A Conversation for Ask h2g2

Wind turbines

Post 1

MonkeyS- all revved up with no place to go

On a recent trip to Devon I saw several wind turbines that weren't the classic 'windmill' design: they were upright poles with the turbines on the side of them, sort of a helix shaped blade, giving them a 'barbers pole' look. Does this make sense?

Anyway, I just wondered how efficient these were compared to the traditional turbines. I'd imagine you could group more of these together, less weight than the conventional design too.

Has anyone else seen these, or did I have one too many pints of the local beer? Do they have a specific name?

Wind turbines

Post 2


They are discussed here


I can see where they have their advantages, wind direction doesn't matter, greater mechanical stability (lower shear forces acting on them).
But I can also see their disadvantages - simply through the law of levers it will take a greater force to turn them as the force must act much closer to the fulcrum/centre of rotatation...

Interesting to hear what some resident engineers have to say...

Wind turbines

Post 3

MonkeyS- all revved up with no place to go

Kewl! Thanks, Orcus, some good reading to be had. I think, for residential applications the vertical turbine would be more preferable (less space, less intrusive), but would be interesting to see what the power output, noise level etc is compared to the usual windmill type turbines. Also, from an environmental point of view there is less chance of damage to birds flying by, though I think I read somewhere that the claims about this don't hold too much water.

Wind turbines

Post 4

RadoxTheGreen - Retired

Bristol has one of those silly turbines at the city end of the M32. Nobody really saw the point of it when they put it up.

Wind turbines

Post 5

Spaceechik, Typomancer

In California, we call that type "eggbeaters"; there's a whole forest of them North of Mojave, near Boron. Visually, I like the windmill types, but they do tend to require a higher wind velocity to be more efficient, and can interfere with each other if too close together.

Eggbeaters are slightly more efficient, but they're not as cute...smiley - laughhttp://tinyurl.com/3ugtjfa

Wind turbines

Post 6


smiley - erm Was it just me, or did half the text on Orcus's link seem to be missing?

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Post 7

Not the monkey - Skreeeeeeeeeeeee

There are vibrational issues (with knock on impact for maintenance) Think of how much the big blades must shake and how they transfer all the vibration to the axis. But I believe the ~vertical axis~ ones you mean are less efficient. Swings. Roundabouts.

An ex-Researcher who I know in RL is a genuine, perfessional expert. I could get the full gen from him.

Wind turbines

Post 8

Not the monkey - Skreeeeeeeeeeeee

Maybe SCs right - slightly more efficient.

Therell be manufacturing issues also. More complex blade arrangements = bad.

Wind turbines

Post 9

Reddy Freddy

>> Eggbeaters are slightly more efficient, but they're not as cute... <<

Yeah, because we choose our power generation for cuteness. I mean, who can resist these puppy-dog eyes? http://3.bp.blogspot.com/_f0bvyZMrZ9k/S62mpQhOLgI/AAAAAAAAEb8/PGet20uLJyM/s1600/coal-fired-power-plant.jpg

RFsmiley - evilgrin

Wind turbines

Post 10


In simple terms, the most efficient configuration is a rotor plane normal to the wind direction and a rotor axis parallel with it. So if the wind always blew in the same direction at the same speed, we'd have propellers on sticks every time.

Unfortunately, the wind doesn't. Vertical axis wind turbines (VAWTs) have the advantage that they always face the wind even when it's continually changing direction. They're also less noisy than conventional windmills of equivalent power because the rotor tip velocities are lower (not so far out from the rotational axis). You can pack them more densely too.

VAWTs would probably be the norm except for the fact that the wind strength varies too. Whatever kind of turbine we choose has to work efficiently when the wind is weak (most of the time) and yet be robust enough not to come apart when the wind is strong. With conventional windmills, you can get round this by pitching the blades, and the slew gear used for this is fairly reliable. With VAWTs, an equivalent adjustment to reduce the blade area presented to a stronger (ie higher speed) wind is proving more problematical. VAWTs might turn out to be limited to use in places where the wind speed range is small, and particularly to urban locations.

