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NASA COMMENTS OF
WIND TURBINES
WINDMILL
LINKS WIND
TURBINES
One
can look at two or three blade windmills and see that
most of the wind goes between the blades without effect.
One
of the reasons is that the mis-definition of energy
creates the assumption that higher velocity blades
deliver more power, since power is proportional to force
times velocity with the erroneous definition of energy.
But when definitions are corrected, power equals force
only. (See Energy Mis-defined.) Therefore, two more
blades could be added, which would increase output by
two thirds at almost the same cost.
Windmills for generating electricity would be much more
practical than assumed, except that their efficiency is
not being properly utilized.
The
overall efficiency of a windmill has to be directly
measured, it cannot be calculated, because there are too
many interacting factors. A good guess at design
efficiency can be made by direct observation. Only
measurements under operating conditions can improve upon
direct observation.
So
the US government spent a large amount of money
(probably more than a billion dollars) during the late
seventies and eighties creating experimental windmills
for testing their practicality. The results were
worthless, in spite of having tested dozens of
windmills. None of the experimental windmills were
designed for good overall efficiency, and the most
important questions were not studied.
Overall
efficiency means the amount of electricity that can be
generated over time on a cost basis. In other words,
will a kilowatt hour cost ten cents, twenty cents, or
what?
Two
factors are important in determining overall efficiency
of a windmill. One is its ability to use low velocity
wind, and the other is its conversion efficiency.
The
ability to use low velocity wind determines whether the
windmill is working or doing nothing while wind
velocities are low, which is a large part of the time.
For
example, an area might have wind of 15 miles per hour
(mph) or greater 20% of the time, and 10 mph or greater
40% of the time. A windmill that can use 10 mph wind is
operating 40% of the time, while one requiring 15 mph
wind is only operating 20% of the time, which is half as
much.
The
windmills tested by the experimenters would not use low
velocity wind. The minimum wind speed required by their
"best" designs required more than 15 mph wind
speed. There is no reason why 5-10 mph winds could not
be utilized to create highly efficient windmills for
generating electricity.
To
utilize low velocity wind effectively, there has to be
more blades. The researchers primarily studied two blade
systems. They never even made comparisons to systems
with more blades.
Conversion
efficiency also requires more than two blades. More
blades allows lower rpms, which results in less
turbulence, so conversion is more efficient.
A
quagmire of technicalities does not change these overall
facts. Arguers will talk about torque and velocity
trying to prove something, but it proves nothing,
because there are infinite options in integrating all of
those factors.
For
example, they repeatedly say high rpm rotors are needed
for generating electricity. That's mindlessness.
The
tip speed of the blade increases as the circular
diameter of motion increases. In the government
experiments, two blade systems were used, with rotors up
to 300 ft long. Tip speeds were in excess of 200 mph,
which created problems with noise and vibrations. Normal
rotation was 18 rpm. This means more than 3 seconds per
revolution.
Notice
that the rpms have to decrease as the diameter of motion
increases. Otherwise tip speeds would by excessive. So
the rpms are determined by the diameter of motion, not
the number of blades.
Arguers
say high rpm at low torque is needed for generating
electricity, instead of low rpm and high torque. Fewer
blades is how to do that. But they need a gear box
regardless, and they make low velocity winds unusable
with that approach. A gear box makes the torque-speed
question irrelevant. And they contradict themselves to
an extreme by using large diameters of motion, which is
what really requires low rpms.
They
could get the same rpms by using a smaller diameter of
motion with more blades. They would then need more
rotors per unit output, but those concerns are trivial
technical challenges which are easily solved. Throwing
away the low velocity wind and creating turbulence
result in loss of efficiency.
The
government experimenters said they could produce
electricity at the usual price by using their large two
blade systems, which required wind speeds in excess of
15 mph. This means that if systems were designed to use
lower velocity winds with less turbulence, they would
have produced electricity cheaper than other sources.
The
design of the government windmills was extremely
expensive due to the large size. Supposedly, the larger
the size, the greater the efficiency. That point was not
tested, but general appearance indicates that the
technical difficulties of getting control of forces that
high off the ground was not as cost-effective as smaller
designs would be.
Let
me say this in plain English. Anyone can look at an
old-fashioned farm windmill, which had about 18 blades,
and compare it to an experimental windmill, which had 2
blades, and see that the farm windmill was extremely
efficient, and the experimental windmill is extremely
inefficient. It is quite visible that unused wind goes
between the blades with two and three blade systems.
Propagandists use a lot of numbers and jargon to deny
the obvious, but their numbers are not fact.
Modern
wind farms use three blade systems, which is a major
improvement over the two blade systems which were
studied. Diameter is reduced from about 300 ft to about
120 ft, which reduces tip speeds and cumbersum stress
forces. Whether four or five blades would be an
improvement depends upon mechanical factors and
reliability; but if smaller diameter and multi-blade
systems were designed, they would be more practical for
small users and home owners.
Relativity
Global Warming
Ice Ages
Asteroid
Geology Earth's Core
Tornadoes Windmills
Transgenic Crops
The Sun God
Art that Proves
Nov55L inks
WINDMILL
LINKS WIND
TURBINES
CONTACT:
nelson@solarnavigator.net
07905 147709 (UK)
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