Actually 3KW is well below the peak outputs I've seen from the machine, but 3KW does happen often. In 'average' 10mph winds we see around 400W which is really what the machine is designed for.
Birds are a *none issue* with wind turbines.
Noise is a *none issue* - if they are designed to run nice and slowly and furl properly you can barely hear them. Some machines are loud, but they are too fast. The loudest thing about this 17' machine is the quiet growl/hum of the alternator when current is flowing.
We've built machines like you describe, with a single magnet rotor and a nice coil of silicon steel behind the coils. It does save on magnets to be sure, but we introduce some other problems... the bearings are under a much greater load, and we have iron losses. A nice slotted core would be the best way to save on magnets, but we'd introduce cogging then. In a wind turbine, it's very nice to have 0 cogging and 0 iron losses - this design with dual rotors gets us there, at the cost of more magnetic material. The other benfit is fairly easy construction.
With no 'line loss' (meaning IR losses in the line between the wind turbine and the batteries) - this alternator produces very nearly 4KW @ 200 rpm. No matter what approach we take, it does take quite a lot of magnetic material to achieve this.
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Actually 3KW is well below the peak outputs I've seen from the machine, but 3KW does happen often. In 'average' 10mph winds we see around 400W which is really what the machine is designed for. Birds are a *none issue* with wind turbines. Noise is a *none issue* - if they are designed to run nice and slowly and furl properly you can barely hear them. Some machines are loud, but they are too fast. The loudest thing about this 17' machine is the quiet growl/hum of the alternator when current is flowing.
We've built machines like you describe, with a single magnet rotor and a nice coil of silicon steel behind the coils. It does save on magnets to be sure, but we introduce some other problems... the bearings are under a much greater load, and we have iron losses. A nice slotted core would be the best way to save on magnets, but we'd introduce cogging then. In a wind turbine, it's very nice to have 0 cogging and 0 iron losses - this design with dual rotors gets us there, at the cost of more magnetic material. The other benfit is fairly easy construction. With no 'line loss' (meaning IR losses in the line between the wind turbine and the batteries) - this alternator produces very nearly 4KW @ 200 rpm. No matter what approach we take, it does take quite a lot of magnetic material to achieve this.