Bob,
A quick list of possible RFI would include static (same as P-static on
aircraft), but I would think that can be handled by static dissipaters,
also as done on aircraft. From articles I've read, it does appears that
at least two different technologies are involved with the electrical power
generation: AC alternator directly driven by the blades, but resulting in
non-constant frequency; DC generator driven by the blades and feeding a
combination of storage batteries and large inverters to produce 60 Hz.
Since the grid demands 60 Hz, I presume that the alternator systems use an
inverter to provide isolation and create the constant 60 Hz output from
those systems. Either way, I do not recall seeing very many posts on this
reflector from persons living near wind farms. Having worked on the
design of medium large (30 kW or so) inverters years ago, I can vouch for
their potential to create havoc on power lines. On the other hand, when
running at a fixed frequency and a reasonably constant load, the circuit
components can be optimized to provide a lot of noise attenuation and yet
still have a high efficiency system.
One other possible form of interference to consider: are you a fan of the
higher bands, like 6m and up? If so, those big blades act like "choppers"
and I have read reports from VHF and UHF ops who have tried to copy weak
signals thru the blades of windmills and suffered the problem of signal
chopping at rate controlled by RPM of the blades. There might be some
effect from blades on HF signals, but that would depend upon band you are
using, angle of arrival of those signals to your antenna, direction, and
so forth.
As for noise, we have some large wind farms in NW Iowa (I live in eastern
Iowa), and I have stopped to take photos when passing by those farms near
sunset. I have stood within 100 feet of the base of operating wind
turbines and can tell you that there are two sounds, neither of which is
loud or objectionable to me: a low level whine sound from the gear box up
at the turbine itself; a low level "hum" of sorts from the blades. The
speed of rotation is not fast enough to create loud "swooshes" or
whistling from the blades. Perhaps others have heard different sounds,
but that's what I have experienced in the two times I did photography
among the turbines. I spent about 30 minutes to an hour each time, and
all of that time quite close to a number of the machines (on a public
road).
This trial system sounds small scale. The 40 foot pole is quite a bit
shorter than used in the major wind farms (which I believe those support
towers to be in the 170 foot class, at least). Also, if the blades are
less than 7 feet in length, I think the only bands that might suffer
chopping effects will be VHF and UHF. The blades on the systems I
photographed were on the order of 75 feet in length, or more. Take a lot
of data if you can, but bear in mind that with respect to output power,
the output from this trial system is a fraction of what major units can
deliver.
73, Dale
WA9ENA
rbaker <rbaker@cloudnet.com>
Sent by: rfi-bounces@contesting.com
10/05/2009 07:19 PM
To
rfi@contesting.com
cc
Subject
[RFI] WECS
Hello all--- Does anyone have any information concerning possible RFI
being produced from a Wind Energy Conversion System ?? There is a
proposal to put one in our residential area.It will be up on a 40'
monopole,with a maximum rotor ( blades ??) diameter of 6'8",producing
1000/1400w/48volts,depending on wind speed.This is a test case, as our
city has no regulations concerning wind generators--towers yes--but not
a WECS!!My concern is the possible production of static charges from the
blades,sound, RFI from the generator,attenuation of my signal by the
rotating blades to the SW.eg.the S. Pacific.
Have fun with this one, people!!
73
de Bob W0ROB
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