Hi,
I've seen some 10 kW wind machine projects using induction generators and I've been involved in one project like that, too.
In my opinion it is quite difficult to utilize induction generators, if you'll use them for battery charging; it is easier to use them for heating element systems, however. The gearbox you would need would also create some problems.
How I would do it, if I had to make such a machine.
(That kind of project isn't an easy or a small one. Problems of making a wind machine reliable and safe are getting fast much bigger, when increasing the size of the machine...)
1)
If the cost is not your main concern I would use experiences gained by 'Otherpower' DanB and others and just increase the size of the general design as used by many others. Magnets for the generator would cost quite a lot but you could make it.
2)
You might start your calculations with the wind rotor of 10 m diameter. There are several methods to make it, but using the same method as has been used for the 'Otherpower' 20 feet wind rotor you can probably make it durable and working.
3)
The generator I would build by 'stacking on the same axle two axial flux generators' of the same design as many other people posting here have made them. You would need three magnet disks; in the center a disk with magnets on the both sides of the steel disk. And you would need two stators.
The calculations for the generator you could start by calculating the power you could get by 'stacking' together two of the generators of 'Otherpower' 20 feet wind machine. The effectivity of the generator will go up, when the size increases. It doesn't matter, if you'll increase the number of the stator coils and magnets by adding more disks and stators or increasing the size of the magnet disks. So with two generators like that you can draw more current out than just multiplying the 20 feet wind machine generator's current by the number two...
The axle you'll need for a wind rotor of 10 m diameter should be in my opinion at least 10 cm diameter...
- Hannu