics inside
4:10the Hub we typically find three motors
4:13these are attached to the hub and their
4:16gears into lock with the geared bearings
4:18this allows the blades to be tilted the
4:21bed plate and all the main components
4:23are covered with a fiberglass housing
4:25and this forms the the cell the case
4:28protects the components from the winds
4:30the Sun the rain Etc on the top of the
4:33Nel we find a wind vein which will
4:35determine the wind direction and there's
4:37also an anemometer to measure the wind
4:40speed the wind vein will determine the
4:42wind direction and the controller
4:44releases the brakes this allows the
4:46motors to turn the the cell to align it
4:49with the wind once aligned the brakes
4:51are reapplied the wind flows over the
4:54blades forcing them to rotate this
4:56rotates The Hub which rotates the shaft
4:59the shaft rotates slowly but with high
5:02torque the bearing supports this and
5:04allows the low friction rotation the
5:06shaft will rotate the gears in the
5:08transmission and then the output shaft
5:11connects onto the electrical generator's
5:13rotor the rotor turns and induces a
5:16voltage generating electricity we will
5:18see this in detail in just a moment the
5:21output of the generator flows through a
5:24cable and down the tower to the
5:26Transformer where it will be sent to the
5:28electrical grid and distributed to the
5:30towns and houses other power generators
5:33such as solar or nuclear will also feed
5:36into the grid you can also see our video
5:38on how solar panels actually work wind
5:41and solar are a great combination of
5:43renewable energy because it's always
5:46either sunny or windy the blades are
5:49typically made from reinforced glass
5:51fiber which makes them very strong and
5:53very lightweight that allows them to be
5:56longer so we can capture more wind
5:58energy metal or wooden blades are
6:01expensive they're heavy and they're more
6:03likely to fail heavy blades are hard to
6:05turn and they're also harder to stop the
6:08blades will have an aerofoil shape to
6:10them the shape changes along the length
6:12of the blade and often twists along the
6:14length to improve the aerodynamic
6:16efficiency smaller wind turbines usually
6:19have a fixed angle blade but large
6:22turbines can change the angle of the
6:24blade the front of the aerrow foil is
6:26known as the Leading Edge the rear is
6:29called called the trailing Edge the line
6:31between these two points is the cord
6:33line when the blade tilts the difference
6:36between the cord line and the relative
6:38wind direction is known as the angle of
6:40attack the blade will obstruct the path
6:43of the wind forcing it to go Under and
6:46Over The Arrow foil air is a fluid and
6:49when an object passes through fluid we
6:51get friction across the object's surface
6:54and also get resistance from the shape
6:56of the object we call these forces Dr
6:59drag and they act parallel to the wind
7:01slowing the blade down the arrow foil is
7:04designed to minimize drag forces and
7:07maximize lift the air will have a longer
7:10distance to travel over the top due to
7:12the curved profile that means the speed
7:15has to increase along the top and it can
7:17slow down along the bottom resulting in
7:20the two streams arriving at different
7:22times as the air speed increases the
7:25pressure decreases therefore a lower
7:28pressure region develops over the top
7:30and a higher pressure region along the
7:32bottom the higher pressure side
7:35naturally pushes the blade into the
7:37lower pressure region creating some of
7:39the lifting Force we also have air
7:42colliding with the underside of the
7:44blade providing a force the air on the
7:46top and the bottom are being deflected
7:49downwards this downwards momentum
7:51creates an equal and opposite upward
7:54force and this helps push the blade into
7:56the lower pressure region also adding to
7:59to the lifting Force the tip of the
8:01blade has a higher velocity through the
8:03incoming Windstream than the Hub so the
8:06lift and the drag will be different the
8:08shape of the blade is Twisted to try and
8:11account for this and improve the angle
8:13of attack we tilt the entire blade to
8:15alter the amount of lift produced as the
8:18angle of attack increases more lift is
8:21generated but at a certain point the
8:23streams will separate and become
8:26turbulent this reduces the lift and
8:28increases the drag which slows the
8:30rotation down we can see with this model
8:32wind turbine that if the blaze are
8:35perpendicular to the wind then the
8:37maximum drag occurs with no lift and so
8:40the blades do not turn and therefore no
8:42voltage is generated but there's a lot
8:45of force on the tower if the blades are
8:48parallel to the wind then very little
8:50lift is generated the rotation is slow
8:53and only a small voltage is generated
8:55it's also very easy to stop this
8:57rotation but if if we tilt the blades to
9:00an optimal angle we generate a large
9:03amount of lift the Hub spins very fast
9:06and so we generate a few volts the
9:08blades design will have an optimal angle
9:10of attack and we can find that on the
9:12design chart we can see with this DC
9:15generator the faster the Sha rotates The
9:18More Voltage is generated but if it
9:20beens too fast for too long it becomes
9:23very hot and it will eventually destroy
9:25itself our generator might be rated for
