Re: Pipestone

On Thu, 07 Jul 2005 10:02:55 -0500, "Aubrey McIntosh, Ph.D."
<newsposter@xxxxxxxxxxxxxxxxxxxxxx> wrote:

>...

>I have put a brief annotation and some of the photos at
>http://aubrey.vima.austin.tx.us/pipestone.html

Something I've wondered about since seeing GE's recent ads for
their wind generators, is those relatively thin-looking three blade
propellors (or in this case propellees?). It seems like they don't
'catch' much of the air, as opposed to the typical old farm windmill,
as seen in pipestone1116.jpg, that has a few dozen blades and pretty
much makes a solid circle of blades that catches all the air coming
through. It seems with more blades one can get more torque and
generate more power with a particular wind speed, as opposed to having
a larger number of three-blade generators at presumably greater
overall cost for the amount of power generated. Does someone know more
about the aerodynamics and economics of this?

I looked around a little and read this tidbit I found a little
surprising (it wasn't well-known to me):
http://www.windturbinecompany.com/technology/index.html
"It is well known that 2-blade turbines capture approximately 97% as
much energy as 3-blade machines with the same rotor diameter."
If that's to be believed, the power generated does NOT increase
substantially with an increase in the number of blades.

-----
http://www.mindspring.com/~benbradley
.

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