DC or AC Generator

Have you looked at automobile alternators?

What do you intend to power?

I agree with Brain here. Find out what you want to power, so you can pick the right storage device, DC to DC(Battery) or AC for Direct connect (No clue).

You could always use a motor, attach blades to the shaft.

A motor is a generator and a generator is a motor, depends on the prime mover.

This probally doesn't help.

There are permanent magnet alternators available for this purpose. Here's one source.

There are a lot of tape drive motors that are DC permanent magnet type.

Best is about 1800 RPM 70-100 Volt ~1/2 HP wind genapplications. They cost $15-30 plus freight on ebay.

Anything bigger you will not find surplus and you must buy new. Alternators will also work. You can find 24 volt military alternators out there cheaply on ebay etc for $100 or less. 25 volts 50 amps or so = ~1.6 HP

First decide how big the windmill is going to be, two factors are important, how high off the ground and what the diameter of the propeller will be.

Search around on the web for some formulae to tell you the aproximate power output will be for that size and several different wind speeds.

Try and find out what the usual windspeed and direction you get in your area.

Using this power output, pick a generator that will need slightly less than your average power output.

Design the windmill so that it can park itself (usually either moving to a position at right angles to the wind or the blades are freed to let the wind blow thru without them turning)and spill all the wind in some way if the wind gets too strong, or you just want to do maintenance or similar. WITHOUT GETTING TOO NEAR IT, eg. Remote control!!!! A proper braking function is needed to slow and stop the windmill.

Make sure that when you have stopped it, that you can put a heavy metal dowel though the mainshaft so that you do not get injured when working on it.

Make sure that you can put a padlock on it to stop any unauthorised persons starting it up!

Think the whole project thru very, very carefully and write down all your requirements. Stick to your list, do not cut corners later.....make sure that you work and design in a safe manner.....

Even quite small windmills of a meter diameter can give life threatening injuries when the wind is strong and parts of your body get in the way.....!!!

Keep CR4 informed so that we can follow your working and know where to send the "Get well" cards if you get injured....

Choose Any-- just optimize the available power output.

Signal Conditioning circuits will conver ac /dc/Mixed /varying frequencies to Grid Frequency-50/60 Hz.