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Forum Index : Windmills : Where Do I Start?
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| Rooster Newbie  Joined: 22/05/2014 Location: United StatesPosts: 7 |
Hi guys, I am Rooster from SE Kansas, USA I have been poking around the forum for a few weeks, and around the internet for a few months and some information I just cant seem to find. I am ready to start an axial project. But as I look at one project to another, one SEEMS just like the other until you get into the meat of it and they are completely different!! Things like: Magnet shapes - round, rectangle, wedge - what is best, cost comparisons vs output...etc? Same thing on Coils -ovals, wedges, round...??? And then...why is one guys coil 30 turns of this and another guys 200 turns of that? Could someone point me in the right direction...is there a good place to find these discussions? Where is a basic primer on how to design your system? I appreciate any help, you guys really have a nice forum here and loads of great information...I'm just having some problems sorting through it I guess? I've done some searches...lots actually and I just cannot get what I am looking for? |
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| kitestrings Senior Member  Joined: 23/04/2014 Location: United StatesPosts: 102 |
Rooster, Here's a few thoughts. For axial's I'd read a lot more here and on fieldlines forum, and Hugh Piggot's site. The FAQ's will help a lot. I'd also recommend books by Hugh, and the Dan's (Otherpower). Generally the more turns the more voltage for a given magnet size, but its all a balance of matching power from a given rotor size to an alternator design. And, there are trade offs on things like costs and durability of magnets, spacing and size of magnets, space and configuration of windings, etc. etc. There's not a single, simple answer I'm afraid. Welcome, ~ks |
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| Rooster Newbie Joined: 22/05/2014 Location: United StatesPosts: 7 |
Thanks for the info! |
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MacGyver Guru  Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Rooster First off, welcome to the 4m. I live in Texas, so we have nearly the same amount of constant wind, which will determine the size of your turbine, etc. First off, you must know what your output needs are going to be. Then, you can go [HERE"> to see how large your turbine (HAWT) needs to be, depending on your average wind speed. When you know your wind constant, things like cut-in voltage and so on become more real and less of a stumbling block. Once all that is done, take the advise, which has been previously offered, and READ, READ, READ all the posts you can before you start laying out your project. I have built several FAILED axial-flux machines, so I know what I'm talking about there. Things look pretty easy until you get into it a ways and realize you've blown it a few steps back. Planning is essential and it's easier and cheaper to change things on paper than to re-re-rebuild stuff. A "test coil" is essential. You'll chose your wire size, depending on the amount of current you wish your alternator to produce. Again, wind, turbine size and so on all come into play BEFORE you build anything. Once you have determined your wire size, it becomes necessary to wind a coil and chuck it up into a lathe, so it can be spun up to a reasonable operating RPM like around 350 rpm or so, which is about what you can expect a good turbine design to crank out under load in a stiff wind. Spinning it in a lathe (controlled spin) will tell you things like magnet spacing and number of turns per volt. Again, current is wire-size dependent. Once you know how many turns create how much current and voltage for your magnet size and spacing, it becomes merely a task of laying it out and building it. You must also chose whether you want it to be a skein-wound single-coil arrangement or the more traditional 3-phase layout. Lots of choices before you build. It's not rocket science, but it's also not a slam-dunk. Go slowly and continue to ask LOTS of questions and you'll be okay. There are several (most) guys here, who have built SUCCESSFUL axial-flux alternators and turbines that will chime in with very good and accurate advice, when you need it. When you need it depends on how much you have read and learned, so that's your next step. I know you're anxious to get something into your lathe or mill, but it's baby-steps time. You do have a lathe, I hope! :O) . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
