building your own wind turbine for a 24v system

So we are off grid and have a 24v system and right now we're strictly solar. We're wanting to add a wind turbine so we have power on a cloudy day but I'm having trouble finding permanent magnet dc motors that have a high enough voltage to rpm ratio to give me 24v at a normal wind speed. Is there any way to get around this? I found this diy article (attached) but it doesn't explain enough for me to know exactly how to build it. If anyone has any ideas on what I could use to get 24v at around 400 rpm or could explain better how to do the steps in the article (for someone who only knows a little bit about electrical stuff) I would really appreciate it!

I bought a book years ago for like $50 called "Homebrew wind power", which details all the steps to making your own turbine. I think they run the website otherpower.net or something as well. I skimmed through the book briefly when I got it, but have been waiting until I moved out to my property to start work on it. So I'm not an expert on the subject.

While you're building your alternator, I believe it's the size of your copper wire and the amount of times that you coil the wire that determines the voltage. As long as you or someone near you is able to cut and weld metal, work with fiberglass resin, and carve the blades, you can build a turbine based around your needs. The book is also pretty good about explaining theory behind all of the steps they take when building.

A 7' diameter turbine from their book will generate around 275 watts at 400 rpm.

I have used a stepper motor for the generator and get 24 volts with a good wind. This motor has 2 phase AC output so it needs a rectifier to convert it to DC. I am using 14" blades.
You could also try a 90 VDC servo motor which may be easier for you to find. Old treadmills use this motor. The trick is to match it to a set of blades to give you the output you want.

@MorganG: What are your wind-speeds like for averages? Is there any reason why you wish to build this system instead of purchasing one in the ~$500.00 USD range? 400W turbines seem to be plentiful in that wattage range and many come configured for 24V. Although I can't speak for reliability, an example is http://www.amazon.com/DC-HOUSE-Residential-Agriculture-Installation/dp/B00PBT6ZKY

Without a doubt, here is the best forum on the planet for home brew wind power. And a nice bunch they are:


http://www.fieldlines.com/index.php?board=5.0


There's a little bit of everything, but the common/favorite kind of build is a permanent magnet alternator with a cast resin stator.

tons and tons of posts and info.

http://www.fieldlines.com/index.php?board=5.0

Don't underestimate the need for a good tower. Tall enough and strong enough. It should be ~20 feet taller than the nearest building/tree to get the turbine into that nice smooth undisturbed air.

As per my experience while you have to build your alternator, it's the size of your copper wire and the amount of times that you coil the wire that determines the voltage. As long as you or someone near you is able to cut and weld metal, work with fiberglass resin, and carve the blades, you can build a turbine based around your needs.

Old car differential
Mount vertically, bolting bottom wheel with tyre or not to a solid structure or foundation
Inside a 4 legged solid frame, box steel or pole.
Mount differential output, with attached to it a V-belt pully, that goes to your 24 volt truck alternator
Vertically cut two 200 litre solid plastic drums (44 gal for the last remaining country using old imperial) in half.

The windmill i saw operate over a decade when a young lad used two steel drums, not ideal as rust.
The unit am intending to construct i will use 2 x plastic agricultural drums, farmers have plenty of empties lying around.

Mount them at 180° creating a ~ or vertical double cup
Set the other 2 halves directly above but horizontal axle is at a right angle to bottom h-axle

Have seen many 200 litre drum windmill designs and constructs, but even lengthy searching seems to not result in anyone using a car diff.
Most differentials have a reduction of approx 4:1 , which means your output rpm will be 4 times faster.

Thoughts, ideas, information welcome before build start

Neat project. That's an interesting approach! Do you get steady trade or ocean/offshore winds at your location?

A couple of thoughts:

I wonder how much resistance the differential would add. There's a potential energy loss. Also, you may need a disconnect/clutch so rotation can begin.

Vehicle alternators are tricky because of the amount of power they consume to flash the rotor and create the magnetic field. At low rotation speeds, that's a lot of energy loss. The biggest advantage of a generator (DC motor with permanent magnets) is that it will produce fairly efficiently at low speeds.