Low wind turbine?

I read about a turbine that had magnets on the ends of the blades and coils in the frame around the blades, like a magneto. It claimed to work in winds as low as 2 mph, though they didn't mention how much/little electricity would be generated at that speed. I was interested right up until I saw the price. $4,000 + for it. Is that price because of R&D and patents and advertising costs or is this type of turbine really that expensive to manufacture?

Isn't there a DIY windmill that can match that performance, maybe from a bicycle wheel? What am I missing, here?

I want to make 500 Watts per hour from 4-6 mph winds from an inexpensive DIY wind turbine that runs magnets at the end of each blade by coils in a housing around the blades. Is this possible or not? How many will it take to accomplish that? Or, what diameter would the blades circumference need to be to capture 500 Watts worth per hour in 4-6 mph winds?

Maybe I'm just ignorant and 4-6 mph winds simply aren't worth capturing. Maybe it would take a month for a DIY turbine in low winds to store a day's worth of electricity for my home. 29 more and we're in we're in business? lol. Not.

Anyway, I want to charge a battery bank with it, if possible and I can DIY the turbine at a low enough cost. I'm live in an area where the county doesn't interfere too much, so long as I don't erect a huge tower. This is strictly roof level.

Doable or not? Pretend I have constant 4-6 mph winds year round, 24/7 with no slack. Would it be worth it then?

Bill, what you are looking for is a Savonius turbine. There are designs all over the web and on YouTube about how to build them out of 55 gal drums, paint cans, coffee cans, and all other sorts of cylindrical junk you can scrounge up. They work for steady, low-speed winds, and the power output goes up as the cube of the windspeed. I don't know that there are any commercial size Savonius designs, the most I have seen is that they put some Savonius type fins on a Darrius design (eggbeater) to improve its low-wind performance.

Here's an example (with some cool music):

Thank you very much. Now that I know what they're called, I can look up info on them much easier.

I'm actually working on a way to passively and/or actively make wind [no, not THAT way ] on demand and am looking for a setup to harness that energy. Won't make a ton of electricity, but I think it'll provide a small amount steadily over a 24 hour period. Then again, it might not work, so I'll try it out before posting about it.

Creating wind... Are you thinking of a solar tower?

Yes, and no. Yes, I'd like to set up a small tower that will draft via solar. Would probably set up to heat a mass with solar and let it radiate heat into bottom of the tower.
And no, because I'd like to use a rocket stove to drive the tower without the sun when needed. Could heat a mass to radiate heat into the bottom for an extended time, I suppose. Or just pour the coals to it straight with the stove.

We saw that the exhaust from our rocket stove really took off when we added a secondary air intake near the top of the flue. I'm wondering if a solar tower could also increase the speed of the hot air using this same technique.

At this point I don't know if this would work or if its even worth doing, so no plans to do it. Just toying with it in my head.

The traditional way to turn heat into electricity is a steam turbine. A little dangerous, with the phase changes and all, but still possible. Probably has higher efficiency, practically speaking, and smaller footprint than a rocket stove + windmill.

You may well be right about efficiency, mechanically speaking. Steam works, that much has been demonstrated with a rocket stove. But, like you pointed out, it can be dangerous. And, steam engines need attending to as it runs, so they're not passive at all.
The solar tower would be more passive, operating whether you're there or not via solar. Might be a nice touch to be able to actively run it at will when you choose, as well, making it both an active and passive system.

It all sounds neat until output and cost are considered. LOL. Whole idea will fall apart if it costs a zillion bucks per watt. There will be a lot to establish before really considering building a DIY version.

Oh, and one neat thing I read on wiki about the stack effect. It said a 20 foot flue will draft twice as hard as a 10 foot flue, circumference being equal.
To me, that inferred that 2 ten foot flues would draft as hard as 1 twenty foot flue.

Height of the tower is the main obstacle that makes a home version so challenging. But, if I can use multiple flues off the same bell, (1 turbine at bottom of bell) then I don't have to go so high to get the effect of a very tall tower. Combined with a secondary air intake near the top of the flue to increase velocity, perhaps it could be made feasible.

Or not. Just don't know at this point. Too early to tell.

My understanding is that the velocity of the air in a stack goes by the cube of height. That's assuming that the diameter of the stack isn't so large that it heats unevenly or so small that there are hydrodynamics that take swamp out the height effects.

Expect everything to cost more than electricity off the grid. If you want to spend less money, alternative energy will only work if you can use less of it. I'm not saying that to discourage you. It's just reality. Cost per kWh is only one factor. Independence from the grid, that clean fresh green feeling, etc, are all worth something. You'll just have to decide how much they're worth.

Agreed.
Like I said, this may not be viable for home use. When I look at current solar towers, I see massive innefficiencies, or missing things that could be added for better performance and reduce cost.
For instance, why not put a trash inceneration facility near the tower and use the exhaust heat to heat the air in the tower, above the turbine? That would really get that tower sucking through the turbine, even after using the waste heat to run steam turbines. It would still be hotter than air trapped beneath the glass around the tower, right? Using a tower like that to tap the waste heat from several facilities around the tower might eliminate the need for miles and miles of land with glass or plastic above it, There are places with facilities near to one another right now that could power a tower, instead of just wasting the excess heat they produce, even after they use it for steam generation. Heck, the bottom half of the tower should be painted black to catch and use even more solar heat to help fuel the stack effect.

Anyway, it's just an idea or two, that's all.

Hello permies, I am a newbee and hope to learn and contribute to this, and am excited finding so many people buying busy with the change. My name is marcel from the Netherlands living now in Istanbul turkey.

I have seen a very good design from turbina energy which is using permanent magnets and is a vertical axis wind turbine with CAPTURE SCOOPS this tunnels the wind from any direction making it operate on very low speed 1,5 mps

http://www.alibaba.com/product-free/105057332/TURBINA_VAWT_300.html

In alibaba you can find permanent magnets for around 600 +usd.

I am looking for people who are interested to work out this concept together into a cad design and working prototype?

Regards

Marcel

Check out Sharpe Cycloturbines.