h a l f b a k e r y
I didn't say you were on to something, I said you were on something.
add, search, annotate, link, view, overview, recent, by name, random
news, help, about, links, report a problem
or get an account
A one meter rainbow wind-wheel can make about 300
There's a problem that people don't want to install large
and clunky (and expensive) wind turbines, even in
In comes the rainbow wind-wheel power. Simply connect
of them along your wall. They don't turn to
they are static, but they work well because of the
effect" of the wall. Since millions of them will be sold,
their price will be dirt cheap (its a bike dynamo and a
simple plastic wind wheel).
You'll be making 15 kw for a very low cost. Connect them
to batteries and an inverter, and you get quite a good
tariff from the electric company. No heavy installation,
almost no hassle! And if it flies off the building, almost
damage is done, because each one hardly weighs
Its nice and colorful. And it makes almost no sound. As
opposed to the noisy mini wind turbine from Hong Kong.
This one is a stand alone turbine, so there is practically
sound at all. (See links)
rather than this
[pashute, Jun 24 2013]
which sounds like this
[pashute, Jun 24 2013]
[pashute, Jun 24 2013]
||I'm writing this because I'm actually investing in a
prototype. Your thoughts?
||I question the 15kW, and the "very low cost".
Unless they are geared together and turning a
single turbine, even a $20 turbine is a thousand
bucks for fifty of them. Tack in another few bucks
a piece for the wheel, and maybe 5-10 for
structure and power transmission.
||Also, while you gain some wind speed from airflow
over the building, you lose more to drag over the
building. Get about 15-20 ft above it and that
changes a bit, but as always, the higher the better
||I'm not saying it isn't viable if you happen to be in
a high wind area, or have a building that rises
significantly above the surrounding terrain (natural
or artificial), just that I'd take those numbers with
a grain of salt.
||You probably mean alternator/dynamo rather than
||A 15 kw solar panel system costs in Israel, about
$80K. Most of the cost is the solar panels, and
about 15% goes on the construction and a DC to
AC inverter for producing on-grid electricity. So
the generation system (the panels) is about $60K!!
||The wheel (turbine) will cost 5 dollars each. The
alternator with internal gear, bought in bulk from
China (where its manufactured anyway) will cost
at most $80 each. Give another $15 for
infrastructure and installment, you get 50 x $100 =
$5000. One twelfth of what the pv costs!!
||And an equivalent 15kw wind turbine tower costs
$7,500 (on Alibaba) for the turbine+generator, and
$10,000 for construction+pole. Typically companies
sell systems like this at double and triple the price!
||So its still at least a third of the price.
average wind speed in your area, and what's the
efficiency of the generator?
||As an additional factor, what's the lifespan of the
alternator, and ideally the wheel itself. (If it's plastic
in a high sunlight environment, it's not going to last
all that long, even with UV stabilizers).
||Using the best averages I can find for Israel (Ben
Gurion and Haifa airports), I find a best average
wind speed of 8mph. For a 1m diameter turbine,
that's only going to produce (at most) about
79W/turbine with a 100% efficient turbine. You do
a bit better if you take the average power
production, since it goes up as the square of wind
speed, so short periods at higher wind speeds
produce more, but it's still not good.
||So I make it more like 100-150 turbines to get up
to 15kW. That's going to put it in range of the full
sized turbine you were talking about, but again,
unless you live in a particularly windy area, you
aren't going to get faceplate ratings.
||Also, are you sure your solar prices are current? That
seems high. I can find the panels here in the US,
retail, for $23k (total for 15kW), microinverters (one
per panel) for
||If you don't have a roof or similar structure to mount
them on, then yes installation will add cost, but not
that much for a near ground installation.
||Hang on a second. This is loopy. But first the
[mfd]. As I understand it, the essence of the idea
is lots of small wind turbines. But the first link
shows lots of small wind turbines. So I'm missing
the novelty here.
||Anyway, on to the loopery. First, noise - is there
any indication that 100 of these will be quieter
than a single 15kW turbine? Second, in what way
do they benefit from the "ground effect of the
wall". Third, is it honestly likely that it will be
cheaper to make 100 sets of small blades and 100
small generators, and wire them all together, and
provide the regulation necessary to prevent the
spinning ones from just turning the other ones
into electric fans?
||And finally, are you planning to mount these on
top of the wall, or attached to its face? (If the
latter, they will receive no wind, whatever
direction it's blowing from.)
||And more finally, why the comparison with
||And even more finally, do you really want to look
at 100 visually obtrusive brightly coloured spinning
||I think by "ground effect" he means the fact that
while rough terrain or buildings slow the overall
wind speed in an area, right at the roof-line or
corners you see some increase in speed (relative
to that slowed speed).