There are lots of different types. Try Googling VAWT (images).

Wind turbines

Post 11

Ancient Brit

Nature has it's own way of harnessing wind power in the form of a tornado, more like a screw than a windmill.
It's hard to see how harnessing wind power to generate electricity can be efficient. Wind farms have to go where the wind is and of course that is rarely where the power is needed. However it has to be good for the economy, not so much in the distribution of green power, more as a means of distributing wealth in the design, manufacture, transport and construction of the requisite equipment.

Wind turbines

Post 12

Spaceechik, Typomancer

RF, didn't you see the smiley - laugh? smiley - tongueout Wind and solar are as cute as it gets...

The VAWT design is mostly what's being allowed within city limits, where they're allowed at all. When I lived in Northern California, they were not so rare as they are within Los Angeles proper (if there is such a thing...)

The VAMT is more efficient if you're going for small home power generation, in that the yield isn't much, but most single households don't need that much. With a battery system hooked up, and a small PV array, you could conceivably generate all the power you need and be completely off grid.

Wind turbines

Post 13

Taff Agent of kaos

or you could be on the grid and putting power into the system when you are not using it and there by reduce the amount of fosil fuel being used

smiley - bat

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Post 14

Spaceechik, Typomancer

What Taff said! smiley - biggrin

Actually, that's probably better overall, as you wouldn't need to have a battery system to store the juice when it's generated, for when it's needed.

Wind turbines

Post 15

Ancient Brit

The windmill and waterwheel are/were direct applications of natural power. It is doubtful if any attempt to convert them into another source of power to be distributed and applied universally can be of overall benefit to the environment.
The neatest/cutest form of energy is the sun. smiley - smiley

Wind turbines

Post 16

Not the monkey - Skreeeeeeeeeeeee

Actually, urban environments are the worst place for wind turbines. The turbulence makes them inherently inefficient. The sensible people are looking offshore. Yes, the installation and maintenance costs may be high, but these are outweighed by various other factors.

Wind turbines

Post 17


I had a very interesting discussion over lunch with a former colleague in the Forest Service last week.

When the FS was set up, it was given land that wasn't much use for any other agricultural purposes, so a lot of it is on tops of hills or in remote rural areas.

Guess what they've just realised that that land is prime for!

Wind turbines

Post 18


The thing about offshore wind is it will *always* be more expensive than onshore. Savings made by economies of scale in making the blades (for example) can be transferred to onshore.

Why build something where it's subject to salt corrosion, the vagaries of sea states and where you have to get a boat to service it (weather permitting) when you can build it cheaper on a hill and just walk to it for repairs?

Wind turbines

Post 19

Not the monkey - Skreeeeeeeeeeeee

Well it cant be any worse than planting ghastly, regular rows of Sitka Spruce on it.

Even so...there possibly arent *that* many tracts of land to get the economies of scale you can get at see. Plus - hills arent good for wind.

What we *really* need - Ive said it before and Ill say it again - is massive subsea turbines in the Pentland Firth, one of the worlds strongest and most reliable currents. As things stand, this faces two great obstacles:
- the technical challenge of protecting them against the house-sized boulders that are also swept along by the current.
- the (seemingly insuperable) legal barrier of the Crown Estates&#39; ownership of everything from the shore out to the territorial limit.

That or nuclear.

Wind turbines

Post 20

Not the monkey - Skreeeeeeeeeeeee

>>Why build something where it&#39;s subject to salt corrosion, the vagaries of sea states and where you have to get a boat to service it (weather permitting) when you can build it cheaper on a hill and just walk to it for repairs?

I suppose the thing is it might be possible to build and operate them *cheap enough* to make it worthwile, weighed up against other factors.

Its a genuinely complex equation, though. Some of the terms (installation and maintenance costs; residual land values*; efficiency) are easy to measure. Others (public acceptability: think of just how *much* land would be needed)...less so.

* But which I mean What else could the land be used for? For example...there&#39;s lots of empty land in Scotland. What would covering it with windmills do to tourism?

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