constraints on size

[angus]

Hi. Have been around for a while and have understood most of what has occured in building the 7 , 10  and the recent 20 footers over at the two Dans place (sorry).

 In my case I live in an area of 15mph (yearly average) winds and my household uses

about 50kw hours of energy every day (yes I should do something about that).

 So I have been thinking of building a 30 or 40 footer.

 The question  is/are - there  must be some physical , material , technical constraints on how large  the stator, rotors, tail, blades etc. can be built ?

 Sorry if this has been covered before and thanks for any advice.

Angus (the older I get the better I was).

[Flux]

If you can cope with the rest of the problems of a 40ft machine including methods of control you shouldn't need to worry about the alternator.

I personally wouldn't use an axial alternator for this size but it is certainly possible. As you make the discs bigger you need to start thinking about stability, perhaps you will need some radial ribs to help support the considerable magnetic attraction. Bearings will need to be considered carefully and I would prefer to see them further apart on a large machine.

Unless you can go to high voltage you will be limited in wire size.Without slots you can't use thick wire because of eddy currents so you may have to use several strands in hand and possibly twist them slightly rather than random winding the strands.

You will need lots of magnet to keep it slow enough for direct drive. If you use the same ones as Dan's 20ft and increase disc size to double the number of poles you should be in the right region.

I can't see any fundamental problem. I think commercially it has been considered that the problems above 100kW make it advisable to go to a radial design or you have to start stacking discs and that is wasteful of magnet material.

Flux