New 12 Foot turbine and some data

[DanB]

Tuesday around noon our friend Mike came up to build a 12 foot diameter wind turbine.  We had the parts water jet cut in advance.  Mike made a very nice new plastic mold and brought that with him.  It took basically a day and a half to knock this one out, it came out nicely!



Pictured above is the back side of the alternator.  This is about the same as the last few 12 foot turbines we've built, but we did away with the square stator and built a better stator bracket.  It's a fairly robust machine I think.



Pictured above is another shot of the same machine.  As with the last few we've made....
The magnet rotors are 15 inches in diameter.  Each rotor contains 16 N42 grade magnets, 2 inch diameter x .5 inch thick.  It's a 24 Volt machine.  In the past we've wound these with two strands of 13 gauge wire in hand, 35 turns in each coil.  This time we used 4 strands of 16 gauge in hand.  The coils came out much nicer...  but a bit small, we could've fit another strand in there easily.  The stator on this machine is .625 inches thick and it reaches 25VDC at 120 rpm (which is the same as all the other 12 foot machines we've made).



I've posted the above graph before.  We made this last July at a workshop in MO.  The black line represents power at the shaft from a 12 foot diameter blade, assuming cP of .25 at sea level.  The blue line is based on a few data points of measured power into the alternator (power required to drive the alternator while it's hooked to batteries) - we measured foot pounds, and rpm.  The red line is also estimated but based on more data points... and that is the power that we got out of the alternator.  On the X axis we have wind speed, and rpm - assuming a constant TSR of 7 (which is not very realistic but fun to think about I guess).



A few weeks ago we installed an APRS data logging anemometer on our neighbor Toms tower at 50' in height.  The unit also logs voltage and current.  The graph above is from 10 hours last Monday night.  Our peak gust that night was about 60 mph.  Each data point represents a 1 minute average.  This is in the mountains, the turbine is at 60 feet - it's a turbulent site to be sure.  I would love to see how it looks on a 'good' wind site.  Fun stuff anyhow - looking at this, the machine doesn't look terribly efficient, but it is definitely within reason and I expect it would look better on a less turbulent site.  I can't wait to get more data... on a windier day so we can see the full power curve after it's furling more.  This machine is basically identical to the 12' turbine we built this week.

[jlt]

Your designs keep getting more refined.great work.I built  A 12ft with 15" rotors but with 2x1x1/2 mags. and 120 turns 14 wire in it.had to squeeze the coil's a lot to fit . had to wire it in a jerry configuration to keep from stalling out.mine is 48 v .It's still on a test tower after 2 years. hoping to find the time to get it up on real tower this summer.I only have to short out one phaze to stop it .if i short out all three it's stops like throwing in a crowbar . like in half a turn. Going to use a 5 spoke stator on my next one. how many inches of offset did you put in yours. 

[Dixie]

Your designs keep getting more refined.great work.I built  A 12ft with 15" rotors but with 2x1x1/2 mags. and 120 turns 14 wire in it.had to squeeze the coil's a lot to fit . had to wire it in a jerry configuration to keep from stalling out.mine is 48 v .It's still on a test tower after 2 years. hoping to find the time to get it up on real tower this summer.I only have to short out one phaze to stop it .if i short out all three it's stops like throwing in a crowbar . like in half a turn. Going to use a 5 spoke stator on my next one. how many inches of offset did you put in yours. 

The spindle is offset 8.5 inches from the center of the yaw bearing.

[Flux]

I think you are right to use thinner wire with more in hand, it's easier to wind, has a much better stacking factor and you waste far less space where you bring out the inside connection. I have always done things this way, perhaps mainly because I use wire up to 1.2mm thick for my normal business and not the thick stuff, but when I have been forced to use very thick stuff it is not easy on small coils.

There is conceivably an issue with circulating currents with several strands in hand unless you are careful but I suspect that is balanced against the fact that anything thicker than about #12 will be starting to see eddy current losses.

