GOT KIDS?!? Click here for a fantastic NASA lesson
for kids (and adults) on lift or to chat with NASA engineers
and other folks who study NASA airfoils.
Think you can't afford wind power? Think again; there are many ways
to get your equipment free or inexpensively at this link.
Click here for more free classes, wood shop and power tool overviews,
basic novice, intermediate and masters classes, along with videos,
CDs and hands on seminars on blade carving.
Visit the WindGenZen HOME PAGE for Kits, Price Comparisons, Blade Templates, CDs and
Online Classes on how to get the LOWEST COST PER AMP
Here is a discussion on airfoil,
reynolds numbers, lift/drag etc. from Hugh Piggot's educational
website. They provide classes as well
and are being built and used around the world. They
are great projects if you want are capable of
designing and building the type of alternator described
at Otherpower.com.
Below you will see a typical annual
distribution of wind speeds for an area with a 12.3 avg. wind speed.
Actually in San Francisco, we often see 40-50mph winds during winter, but using this distribution,
notice there is a lot of kwh power beyond the typical 20-25mph stall speed
of low speed airfoils. This power is only available if you have a gen
that can handle it and a blade that can produce it without stalling. This
power distribution explains why NASA Jerry prefers airfoil profiles with
higher stall speeds to capture the large amount of kwh power in the
upper end of the annual spectrum:
Here is a technical paper on large (100kw and
larger) wind turbines, describing some complex airfoil theory, gearboxes
and AC vs DC advantages and disadvantages as described
at windmission.dk.
Click here for super-low prices. Build a system for a little over $1000.00 that can
grow to take a family of FIVE off the grid - permanently
We have tested 'hollow' metal blades that claim to start up
in super-low wind speeds. That's great, but there is no power
at low wind speeds!!!
Hollow airfoils start up in low wind speeds, but they also
stall faster, make noise, lose power and won't spin correctly in solid
winds, so you miss tons of power from the middle and
top end of the powerband where you want it most.
This way when winds are strong, you get a good powerband without
the noise and when winds are light you still get power comparable
to hollow airfoils, without the noise, vibration or power loss at the
medium and top end.
The best blades are a full foil shapes, as recommended by NASA and
used in professional Wind Generators and used in well funded government studies.
A full foil is has a curved top and a rather flat or slightly convex 'belly'.
This shape will not stall as soon as hollow shapes and provides much more power throughout a wider powerband/RPM speed.
This assumes a proper angle of attack. Consider the following graph:
OOOPS! After about 16 degrees a cambered airfoil stalls. We usually
carve WindGenZen blades with a twist of about 8 - 10 degrees near the center
and 2-4 degrees near the tips to provide a uniform twist that changes
with the velocity of that section of the blade.
For low wind conditions, we can carve a higher angle of attack at
no charge for faster startup.
Here are some basic shapes to consider:
In the drawing above, the red line (bulge) is similar to the NACA 4418; unless
you specify a Wortman or 0417 curve, this is what we carve. There is no charge
to add the cut-away at the trailing edge (blue line) or the concave area (green
line) suggested by a high speed turbine blade designer. The problem with both of
these cutaway sections is the blade suffers a lot in low winds (up to 20% loss)
and suffers a little in medium winds (about 13% loss), so we usually carve something
similar to the RED line in the sketch, similar to the NACA 4418 unless you specify
an added curve.
(4 foot end section up close and personal)
The NASA physicist suggests that this shape (he has all the graphs) is the
most durable, best overall performer in the wind ranges you'll find. It doesn't
make sense to purchase a blade that 'starts at 3 mph' if the difference in
amps is only about .3 amps?!? The hollow blades won't provide the real
amps available when winds get to 15-30 knots and completely die off when
winds are hitting 35-50 knots. They can also get quite noisy. The blade
we carve will often start up in 6-9 knots (big deal), but the power curve
really takes off in 12-20 knots and at the top end they don't stall out
until you get well past 50 knots so they remain quiet and powerful through
a much broader range where the difference in amps is substantial.
That NASA Physicist who taught me to carve these blades said '...of all the folks I've met, sailors and engineers, you're the only one who took my lessons and made them work for your life.'
The reason is I avoided the temptation of a metal blade and wanted a real air foil.
I use these blades for almost all my power. They are efficient, quiet, take a beating in high winds, very reliable, easy to maintain (almost zero) and are very inexpensive compared to other systems; It's wood. It has wonderful tensil and compression characteristics; we've flown them in hurricane winds.
And wood is a renewable resource anyone can learn to work with. That is a big part of the Wind Gen Zen philosophy.
Next, a sailor who pulled in next to my boat while the generator was spinning remarked '...I used to own an AmpAir and threw it out. It sounded like a damn helicopter over my bunk. Your blades are 10 times quieter. I want one!'
Let me state for the record that AmpAirs are common, they work and various wind gens also attach to water driven props and that's all great. I like it.
But the WindGenZen larger 6 foot blades put out nearly twice the power in the same winds; it's a simple fact of blade sweep area. Also, these blades spin a bit slower in upper storm and hurricane forces due to diameter (safer and quieter), and they're much quieter at all speeds due to a higher stall point, and very powerful. If we made a 3 foot blade like the AmpAir it would probably spin faster, make some noise and wouldn't put out as much power.
With so many opinions, what can you believe?!? Well, remember this if nothing
else: any wind gen is better than no wind gen!
Please note: if you do not specify a shape, your blade may be either
a class cut blade, a Jerry cut (most common) or a WindGenZen cut depending
on what we have in stock and if possible, a best guess of your local wind
conditions based on your address.
Tip and foil shapes for wind generators
Learn about using smoke tests in airfoil design.
and the 
ROCK!
(4 foot end section up close and personal)
