The GE Haliade X, smaller but not by a lot, maxes out at 7 rotations per second, giving a rotor tip velocity in the vicinity of 80m/s. Generally noise considerations mean you don't aim for a tip velocity faster than that, although for a turbine that is only installed in offshore or other uninhabited locations, you might design for a higher tip velocity. Despite some advantages to higher velocity, though, considerations related to erosion caused by high speed impact of dust, water drops and ice particles become an issue long before you'd get to supersonic speeds.

> The GE Haliade X, smaller but not by a lot, maxes out at 7 rotations per second

I think you meant per minute.

Per second would mean that the rotor tips are travelling faster than SR-71.

Yes. Thanks.

Although I'm glad it's not reality, the imagery of a massive wind turbine whizzing around at 420 RPM is pretty amusing

> Regular turbine spotters judged that the best sound balance was usually to be heard from within large concrete bunkers some thirty-seven miles away from the wind farm, whilst the engineers themselves operated their turbines by remote control from within a heavily insulated spaceship which stayed in orbit around the planet - or more frequently around a completely different planet.

Hehe, just to let you know your effort wasn't in vain, I got that.

That is crazy, but, on the other hand, seeing this rotate faster than once every two seconds would be insanely fast.

We just need to hook it up to a flux capacitor and the next typhoon will give us time travel.

I did the math, but we didn't hit 1.21 jigawatts

Back in the day, it was still spelled Giga but pronounced Jiga. I heard from some old-heads at power company.

Jigga What, Jigga Who

Hard Watt Life

Gettin' jiggy wit it

Here's turbine in Denmark that lost its brakes and disintegrated in 2008. The description says the tower was 60m tall.

https://www.youtube.com/watch?v=7nSB1SdVHqQ

You'd think there would be a backup brake kit on these

I thought they would feather the turbine blades so that they didn't generate rotation. Maybe that failed as well?

On the smaller turbines I worked on, the speed of rotation was controlled by feathering the blades as you’d expect. Braking was also achieved the same way, with the friction brake acting as a “handbrake” once the blades were slow enough.

One thing that some people don’t consider is that the direction the turbine faces is also controllable and therefore used for braking. A lot of people think the turbine is blown by the wind to face the correct direction, but there is a separate wind direction sensor and a motor to turn the turbine.

The friction brake could be applied at speed, but that was for emergencies.

There is so much power in the wind. If you are a little late with feathering you might end up having too much momentum to be able to use a friction brake without burning it up. So a long period of steady wind followed immediately by an increase to the point where you can no longer stop the machine is quite risky: all that stands between you and certain destruction is either a lucky lull in the wind or your continued ability to feather it and that can get surprisingly hard when you are dealing with high winds. To the point that if you go 'coarse' at high RPM you end up pulling over the tower due to the extremely long arm for that force to take effect.

Never ever underestimate what the wind can do. Wind turbines will always have some latent risk (as do most other activities and constructs). For every design there is a pathological set of circumstances that should never happen. But once in a long while it does. What should surprise you is that so few of these accidents happen that they are news.

If they do break the sound barrier, that's also when the efficiency drops iirc. So I guess they'll switch it to a heavier load or RPM, or apply the brakes?

Not sure how that works for a wind turbine

Rotating blades like this should never go beyond the critical Mach number where local airflow on the blade upper surface reaches Mach 1.0 (about Mach 0.8ish). The shockwaves that form are attached to the surface and like to shift around with slight changes in conditions, which cause awful vibrations. I'd expect the blades to be braked in some way to never exceed critical Mach number.

Isn't there a great resistance to overcoming it? So basically it would stop accelerating before ever crossing it.

But, AFAIK, windmills wre immobilized when the wind gets too strong, in order to protect them. If the tech allows it, they can also be made to catch less window. Some Dutch wind mills could be rotated, and the cloth covering the arms could cover less surface. Modern windmills adapt their position automatically. Look at [0] and search for "Ten Have / Beckers".

