TheBackShed.com

Forum Index : Windmills : Efficiency vs Consistency

Author

Message

Storm

Regular Member

Joined: 12/09/2005
Location: Australia
Posts: 43

Posted: 12:21pm 28 May 2007

Copy link to clipboard

Print this post

I often see the three bladed props promoted as fantastic in terms of their efficiency and two bladed props even better (although unbalanced), in reality i.e. not ideal locations and wind conditions how many are able to start-up and make decent power consistently? Are the 5 bladed props more suitable for overall power output in unfavourable areas? Do the 5 blades start up earlier and limit output therefore self furl again making them an easier machine to build?

In Ideal conditions the less blades the better right but I wonder how many people out there are running both 3 and 5 bladed props and which over longer periods make more usable energy? Many people have expressed to not bother with 3 blades as they aren't consistent, what do you say?

Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5116

Posted: 12:12am 29 May 2007

Copy link to clipboard

Print this post

Its a bit like the turtle and the hare.

My main windmill ( the hare ) is a 3 blade HAWT, and when the wind is blowing from the one direction long enought for it to get started, and the wind is strong enough to get the windmill up to charging voltage, it can indeed feed 10 to 20 amps into my batteries. But this is a very rare event this time of year.

My other windmill ( the turtle ) is a slow running VAWT based on the Lenz design. It only makes 1 to 2 amps, but it does that for several hours a day!

At the end of the day, the turtle wins. So yeah I agree, a 5 blade prop is a better choice if your in a low wind area like mine. Dennis did some work on this, he found a 5 blade turbine on a unmodified 100 series stator made the more watt hours than any of the high speed 3 blade modified stator windmills.

I think if your in a good wind location, and I mean like on the coast or open plane, then a high performance 3 blade windmill is the go. But for most of us, maybe its time to have a re think and go for more blades on our HAWT's or drag type VAWT's. They may not achieve the 300 plus watts we could get, but over the duration of a day the slower windmills may be giving us more power.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

petanque don
Senior Member

Joined: 02/08/2006
Location: Australia
Posts: 212

Posted: 02:16am 31 May 2007

Copy link to clipboard

Print this post

I think that without detailed modelling from data obtained from the actual site it will be difficult to make the right decision.

Wind by its nature can be very variable and a small change in location can make a big difference to the power available in the wind.

I think it is a marketing issue that if manufacturer can claim a higher output many purchases will think it is a better product.

I think it would be true that a windmill that produces 200w in a modest breeze for a large part of the day would be a lot more reliable power supply than a 500w machine that produces very little most days because it needs a very strong and consistent wind to produce any worthwhile output.

Has anybody experimented with oversize blades so full output can be produced in only a light breeze?

I would imagine the furling and over speed protection would need to be good.

Regards

Don

Gizmo said

I think if your in a good wind location, and I mean like on the coast or open plane, then a high performance 3 blade windmill is the go. But for most of us, maybe its time to have a re think and go for more blades on our HAWT's or drag type VAWT's.
Glenn

Print this page

To reply to this topic, you need to log in.