Savonious Rotor - 1995 - 1999 By
Chris Simpson
( VK4TCS) 18 Lindfield Dr., Petrie.,4502, QLD.
Mail: grimcomp-chris@powerup.com.au
This is an on-going story. The
original idea was to provide a modest amount of energy to charge some batteries so the
family could visit a "weekender" without missing too many of lifes comforts. As
I wanted to keep some trees on the hill for general storm protection I decided that a 3
tier 44 gallon drum system mounted atop a 4 metre tower should provide plenty, despite
windage restrictions. I thought that the wind would rush up the hill and be funnelled
under the canopy of trees, and through my wind generator. This proved yet again the
general rules for windgenerators, position, position,position.
After clearing some trees, enough for good operation, I then had a battle with "the
generator". I used a 12v alternator because I had a few lying around, in hindsight
this was my second error. I built a regulator which would turn on the fields and ramp up
the field power with increasing rpm. The idea was to turn on the fields when the rotor was
turning fast enough for a "positive" power gain, and the "ramp up"
voltage adjusted to "best fit" the wind power being applied. I had built a large
pulley (910mm) onto the main shaft and had decided to try 58,70,105mm pulleys on
alternator
.
I found that the frictional losses from a V belt pulley considerable. I cleared some more
trees, and added another 4 metre section to the tower, I also tried a flat belt, this
worked a lot better, but I was still dissapointed with the output. At this point I decided
to rewind a 55amp alternator for 24 volt operation as my battery bank had also evolved
into 24v. I also fitted out the shed with 24v fluro's. As this was "another
test" and I had never seen the rotor turn very fast, I didn't protect the field
winding (12v) from over voltage. Another mistake. I did learn from this experiment
however, that I needed to utilise more of the "more frequent low winds " so I
replace the rotor, modified the regulator to deliver a "max" of 12v and eased
the ramp voltage back, so it would apply the fields less aggressively and allow the rotor
to turn more easily.
This provided more power over time by not excessively loading the rotor and utilised low
winds better, but I still was not satisfied and believed I should be getting much more
output. I also needed something which could spit out power at low rpms ( alternators were
looking shakey... ) I decided to then re-wind another 55amp alternator, this time for
about 72v output (60 turns per coil). I changed it over and mounted a bridge and big 400v
electros up the tower. This time round I was going to shove this power into a switchmode
down- convertor, and primarily control the charge current via the available high voltage.
I couldn't get back for a few weeks, when I did I found severe corrosion on the bridge and
electro board.
I also got an enormous shock touching it, (as I believed it "had" to be
discharged, with that much corrosion.) Another mistake. I re-appraised this system as
having too many negatives. ( field power required, a very robust switcher, and corrosion
from HV DC to name a few, but this system still showed much promise!) I then decided on a
permanent magnet generator (motor). I built an up-converter switchmode regulator an tried
again. I had some fine tuning to do on the converter, including blowing it up once, before
I was happy with it. I also decided to build a voltage monitoring unit into it which would
turn on the main Vcc when the generator was supplying, to conserve power. (18Ma to less
than 1 ) The unit also isolates the battery charging if they are fully charged (around
29.6v) and then dumps the power into a resistor bank.
There is also an undervoltage battery alarm. Another feature which I have yet to see in
operation is, at a preset transition point the up-converter is switched out to let the
generator charge direct. I have roughly set the generator volts to 25v but I have yet to
find the "smooth" changeover point where the up-converter load will be the same
as the "battery charging" load. I have no fancy control or protection on
"direct charging" as yet too, (except a C.B.) this is my next job, before
another opps! I only just recently bought an anemometer, so now I can be more subjective
and scientific about my findings. The rotor begins to rotate at 3.4 m/sec. with the latest
generator. Once turning, it can drop to 2.5 m/sec ( frictional hysteresis) and remain
turning. I have set the regulator unit to begin charging with a generator voltage of 5
volts and it will happily charge to 20 amps or more ( capable of a lot more, metering
isn't ) with the right winds. As you can see this has been more than a pain in the butt,
but I assure you there is nothing better to see a plan come together, and to generate YOUR
OWN CLEAN power. ( particually when looking out over "black-outs - if you have a
slightly nasty streak , try turning on all the lights and wind the stereo up! " ) I
hope this set of documentation can take some of the pain out of building "your"
first windgenerator, here are a few tips - * position position position, somewhere high,
with good un-obstructed winds. * use a permanent magnet generator with as many poles as
you can get. * keep things simple, robust and long lasting * consider a propellor system (
not a drag system) if "lots" of energy is required. * most of all, keep at it,
it's worth it!
* * * I would also like to mention to any "greenies" out there who are disturbed
at my tree felling, I have 50 acres of land which is "locked up". Without some
control over my land, I may as well give it to the developers, please realise it is much
more important to educate people on conservation rather than beat them over the head with
some legislation. I conserve 80-90% of flora and fauna, I set a green example for the
future, and I don't want trouble. Our survival depends on maintaining a stable enviroment,
the fight must be to stop those that are making short term profits at the cost of our
enviroment. We have an absurd situation where those that are "making the most
(globally) " , also make the rules, and don't give anything back to the communities,
not even taxes. - for intelligent creatures , we're pretty dumb..........Chris
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