||I'll admit that I don't agree with the statement
that these will work particularly well as a result,
and none of my calculations above take that into
account. Unless you have a truly prevailing wind
direction, you are probably going to need to
double to triple the numbers I mentioned, since
for any wind direction, half your turbines won't
intercept any (on the edge parallel to the wind,
and a quarter (on the trailing roof line) will
||And of course that ignores the interference of one
turbine with it's neighbor, which will tend to
reduce the speed of the wind intercepted at a
||As far as the mark, I would suggest a mark for
expiry, since micro-wind is WKTE, but I took this
to be a request for information about actually
making such an installation.
||I was really directing it to [MB]'s comment. You're
right that in practical terms probably all your turbines
generate some power, but the net result is roughly
equivalent to having half of them parallel to the
wind, and half perpendicular.
||and all of them up against a wall? Seriously, the
energy available to a discoidal rotor stuck to a wall is
minuscule. The only wind will be parallel to the
wall, which will not be captured with any significant
efficiency by something that rotates in the plane of
||Given that [pashute] is a "Mathematition", a few
numbers wouldn't go amiss.
||The common version is along either the edge or
ridge of the roof, not flat up against the wall. I
assumed that was what he meant.
||Max, I never said it makes less noise than a
turbine. A well designed turbine does not make
much noise, and from my experience, the
rainbows make a soft sound similar to the flutter
of leaves, not something people would be annoyed
||I DID say that it makes less noise than mini-power
system. Please look at their website and linked
videos. The noise comes from the multiple
turbines connected to each other MECHANICALLY.
There are other videos on their site where it is
even more apparent. Browse it and you'll see. In
my idea there is no mechanical connection.
||Also, please notice it is listed under BUSINESS and
not Science:Energy, because it is not a mechanical
invention, it is a novel setup and location, or more
correctly a "new system".
||And PV is relevant, because PV and wind are
payed with a tariff by electric companies around
the world, as renewable energy. In Israel, currently
only PV gets installed, and almost no wind
installations, although contrary to what MechE
wrote we have places with scorching winds. About
MechE. First thanks for your time and excellent
||The proof is in the facts. I have had some along my
wall, and some on the roof. Surprisingly, the ones
on the wall turned at times better than the ones
high up. There's a buildup of pressure.
||Did you ever walk near the corner of tall buildings?
As a religious Jew my Kipa (skull-cap) went flying
every time I came to work, in the Jerusalem Tower
building 25 years ago. The gust of wind was only
along the wall. Of course I don't mean flat against
||And yes, there are many malls that put up wind
swirls and small flags that flutter and turn
constantly. They could also have advertising
revealed when turning.
||The scientific textbooks claim there's too much
turbulence there and therefore it works less
efficiently. There are numerous cases where
generalizations like that have been proven wrong.
Its worth the try.
||(Just recently I read of swallow tails, being studied
for ages as an aerodynamic price paid for male
extravagance similar to the peacock tail, and
hindering the swallows flight, but found to be an
aerodynamic mechanism for high speed extreme
||Those are the PV prices here. A company of
course pays less, but so will a company making
||Maintenance: So the turbines will be changed
once in two years. I still think the price is
negligible. And because its nice to look at, will be
paid for gladly. (perhaps some ornaments will
added). The brushless alternators/dynamos and
continuous magnetic gears have a 20 year
||Winds: For "some reason" downplayed by many,
Israel has prevalent and strong winds in places. In
Efrat there is a hill with pine trees that grow
parallel to the ground. And doors on the wind side
had to be moved away. In my town, Bet Shemesh,
I was at a synagogue discussing installation of
various systems, in the summertime, with less
winds. We were not thinking of wind energy, but
when he took me to a porch that leads to the
roof, the door had been thrown open and off its
hinges, an hour before. And the building curator
said it happens constantly. In the Golan I was told
at a school that no wind system I devise will stand
the winds, since a half ton water tank had been
blown from the ground, and landed on the roof of
a two story building, in a common winter day.
||As a young man of 19, I remember watching in awe
as a "sail" wind tower invented by Alexander
Zarchin was torn to peaces and sent flying
hundreds of meters, in a wind storm. I wonder if
anybody ever recorded the remains or the tower
itself. I never found any material about it. I was
the only person outside at the time.
||Since (almost) nobody here really believes in co-
existence anymore, it may sound foolish, but the
truth is that a common Jewish-Arab wind project
would be great for everybody.
||Of course prevalent winds are in areas where
Druze, Jews and Arabs live in close proximity:
They reach 8 and 10 m/sec which is double your
numbers. Gilboa (Maale Gilboa, Meirav), the
Gallilee mountains (eg. upper Nazareth, Daburiah,
Manarra, Safed), Carmel (Ein Hud, Usfia, Daliat El
Karmel), Judea (Halhul, Hanokdim, Tekoa, Efrat,
Otniel, Susya), Samaria (you can't stand up in the
winter at the archaeological site of the Shilo
tabernacle), and the Negev mountains (where not
even army camps have been established).
||But a good and constant breeze is available in Tel
Aviv (along the coast, much stronger than at Ben
Gurion). - And a 15kw system, never produces 15
||Bottom line: IMHO worth the try. I hear the
||Well, fair dos then, and kudos for trying it.