I contacted the manufacturer, and they gave me this:
1) The tower is to be made out of water pipe, as electrical conduit is softer.
2) Welding cable is to be used, as the gererator has no slip rings (for yawing in the wind). They say that welding cable will twist until it can't twist anymore, then it will unwind itself, eliminating the need for slip rings.
I guess the type of pipe is not really a big deal (except for NEC). I'm probably just going to use the system for a few lights... make them 12V CPFL. I guess it's no big deal, I was just mad that they can sell these things without being UL listed. I don't wanna fail an inspection years down the road b/c of an oversized garden pinwheel..... :-D
