Author Topic: VAWT update  (Read 3848 times)

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(unknown)

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VAWT update
« on: October 25, 2008, 09:16:17 PM »
I completed the fabrication of new hybrid VAWT blades. In a sided by side comparison with the old design using just observation  the design preformed better by a factor of 2 to 1.  At this time I do not have the ability to measure RPM but by just using a peace of tape as a point of reference, the increase in performance is very noticeable. The next step is to make a full size model and connect it to a generator and mount them on a mast.





« Last Edit: October 25, 2008, 09:16:17 PM by (unknown) »

windstuffnow

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Re: VAWT update
« Reply #1 on: October 25, 2008, 07:45:22 PM »
  What are you comparing it to?  You really won't know the performance of it until it's connected to a load.   Do you have a genny for it?


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« Last Edit: October 25, 2008, 07:45:22 PM by windstuffnow »
Windstuff Ed

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Re: VAWT update
« Reply #2 on: October 25, 2008, 10:33:27 PM »
Like Ed says....also might be useful to be able

to adjust the angles to get optimum  performance?
« Last Edit: October 25, 2008, 10:33:27 PM by Norm »

KilroyOdin

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Re: VAWT update
« Reply #3 on: October 26, 2008, 03:05:44 AM »
Hi, in the past I constructed some generators using techniques very similar to those founded and illustrated on this site. They were small using ½ inch rare earth magnets and 5 amp wire. I did this just to see what problems would be encountered. I found the experience to be straight forward and I was impressed with how well the techniques worked. I still have to construct a larger generator.    



The comparison of rotation was with a simple drag configuration constructed with 4 inch PVC pipe. The materials used for the new design are much lighter.  



What do you use for a load when testing the output?
« Last Edit: October 26, 2008, 03:05:44 AM by KilroyOdin »

KilroyOdin

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Re: VAWT update
« Reply #4 on: October 26, 2008, 03:14:45 AM »
Hi Norm, the angle I am using is 9 degrees  as illustrated from the Lenz plans. I read some where that greater than 13 degrees would cause a stall condition but I can not remember where.

« Last Edit: October 26, 2008, 03:14:45 AM by KilroyOdin »

KilroyOdin

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Re: VAWT update
« Reply #5 on: October 26, 2008, 06:41:04 AM »
Testing some software with this posting. The image shows genrator concept.

« Last Edit: October 26, 2008, 06:41:04 AM by KilroyOdin »

windstuffnow

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Re: VAWT update
« Reply #6 on: October 26, 2008, 09:36:20 AM »
 I've used several different methods to find shaft power of the turbine, the one I like the best is an alternator set up to allow the stator to pivot on a bearing with an arm attatched to a spring scale.  The stator is slowly shorted through a rheostat and you can measure the torque and rpm.  From there you can calculate the actual shaft output.  The alternator/prony brake also works as an alternator and you can calculate the shaft output from the alternator output - not quite as accurate but it works.  As long as you know the windspeed, torque and rpm you have all the info needed to find the overall efficiency of the unit.  


 .

« Last Edit: October 26, 2008, 09:36:20 AM by windstuffnow »
Windstuff Ed

KilroyOdin

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Re: VAWT update
« Reply #7 on: October 27, 2008, 04:16:38 AM »
I had the opportunity to observe the performance of the new blades as a storm front move through and it showed some unique characteristics, namely a high RPM was reached very quickly and appeared to stabilized and remain constant as the wind speed varied. I need to configure a data logger that will record wind speed , RPM of the VAWT and voltage output of the generator.    

« Last Edit: October 27, 2008, 04:16:38 AM by KilroyOdin »

windstuffnow

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Re: VAWT update
« Reply #8 on: October 27, 2008, 08:30:12 AM »
  That is the characteristics of the Lenz2 type wings.  I noticed that in several versions of the open wing design.  The higher the wind the less efficient it will become.

