Hi DaveS,
I
didn't say that I expect Dr. Dabiri to “validate” the Sharp
Cycloturbine. I want him to understand it because it is well suited to
his purposes. Please avoid pejorative paraphrasing.
I
showed you my paper that explains, among other things, that VAWT are
inherently more efficient than HAWT. Astonishingly, you then reassert
the false claim that VAWT are less efficient than HAWT because the
blades move upwind. That's nonsense made up by people who don't
understand VAWT. It's an old troll's tale that probably originated when
some naïve person noted that drag type VAWT experience drag on the
blade moving upwind which reduces efficiency, and then he uncritically
assumed that lift-type VAWT are also subject to the same drag. That's
false physics. I’ve warned you that there is a lot of false information
about VAWT on the Internet, and I’ve given you examples. Please apply
your skepticism to your own assumptions, as any researcher should. If
you still insist that you are right, then show me your evidence in
vector form. You can’t.
The
advancing side of a VAWT produces much more lift and thrust than the
retreating side. Yet if your false physics were correct, the opposite
would be true.
Here
is a simplified explanation: For a VAWT with a TSR of 3, and ignoring
the effect of wind shadow from the upwind blade pass, the average TSR
on the advancing side is 3.5, and on the retreating side the average
TSR is 2.5. Lift is proportional to the square of the apparent wind
speed. So the ratio of the advancing side to the retreating side, in
terms of blade lift, is 12.25 to 6.25. In other words, the advancing
blades produce almost twice as much lift and thrust. Also, the blades
of lift-type VAWT have high lift to drag ratios. So when they are
heading directly into the wind, with no angle of attack, they produce
only minimal drag. The claim that VAWT are inefficient because the
blades move upwind is just negative propaganda kept alive by people who
-- if they are not simply ignorant -- wish to denigrate VAWT.
The
Windspire wind turbine used by Dabiri was basically crap and they duly
went out of business. My guess is that Dr. Dabiri used what was most
convenient to use at the time -- in terms of cost and close spacing.
The flaws in the Windspire were that it used a very large cantilever
with inadequate strength (some broke their foundations in high winds),
it was too close to the ground, and it was a fixed-blade VAWT operating
at a TSR which was too low to be efficient, plus the blade chords were
too short to be efficient at that TSR. As a result, it spun too slowly
for its direct-drive generator, which raised the cost of the generator.
I
saw an image of a wind turbine Dr. Dabiri designed, or had designed,
and I think that he used some of them for his test site in Alaska. If I
find that reference, I'll send it to you. Here is a reference
mentioning new designs from CalTech that they planned to test in
Alaska:
https://www.caltech.edu/news/caltechs-unique-wind-projects-move-forward-39703
I
just found a video that shows a brief shot of a small VAWT he will be
using in Alaska, but I’m not sure if this one was designed at CalTech.
This is where I saw the VAWT I referred to:
https://www.youtube.com/watch?v=FNUSphVmnuE
And here is his 2015 updated lecture that includes images of those new VAWT:
https://www.youtube.com/watch?v=pAGAcGoyP8Q
I particularly like this 2012 Dabiri lecture because it make the concepts especially clear:
https://www.youtube.com/watch?v=Bc4GRaAyE9c&t=54s
Whats is “COTS”? He doesn’t use that acronym. Are you coining an
acronym without identifying it?
A
tall, stacked Sharp Cycloturbine could be suspended from an overhead
cable. Many of them could be suspended from the same cable. So they
could be used just like the Dabiri used the Windspires, but they would
be more powerful and produce even less turbulence (because accurate
pitch control reduces turbulence). Then Sharp Cycloturbines could be
combined into arrays to further increase their efficiency and to
further reduce their turbulence. And the arrays can orient to the wind,
so new patterns are possible to enhance wind flow across a wind farm.
The arrays can be very tall or very wide. If very wide they can be
suspended at different elevations to take best advantage of the wind
energy flowing above them, as usual, and also below them by means of
leaving gaps between the vertical layers of the arrays. Of course, that
means more analysis and testing, but it promises to improve on what Dr.
Dabiri is currently doing. It could potentially make wind farms using
small-scale VAWT much cheaper than wind farms using large-scale HAWT.
But Dr. Dabiri has to complete his present project because it is
already funded from grants. So even if there is a better idea, he can’t
switch to it in mid-stream. That is a flaw inherent in academic grants:
if they discover something better along the way, they can’t follow that
lead until they complete the project they are working on.
Your
comments seem to assume that if I reveal a new insight in my paper --
that VAWT are inherently more efficient than HAWT if appropriately
configured -- it couldn't be true if everybody doesn't already know it.
But new ideas are new because people don't already know about them.
Lots of people have good ideas that people don’t listen to. It took 25
years of promoting submarines for people to take the concept of a
submarine seriously.
You
make a dubious claim that the lowest weight per unit of power predicts
the lowest cost of power. That is a good rule of thumb because weight
and cost are fairly closely correlated, but it is not a law of physics.
There are usually exceptions to rules of thumb. Often, achieving
extreme lightness can be very expensive when exotic materials or
processes are required . For HAWT, three blades, although heavier than
two blades, cost less in the long run because they are more reliable
due to better balance when yawing. For VAWT, three blades are better
than two blades because, although heavier, three blades smooth out
rotor drag pulses that can cause fatigue problems for the rotor as a
whole. Consider a car without shock absorbers. It would be lighter. But
it would be far less reliable. So it is important to consider new kite
ideas in terms of whether they might also be exceptions to the
weight-cost rule. Some probably will be. The weight of the ground
station must be considered as well, and some will be much heavier than
others.
The
KISS rule of thumb when applied to VAWT assumes, uncritically, that any
additional moving parts, such as blades that pitch, means that
reliability will be reduced and costs will be increased. The people who
make that claim are thinking about conventional blade-pitching systems
where that rule of thumb does apply in most cases. But if you study
VAWT and the Sharp Cycloturbine, you will learn why the Sharp VAWT
promises to be cheaper, more reliable, more efficient, and able to
capture much more wind energy than is even predicted by its higher
efficiency (because it can capture much more energy from wind gusts).
The blades of the Sharp VAWT are more durable because they are
protected by the shock absorbing effect of using cord bearings and free
pitching. Turbulence does not stress the blades nearly as much as for
rigidly mounted blades. And V-blades greatly reduce bending stresses.
The pitch control should be more accurate than other mechanical systems
and it costs almost nothing and has almost nothing to wear out. So the
Sharp Cycloturbine is one of the exceptions to that
complexity-reliability rule of thumb if one assumes that blade pitching
adds complexity.
But
then, if one looks even more closely, in the case of the Sharp
Cycloturbine the blade-pitching actually reduces complexity if you
consider the various kinds of complexity, such as the machines and
processes required to produce it, the complexity of the overspeed
control and self-starting devices, the need for more parts and more
specialized parts, versatility, ease of shipping, etc. So from that
perspective, the Sharp Cycloturbine actually conforms to the
complexity-reliability rule of thumb because it is so easy to make
using relatively few, common, inexpensive materials and parts.
PeterS
