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7:49pm on Wednesday, 2nd August, 2006:



Sometimes, outside garages and petrol stations, you see these signs that rotate in the wind. They usually have the name of some product on one side and the manufacturer on the other (GTX Motor Oil / Castrol). When I was a child, they were generally circular, like a speed limit sign, but nowadays they're rectangular with a curve of about 45 degrees at the edges so that the win will make them turn even if they're hit at right angles.

These signs can spin pretty damned fast at times, but even in only a slight breeze they usually turn. They're not all that tall — maybe three or four feet — and they don't make all that much noise, either, unless they've got bent or gone rusty. They don't need to face the wind, unlike windmills, so they can be placed in awkward locations such as next to chimney stacks or in alleys.

I wonder how good they'd be for electricity generation if you stuck a dynamo in the base? On a large scale, they'd be worse than windmills as they'd suffer if the wind at the top was coming from a different direction than the wind at the bottom, but on a small scale (such as in my garden) that wouldn't happen. They'd be cheap to manufacture, but whether the energy required to make one would be more than it could generate in its lifetime I'm not so sure. If such vertically spinning wind catchers do make a net profit of energy, though, then they could be a lot more useful as a means of generating power than the large, industrial windmills currently being constructed as a sop to the renewal energy crowd. Every household could have one, and reduce their reliance on the National Grid accordingly.

I'm sure there's a reason why such devices aren't ever used for power generation, but as I don't know what they're called I can't find anything on the Internet about their disadvantages. Vertical axis machines usually talk in terms of blades rather than a single sheet, and they're on a power station scale rather than a personal scale.

Maybe I'll just work on a device for rain power instead.

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Copyright © 2006 Richard Bartle (richard@mud.co.uk).