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Background

A colony of humans has settled on a remote planet where there is little to no sunlight, but there is a plentiful amount of earth metals. E.g.- Iron, aluminium, Titanium, etc. There are high speed consistent winds that make it ideal for harvesting electricity from wind (speeds of 60 - 100mph.)

Question
What type of wind turbines would be ideal for this environment? I ask this as I got the impression that regular 3 prop wind turbines would rip themselves apart at these speeds. Any suggestions?

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    $\begingroup$ Consistent in direction or changeable? $\endgroup$ – Joe Bloggs Aug 29 '18 at 12:40
  • $\begingroup$ Yes regular wind turbines are sensitive to extreme conditions. This is because they are built to be cheap and efficient for normal Earth conditions. But why bring a regular turbine? Bring a rugged and tough turbine. $\endgroup$ – MichaelK Aug 29 '18 at 13:31
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    $\begingroup$ how are there high winds with no sunlight? What is supplying the energy differential? $\endgroup$ – John Aug 29 '18 at 14:36
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    $\begingroup$ You should let your question sit for a while without accepting an answer, at least 24 hours. There are people around the world who may be asleep right now, but have the best answer! $\endgroup$ – kingledion Aug 29 '18 at 15:22
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    $\begingroup$ If you've got high winds and no sunlight, you don't need wind turbines. You just go to whatever geothermal feature is providing the energy for the winds and hook up a standard steam turbine. $\endgroup$ – Mark Aug 29 '18 at 22:04
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A variable pitch airplane propeller

There is no advantage to high rotor speed past a certain point

Rotor tip speed advantage maxes out around 80 m/s, with marginal energy efficiency gains dropping to 0 at about 110 m/s. Why do I bring this up? Because it tells us how we want to design rotors in high speed winds. Instead of a lighter rotor designed to move with the wind, we want a heavier and larger rotor designed to survive constant wear. Also, there is a certain point of rotor length in high speeds where we will lose our return on investment. THe higher the wind speeds, the faster the rotor moves, the faster the outer tip moves. THerefore, to keep the outer tip from getting too high, it would be more efficient to use smaller blades in higher winds.

Wind turbines can already survive high speed winds

According to wikipedia, a common survival speed is 60 m/s (134 mph) while some turbines are rated up to 80 m/s (180 mph). Turbines will lock their rotors at higher winds speeds to prevent damage. Commercial ones I looked at will tend to lock below 30 m/s; which is 67 mph and lower than your planet's wind speeds. A high survival speed just means that the mount and blades won't be blown down by winds of a certain speed.

What you need is pitch variation

Pitch variation will allow a turbine blade to change the angle with respect to the wind. There are papers proposing electronic control algorithms for rotor pitch that can capture wind speeds up to 50 m/s (111 mph, good enough for your world). The reason you need variable pitch is that your wind speed changes (from 60 - 100 mph) cover a wide range. Efficient production at 60 mph won't require the same pitch as efficient production at 100 mph.

Variable pitch wind blades don't exist commercially, as far as I can tell. There have been some research examples.

However, plenty of aircraft have variable pitch propellers. For example, the C-130 Hercules military transport aircraft from the US has such a propeller. Your turbine design will look like a airplane propeller, with electronically controlled variable pitch rotors. Note in the picture below, each rotor has a circular attachment to the hub. This will allow it to rotate the angle between the blade and the oncoming wind.

enter image description here

Conclusion

Airplane rotors can obviously adjust their pitch successfully in winds speeds higher than the 60 - 100 mph you propose. Algorithms for controlling pitch to optimize power production have been proposed in literature. And turbine installations can already withstand wind speeds upwards of 180 mph. Put these three concepts together to develop a successful high speed wind system.

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  • $\begingroup$ This is not an answer. This is really good commentary that should be in a comment on the question to guide people proposing answers. $\endgroup$ – SRM Aug 29 '18 at 13:14
  • $\begingroup$ I see. It happened to break at a point that looked done. I withdraw my objection. Maybe add a “work in progress” tag next time? $\endgroup$ – SRM Aug 29 '18 at 13:26
  • $\begingroup$ @SRM: Or just wait to publish until the answer is done; there's no reason to post partial answers. $\endgroup$ – Matthieu M. Aug 29 '18 at 14:04
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    $\begingroup$ @alex_d Ooops, now I can't find it. I edited a bit. $\endgroup$ – kingledion Aug 29 '18 at 14:19
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    $\begingroup$ Variable pitch rotors have been in use for years in megawatt wind farms, otherwise they would not be able to scale up $\endgroup$ – PlasmaHH Aug 29 '18 at 15:10
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Short Answer: Yes.

