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Old 09-16-2011, 10:25 AM   #1
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wind turbine

Hi I am building a wind turbine from a tread mill motor 1 hp I came to the part to make the blades, anyone know which is best 3 or 5 blade and what diametr? I and charging a 12v battery 256amp with this turbine.


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Old 09-16-2011, 11:05 AM   #2
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wind turbine

I don't really know (not that kind of engineer). But all the huge commercial wind turbines I've ever seen had three blades.


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Old 09-16-2011, 12:13 PM   #3
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wind turbine

I'm confused. How or why is there a motor involved to make a wind turbine?
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Old 09-16-2011, 12:40 PM   #4
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Originally Posted by brric View Post
I'm confused. How or why is there a motor involved to make a wind turbine?
DC motor turned from an external source becomes a generator!
Yes I am a Pirate, 200 years too late. "Jimmy Buffett"
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Old 09-16-2011, 09:05 PM   #5
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wind turbine

DC permanent magnet motors make the best homebrew wind generators. I've built 5 or 6 of them since I was a teenager. Alternators, wired correctly, work very well too, but you have to find one wound for low speed operation.

Think of the old water pumper windmills. Lots and lots of blades, right? The more blades you have, the lower wind speed required to get it turning (more torque). The drawback is instability at high rpm or inability to reach a useable speed for power generation. 2 bladed machines can spin the fastest but create harmonic vibration issues with pole type towers especially. And they need to be balanced very well. All the larger (1-3 kilowatt) machines I ever worked on used Sitka spruce blades, incredibly strong long grain wood. Now it's all about composites.

The best compromise is the 3 blade setup. That's what most small and large commercially available units utilize.
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Old 09-17-2011, 08:42 AM   #6
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wind turbine

I think the home built wind turbine idea is pretty cool, not that you will ever get significant power from a small turbine (see Betts law regarding maximum power potential for a wind turbine), but the idea is very nice. Kind of like our garden, we enjoy it, even though it will not replace the grocery store.

However, I am missing something here. You said that you were planning to charge a 12V battery at 256 amps. That would mean approximately 3000 watts electrical output, which is about 4 HP, yet you are using a 1 HP motor. This does not work, if you want to put out 256A you need a much larger motor.

As for the blade diameter, you determine that by the design power output. For efficiency, I would assume not more than 30 percent conversion efficiency from maximum theoretical wind power to actual electrical output. Even 30 percent is pretty optimistic for a home built device.

Post some pictures of the final product, I would be curious to see it. I bet there is an entire subculture of home built wind turbine enthusiasts out there who can share ideas about everything from blade design to power control. Good luck.
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Old 09-17-2011, 12:11 PM   #7
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HUGE subculture. I go to the Midwest Renewable Energy Fair in central Wisconsin every year. For 5 years I helped a friends dad with his small business installing small solar/wind systems. We did several in northern MN, lots of remote cabins. I actually have 4 64 watt solar panels and a few Surrette 8 volt 1100 amp/hr cells in the garage waiting for my new roof to be done in the spring, and a Trace 4kw inverter. Someday....

The highest output I've ever seen out of a true DC wind generator is about 1000 watts at 24vdc, anything more becomes difficult due to line losses to the battery. We installed mostly 2-4 kw AC machines running 28-128 volts (3 phase), then rectifying it at the charge controller. That way you have much more flexibility to step up/down voltage as needed.

There are literally TONS of publications, blogs, newsletters, magazines, etc that deal specifically with home made power generation like this. Look em up!


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