[0] https://en.wikipedia.org/wiki/Windmill_sail

I presume the pitch is adjustable, so unless the mechanism fails you can just relax the pitch like pointing a sailboat directly into the wind to depower the sails.

The mechanism is designed (or at least should be designed) so that if anything breaks the blades rotate to the no power position. There is a lot of engineering and redundancy that i'm only partially aware of.

I guess the real question is how bad can conditions get before the "no power position" is still too much force for the structure to withstand.

You can't escape the fact that the blades are a ton of surface area on a long lever... and if the winds are both forceful and directionally chaotic, there isn't really a "no power position" to be found.

Going back to the sailboat metaphor, it's the conditions where you douse the sails entirely. At most flying a little storm jib. Pointing upwind is just to enable doing so.

The tower catches more wind than the blades and will fail first. And the tower is built dor the force of strong winds with the blades resiting the wind.

Though they are built in rural areas and at sea so even in the worst case disaster (manufacturing flaw, not wind) nobody is hurt.

Even if pitch is adjustable the problem is very non-trivial given the size of the blades and different wind speeds and directions on different elevations. Putting the blades in no-power position along the main wind direction, but having small sidewind 200m above the surface would rotate it.

Do you transport something like this in pieces, or as a single blade?

A German company says they can transport blades of up to 100m length as a single piece [1]. For longer things I'd guess there is no option other than to manufacture them on site or near-site, as the Danes are doing for offshore projects [2].

[1] https://www.doll.eu/de/produkte/schwertransport/nachlaeufer-...

[2] https://www.wiwo.de/technologie/wirtschaft-von-oben/wirtscha...

That is on land, there is a reason a lot of wind production is close to a harbor.

So near-site in practice means, near-harbor.

Possibly you can have an agile vessel doing the last stretch so that you can change that to ~near-sea.

the US Midwest has a ton of wind power, if you drive through there you have a decent chance of seeing a truck carrying a blade. pretty interesting stuff. obviously those are a lot smaller than this windmill though.

If you drive through Iowa, it seems like you will see nothing but windmills. Just an enormous amount of installed capacity.

I guess it makes sense that they put them near major roadways, for easier access, but I find driving through a wind farm to be intensely distracting. The rotation of the windmills during the day, and the strobing warning beacons at the top at night, really tend to pull my eyes off the road ahead.

The blade is usually manufactured as a single fiberglass piece. With how big this thing is I imagine it's manufactured somewhere directly at the shore, and just lifted onto a boat directly from the factory.

The base is segments (shaped like calamari rings), which are big but usually can be transported by road, but the big ones probably can't pass under bridges.

How technically challenging is building(?) printing(?) these pieces? Presumably they need to withstand enormous amounts of strain. Can you produce an impromptu factory anywhere, or does this require sophisticated equipment that benefits from fixed installations?

It's a pretty complex and manual process. You need tons of space, and it's usually built with composites. It's pretty challenging to inspect them for flaws once they are built too.

Afaik, they are built in dedicated factories but usually on the same continent (at least!) as where they are going to get installed.

> shaped like calamari rings

... but why calamari rings specifically?

The blades are transported in single pieces, on trucks with steered rear carriers, as in this video: https://www.youtube.com/watch?v=iTpZ5V4HrK4

The blades in this topic are about 4 times the length of the ones in the video. It's a whole different world.

I'm going to be stuck watching videos of these things being delivered all day now.

Depends, regular ones as a single blade since they're assembled in the factory. But there are attempts to do it differently because of the inconvenience. A swedish company make wind turbine towers out of wood that can be assembled on site: https://modvion.com/

Here are some images to give you an idea of the size of large wind turbines https://growsverige.se/2023/02/11/storleken-svindlar-pa-nya-...

Birds won't be happy, unfortunately. Yet, better than wrecking Earth's cycles by pumping to much garbage in the atmosphere like we do today.

Not trying to pick a fight but just posting because I hear this often from my friends, re birds being happy.