I partly agree, and a test coil is required to be done, but you dont need a lathe and 350 rpm to test a coil, you can simply spin the magnets by hand an maintain around 60 rpm (1 rev per second), from there using a little math calculation you can simply calculate the number of turns required to suit a cutin speed. I would suggest a cutin of 80 to 120 rpm target. It is also not important what wire size you wind a test coil with or the number of turns used, as its just a test coil to work out all the details and calculate the turns ratio for the final coils to be made to. As for wire size in the final coils, the answer is simple, use the biggest wire you can that will fit within the allowable space you have, the less gaps between each coil the better, most times the magnet size will effect the space allowed for the coils, as normally the hole in the centre of the coil is the same size as the magnet. Pete. Sometimes it just works |
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| Rooster Newbie Joined: 22/05/2014 Location: United StatesPosts: 7 |
Actually...I "run" a machine shop for a CNC cutting machine manufacturer...LOL I would work at what I'd believe almost everyone on this forum would call their dream shop! CNC plasma cutters, mills, lathes.....everything we need, lol! I am reading, as much as I can as fast as I can...the links have been greatly helpful. Really I think my next decision at this point is whether to make my first attempt at a "smaller" model or go for the gusto? Magnets are expensive! LOL I am "building" a chicken farm, and plans are for each of the barns to be self sustaining, requiring zero power from "the grid". I would think a 300 watt mill would be more than enough for each barn. All they would run are some lights and fans. |
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| Rooster Newbie Joined: 22/05/2014 Location: United StatesPosts: 7 |
This kinda gets back to my original question...I know I want to be in the 500-1k range...but the more I read the more confused I get, lol! I have looked at many projects that look to be similar..but have completely different approaches to reach sometimes close and sometimes very different ends. why does one guy wind a circle, the other a rectangle and yet another a wedge? So yes, I guess I do have much more homework to do! I race lawnmowers....and we have a similar forum, and like you guys we get completely lost newbies(Like Me)that do not have a clue. We tell them the same thing, read read read!! But I guess what I am looking for are some things like we tell new racers, how fast you go is determined buy how much you know and how much you spend! So I guess my first step is ...wheres the dollars spent to watts generated chart?!? |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Rooster Using the link I gave you in my first reply, Alton's Calculator, I plugged into the formula a HAWT turbine of three blades and a diameter of 8 feet. Then I clicked "Calculate" and down the page got these results; 5 11.2 672 68.5 84 1155 3.33 5.5 12.3 813.1 82.9 92 1537 In 11 or 12 MPH of wind (which living where you do is likely every day of the year, just like myself, living down under (you) here in Texas) Going across you'll see that will produce around 1K to 1.5K of electricity. 500K requires only about 8 MPH of steady wind, but I didn't want to copy and paste the whole chart, so this is all I'm posting here. You can go to the link and plug in your own numbers. Now, that being said, you can determine your turbine size versus your needs versus your wallet size. If you're married, run it by the boss before starting this adventure. Really; not kidding even a little bit on this one! Of course, it all comes down to your basic food, shelter and sexual requirements, I suppose, but if it were I, I'd check with the boss first! As for the shape of the coils, the rule of thumb (another marriage term)is you wind the coils the same shape as your magnets' shape. This makes use of the flux field created my the magnet array more efficiently. I'm ruling out a single-phase skein-wound machine at this point, but that too is an option, depending on if you're going to charge batteries only or also want to splice into the grid. A single-phase contraption will tend to "cog" I think. I'm just guessing on that one, because the one I built never made it that far; it tore itself up because something came loose and I was too disgusted to rebuild it, so I just built something else altogether. Best wishes; you're on the right track. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
Eh Mac, You don't take the numbers on Altons calc's as what one WILL make for a certain blade size. The calc shows for 100% efficiency and years ago talking with Alton on IRC he did say around 30% of the output figure would be close to accurate, providing the built turbine was accurate with little friction or cogging. Also blade geometry plays a big part in efficiency. |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