9:28say 2 megaw so we have to tilt the
9:31blades to control how fast the blades
9:34rotate and that controls how much power
9:36we generate and that helps us to stay
9:39under the maximum rating of the
9:41generator the wind turbine won't start
9:43until a minimum wind speed is reached
9:46this is the cut in speed the wind speed
9:49increases and the power output also
9:51increases at a certain wind speed the
9:54wind turbine will tilt its blades to
9:56stop generating power and the brakes
9:58will will be applied to protect the wind
10:01turbine this is known as the cutout
10:03speed the anemometer measures the wind
10:06speed and the controller changes the
10:08angle of the blades so how many blades
10:11do we need the blades will each generate
10:14lift which causes rotation but they also
10:18generate drag which will slow the blades
10:20down using this model wind turbine we
10:23can change the number of blades to find
10:25out with one blade it's very slow the
10:28structure is also very unstable it
10:31doesn't produce much voltage and it's
10:33very easy to stop plus it didn't
10:35self-start so this is not a very good
10:38design with two blades we notice that it
10:41will self-start it's much more stable
10:44and it can produce a much higher voltage
10:47with three blades it produces only a
10:49slightly higher voltage but it is now
10:52much harder to stop because it's
10:53catching much more wind energy with four
10:56blades it again produces a slightly high
10:59higher voltage but with five blades the
11:01voltage has started to drop slightly and
11:04at six blades again this produces an
11:06even lower voltage but it is very hard
11:09to stop so the three four and five blade
11:12versions produce the most energy the
11:15three-blade version is very stable and
11:17it also costs the lease to build so this
11:20is the obvious choice two blades is also
11:23common in mediumsized turbines and
11:25that's because it's cheap and fairly
11:27stable micro wind turbines might have
11:29many blades and that's because they are
11:31installed lower so that they experience
11:33slower and weaker wind speeds large wind
11:37turbines rotate quite slowly the blades
11:40are very long so the tip of the blade is
11:42traveling much faster than the Hub at a
11:45certain point the blade tip will travel
11:47so fast they will break the sound
11:50barrier this creates a sonic boom and
11:52the forces will start to rip the blades
11:54apart even at low speeds there's large
11:57centrifugal forces acting on the blades
12:00Additionally the generator needs to
12:02rotate at a certain speed to produce 50
12:05or 60 hertz electricity which will be
12:08supplied to our homes the gearbox
12:10increases the speed so the rotor doesn't
12:12need to rotate very fast to achieve this
12:15small wind turbines have a large taal
12:17finin which allows them to align their
12:19blades into the wind without this they
12:22will turn away from the wind and so the
12:24wind energy will hit them the cell and
12:26the tower first Which is less efficient
12:29vertical wind turbines do not need a
12:31your system they will work in any wind
12:33direction but large wind turbines don't
12:36use a talin and that's because they
12:38would need to be so ridiculously large
12:41to work and that's going to add a lot of
12:43moving weight they also swing in
12:45turbulent winds which is a lot of
12:47uncontrolled force on the structure the
12:49bearings and the blades so Engineers
12:52instead opted to use a wind vein which
12:55indicates the direction of the wind and
12:57a computer then controls some motors
12:59which will rotate the bed plates around
13:02the large gear on the tower to change
13:04the direction of the cell so that it
13:06always faces the wind for Optimal
13:08Performance some brakes will then hold
13:11the turbine in position once the the
13:13cell is aligned with the wind a small
13:15encoder tracks the rotation of the the
13:18cell in large turbines that's because
13:20the power cables need to connect from
13:23the generator down into the tower if it
13:26rotates too far it will twist the cables
13:29and eventually snap them often then the
13:31cell will turn in the wind but a short
13:34time later the wind direction will
13:36change back and so then the cell turns
13:38to realign with this and undoes the
13:40twist the cables are suspended to reduce
13:43the twisting and the computer controls
13:45how far th the cell can turn to avoid
13:48twisting them it will stop and rotate in
13:50the opposite direction if needed small
13:53turbines just use slip rings to avoid
13:55that but large turbines produce a lot
13:58more power making it cheaper safer and
14:01easier to just use a cable and track the
14:03rotations small wind turbines are
14:06typically direct drive they often use
14:08permanent magnet generators like this
14:10one large wind turbines turn much slower
14:14so we use gears to increase the speed of
14:16the rotor to produce sufficient power
14:18and output frequency at the generator
14:21typically we find a three stage gearbox
14:24consisting of a planetary gear set and
14:26then two spur stages the input shaft is
14:29low speed but high torque the gearbox
14:32converts this into highp speed low
14:34torque the rotational speed is
14:36controlled by the pitch of the blades so
14:39the input speed might be just 18 RPM and
14:42the output speed is 1,800 RPM we need to
14:46achieve this speed to control the output
