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Comment by jacquesm | Hacker News Reader

This is spot on and the real reason. Thank for posting this, I was working on a much larger comment but yours is better because it says the same thing in fewer words.

If tower thump were not an issue then a one bladed turbine would be the best possible turbine (cost efficiency wise).

Further down he's even arguing for turbines with 12 blades, it's a ridiculous number and quite inefficient unless you want very high torque at low rpm such as for directly driving a mechanical waterpump.

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Jacques, you are too nice, you could have said you have also the practical experience of what is building a windmill[0]. A very nice read for people enjoying both using a computer and their hands building stuff.

[0]: http://jacquesmattheij.com/how-to-build-a-windmill

Is there any particular reason why that piece never uses the phrase "wind turbine"? That's actually what it is, right?

At the risk of stereotyping; because he's Dutch? :)

Because lay-people call them windmills.

You mean a real, practical, one bladed turbine like these guys? http://www.powerhousewind.co.nz/story.htm

Even though 12 blades are less efficient, the article points out that they may have advantages for the bigger system of a whole wind farm, availability of sites, production, transport, control and non-generating time. It's not beyond belief that all those other advantages could counteract the reduced efficiency. You can't really know from intuition unless someone actually studies it.

Another example - commercial aircraft are known to have a relatively inefficient shape, but that's cheaper to produce than the more complex and more aerodynamic alternatives even though they would reduce fuel costs.

It's significant that high-solidity turbines with many blades are in use. As you say, they're quite common in small-scale settings like water pumping.

An article purporting to 'discover' that design would probably be more shocking if it wasn't already in common use for sensible applications.

cool. I thought I had read in an issue of Popular Science or Discover magazine that one blade was theoretically the best but I don't know enough about it to say for sure.

you're probably thinking about a propeller - as in the type on an airplane or boat that puts energy into a fluid.

I'm not an expert but I'm pretty sure there is a big difference from a device trying to pull energy out of the fluid.

A quick google didn't lead me to an authoritative source, but I know I have read many times that a one-bladed propeller is the most efficient.

Interesting. Isn't a fish fin (as in the fins on the side etc) essentially a one-bladed propeller?

Oh, I had thought an infinite number of infinitely thin blades got you the closest to Betz's limit?

Wouldn't that just be a disk?

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