Try the search feature on this board... and check out some of the designs/discussions on our "otherpower/wind" page.
I, and a few other folks recently posted some comments to this story - they may be helpful: http://www.fieldlines.com/story/2004/7/27/181631/793
With that said, I'll respond to the questions directly below:
"# I have noticed that some designs have what appears to be magnets on one or both sides of the stator. What's the difference between single sided or double sided magnets around the stator? "
There are some differences in the power curves of alternators with, and without laminates. Usually a machine with magnets only on one side of the rotor would have steel laminates behind (or around and inside) the coils on the other side. The advantage of doing this is you'll need fewer magnets. If the laminates are slotted (so that the coils are actually embedded inside them) - you can have a very narrow airgap, and very strong flux through the coils. This allows you to use lots less magnets, less wire - and basicly get a lot more power from a much smaller, and perhaps less expensive machine. But the process of finding good laminates, machining them.. etc - may be a bit more work and beyond the capability of some folks.
The advantage with having magnets on both sides is... simplicity perhaps. (that design will require a bit more magnet) The other advantage, which is a big one in my opinion...
anytime there is stationary steel in the stator there will be some losses due to hystoresis and eddy currents. There will also always be some loading on the bearing if its an axial flux design. (almost all the homebrew designs here are Axial Flux designs...) So it will not turn quite as freely - it will take a higher wind to start turning and may be slightly less efficient in low winds. A machine with no steel in the stator will turn absolutley freely.. the only torque required to get it turning will be that required to turn the bearing (not much).
If the stator is slotted, with the wires embedded inside the steel laminates, it will probably cog to some degree. Cogging is the term we use to describe the affect when the magnets land in a preferred spot (the magnets are more attracted to the steel between the slots, than they are to the slots...) - and a certain amount of torque is required to overcome this. Depending on how the stator is designed - it may, or may not be a problem. Most commercial wind turbines use a radial flux design (the magnets are arranged around a cylender rather than around a disk as in the axial flux design) and the coils are usually embedded within steel laminates. With that in mind.. it's certainly not a bad way to go, and it would make most efficient use of your magnets and your wire. But again.. slotting laminates might be tricky for most folks building at home. And furthermore - I tend to prefer the idea of a machine thats simple to build, that spins absolutely freely with 0 iron losses and 0 cogging, again, the drawback being.... you'll spend a bit more on magnets and wire and the machine will be a bit larger/heavier.
There is a lot of discussion/debate on the different ways of making these if you look around in past messages here.