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« Last Edit: October 27, 2008, 08:30:12 AM by windstuffnow »
Windstuff Ed

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Re: VAWT update
« Reply #9 on: October 28, 2008, 09:01:11 AM »
"Coil Plate" and "Metal Plate".

The metal plate needs to be laminated iron, or rotate with the "Magnet Plate".

A solid metal plate fixed to the coil plate will be a large brake due to eddy currents.

Just in case someone finds the image who dosen't know.

G-

« Last Edit: October 28, 2008, 09:01:11 AM by ghurd »
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KilroyOdin

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Re: VAWT update
« Reply #10 on: October 29, 2008, 06:49:20 AM »
Hi, I was not  aware of that affect. You have picked my curiosity.  Has anyone perform testing of the event, are there links to data showing the results?  Thanks for the heads up.

« Last Edit: October 29, 2008, 06:49:20 AM by KilroyOdin »

ghurd

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Re: VAWT update
« Reply #11 on: October 29, 2008, 08:31:09 AM »
Simple demonstrations.  

Place a coin and a neo on a heavy-duty aluminum cookie sheet.  Shake it around.

Drop a neo down a 8' piece of 1/2" copper pipe.

Place a piece of angle aluminum at a steep angle, and drop the neo down so it slies to the bottom.

Place a neo on a 1/8" thick piece of aluminum plate and slide it in circles as fast as you can.


The solid fixed backing plate is about the same as a coil with an infinite number of turns, 0 ohms resistance, and shorted output wires.


I doubt anyone did serious testing for results.  All that matters is it is bad enough to keep the windmill from working.

G-

« Last Edit: October 29, 2008, 08:31:09 AM by ghurd »
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KilroyOdin

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Re: VAWT update
« Reply #12 on: October 29, 2008, 06:05:21 PM »
Hi, I thought a laminated metal plate was a fabrication technique to solve the problem of not having a metal plate available of suitable size for construction.  The photo I posted of the small generator driven by the lathe was constructed using  a metal plate and coils in a stationary position functioned well. Have you had any experiences with eddy currents from generators that you have constructed?    
« Last Edit: October 29, 2008, 06:05:21 PM by KilroyOdin »

ghurd

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Re: VAWT update
« Reply #13 on: October 30, 2008, 07:29:54 AM »
I would not construct a PMA with obvious eddy problems.


I expect you did not drop a neo down a copper pipe.  (Aluminum would work too)

I just did it for you.  And my wife wonders what I do on days like this.

Unknown grade HD neo, certainly N35 at most.  Slightly under 1/2" x slightly under 5/8" x 3/16".

Brand new thin-wall 1/2" copper pipe 10' long.

The magnet fits loose in the pipe.  There is no corrosion on either part.

At about a 45 degree angle it took 19.5 seconds to fall through.

As close to verticle as I could guess took 9.5 seconds to fall through.


Only PMA eddy experience in induction motor conversions.  They are laminated and have some iron losses, partly due to eddy currents.  It can be felt as a difference in how hard it turns with magnets compared to before the magnets were added.  Dinges Peter did some in depth testing of iron losses in a small conversion you may find interesting.  There is nothing I can do about it in a conversion, so I don't worry about it.


If you are not having a noticable problem with eddy currents in the rear disk, I expect the lathe is too powerful to notice it being dragged down, or the air gap is far too large (if the air gap is too large, the coils are too thick and much of the copper is just adding resistance).


A dual rotor has no real iron losses and that's why they spin up so easy.

A single rotor with laminations, or a conversion, has iron losses. And that's why they "drag" even before there is a load.

A solid, non rotating disk will hold the PMA back like a dragging brake.


Ed's page shows a LOT of PMAs with laminated cores.  I doubt he ever cut a corner because of a lack of proper material on hand.


The eddy currents get worse with speed.  

Do not underestimate the effect. It stops trains and roller coasters. It may be in use as a fail safe elevator brake.  Maybe google "magnetic brake".

G-

« Last Edit: October 30, 2008, 07:29:54 AM by ghurd »
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