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Looking plans for a low wind wind genny !!
By pcs1st, Section Homebrewed Electricity Posted on Tue Oct 19, 2004 at 02:20:46 AM MST
Looking plans for a low wind wind genny !!

Hi all been looking for plans for a low wind wind genny i live in KY on top of a small mountain and have found plans for wind gennys but they all seem to take about 10 mph to start i was looking for something like the condor where it can make power at any wind speed i no it will be low and i would like to supplement my solar panels. I am also looking for a small hydro set up has to be small i mean i am building a underground house and there is a cave opening in it and the cave has a small spring that runs year around it flows about 1 gal a minute and has a head of 10 feet from where it comes out of the wall if anyone has any ideas let me no.
Thanks
pcs1st

Looking plans for a low wind wind genny !! | 10 comments (10 topical)

Re: Looking plans for a low wind wind genny !! (3.00 / 0) (#1)
by Flux on Tue Oct 19, 2004 at 03:19:25 AM MST

Go for a dual rotor design with no iron in it, such as Hugh Piggott's design or the design that Dan B has posted below.

They will start up in low winds and be producing useful power at 10 mph. should start to see something at 5mph if you optimise it for low winds.
For 8ft you ought to see about 60W at 10mph. Perhaps about 90W from 10ft.

When you get a bit of experience you could try a bigger one.

Flux

Re: Looking plans for a low wind wind genny !! (3.00 / 0) (#2)
by PowerBox on Tue Oct 19, 2004 at 04:31:59 AM MST

If you really need a low speed power generator,it's better you use a battery excited variable speed induction generator. You can produce power at a very wide range, 10RPM to 1800RPM depends on your induction motor speed. If you're interested, I have a 5KW double feed battery excited Induction generator design under development. You will use your solar panel to charge battery and provide exciting current to the induction generator.

Re: Looking plans for a low wind wind genny !! (3.00 / 0) (#3)
by DanB on Tue Oct 19, 2004 at 06:14:09 AM MST

Im not quite clear on what you mean powerbox... it'd be fun if you'd share more detail about what you mean by "batery excited variable speed induction generator". But the 'battery excited' part makes me think it would not be ideal for small, very low speed wind turbines -because I'm thinking that you need to use a bit of power to excite the machine. In low winds we have very little power to begin with, so it's hard for me to imagine that anything but a pemanant magnet alternator would be less than ideal.

http://www.hydrogenappliances.com/bladekitsEXTNMOV.html

I think, for power in very low wind speed the trick is... a nice free spinning alternator matched up to a fairly large prop. I read about the 'condor' with an 88' prop, and they are suggesting 10 watts @ 1.8 mph from an 88" prop - which is quite impressive, but I'm a bit skeptical - it seems impossible. 1.8mph is very low wind and I would be impressed if the machine even turned at that speed let alone made any power. If we could get 10 watts at 1.8mph then we should be able to get over 80 watts @ 4mph - this is way over the top for a 88" prop. Even if we take the least optimistic predictions off that page, 25 watts @ 4.6mph... if that were possible then I'd be looking for 200 watts or so @ 9mph - impossible for such a small prop. Not even my 14' machine can do that though it comes close. At any rate... I think the 'condor' is breaking the laws of physics there, or... they've mis-measured something... even though I suspect that machine may do a nice job in low winds, it would be nice if the numbers were a bit more realistic.

In my opinion, for good power in low winds you want an nice big prop and a well matched free spinning alternator - and don't expect to break the laws of physics!

[ Parent ]

Re: Looking plans for a low wind wind genny !! (3.00 / 0) (#4)
by DanB on Tue Oct 19, 2004 at 06:20:34 AM MST

Here on this page they say it very clearly... 10 watts @ 1.8 mph.
http://www.hydrogenappliances.com/windturbinetypes.html
If true, it would be very impressive but I believe it's impossible by a factor of close to 10. Unless you're willing to install a huge wind turbine - I think you can pretty much forget about getting much useful power at windspeeds below 6 or 7 mph, unless (like they say in the condor ad).. you are charging batteries at a remote location that rarely gets visited and needs very little power.

A good low wind machine should probably startup around 5 or 6mph (maybe a touch below) and start charging at 6 or 7mph.

[ Parent ]

Re: Looking plans for a low wind wind genny !! (3.00 / 0) (#5)
by Flux on Tue Oct 19, 2004 at 07:41:03 AM MST

pcs1st

You will have to buy a Condor, looking at that link, you will never make anything to match that, neither will anyone other than them.

Dan's figures are realistic, there just isn't that power available in low winds.

Flux

[ Parent ]

Re: Looking plans for a low wind wind genny !! (3.00 / 0) (#10)
by bkrahmer on Thu Oct 21, 2004 at 11:32:44 PM MST

From the dealings I've had with them, I'd say they amplify their true results by 5-10x. If you search the archive, you'll find the whole story of my experience with talking to them.

[ Parent ]

Re: Looking plans for a low wind wind genny !! (3.00 / 0) (#6)
by Gary D on Tue Oct 19, 2004 at 08:58:48 AM MST

Perhaps a link to the perfect turbine is in order? The charts show available power vs. harvestable power. Any claims that a turbine can do better than the bentz limit must be view with skepticism. A link from Otherpower's link page... Have a good day! Gary D.
http://www.ndsu.nodak.edu/ndsu/klemen/Perfect_Turbine.htm

Re: Looking plans for a low wind wind genny !! (3.00 / 0) (#7)
by DanB on Tue Oct 19, 2004 at 09:29:14 AM MST

Yes...
according to Betz, the most you could get into the shaft with the condor assuming the blades are perfect, @ 2mph would be around .8 watts, about .4 might be realistic output from the alternator after the blades overcome the bearing friction (if they even started to turn). So perhaps I should correct my earlier figure, they are probably off by more like a factor of 20.

I find pages like that frustrating because lots of folks believe everything they read. I think it's misleading, folks see that sort of thing and unless they know better, such a machine seems like a real good deal compared to anything else.

[ Parent ]

Re: Looking plans for a low wind wind genny !! (3.00 / 0) (#8)
by hvirtane on Tue Oct 19, 2004 at 12:01:25 PM MST

10 mph is not that bad.
You need to use quite big blades to get
much power at that wind speed, however.
Most of the designs as people
are using will start delivering
power at slower wind speeds.

---
For example at 5 m/s wind:

3 m diameter (horizontal axis) rotor : 152 W

4 m 262 W
5 m 396 W
7 m 762 W

This is from a book:
Horst Crome:
'Handbuch Windenergie-Technik'
ISBN 3-922964-78-8
Staufen bei Freiburg, ökobuch 2000
p. 28
---

You can maybe get best results
with direct drive PM generators,
but you can of course use
other kinds of generators, too.

An induction generator
is one possibility.
But it isn't easy to find
slow speed ready made
induction generators,
so you would normally
need gearboxes.
I'm slowly working with a kind of
drawing how to make induction
generators yourself. I found
drawings in an old Finnish book.

- Hannu

Re: Looking plans for a low wind wind genny !! (3.00 / 0) (#9)
by Gary D on Wed Oct 20, 2004 at 08:57:35 AM MST

A new day, a new perspective. If you look at Dan's link, you'll notice the annemometer is near ground level. You can't tell how high a tower this machine is on. So it would seem there should be a disclaimer stating (dream on) NOT apples to apples windspeed wise. 40 to 60' height difference perhaps? Who knows? ;-/ Gary D.

Looking plans for a low wind wind genny !! | 10 comments (10 topical)

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