17' wind turbine in West Virginia

[Dan Lenox]

Background:
I wanted to build a 2-3kw wind turbine and after finding the OtherPower.com website ran across their 17' one which looked like what I had been wanting.

My wife and I live in NE part of rural West Virginia on about 7 acres on top of a mountain ridge with an elevation of 3000'. From our property we have a
panoramic view of about 50miles in almost a 270 degree radius. There is always wind here and it was the logical choice for me to make and install
my wind turbine.

I did not want a tower with guy wires but instead wanted a free standing unit. In the end I went with a 70' free standing lattice tower from AN Wireless.

I required a retractible 10' tower stub to essentially bring the turbine down to the top of the tower for maintenance, this I had to design and custom build
it myself. In addition I needed to design and build a davit crane which will be permanently be mounted on top of the tower in case I need to remove the turbine.

In addition I fabricated three work platforms that make it easy on the feet once at the top of the tower.

My axial flux generator was built based upon DanB's 17' design posted on the OtherPower.com website. My yaw bearing and components have been considerately
'beefed up' from the from the original 17' turbine. Structurally it is closer to the 20' diameter one that DanB built a year later.

A positive stopping mechanism will be used as my area is prone to high winds, I will be using a mechanical disc brake caliper that is engaged using a 12v dc
linear actuator. This provides positive stopping and release of the brake pads from the brake rotor, unlike hydraulic calipers.

A complete project build website has been made which has far more detail that that which follows, it can be found HERE: http://www.briery.com/wind_turbine

With winter currently upon us the blades and tail will have to wait until spring before they can be put up on the turbine and be fully operational.

Dan Lenox

[Stewart Corman]

Dan,
I am the first to repond to your thread and just had some free time to go through your entire website ...I am both impressed with your website as much as the actual project.... great work all around.

Firstly, I had thought I saw a reference to your project posted elsewhere, and I now remember the conversation on Otherpower about where to place the extra imbedded epoxy balancing weights on the root vs the tip end ..guess you got that worked out as documented on your site

Secondly, I really don't understand why so many of you are opposed to guyed towers ..IMHO, even if I had your very substantial tower, I would still put four guys going up to the top ...me personally don't like climbing more than 20 feet up, so a tiltable tower is a must and makes servicing much more convenient.


Thirdly, in reading on your "Blades" section, I noted several things other than your great fabrication techniques.

I too am using Titebond III and I am gluing up 1 inch thick clear sycamore.
Your sassafrass is interesting and I had no idea it was a harvested wood similar in density to poplar which is a bit lighter/softer than sycamore. But it is the glue joints that give it strength (balsa wood would work with enough glue!).


The size of your blades is fairly similar to mine in that the tips are 6 inches wide and only 3/4" thick ..mine are 12 inches at the root ( but that is 3 feet from the axle ie the 33% station) and they weigh about 16 pounds each + 4 pounds of pipe spar = 20 pounds total. I have devised a tapered blanking routine that has significantly more utility of the raw wood. I will post pics when my glueing table is completed.

I have to give credit to the guys at the OtherPower.com (http://www.otherpower.com/bladecarving.html) website blade carving page for the basic image's used in my airfoil profile diagram above. I have modified it as I found it confusing the way that they originally pictured it, I rearranged the images so that they show (as should be) that the leading edges of the profiles are aligned in a straight line, like they would appear on the actual blades. I had to recalculate the offsets from the blade face to suit the width of my blades, 3 degrees at the tip, 5 degrees at the mid-station and 6 degrees at the root.Your diagram of "blade airfoil profiles" confused me if you actually carved them that way. I would have presumed since the forward face remains flat, that all the carving was from the curved side and that diagram could be for display purposes only. Easier to angle the short root "foot" where it gets mounted than the entire blade length, besides it gives you a thicker cross-section which means you could have more root pitch with the same size blank.

How did you get the twist specs other than using the maximum at root as the glued width would allow? They are not numbers that I would have chosen from looking at the NACA profile and the polar charts. I have seen Otherpower blades in action and they are noisey and not as efficient as they could be and run at too high a TSR ...note that Dave B's 18 footer gets into runaway mode too easily ...you don't necesssarily want highest performance at high WS where you can't use the power available anyway, and rpm/vibration/noise/stress are all amplified ...note that his blades start at 10 degrees pitch (TSR =5) and his new blades will be higher pitch ..all of which could easily be determined before the first chip was cut!

