Alt-BEAM Archive
Message #02207
To: Dennison dennlill@buffnet.net
From: Bruce Robinson Bruce_Robinson@bc.sympatico.ca
Date: Sat, 10 Apr 1999 17:28:05 -0700
Subject: [alt-beam] Re: wind power
> Dennison wrote:
>
> Attach a small propeller to a dc motor mounted on top of a walker. I
> wonder if you could realisticlly power something like that.
>
Now THERE is a topic I know something about. If you want the detailed
math, ask & I'll send it. Here it is simplified.
The amount of power you can get from moving air is proportional to the
cube of the air speed and the square of the propeller diameter. This
assumes the propeller is facing directly into the wind and the energy
conversion is perfect -- in other words, the absolute max you can
expect.
Assuming a 100 mm diameter propeller (4") ...
Beaufort scale 3 = gentle breeze = 16 km/h = 10 mph ---> 0.4 Watts
Beaufort scale 5 = fresh breeze = 35 km/h = 22 mph ---> 4 Watts
As far as electrical conversion, I haven't a clue. My faltering memory
vaguely recalls that not all types of DC motors will act as generators.
Ideas, anyone?
Anyway, if these kinds of numbers are remotely of interest, I can give
you some numbers on the other problem you'll face - overturning forces.
Regards,
Bruce
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