lenz2 VAWT double speed variation

After a lot of thought on the type of wind turbine I should experiment with, I started building this vertical axis wind turbine (VAWT). Its a variation of the lenz2 design, for which I had all the details, thanks to Mr Ed Lenz.
As you can see, its a system of two parts (two halves of a lenz2 wind turbine) stacked together so as to rotate in opposite directions. Magnets are attached to the low end of the top part and coils are attached to the top end of the bottom part. This way the relative rotation speed of the two parts is theoretically double the absolute rotation speed of each part alone. I thought of this configuration to overcome the problem of VAWTs operating at low rotations per minute (RPM), maintaining at the same time the advantage of starting up at low wind speeds.
In the video the lower part of the turbine is deliberately not rotating, because I have not yet built the necessary slip-ring to convey the electricity produced. Wind speed at the time is about 3 bf (3.4-5.5 m/s). The measurement you see on the voltmeter is AC (I built a bridge rectifier to convert to DC a couple of days later).

The materials used for the turbine are:
1 2m long heavy duty iron pipe of 30mm diameter
4 3mm thick iron plates (2 small + 2 large) cut in equilateral triangles used as hubs
4 FY 30 TF (if I remember well) flanged bearing units
12 pieces of aluminum pipe (1cm X 3cm), 6 short + 6 long.
6 sheets of 0.7mm thick galvanized steel, for the wings
12 pieces of 22mm thick plywood, for the wings
18 pieces of Π shaped aluminum ribbons, for the wings

The materials used for the alternator (between the two rotating parts of the turbine) are:
8 neodymium magnets (4cm X 2cm X 1cm)
8 pieces of iron (4cm X 2cm X 1cm) which I placed between the triangular steel plate and each magnet, in order to reduce the gap between magnets and coils
12 copper AWG ___ wire coils of 70 turns each, wired in star (Y) formation (I'll fill in the gap as soon as I measure the wire again, I just used what was available at the time)
Cast no-bake craft clay to hold the coils together (for testing purposes only, so I can easily brake it and reclaim the wire if it doesnt work, plus clay is completely natural and biodegradable unlike PVC resins).

After I built the bridge rectifier and hand tested it (no wind on that day) at approximately the same rotation speed as the one you see on the video, with the bridge rectifier connected this time, I was utterly disappointed. I measured about 0.4 watts of power (2V x 0.2A) generated. I only rotated the upper part of the turbine (the one with the magnets). But assuming the lower part would rotate at the same speed in the opposite direction, would that give me 0.8 watts? If the answer is yes, then its simply disappointing. Ive already tried to reduce the gap between magnets and coils but if I reduce it any more they might collide during rotation.

Any thoughts on how to improve performance would be greatly appreciated.

Category:

Howto & Style

Tags:

• lenz2
• vertical
• axis
• wind
• turbine
• VAWT
• variation
• split
• in
• two
• opposite
• direction

[wiboater4]

After looking at your video. It looks like you have bearings that rotate on the shaft for both wing sections. so you should be able to just attach the stator to the bottom section to turn it opposite.

[kefteskaideftais]

Quite right. That was my intention from the start. And that's what I've done, only I have not used brake disks to have magnets on both sides of the stator (coil ring). I am working on it though! Currently I have disassembled both upper and lower wings (drums) and by next week I hope to have reassembled them so as to have magnets on both sides of the stator. I will have to build a new stator of course, since the current one is too small for the the brake disks I could scrap. We'll see...

[wiboater4]

you won't double the speed in low wind it will divide between the 2 sections. It will cut vibration at higher winds and produce a lot more at higher winds.

[kefteskaideftais]

Thanks for the kind remarks. I've studied your clips of opposite turning lenz2 and I must say I am intrigued to go with your approach using two independent shafts instead of one I'm using. It makes sense because:

a) the chances of the shaft bending under stress will be 0 and

b) I won't have to use an expensive bore-trough slip-ring (about $120 including postage)

I'll try to fit a couple of brake-disks between the two turbine sections to have magnets on both sides of the coils.

Thanks again

[kefteskaideftais]

I just put the whole thing up for about an hour or so, just to see if it works at all. (hence the flimsy support system)

[wiboater4]

I had a weld break on my frame on the one on my dock so I redid it I have my rotors and stator at the bottom now. Still have a few things to put back together on it. Won't get it done for a day or two. Then maybe I'll post a video of what it looks like now.

[wiboater4]

The stator is attached to the shaft, which the lower wings are attached to , so stator rotates with lower wing & shaft and Rotors rotate with upper wings only.

[wiboater4]

I don't have two seperate shafts. The bearings are what's different. The upper bearings rotate On the shaft and the bottom are pillow block bearings attached to the frame. The upper wing has the magnet rotors attached to the wing supports so they rotate with the wings.

[wiboater4]

You don't have to have the generator in the center, I figured out you can put it on the bottom or top also. I got a cheap slip ring on ebay for about $40. It's on the one on the roof , seems to work fine.

[wiboater4]

your on the right track. you need to run the wires down the center of the bottom shaft to a slip ring.