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Posted by Curbie on December 20, 2009, 5:53 am
That video was more interesting, on a home-scale unit I suppose you
could roll up sails for wind funneling to help solve high-wind furling
issues, probably would need to replace them once a year though.
I'd want to do something to protect the machine in high-winds, just
building a stronger (heavier) machine for high-winds seems
self-defeating for generating power in low-winds, I doubt just putting
a brake on a light-weight high-drag machine in high-winds is going to
cut it, and I'd still like to run the math.
Somewhere in the first link you posted, they talked about using
permanent magnets for small machines (.4 to 5kw) it seems they want
magnetic bearings for both vertical and horizontal loading, and I
think you may need to get the whole thing up on at least a 10' mast to
keep snow form interfering with it.
Seems like there's some stuff there to experiment with, have fun.
Posted by Michael B on December 20, 2009, 2:31 pm
Yeah, one like at
would probably need to replace the sails, and they could be
provided with simply a strong spring at their base, so that if
an excessive wind were directed at one or more, the sail could
be pushed back and in the process the incident wind on the
turbine would likely be at least cut in half.
And a drag-style unit will not be going faster than the wind.
So it needs to be optimized for lower RPM, but able to tolerate
The one in the video is not the one I'm pursuing, though. But
you can see that it is being marketed.
Posted by Curbie on December 20, 2009, 7:12 pm
Not quite how I envisioned it, but close enough; the machine would
still need protection from gale winds, snow drifts and freezing rain.
But with a little though I think those hurtles could be over-come.
In the last few years I've been building in Google Sketch-up before
building anything physically, it catches a lot of problems and allows
you to try a bunch of "what if" on the cheap, before spending money.
Sketch-up is free and pretty easy to learn.
I like home-scale wind and had pretty much settled in on the Dan's
(otherpower) 10 footer, but will play with the math and design on this
idea to see what I can come up with. How are you envisioning the
magnet bearing, does your plan use them for both vertical and
horizontal loading and does your plan use the same magnets to also
I'd still run the math which is also free and start with a scale
model, but there seems like enough there to make experimenting
Posted by Curbie on December 21, 2009, 12:50 am
Well, it's pretty clear I don't have a handle on the math for these
machines, I threw together a visual concept in sketch-up to get the
blade size which is 7 Ft.^2 per blade (0.6503213m^2), the concept
machine's overall dimensions are 4' high by 4' wide on a 2' tall mast.
I tried to apply Piggott's power formula =Cp * (rho / 2) * (A^2 * V^3)
with the parameters of Cp = .30%, rho=1.2, A^2=.06503213, and V=4.47
(10MPH) and came up with:
=Cp * (rho / 2) * (As * V^3)
11watts =0.3 * (1.22 / 2) * (0. 6503213 * (4.47^3))
The video is making a 5kw claim and I tried to size the concept
machine to roughly the same size, but clearly have something goofed
Any help would be appreciated.
Posted by Michael B on December 21, 2009, 2:27 am
The 5 kW one in the video was just a reminder about
sails that would help direct the wind, that unit is not
what I have been dealing with.
As for magnetic levitation, I'm not really all that much
interested. Mine is a short unit, I don't really need
anything sophisticated. But the VAWT has far more
advantages to me as an urban dweller with low speed
winds and plenty of obstructions to cause turbulence
and incident direction shifts. The panel that has the
flaps being pushed is 40 sq ft, the others are really
in varying stages of being opened or closed.
I calculate local typical wind speed at 3-6 MPH,
even though the local airport shows a bit better.
And I am going to be using ceramic magnets rather
than Neodymium for my generator, I now have over
70 magnetron magnets. I want close spacing
between magnets and coils, would rather support
my outer rim with more predictable spacing, such
as skateboard wheels. Using a base of 8 ft diameter,
I can have a lot of magnets going past a lot of coils
every rotation. That would be if I put it on the roof.
I'm considering reworking a car alternator and using
the 8 ft diameter base to put some speed into it, in
spite of the associated loss. I have two treadmill
motors and a battery-operated lawn mower motor
sitting nearby if I decide to go DC.