Dual Alternator Wind Generator?

[(unknown)]

I recently tried to submit a post about my first project using a 2.25 HP 230 Vdc 6000 rpm(?) treadmill motor.  The post seems to have dissapeared (did I get the maths test wrong?), but if it turns up I talk about a requirement for 3.5KW per week.  What I meant was 3.5 KwH per week -now I feel stupid.

I just had a thought.  The treadmill motor has a substantial drive shaft and seemingly sturdy bearings.  I could quite easily build a small axial alternator on the end of the shaft.  Has this been done?  Would the two machines interfere with each other?  Could I produce a machine with a wider bandwidth, each of the generators cutting in at different rpm?   What cut-in might be acheived with a small axial design on a -say- 150 mm / 6 in hub?

Thanks in advance,

Mal

[TomW]

I doubt adding another power generating device would be prudent.

Your other post appears to have posted.

It is over here:

http://www.fieldlines.com/story/2010/1/28/6452/73650

It probably is another Scoop [forum] bug that is not displaying it. I looked in your "stories by" link and saw it but it never showed in the story list. When that happens it is a bug. There are many and this is another.

Sorry it is not working as it should, the Home Office is is "working on it". Hopefully that will be done soon.

Tom

[Mal Farrelle]

Thanks Tom.

May I ask why it would not be prudent to add a second generator with different characteristics to widen the bandwidth?  I don't doubt you but I would appreciate the lesson :-).  If not prudent for power optimisation, could such a technique be used maybe to provide runaway braking on a non-furling design?

All the best,

Mal

[ghurd]

While I think a second generator on the back of a treadmill motor would work OK if it was made to cut in at maybe double the treadmill motor's cut in, I do not believe it is a great idea.

If going through the effort to build an axial, it would not be a lot more difficult to build one larger that could work by itself.  And I believe that would be more productive.

I saw your other post earlier.

G-

[wooferhound]

a few stories about putting 2 generators on the same prop . . .

http://www.fieldlines.com/story/2008/12/19/174541/15

http://www.fieldlines.com/story/2003/9/16/85430/5911

http://www.fieldlines.com/story/2007/4/12/185439/597

http://www.fieldlines.com/story/2004/6/26/124229/785

http://www.fieldlines.com/story/2005/4/5/162915/1327

http://www.fieldlines.com/story/2009/5/24/154345/840

http://www.fieldlines.com/story/2007/7/14/442/09914

http://www.fieldlines.com/story/2008/12/9/4162/48929

http://www.fieldlines.com/story/2004/4/18/103424/544

http://www.fieldlines.com/story/2006/10/2/203758/472

[Flux]

You can use two generators in parallel but things get a bit complicated. The usual problem is that the low speed one gets overloaded in high winds and runs inefficiently and usually hot. You could change over with some sort of device to switch out the low wind generator in high winds but it becomes rather complicated.

You are using a lot more material to do the same job and generally it is not cost effective but certainly it can be done.

Neither the treadmill motor or an axial have the correct characteristics to connect directly in parallel and give good results unless you fit chokes in series with the ac leads of the axial to limit its high speed output,there is not much you can usefully do to limit the dc machine output so that had better be the high wind end.

Flux

[Mal Farrelle]

Thanks everybody.

Regarding "using more material" - as I see it I will have the following available for free, just waiting for a rotor and stator set: Tower, Yaw bearing, Tail, Generator Platform.  I had not considered connecting the two machines either in parallel or in series, rather to run two distinct loads.  As the consensus is that it can be done, I may just try it.

All the best,

Mal