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Comment by throwawayboise | Hacker News Reader

It's not the temperature per se, it's icing. I read it here

https://www.bloomberg.com/news/articles/2021-02-14/deep-free...

“When wind-turbine blades get covered with ice, they need to be shut down,” said Joshua Rhodes, a research associate at The University of Texas at Austin who focuses on energy.

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A windmill is basically a inverse airplane - and airplane wings don’t like icing. I assume you could heat the blades but at some point you’re consuming more energy than you’re making.

Planes have deicing boots. Holes in the leading edge of the wing that has a balloon on the inside. A non freezing gel is usually pumped in which expands the balloon out of the hole and causes the ice to crack. It then retracts and this process repeats keeping the wing clear of ice.

Not really usable for wind turbines though, the energy cost would be significant first of all (compare the blade area of a wind turbine to a plane!) The bigger issue is maintenance. Wind turbine leading edges are a very hostile environment compared to a plane and even normal materials get abraded very quickly, plus they are expected to last for many years without significant maintenance. Anti-ice systems would just not be economical if they had to be maintained to a working condition at all times.

Given they can generate their own electricity, wouldn't it make more sense to just heat the blades?

Probably not worth the EROEI

Heating the blades would be nearly impossible with any significant wind chill. I imagine anyplace that has wind turbines is going to have significant wind chill.

If you consider plane propellers, they do not have de-icers and must avoid known icing limits. The rotation of the blade causes the ice to fly off the blade up to a certain point. After that point, thrust will be impacted and altitude cannot be maintained. Dropping to a lower altitude will usually resolve the problem. Wing surface deformation is a larger issue for planes and probably not the solution here

That's because they lose lift though. For a turbine, that wouldn't matter (at least directly).

I have to imagine it's really the overall weight or the unbalanced weight not being good for the bearings and such. Not to mention a blade flinging a piece of ice off when it starts to melt...

The wind turbine spins because of an analog of lift - without “lift” it won’t spin.

There’s also the issue of balance.

>The wind turbine spins because of an analog of lift - without “lift” it won’t spin.

Thinking about it, that does make perfect sense, but just intuitively, I would think say, making a blade that had a flat side perpendicular to the wind direction would work, because the force can still be imparted to the blade. I can also intuitively surmise why that wouldn't work for a plane though.

When dealing with a plane, you want to generate force perpendicular to the wing (i.e. up when the plane is moving horizontally), but in a turbine you want the force to be in the same direction as the blade is moving. I feel like I must be missing something.

You're not - a flat board works as a wing with enough force behind it. There's a description on how a wing works involving Bernoulli's law - but it's more accurate to think of it how your hand feels when you hold it out the window of a car at speed.

And of course old windmills were just boards - and I suspect they only stop working in the cold if the bearings freeze.

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