Nice to see the output data. I suspect the scatter would be much less on a decent clean site bur the mean line through that lot would probably be close to what you are getting.

Flux

[Dixie]

Thanks for the comment Flux.  It'll be fun to get more data, over lots more time now that we have this anemometer working.  Hopefully in a while we can get a nice graph that shows energy and average wind speed which is perhaps the most important thing in my mind.  I'm not sure how the turbulence really affects the power curve overall.  Hopefully this machine we just built will also have an identical data logging unit on it - it will be located on a much cleaner wind site. 

There is a small error in our data...  the unit itself draws about 13 Watts, which is subtracted from our data  (so all the points should be 13 Watts more).  It's also located at about 8400 feet elevation.  How much would you de-rate a wind turbine per 1000 feet of elevation?  I've heard different things...

[Dixie]

Just so you all know.. I'm a very clever border collie, and sometimes DanB comes to town and uses *my* computer.  So if I say stuff here... it's often times DanB or MattB actually doing the typing.

[Flux]

Air density will be quite a significant factor. The power in the wind equation implies that power falls directly as the density.

I can't be too exact here but from memory I think you are down from 1.2 kg/M^3 at sea level to about 1 at 1500ft. At 3000ft it is near 0.8 so you are probably going to see half the sea level figures. I hadn't realised you were so near the sky, that is not a negligible factor and makes your machine look a lot better.

Flux

[rjames]

Nice work...great looking craftsmanship.

My personal thanks to you guys who continue to build, improve on design, etc.

And then also for posting the results and replying to questions asked.
      Rick
   

[DanG]

Looking online I found a neat puzzle: Taking a cubic measure of air from 104°F (40°C) to -4°F (-20°C) increases the number of gas molecules nearly 25 per cent; while going to 8500' altitude takes away nearly 25% of that measures apparent pressure.. . 

I'll leave the link "Danish Wind Industry Association: Guide to the Wind Turbine Power Calculator" for y'all to play with:

http://www.talentfactory.dk/en/tour/wres/pow/index.htm

(Using their system I calculated a 22% de-rate factor at 8500')

[poco dinero]

Air density will be quite a significant factor. The power in the wind equation implies that power falls directly as the density.

Yes, and that means that if your rotor diameter is a perfect match to a given alternator at sea level, you will need to increase the rotor diameter by the following equation as you increase the altitude at which the wind turbine is installed, assuming you want to preserve the perfect match of the rotor diameter to the alternator:

     D(alt)  =  D(sealevel)  *  Square Root of [rho(sealevel)/rho(altitude)]

          where    D = Rotor Diameter
                       rho  =  air density

According to the ICAO table of standard atmospheres in my Mechanical Engineers Handbook, for an altitude of 8400 feet the ratio of [rho(sealevel)/rho(altitude)] is 1.286.  The square root of 1.286 is 1.134.  So, if a 12 foot rotor diameter is a perfect match for a given alternator at sea level, that same alternator needs a 13.6 foot rotor diameter to still be a perfect match for that alternator at 8400 feet. 

Air density does indeed make a big difference.

poco

[poco dinero]

(Using their system I calculated a 22% de-rate factor at 8500')

22% seems a bit high.  I calculated  about a 13% de-rate factor in Reply #9 above, using the ICAO Standard Atmosphere data.

poco

[Seekscore]

I had a good time building this machine. Its amazing how much power they have in a place that has no power. Working with these guys, you can definitely tell they have been there and done that. Thanks for all the help.

Now it just a matter of getting it powder coated, Getting the blades and tail vane installed and waiting on the FAA to give me the okay so I can get my tower up. I am planning on putting it on a tower where the top of the blades will be 65'. I live out on the plains so I should have a good wind site. As best I can tell, from observation and the web, my site has an average wind speed of 12 mph. I do plan on getting a data logger so I can be another data point for the 12 ft' machine.

