as well, so don’t skimp
here. Also, set the
WindPitch about two
feet away from the fan
and not directly in front
of it, since the wind will
be more laminar
(smoother) at this
distance (Figure 7).
Finally, turn the fan
on to its highest speed
setting and witness the turbine
blades spinning. If the turbine is
oscillating (yawing) wildly (which it
can do in high winds produced by
fans), you might want to adjust the
set screw on the mounting pole to
keep it steady (Figure 8).
For the following experiments,
keep the distance between the fan and
wind turbine the same — don’t change
it or else your data will be invalid.
With the WindPitch output wires
connected to your microprocessor
setup and your computer running the
REEL Power software, adjust the 100
ohm [load] potentiometer to full
resistance. You should witness a plot
like Figure 9 where you can see
voltage, current, and power
Figure 7. WindPitch/Fan
Setup with BS2 Board of
Education.
displayed. Even though the REEL
Power software says Solar Panel
Interface, this software will do fine
for the WindPitch experiments since
they are all DC and don’t involve any
three-phase AC like the Whirlybird™.
When you have all of this
working, you’re ready to start
experimenting with this neat product.
Adjusting for
Maximum
Power Point
carefully align the small “dash” mark
on the inside of the hub with the flat
part of the alternator shaft (Figure 6).
Push the hub onto the shaft until it is
nearly flush with the fuselage. If you
don’t properly align the dash mark
and flat part of the shaft, it won’t fit
together.
The next thing to do is set the
whole assembly in front of a large
table or floor fan — preferably one
that is about 16 inches in diameter or
larger. The diameter of the fan blades
should be at least 50 percent larger
than the overall WindPitch blade
diameter to deliver adequate wind; a
smaller electric fan will work but not
Figure 8. Fuselage
Set Screw.
Figure 9. Typical REEL Power view
of Voltage, Current, and Power.
In order to form a baseline for
the performance of the WindPitch for
all conditions of blade types, blade
pitch, wind speed, and so forth, we
first want to know how to determine
the Maximum Power Point (MPP).
This is to create an even testing
environment for all conditions. Recall
from Part 1 that the MPP is achieved
when the impedance of the power
source equals the impedance of the
load. This is done by adjusting the
100 ohm load resistance pot to
match the impedance of the three-phase alternator. From previous
experimenting, I have already
determined that the average
impedance of the WindPitch three-phase alternator [after being full-wave
rectified] is between 50 and 75
40
April 2010
