| I thought I would never do this, but I bought a wind turbine. Ive had good luck in building dual rotor machines for a while, and I think I will build another dual rotor this summer to replace this Bergey because it is a relatively small diameter machine (8.2 ft) and it just does not have the low wind performance available in say a 14'-16' machine. It is still fun to test it out and see what its capable of. I have seen over 1500W from it and its rated at 1000 so thats not too bad. Ive had some problems with it, but thats MY fault lol. Here we go...
This is a Bergey XL.1 Its an 8.2' diameter machine with gravity furling (or Autofurl like bergey likes to say). MADE IN CHINA stamped all over it. It costs roughly $2500 with the controller. (expensive experiment) They rectify in the nacelle and bring DC down the tower on 2 slip rings...not sure I like this, but I see it leading to some more control experiments being done with some IGBT's perhaps. I think I like the controller because your able to run without a dumpload and the controller automatically dynamically brakes the machine when needed to prevent overvoltage. Similar to how my past systems worked. I had to make the green pipe adapter you see below the machine to adapt it to the tower I am using currently. I think out of the box it requires a 4.5" OD tower pipe to be mounted in. Im horrible at taking pics when Im building all this stuff up because its only me in the shop most of the time so if i miss anything of interest, just ask. I wish I had some actual numbers but I just had a problem with my pentametric (i use to record all power production) and I just bought a nice wind and data logger and it hasnt arrived yet, so soon Ill post some numbers.
Heres where it sits currently, 90' up. If anyone on this board has one of these, please do not sand off the small ridges on the back of the blades :-P I DID. Big mistake. I dont recall reading in the manual where it says not to do this. But, supposedly, your NOT TO DO THIS. To tell you the truth, they sort of look like a manufacturer defect and its this little ridge that makes the machine so quiet. I wish i had a BEFORE pic of what it looked like. To make a long story short, I removed the ridge because I thought it would make noise. Well after i removed them, it made ALOT of noise. Generally at low wind speeds however. This was unacceptable because I have been spoiled this whole time I have experimented with dual rotor machines and I really like to run them slightly in stall because they are so slow and quiet but at the same time relatively powerful.
This is the current Bergey XL.1 airfoil. No twist. No taper. Constant pitch with a little bit of the trailing tip cut off. The ridge was located at the top of the airfoil at the highest point.
Looking up the blade, you can see I came up with a way to compensate for my stupidity lol. I was going to put leading edge tape on anyway, so I just stuck something under it to create a "ridge" so to speak very similar to what was there. I actually used monofilament fishing line close to the same size as the original ridge. I taped it off at the root and pulled it taught and folded it around the tip and taped it to the front of the blade. I then covered it with leading edge tape, making sure there was no bubbles or creases in the tape, and folded the excess tape around the leading edge. After the edge tape was applied I used my fingernail to run the length of the fishing line and make sure the new "ridge" was exactly uniform and it was adhering well. Before the tape was fully adhered to the root and tip, I cut back the monofilament .25" so the tape could overlap and form a nice (hopefully) weather tight seal. Centrifigual force usually keeps most water out, but time will tell.
Here is another shot of the ridge I created. Its DEAD QUIET now. ALL the time. I think this works by creating slight turbulence at the back of the airfoil causing it to smooth out the trailing edge currents as the air moves around the blade. It also might make the blade profile apear to seem thicker at lower speeds. Im not sure and this is just speculation. Maybe someone else can chime in on this. I know the SWW Skystream 1.8 uses the same technique but on the leading edge (top and bottom).
Now some cool pics of past projects:
Heres my place from 90'.
8Kw of grid tie PV for the front house. (Im still off grid)
...yes, thats a tractor i have to fix this spring.
520w tracker I built up. This floats the house bank till sundown. Ive seen 650W out of 4 KC130's and an MX60. Pretty cool if you ask me.
the back of the tracker. single axis. It uses one of the Red Rock Energy boards. Pretty cool little circuit. No failures yet. :-P
Roy R
KB2UHF
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