Mike

[Boss]

Dan and Tom can you tell us more about the data logger you employed? I googled "APRS data logging anemometer" but too much stuff came up to make heads nor tails of it. I hate it when a site says call for a price.




I don't need an exact price, damnit! Are they talkin' hundreds, thousands or what?

The APRS solar powered wind data logger is designed as an affordable solution for a wind site evaluation and to gauge wind generator performance.

Using a Secure Digital (SDTM) card for convenient data downloads to record wind speed along with the time and date.

The 128-megabyte SDTM card is inexpensive and capable of storing weeks of data at 3-second intervals or at longer logging intervals months of stored data.

Almost any spreadsheet program (Microsoft Excel, OpenOffice.org) can be used to analyze (view, graph) your wind data. With the Web-based software the analysis is even easier. Upload your data and the systems software will plot and provide basic statistics all automatically.

Then it seems silly to have a PV and battery if they are sending data wires down the pole
most of us have power near the tower, but our PCs are often further away.
I do have outdoor WiFi though
Beam it to me man
 

[DanG]

Mike! Good luck to you on your permit! I've got Danbuilt #124, a ten-footer waiting for property to homestead.. and my pipe-dream is also a tower (and land) to put it on!
 
Poco? As a curiosity I've just input your calculated elevation adjusted equivalent rotor diameters into RossW's OtherPower IRC channel bot (RossBot ROCKS!) for "theoretical watts available" and the output of the 12-foot comes to (310/398) 0.77858575727181544633901705115346% of the 13.6-foot rotor...

Sure looks like 22% to this non-mathematician wrench-twisting mechanic...

1940.5 watts possible from 12.0 ft dia prop (113.1 sq ft) in 15 mph wind (density of 1.225000) for 310.5 watts output assuming generator is 80% efficient and Cp of 0.20.

2492.4 watts possible from 13.6 ft dia prop (145.2 sq ft) in 15 mph wind (density of 1.225000) for 398.8 watts output assuming generator is 80% efficient and Cp of 0.20

[tecker]

I think this turbine is a compliment to your collaborative skills and I think one could say this is a solid unit .

[halfcrazy]

Dan and Tom can you tell us more about the data logger you employed? I googled "APRS data logging anemometer" but too much stuff came up to make heads nor tails of it. I hate it when a site says call for a price.




I don't need an exact price, damnit! Are they talkin' hundreds, thousands or what?

The APRS solar powered wind data logger is designed as an affordable solution for a wind site evaluation and to gauge wind generator performance.

Using a Secure Digital (SDTM) card for convenient data downloads to record wind speed along with the time and date.

The 128-megabyte SDTM card is inexpensive and capable of storing weeks of data at 3-second intervals or at longer logging intervals months of stored data.

Almost any spreadsheet program (Microsoft Excel, OpenOffice.org) can be used to analyze (view, graph) your wind data. With the Web-based software the analysis is even easier. Upload your data and the systems software will plot and provide basic statistics all automatically.

Then it seems silly to have a PV and battery if they are sending data wires down the pole
most of us have power near the tower, but our PCs are often further away.
I do have outdoor WiFi though
Beam it to me man
 

APRS World does have prices on there website but it is for each piece I would Email Jim he will get you any thing you need. A lot will depend on what you need like a solar panel or current sensors. But the basic data logger prices are here http://www.aprsworld.com/wind2/pricing.php and Jim will customize anything for you.

[poco dinero]

Sure looks like 22% to this non-mathematician wrench-twisting mechanic...
 

Hello DanG,

Not sure I understand your math.

What I was trying to say, and probably screwed up, is that you need to increase the rotor diameter by 13% as you take a perfectly matched rotor/alternator combination from sea level to 8400 feet altitude and expect it to still be perfectly matched.  I stand by those calculations.    Not sure how that translates into a "de-rating"  factor, and presently too blasted from pain medicine to sort it out.

poco