Vertical Axis - Overspeed Control - How?
By unbsj, Section Homebrewed Electricity Posted on Sun Oct 09, 2005 at 06:46:09 PM MST
Looking for advice on how to restrict rotor speed of vertical axis design

I'm researching wind turbine designs for a term project. While I've seen advice on this website regarding rotor speed control for horizontal axis designs, I've not found anything about how to control the speed of vertical axis designs. Any advice or resources you can suggest? Thanks.

Vertical Axis - Overspeed Control - How? | 11 comments (11 topical)

Re: Vertical Axis - Overspeed Control - How? (4.00 / 1) (#1) by windstuffnow on Sun Oct 09, 2005 at 02:39:51 PM MST

You can simply mount the wings on a pivot, use a spring system to hold them at the proper angle while in normal operation.   When the machine starts to overspeed the centrifugal force moves the wings into a stall position thus maintaining a moderate speed.  This would require some calculations finding the proper spring tension, as well, make the machine more complex.    A simpler method would be to short the stator making it operate with a very high load on the shaft.    An adjustable eddy current generator controlled by rpm or centrifugal force.    Good old fasioned brakes ( stop and lock method). There are probably a dozen or more different ways to control the speed of a VAWT... .     Have Fun! Windstuff Ed

Re: Vertical Axis - Overspeed Control - How? (4.00 / 1) (#2) by MountainMan on Sun Oct 09, 2005 at 06:48:12 PM MST

Ed, You forgot your best method from  your test "tower".  Just tilt the bucket of the tractor down so the VAWT is out of the wind! jp MountainMan, Julian California http://www.real-home-based-business-opportunity.com My ultimate hobby project is to build a ten foot tall robot. [ Parent ]

Re: Vertical Axis - Overspeed Control - How? (4.00 / 1) (#3) by windstuffnow on Sun Oct 09, 2005 at 08:01:02 PM MST

LOL ..Ya know... I was actually going to add that one in and even chuckled while thinking of it.  I figured if someone hadn't been following along it might have made me seem like some kind of lunatic so I decided to leave it out.... Thanks for bringing it up ! good for another laugh...  Although a similar control system could make that a fairly good idea. . Have Fun! Windstuff Ed [ Parent ]

Re: Vertical Axis - Overspeed Control - How? (4.00 / 1) (#4) by Peppyy on Mon Oct 10, 2005 at 09:46:21 AM MST

Some of the finer old spring wound time insturments had a flywheel with air dampers on them to regulate speed.  I can imagine this working with a fixed amount of force but it would need to be modified to work with higher forces. Perhaps a centrifugal clutch of some kind used to engage a brake at a given rpm. The clutch could be connected to the shaft as normal but the drive could be fixed so as not to allow the machine to obtain a speed above the clutch engagement speed. Pep

Re: Vertical Axis - Overspeed Control - How? (4.00 / 1) (#5) by Ungrounded Lightning Rod on Mon Oct 10, 2005 at 12:49:39 PM MST

Brakes dump the power as heat - and wear.  You'll likely burn 'em out pretty quick if you try to depend on them. Better to do something that modifies the airfoils or airflow so they don't collect as much from the wind in the first place IMHO. Also:  Some of the VAWT designs (mainly the mostly-drag types) don't normally run at high TSRs.  So there's some question of whether you need to actually bother.  If you build 'em strong enough to spin at a tip speed of, say, 125 MPH without coming apart, you can just reduce the load on your genny so it won't burn up (and and the rotor won't have as much air drag) and let 'em spin.   Then the farmhouse will probably blow away and the tower come down before the rotor comes apart. [ Parent ]

Re: Vertical Axis - Overspeed Control - How? (3.00 / 0) (#11) by spinner on Thu Dec 01, 2005 at 08:05:16 AM MST

agree on the strength idea....basically that's what I've done so far...tho plans include the ability to have my dualhelix VAWT be able to travel lower or higher in response to windforce spinner [ Parent ]

Re: Vertical Axis - Overspeed Control - How? (4.00 / 1) (#6) by nanotech on Mon Oct 10, 2005 at 05:39:31 PM MST

If you're talking about automatic systems, there are others out there with more knowledge/experience than me. But for a brake system? How about a rod or baffle that you insert into the center that would completely disrupt the airflow between the upwind and downwind vanes? I guess another one would be to have some way of lifting the "top plate" so that the airflow would vortex out the top...... __________________________________________ My ship finally came in, but it was the Kobayashi Maru!

Re: Vertical Axis - Overspeed Control - How? (4.00 / 1) (#7) by joemac2005 on Mon Oct 10, 2005 at 08:15:20 PM MST

Just wondering,,  what kind of speed do you get? I was thinking the VAWT would turn slow and kind of self limits... Also how big is the rotor?

Re: Vertical Axis - Overspeed Control - How? (4.00 / 1) (#8) by wind4Reg on Fri Oct 14, 2005 at 09:26:36 AM MST

I think the best system would be to use magnetic brakes like the ones used on some of the landspeed racers. No parts to wear and they have tremendous stopping power. That is the system I plan to use when I build my big VAWT. Reg.

Re: Vertical Axis - Overspeed Control - How? (4.00 / 1) (#9) by FishbonzWV on Fri Oct 14, 2005 at 05:57:00 PM MST

I might be way off base here but...what about mounting the genny system on a large stiff spring like a car spring. When the wind gets to a certain speed the whole genny leans over ever so slightly changing the air flow through the wings. Just a thought. Bonz

Re: Vertical Axis - Overspeed Control - How? (4.00 / 1) (#10) by electrondady1 on Fri Oct 14, 2005 at 07:44:38 PM MST

i have thought along those line as well .that control system would .  self regulating . tuneable,  adjustable , deflection. [ Parent ]

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