Meanwhile,
the race gets hot. The big green Mallard is like a buffalo in
a storm. It points its head rock steady into the wind and does what
it is programmed to do. The buffalo survive, the Mallard generates
electricity. The massive blades gulp the howling air and do so quite
easily. A slight struggle arises as the wide sheet-metal tail-vane
momentarily fights to stay in the wind. It wins the battle and the
rotor spins until the wind gives up. The Mallard is very comfortable
at this speed and wouldn’t mind seeing it on a more constant basis.
Output:
Power output is as good as it
gets. Twin Air-X’s are outputting 400 watts each, occasionally
stretching their limits to 550 watts in brief gusts. The ammeters
are pegged at 30 amps, real world amperage might be around 45 amps.
Voltage is pretty well controlled at 14.7 volts or slightly less.
The Mallard, the shaggy monarch on
the southwest roof, is starting to shine. Still well below the Air-X
output, it’s generating 15-20 amps at the high end of this wind band at
about 14 volts. Although
a microprocessor controls the voltage output of the Air-X’s, the Mallard
will continuously feed electrons to the battery as long as its voltage is
above battery voltage. It cares not one bit about what is going on
inside the Air-X.
Could be, I begin to think, this
beast needs some control.
The Air-X units have an integral charge controller inside the fish-like
body. It senses the voltage on the batteries and limits its output
to avoid overcharging them. It is user adjustable within a narrow
range. The Mallard is an uncontrolled device. If the voltage
generated in the unit is higher than the battery voltage, it charges the
batteries whether they like it or not. Overcharging batteries can
cause damage and produce hydrogen gas in the process.
One type of external charge controller often used to regulate uncontrolled
sources is a diversion load controller or dump load controller. It
is placed on the battery bank and when the batteries are full, it diverts
the excess charge to an electronic bottomless pit like a hot water heater.
When the battery voltage falls again to some percentage below full charge,
the diversion load shuts off and battery charging resumes. I have
one of these, I just haven’t installed it yet.
35-45 MPH
Forget
about sleep! It’s not going to happen. This wind regime
doesn’t occur very often, but when it does...
The Air-X’s
continue to spin wildly; howling and occasionally screaming at the wind.
Up and down they accelerate; both are in a constant frenzy. One will
spin out of the wind, decelerate rapidly then charge right back into the
wind for more. This is excitement! But things deteriorate
rapidly.
A quick
flutter on the west side, east side holds into the wind then spins out.
Peace rushes in but only for 30 seconds and then the fury resumes.
At the upper end, they seem to spend too much effort in fighting the wind,
and it appears that they are losing the game and being battered
unnecessarily. Out of mercy, I’ll throw the stop switch - they’ll
fight the wind again some other time. For the Air-X, the battle is
over, the wind has won. Faithful, hard-working, robust,
it is
all that I could ask for in a small wind generator.
The
Mallard, still a magnitude quieter than the Air-X’s, has plenty of fight
left. I can see and hear the tail-vane occasionally shudder as a
gust of wind tries to take it from the side and knock it out of the wind.
The gust fails and only serves to spin the rotor faster. All six
blades are moving so fast I can’t see them anymore. Striking back at
the wind like Hell hits the sinful, the Mallard searches
for,
and hunts down the wind. The sound is like 1000 . . . no, 2000
Tibetan monks simultaneously chanting “OMMMMM” into a microphone with no
pause for breathe, just a long continuous chant until the wind gives in.
Oh, what a glorious battle! This! This is how electricity
should be made!
Output:
With the Air-X’s shut down, power
output is left up to the Mallard, the fighting monk. Output is
around 20-30 amps with uncontrolled voltage that may temporarily exceed 17
volts. While the batteries will accept the high voltage especially
if they are in need of charging, the AC inverter that converts battery DC
voltage to 115 VAC complains. Above 17 volts the inverter shuts down
the AC side of my electrical system and I have a momentary brownout for
having too much power!
45-50+ MPH
Stand back!
This could be the end of us all! The Air-X’s are out of the picture
now. Like Davy Crockett left standing alone at the Alamo, the big
green Mallard is on its own to defend the roof against a menacing 50 mph
wind. It could be that it is at the peak of its endurance, but then
again, maybe not. “Bring it on, you dirty sons -of-Satan!” the
Mallard taunts the wind. A strong gust suddenly attacks off to the
right in an attempt to spin the machine out of the wind and kill it.
The big, green, sheet-metal vane shudders slightly and the Mallard quickly
flicks its head to capture the gust, accelerate, and almost immediately
face back to the prevailing west wind for more. Thump, thump, thump.
The mast starts vibrating above the top mount making contact with the trim
across the lean-to roof. Uh-oh! Could this be the weak link, the
Achilles heel that brings the big green Mallard, the king of the wild
frontier, to its knees?
Another
slight ripple across the tail-vane, but this time the Mallard stays facing
the wind, blades spinning furiously and roaring back at the howling wind.
By God, I think, he’s actually enjoying the battle! Another side
thrust from a gust is handled. Its energy captured but followed by
some turbulence that causes the tail-vane to oscillate left and right a
couple of inches each way and a brief struggle to maintain stability
ensues. But
the long pitch from the center mount to the tail mount results in less
than a half inch variation in the rotor direction so the Mallard has no
trouble in regaining its footing. No flutter, no hunting for the
wind, just head-on, rock-solid stability. No, I’m convinced there’s
more fight left in the big green Mallard.
The energy
in the wind scales with the cube of the wind speed. There’s almost twice
as much energy blasting through the Mallard at 55 as there was at 45 mph.
But I don’t think Ace Bass cares; he’s in the fray until God calls him
home... or the 50 amp fuse blows and it may be close to 50 amps now, I
don’t know, but the wires are warm. This is my kind of wind machine!
Years ago I
lost hateful Hilda because I was a fool and didn’t act. I’m wiser now, age
does that sometimes. So I throw closed the stop switch. I
guess I’ll never know the Mallard’s limits. But I’ll sleep tonight
and dream about it.
Here’s some
links for further information.
Southwest
Windpower (Air-X) :
www.windenergy.com
Mike’s
Windmill Shop (Mallard):
www.mikeswindmillshop.com
AWEA
(American Wind
Energy Assoc.):
www.awea.org
