Peter -
Thanks for weighing in with some grounded experience/knowledge on this one.
Is AVENU completely defunct? SimTable (tm) is always in need of more
notional models to demonstrate it's utility across a wide variety of
domains, especially those likely to be involved in public-policy
decisions. The point of such a model would not be to place flocks of
windmills in an optimal configuration, but rather to demonstrate to the
public (and other policy makers) how flocks-of-windmills interact with
topography and prevailing winds, etc.
- Steve
_F’ing Windmills_
It is good to see FRIAMers enthusiastically holding forth on another
area of their whimsy – the effectiveness of wind turbine arrays. Wind
Energy can provide a significant contribution to our energy supply.
Understanding it helps. Commenters might be interested in the first
seminal paper, Energy Effectiveness of Arrays of Wind Energy
Collection Systems, (1976), by a clown, name of Lissaman. This paper
has been referenced and improved upon many times in the last 30 years.
The most recent revision, by the same author, appears in the book,
_Wind Turbine Technology,_ published by NASA, and reprinted by ASME in
2009. It’s ancient, but the principles, and our planetary boundary
layer have not changed.
The article in Science Magazine is an example of bad science
reporting, illustrating the red neck passion to simplify subtle issues
into easily understandable syllogisms (see contemporary Republican
politics). The reporter discusses “new” vertical axis machines! The
Darrieus Vertical Axis Wind Turbine was new in 1971, while the
Savonius VAWT goes back to 1931. So much for the writer’s research!
That history is in most encyclopedias. In 1976, I gave a paper at
the International Wind Energy Congress in Cambridge, England, funded
by US DOE, noting that the then new VAWTs were not cost effective
compared with the propeller type. I think that’s still true. The
FRIAM response seems a little like superficial science; thinking
things that “look like” or “sound like” something are that thing. An
intelligent, but untutored, opinion may be interesting in philosophy,
it usually isn’t in science.
FRIAM is supposed to be a place where knowledgeable folks can share
it. For those interested:
On complex terrain there are locations that have strong flows. This
is a function of topography and wind direction. One would like to
install Wind Energy Collection Systems at these locations. Usually
space is limited, so some WECS units will be in wind shadows,
sometimes. The array can be designed to maximize the annual energy
capture. This requires annual detailed wind records, a model to
compute the flow over complex terrain and a turbine model describing
the turbulent wake and its dissipation -- indeed a complicated process
well suited to modern computers, and dependent still on poorly known
fluid physics, especially atmospheric turbulence.
The economic trade enters next, where costs are reconciled with the
reduced revenue of units in dense arrays. From hence cometh the
most effective array – not always the max. capture case. And, because
costs are time variant, different each year! The ideas are simple,
the execution exceeding tiresome!
In the dark ages of wind energy, with funding from SBIR and DOE,
Lissaman and Quinlan developed, and AeroVironment marketed, a software
model, AVENU, by which one could take a contour map of a site, define
a wind speed and direction, place multiple turbines on it and compute
the total energy capture, including interference. One could then drag
the turbines to putatively better locations, and observe the effect.
Easy on a computer, not so in the cruel world! I always thought that
the verb “drag” was especially vivid here, having actually, with a
cursing crew, moved 30-ton turbines by dragging them from one piece of
California low desert to another.
We sold the software here and abroad for $25,000 a crack, including a
free Mac II, since our European customers were PC operators. It was
not a successful product financially, but has been used extensively in
array design for the last 30 years.
I have not read my friend John Dabiri’s Caltech report, but have put
in a call to chat to him. I taught wind turbine stuff at Caltech to
grad classes when John was in grade school, and expect that his will
be an excellent contribution. I will report on same to FRIAM when I
have studied the paper itself.
My title, “f’ing”, referred to “flocking”, certainly a very
interesting phenomenon, as is the other possible adjective. One can
achieve favorable array interference in water, air or on land. I have
made technical contributions to all: wet, dry and dirty flocking. The
conclusions are sometimes surprising. For example, in a Vee formation
of migrating geese the leader, at the tip of the Vee, experiences the
most favorable interference. It’s nothing like “breaking the trail”,
the magical anthropomorphical explanation! Since I published this in
1970, folks have asked why the strongest Alpha animal would take the
easiest position.
My reply is, “They ain’t Boy Scouts! If you were the strongest
member of the team, wouldn’t you take the easiest job?”
I would, and do, as does every FRIAMer who employs a gardener!
Peter Lissaman, Da Vinci Ventures
Expertise is not knowing everything, but knowing what to look for.
1454 Miracerros Loop South, Santa Fe, New Mexico 87505,USA
tel:(505)983-7728
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FRIAM Applied Complexity Group listserv
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============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org