@ Bryan1 Oops! My bad. I never knew that. Fortunately for Rooster, who lives in southeast Kansas, USA, the average wind speed is far and away higher than the 11 or 12 mph I used when I punched in the numbers. If those figure are only 30%, I assume to actually get that at 100% the wind speed would have to be 3 or 4 times more, which is actually a reality in Rooster's neck of the woods. Remember the film, Wizard of Oz? That was Kansas! . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| kitestrings Senior Member Joined: 23/04/2014 Location: United StatesPosts: 102 |
Yeah, this is not right Mac. The Betz limit on an 8' dia. turbine at 8 mph is only about 75 watts; a good turbine might get 30-35% of this as usable. Similarly at 10 mph the Betz limit is under 150 watts; one might extract 30-35 watts. Now the available power goes up with the cube of the windspeed, so if you do the math at 20 mph you might see 100+ watts; at 25 mph maybe 250 watts. There's really no substitute for increasing the windswept area if you want to get to even 500 watts, you need to look at what you can practically get in reasonable winds for your site. Spinning magnets past a coil can help you fine tune the number of turns, but it isn't really all black art. For a given surface area of magnets, a given magnet and gap, you can estimate the Telsa (gauss). If you know the diameter and number of poles you can calculate the frequency, and thus the flux/pole. This will give you the number of turns in your coil. Part of what you're up against with regard to size and shape of magnets is the limited winding space at the inner portion of the stator. I'd venture a guess that wedge-shaped might be best follow by rectangular, followed by round shapes as far as efficient use of the available space. But, wedges might not be available in the size you need, or may be prohibitively expensive so there are other factors that come into play. For resources, here's a couple of good starting points: http://www.neoenerji.com/kutuphane/pdf/Axial_Flux_Alternator .pdf http://www.otherpower.com/otherpower_wind_tips.html#reading Not that I'm a mole sent here, but you may find more articles on axial's on fieldlines, and conversely more on F&P and some other alternators here. Good luck, ~kitestrings |
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| kitestrings Senior Member Joined: 23/04/2014 Location: United StatesPosts: 102 |
Sorry, I mangled the first part of this pretty well (damn touchpads). The figures should be: The Betz limit on a 8'ter at 8, 10, 15 & 20 mph is 75, 148, 500 & 1,185 watts (respectively), and you might do well to fetch 30-35% of this. So at 20 mph, or a little under, you might get the 500 watts, but not at lower windspeeds. ~ks |
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| Rooster Newbie Joined: 22/05/2014 Location: United StatesPosts: 7 |
Thanks all for the replies. I think I have decided for my " learning" build I am going to do the Dan's 10 ft. I like the design and simplicity of it. It'll be awhile before I start actually building. But having plans I can now start Gathering parts. Thanks for all the links and pointing directions. I'm home sick today so it was a good day to get links to more reading. Lol |
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| Rooster Newbie Joined: 22/05/2014 Location: United StatesPosts: 7 |
Well then the 10 footer sounds like a good choice. As Mac stated, we see 20 almost daily here. Especially where I live just off the top of a hill with no trees, the almost constant 10mph winds can be frustrating trying to get work done. It's actually surprising to go out side and NOT have wind! |
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| Rooster Newbie Joined: 22/05/2014 Location: United StatesPosts: 7 |
Ohh, And Dorothy was from Sedan,Kansas. Which is 30 miles from me, lol!! I have walked on the yellow brick road and patted Toto's head !! So I guess now I'm going to ride the wind!! Lol |
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| kitestrings Senior Member Joined: 23/04/2014 Location: United StatesPosts: 102 |
Rooster, Right, you increase from 8' to 10' diameter, and it seems a pretty modest change...but if you double the rotor size you actually get 4x the power. Compare at the same windspeeds above: At 10' diameter and 8, 10, 15 & 20 mph. The Betz limit is 120, 230, 780, & 1,850 watts. Again with reasonable efficiencies your likely to get 70, 140, 460, & 1,100 watts, but this is a big gain for adding a foot longer blades. I'm glad I'm not there during your hurricane season, but it sounds like you've got good resource if you can hold things together. There's no place like home, there's not place... ~ks |
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