ok, firstly - you dont power the light from the generator, you use the generator to charge the battery, and run the light off the battery. Think of a river feeding a reservoir - the river flow isnt constant, but varies, the reservoir stores the water so you can draw off a constant flow through your tap.
A bog standard car battery is ample for running the sorts of lighting you would need in a shed, especially if you use 12v flourescent lights. The output rating of the generator will determine how long it takes to recharge the battery back to full power. As an example, suppose the generator is rated at 12w, for a 12v output thats 1A. The battery typically will be rated around 30Ahr, meaning you can take 30A in an hour, or 1A for 30h. If you have discharged it down to 20Ahr, then it will take 10h to recharge. So if your lighting takes 10A (unlikely, but good example here) then you will have discharged the battery to that level in 2h. :?
so the setup is = generator - regulator - protection - battery -protection - lighting
the regulator is only needed to prevent the charge voltage exceeding 14.4v, and to limit current if the battery is very flat. The 'protection' in the first case consists of a fuse and a diode (the diode stops the battery discharging back through the charger, its a one way valve), the second is a fuse and a switch.
I cant say much about the mechanics of a generator im afraid, you would need to find the average windspeed for where you are, and work out from that the blade sizes and stuff. 'fraid its a bit of trial and error. I can tell you though that if you double the blade length you multiply the output power by a power of 4 (up to the generators limits), at least for commercial 200MW windfarms anyway
zak can i run my world famous been chopper with a windy thingy ?
i dunno, whats its requirements? maybe you need a mechanical wind power for it, like a windmill for beans!
another thing to remember is that whatever size it is, it will need to be mounted on bearings so it can move to face the wind, the heavier it is the less easily it will move!
If you consider a rutland wind charger - they are about the size of a car alternator, the blades are about a foot long, usually 3 or 4 of them. I dont know if they have any gearing inside to change the rotation speed.
Id be happy to mock a test bed version up if i had the parts, and could then test it see how it works. But ive no parts to do it with at minute.