Have a look at some of the options in this link. I think the one you're interested in would be the Windspire.

enter image description here

"This 30-foot tall, 4-foot wide turbine generates 2000 kilowatts per hour given 12-mph winds, and it can survive winds up to 105 mph."

It's also nice and compact, which makes it even more suitable for the kind of scenario you're describing. You'd probably want to scale it up for your purposes though. There's no particular reason you couldn't make them much, much larger without compromising their ability to handle your high wind speeds.

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    $\begingroup$ According to this, it is rated for 30 mph winds. That means it will lock at higher speeds. This won't work. $\endgroup$ – kingledion Aug 29 '18 at 13:08
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    $\begingroup$ "Kilowatts per hour" is probably wrong. Suspect they mean just straight "kilowatts". $\endgroup$ – Undo Aug 29 '18 at 14:30
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    $\begingroup$ @kingledion oh hey, nice find. I'm sure that's true for a 30 foot version, but if you built a more robust one, I'm sure you could generate power with it at higher speeds. TBH all you'd need to do is add a transmission and variable-pitch vanes, and maybe a flying buttress if the wind is mostly coming from the same direction. $\endgroup$ – Morris The Cat Aug 29 '18 at 14:40
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    $\begingroup$ "2000 kilowatts" aka 2 MW? Not likely: "A GE 2 MW has more than 2 football fields of rotor swept area" This windmill sweeps 30x4=120 square feet. It simply doesn't sweep enough area to make "2000 kw". "2000 watts" maybe. $\endgroup$ – Harper Aug 29 '18 at 17:07
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Considering that airplane propellers go substantially faster than wind turbines but do not fly apart, I think you should be able to rig a windmill equal to your windspeed.

But how boring. Instead, make wind turbines patterned on jet engines! Those go really fast. I could only find one.

wind turbine https://www.youtube.com/watch?v=ygBsb5FKyOo

You can assert that the radial redundancy holds it together better in the high winds of your world. And it is cool looking!

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    $\begingroup$ You are going to deal with big problems equivalent to compressor stall. Jet engines can't handle air flow as low as 100 mph. Now if wind speeds were 1000 mph you'd be on to something... $\endgroup$ – kingledion Aug 29 '18 at 13:24
  • $\begingroup$ @kingledion - really this linked thing was just built in a jet engine housing. The multiple little fins I think is artistic license and the builders idea for an unusual functioning wind turbine - that is not how a jet engine looks. But maybe if there were funnels to concentrate the wind... $\endgroup$ – Willk Aug 29 '18 at 14:48
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Change the blades

Crazy easy. You go to Clipper Windpower and you say "Hey guys, I want your commercial off-the-shelf industrial windmills, but I have very strange atmo pressure and wind speed."

Why Clipper? Because until quite recently, Clipper was part of UTC (United Technologies), a big aerospace conglomerate. And so their Rolodexes will still be full of contacts from ...

enter image description here

Who is The Very Premier maker of propellers in the western world, having made them for everything from the Spirit of St. Louis to the evolved E-2 Hawkeye*. Rest assured, Hamilton Sundstrand propellors have no trouble at all with your wind speeds.

Between both companies they'll easily figure out a new windmill blade for you that "bolts up" to their standard hubs and control systems, and the stock control software doesn't even need to know it's on a different planet. Which means, no new bugs.


* The 8-blade prop, while aerodynamically excessive, is an even multiple of the previous 4-blade prop, and that greatly simplifies the rewriting of the radar software, since the rotodome and other radar systems must account for their own prop shadows).

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  • $\begingroup$ Hamilton Sundstrand is now known as United Technologies Aerospaces Services (UTAS) :-) $\endgroup$ – darthbith Aug 29 '18 at 21:24

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