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17' turbine in WV
By dlenox, Section Diaries Posted on Sat Oct 11th, 2008 at 03:02:45 PM MST
Here are some performance numbers

As you know for the last couple of months I have been busy writing software for monitoring/logging data from my turbine and Xantrex XW inverter. I now have accumulated about 3 weeks of actual run-time data. I have been working with Xantrex and they have been an invaluable help in working out some issues. If interested more information can be gotten at http://www.briery.com/wind_turbine/build_log7.html
It has all been a great learning experience! However along the way I realized that I had measurement problems, from bad analog current meter, irregularities in measuring Hz (rpm), as well as anemometer issues (averaging).
One by one I have been addressing them, but still working on making my own digital anemometer. So I still question wind speed.
Also along the way I realized that my wind turbine has a stall issue in that the generator overpowers the blades. To help I have installed a massive .6ohm, 6kw power resistor, this has helped the turbine in medium winds. I still have a bit of a stall issue, but I am also in a pretty good wind area, so better a bit stalled - than a bit loose - as the following numbers will show...
So I know that my turbine is under-performing, but I'm willing to live with it as it appears to have good high-wind survivability. Over the last couple of months we have has 48mph winds two times and once 58mph. Seems that when the wind really blows here that it is a very gusty wind, with huge bursts of high energy, a number of times I have seen output of 5-6kw!
With all explainations, here are some numbers:
Wind Speed RPM Watts ------ --- ------ 6 105 250 10 120 400 14 145 900 18 165 1400 -- -- -- 34 240 4400 38 255 6400
You will notice one section not present, it is a gray area as with my anemometer averaging and wind gusting I can't get any good readings.
The top end is pretty apparent! At some point large gusts of wind have caused the turbine to begin to 'break away'!!
So far I have been present when these events have occurred and have manually shorted out my line resistor, that appears to get the turbine back under control and slow it down in quick order.
This is one reason that with the software that I am designing that I will have the ability to have the computer automatically switch out the line resistor for me.
I should add that I got the 17lb, 24" long, .62ohm 6kw power resistor from a guy named Nando, he used to be on this board but is nomore. If anyone is interested in purchasing one (less than $50) contact him at [EMAIL="nando37@tx.rr.com"]nando37@tx.rr.com[/EMAIL]
Once I finish up the interface to the anemometer I should be able to get more accurate instanttaneous wind speed measurements. I am working with a PicAxe chip, and will have a wireless ghz transmission that should be easily read for almost a mile...
Hope this helps!
Dan Lenox

17' turbine in WV | 3 comments (3 topical, 0 editorial)

Re: 17' turbine in WV (3.00 / 0) (#1)
by Flux on Sat Oct 11th, 2008 at 10:04:15 AM MST
(User Info)

Interesting to see someone actually trying to get performance figures.

Taking your figures at 6mph you have a Cp of about 1 ( well above Betz) so I would ignore that reading.

At 10 mph you have Cp of 0.4 and that is very good and is what you want in the common wind speed range.

By 14mph you are stalling significantly and you are down to CP of 0.3.

Down to Cp of 0.2 at 18mph and from then on you are stalling like a lead brick and the alternator performance is probably down under 40% so you fall to a Cp of about 0.1.

Based on 105rpm at 6 mph the ideal prop speed would be 300 at 18mph and 600 at 36mph.

These figures are typical of what you get with this type of operation and if it is safe then it is good enough as you will be dumping nearly all the power in high winds and having to deal with 12kW wouldn't be much fun unless you are going for heating or grid tie.

I am almost certain that your method of control is stall and that you are not furling. When you break clear of stall the thing shoots way up. If you make any attempts to get out of stall operation you will need to change the tail hinge angle if you have the usual half a ton of plywood for a tail vane.There have been lots of reports of fried stators here and I suspect that others have got out of stall by changing things from what Dan has done.

I don't know how you are measuring things or processing the data, it's a very tricky business to get meaningful results but at least it is a decent guide.

If you use hot water then changing the line resistor to an immersion heater would be a nice idea.

Flux

Re: 17' turbine in WV (3.00 / 0) (#2)
by dlenox (dlenox@briery.com) on Sun Oct 12th, 2008 at 06:33:38 AM MST
(User Info) http://www.briery.com/wind_turbine

Flux,

Thanks for the input.

The measurements are coming directly from the inverter, every 1/2 second it spews out tons of information, my software accumulates it, logs the instantaneous/average/accumulated totals, then another application displays it graphically.

I'm well aware of the stall and for now it is ok for now. I have a couple of choices one to increase the line resistor fro .6ohms to 1.0ohms from my initial testing (and your recommendation) the 1.0ohm significantly improved performance.

Or maybe next summer when I bring the turbine down for some maintenance I will increase the air gap a bit. And if possible before then replace the plywood tail with some frp to lighten it up.

I am grid tied but don't want to deal with high output(over 4kw), because it's typically under those conditions that the grid goes down then I would be forced to dump that massive load...

Dan

[ Parent ]

Re: 17' turbine in WV (3.00 / 0) (#3)
by dlenox (dlenox@briery.com) on Thu Oct 16th, 2008 at 06:38:05 AM MST
(User Info) http://www.briery.com/wind_turbine

Good wind today, able to fill in some 'gray area' in my numbers.

I'm going to have to modify the output listing from above, took measurements with the .62ohm load resistor inline:

24mph winds, 220rpm, 3000watts output

I was getting spikes of 230-250rpm with close to 4kw output during some quick bursts of wind.

By manually cutting out the load resistor, it brought things back down to 150rpm, 800 watts.

Dan

17' turbine in WV | 3 comments (3 topical, 0 editorial)

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