14:48of the generator we also have a
14:51hydraulic disc brake at the back of the
14:52gearbox because the shaft is low torque
14:55so it's easier to stop the blades are
14:58first used used to stop the rotation the
15:00brakes will then hold it in place for
15:02example during maintenance the doubly
15:05fed induction generator is the most
15:07common generator for large wind turbines
15:10smaller domestic wind turbines might use
15:12a three-phase brushless motor like this
15:14one or they might just use a brush DC
15:18generator like this one tiny DIY wind
15:21turbines can just use a basic DC motor
15:24when we pass DC current through a coil
15:27of wire it produces an electromagnetic
15:29field but when we pass AC current
15:32through the coil it produces a magnetic
15:34field that changes polarity the rate of
15:37change depends on the frequency of the
15:40AC current applied to the coil a basic
15:43generator has a magnet at the center of
15:46the rotor and a coil of wire on the
15:48stator when the rotor rotates the
15:50magnetic field interacts with the
15:52electrons in the wire pushing them
15:54forwards and then pulling them backwards
15:57as the magnet rotates this will create
15:59an alternating current with a sine wave
16:02which repeats every time the North and
16:04South Pole of the magnet rotates past
16:06the coil the electrical outlets in our
16:08homes provide either 50 or 60 hertz
16:12meaning the sine wave repeats 50 or 60
16:15times per second to achieve that the
16:17magnet would need to rotate thousands of
16:19times a second but if we add another
16:22magnet and coil we can reduce the
16:25distance and time taken for the North
16:27and South Pole to pass a coil and so the
16:30rotational speed reduces to just 1,800
16:34RPM the gearbox increases the speed by
16:37around 100 times so we only need 18 RPM
16:41of the hub for the blaze to achieve that
16:43we can see with this simple two- pole AC
16:46generator that the frequency produced
16:48depends on the rotational speed of the
16:50rotor shaft in the wind turbine the
16:53rotor connects to the blades the faster
16:55the wind the faster the shaft rotates
16:58although we do have some control over
17:00the Sha speed by rotating the blades to
17:03change the amount of lift or drag which
17:05is produced if the wind speed is too
17:07fast the turbine shuts down and that is
17:10our cutout speed a generator rotates
17:13quite easily and it will produce a
17:15voltage but when we connect a load to
17:17the generator it's much harder to rotate
17:20this will add mechanical load to the
17:22blades slowing them down so the wind
17:25turbine won't start until a minimum wind
17:28speed occurs and that is the cut in
17:30speed the doubly fed induction generator
17:34consists of a rotor which is attached to
17:36the highspeed output shaft from the
17:38gearbox the rotor has three sets of
17:41coils attached to it these connect onto
17:44some slip rings at the end the stator
17:46surrounds the rotor this also has three
17:49sets of coils inside when the blades
17:52turn the Sha turns and the rotor rotates
17:55but the stator remains stationary the
17:58rot is connected to a three-phase
18:00electrical supply via the slip Rings
18:03each coil produces an alternating
18:05magnetic field at slightly different
18:08times based on the AC frequency which is
18:11applied these are positioned around the
18:13rotor so that they combine and create an
18:16equivalent rotating electromagnetic
18:18field the direction of the rotation
18:21depends on the timing of the phases a
18:24controller determines the frequency and
18:27also the direction of the rotating
18:29electromagnetic field as the
18:31electromagnetic field rotates it induces
18:34a voltage into the coils of the stator
18:37and this generates an AC current which
18:40we then export to the grid if we apply a
18:4360 HZ supply to the rotor then we
18:45generate and Export 60 HZ back to the
18:48grid because the wind is controlling the
18:50rotor speed it might rotate at 1,800 RPM
18:55but it might also rotate slower than
18:57that or it might rotate rotate faster
18:59than that the magnetic field is rotating
19:02and that is attached to the shaft which
19:04is also rotating so these will combine
19:07if the rotor speed drops to say 1,600
19:10RPM that's equivalent to
19:135333 Hertz so we would need a 6.67 hertz
19:18frequency on the rotor coils to make up
19:21the difference and achieve the 60 hertz
19:24the speeds will combine and that will
19:26produce an equivalent 60 Herz Herz
19:28rotating magnetic field which produces
19:3160 HZ at the stator if the speed of the
19:34shaft increases to maybe 2,000 RPM
19:38that's equivalent to
19:3966.67 Hertz and that is much too fast so
19:44we need to subtract 6.67 Hertz and we
19:47achieve that by rotating the
19:49electromagnetic field in the opposite
19:52direction to the rotor if the rotor was
19:55exactly the required 1,800 RPM then we
19:58require zero Hertz which is DC
20:01electricity so we apply a constant
20:04current to the rotor and the magnetic
20:06field rotates only with the shaft at the
20:09same speed as the shaft and so we get 60
20:12HZ on the rotor and 60 HZ of the stator
20:16the controller is constantly making
20:18adjustments to the frequency of the
20:20rotor current to ensure a 60 HZ output
20:23is maintained the engineering design of
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