The choice, if between coal-fired plants and windmills should be pretty obvious to birds. Sure we may not see them getting splashed to bits with coal-fired plants but they are silently getting ill/dying over time.

So are people, yet we are afraid of nuclear power…

Bird death from turbines small-scale and highly predictable. Deaths from nuclear can range from zero to regional catastrophe and it's basically impossible to predict when it'll happen and how bad it'll be.

I'm not anti-nuclear, but the risk profile is SO different from wind.

The worst case is worse, but nuclear disasters are so rare and reactors produce so much power that nuclear is safer than wind in terms of deaths per TWh.

https://ourworldindata.org/safest-sources-of-energy

Let's stop subsidizing their accident insurance then.

https://en.wikipedia.org/wiki/Price%E2%80%93Anderson_Nuclear...

> The Act required companies to obtain the maximum possible insurance coverage against accidents, determined to be $60 million

It’s a necessity, and extremely logical and reasonable.

The most recent "disaster" was Fukushima, the actual cost there is far far greater than $60 million.

The point being that they aren’t able to get private insurance higher than that, so the government has to come up with a way to help.

They’re insured the exact same way the banks are.

> the risk profile is SO different from wind.

As is the power generation profile. Wind/solar/tidal are important to develop, and the risk profile should include whatever peaker or storage backs up the variability in generation.

Because solar and wind are a fraction of the capex and opex, have none of the risk or security headaches, more easily distributed (meaning less grid infrastructure) and don't generate nuclear waste.

People tend to be afraid of things that can blow up and make the surrounding area uninhabitable.

Fortunately, this is an offshore turbine, so it gives a lot of surface area for marine life to live on, which eventually turns into food for birds.

Painting the blades lowers the number of collisions significantly.

But I’ve heard that birds, when flying, are mostly looking at the ground. Perhaps sound is a better way to alert them?

Birds are a lot less happy about mirror glass buildings; in some places it literally rains dead birds.

Just to examine the common claim about wind turbines killing birds -- the number of birds killed by wind turbines is vanishingly small compared to other threats.

https://www.fws.gov/library/collections/threats-birds

234,012 - Collisions: Land-based wind turbines

6,600,000 - Collisions: Communication towers

72,000,000 - Pesticides & other poisons

214,500,000 - Collision: Vehicles

599,000,000 - Collision: Glass skyscrapers

2,400,000,000 - Predation by cats

[Unknown] - Habitat loss and climate change

These are just some estimates of some admittedly very difficult to capture data, but the orders of magnitude differences are revealing nonetheless.

This made me think that people in the West imagine East Asia like Japan or Hongkong, ie. everything is packed and very small. But China in general really is like the US (and indeed the country is of similar size): everything tends to be big. Certainly, coming from Europe, everything is huge in China.

Given that the wind is pushing it, wouldn't the blade tip's speed somehow be naturally limited by the wind speed?

At least in sailing, you can go a lot faster than the wind; I assume the same is true for these blades.

it would be except that the goal of a wind turbine is to generate power rather than go fast

How do you go fast except by generating power? Force times distance over time, that’s how sailboats move too.

It's not the blades that have to go fast, but the generator.

More specifically, power is Torque x Omega (rotational speed) for a rotational system

So yes, faster means more power. Torque is limited by the generator and how much power is "being pulled" from it. (which is a bad description but there you go)

How can you travel faster than the wind that is pushing you?

Apparent wind, and angle

Even if that where true (note that the wind is not pushing the blade directly away, but sideways), the tip of the blade is not responsible for most of the force (since it mostly depends on the cross section area, intuitively).

In other words, wind pushing the middle of the blade could accelerate the tip, even if the tip only produces drag.

Not necessarily!

https://www.youtube.com/watch?v=yCsgoLc_fzI

I don't know about this one, but a single rotation of the turbines recently installed in the North Sea can generate enough electricity to power an average family home for a day.

Wow that is a really interesting and coherent way to conceptualize how much power it makes, and how quickly.