I agree totally about an electric power planar being the ideal tool to reduce material fast and accurately ..expression is that it is the "cat's meow".

Final assembly of rotor looks very substantial ...BTW, looks like you used spring washers under ordinary nuts ...Mark had counseled me that use of Nylock nuts is a much better implementation.

I read about your static balancing and it looks on the money and accurate, but that said, there is no reasonable means to determine dynamic balancing. If one of the blades has more weight at the end than another, even if both have identical total weight, then when it is spinning you will generate vibration. This is the argument for steeper pitch angle and lower TSR, along with greater solidity in the blade planform. Vibration is a square relationship with rpm so the diff between your TSR approx 7 vs a TSR=4 results in a 3x increase in vibration. Doesn't mean a thing until Dave B's 18 footer went into overspeed at 350rpm when it was designed to be under 200rpm! Expect that if for some reason the load is absent, the TSR will double ( general rule of thumb )

Bottom line from above results from Dave B indicate that if you have designed the side furling with a specific WS and corresponding tail weight ..err on the side of it furling too early, until you can actually see it fly in high winds ...you can always add a small weight (ie 2+ pounds) to the tail to have it furl at higher WS later.

All in all, a very impressive build and I wish you all the luck in it flying as you expect it and hope to see some data of KW vs rpm vs WS under load.

Stew Corman from sunny Endicott





qq: what program are you using to draw the simplistic diagrams imbedded on your site?? I have Solidworks, but looking for something simplier??

[Dan Lenox]

Stew,

Yep I am also on the otherpower.com discussion group, lurked around there for quite a while acquiring information. Seems that getting 'smart' is a never ending quest.

My opposition to guyed towers is purely aesthetics. The AN Wireless towers are well designed and I had an engineering study to ensure that the load that I was putting on the top of the tower fell within their specifications.

Yep made stupid assumtions about balancing blades, but I like to show my mistakes as well as inspirations on my website so that others can learn from them as well. It all worked out well and I learn as I go, in the end I think that I got it as close as good-enough as I possibly could.

The front of the blades are basically flat, and back sides have airfoil as shown. One day I had the entire 17' assembly on a hoist and a gust of air caught it and started it spinning, as well as my heart pounding as it took a few minutes and imagination to get the whole thing stop spinning. I just a few seconds it probably went up to about 150rpm...

I used *lots* of locktite - the red variety - to keep things together as well as lock washers.

Can't wait until spring when I can have the whole turbine operational, until then I am finishing up the electrical back-end and battery bank.

Dan

[Rob Beckers]

Hi Dan,

Fantastic job! I've also read the story on your Web site, really very interesting work. You seem to be doing your homework before embarking on a project. When you get the turbine to fly in spring please post back here how things are working out. I would very much like to hear about it.

Using a david crane is a good idea, especially if you expect to do a little experimenting and want to be able to lower and raise wind gennies without having to hire a crane each time. The guys at ARE did the same thing, you can see a picture of it in http://www.greenpowertalk.org/showthread.php?t=3094 (third from the top). I had the pleasure to use it for lowering the 10 kW alternator plus prop. Works like a charm.

I'm not seeing it in your electrical diagram, but hopefully you are planning for some lightning protection in the form of good grounding and a few arrestors. Since you live on top of a mounting this is especially important, that tower is going to function as a giant lightning rod. At the very least I would recommend the (cheap) Delta surge arrestors, see http://www.solacity.com/Docs/Scirocco%20Hookup.pdf for an example on what to use where. The Delta arrestors are not the greatest, but they are a great deal better than nothing and they are cheap. To move up to more serious lightning arrestors would take a whole lot more money.

-RoB-

[Dan Lenox]

Rob,

Yes I have lightning protection using the Delta 3-phase unit as well as using three ground rods at the tower base to ground each tower leg.

The tower wiring goes to my garage where I have another ground rod as well as a circuit panel that contains a Delta 3-phase lightning arrestor. The panel also contains fuses as well as contactor for shorting out the stator.

I also have a 12v dc power source next to the circuit box. It contains a DPDT switch for controlling the 12v linear actuator to engage/release disc brake on top of the turbine. If needed the plan is to engage the brake to slow the turbine down to a reasonable speed, and then short out the stator to stop the turbine. I do not want to attempt to stop the turbine using the stator only, and have heard stories about burning out stators under gusty winds.

From the garage the wild AC from the turbine is routed into my house, where all the electronics, rectifier and battery bank reside.

I updated the block diagram (above) to show these additional components.

Dan