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Forum Index : Windmills : Homemade Stator/Rotor for Savonius
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oztules Guru  Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Tinbender, They are just 8mm plate steel. The first ones were cut out with a guillotine... the center hole cut out with a holesaw and the stud pattern drilled out to fit a standard trailer hub. The magnets are encased in sand and fibreglass resin (to stop the magnets flying out. Most people use a laser cutter to cut them out for them. If you are going to make a large one under your vawt, perhaps you could use the plate as the bottom of the sav, and build it on that (put the stator underneath.) For your modest output requirements, a single disk (6mm thick) or even a flat 6mm ring a few inches wide on a wooden disk should be sufficient as your inch/second rate will be much higher at a lower rpm than mine, and you can use lots of turns of thinner wire (mine are 105 turns of 1.8mm thick) to develop your volts. With only a single plate (no return flux path) mine puts out 24v@115rpm or thereabouts. (48v@115 with second disk in place) The advantage of air core coils (rather than steel core) is two fold.... no drag so very easy spin, and no steel/magnet attraction forces to try and keep in check. You may have noticed that some who are doing neo conversions with the F&P have been bedevilled by drum distortion, caused by the strong attraction to the coils....air coils wont need this aspect of construction to be taken into account, only the torque moments need addressing, and the stator and it's necessary mounts does this for you. Downside is the cost of the magnets, 24 of the 50x12mm ones i have set you back about 12 bucks a piece. I doubt you need that kind of strength for your expected outputs. I have yet to see any Vawts do much more than a few hundred watts, although I am hoping Vawtman will prove me wrong. I like Vawts, but they tend to be an amusement rather than a very useful adjunct to home power. Best of luck with it. You now have two types to ponder, There are lots of smart people on this site that can coach you on both types. Some feel the steel core radial is worth a go in your circumstances. I tend to disagree (but not strongly, just think the iron loss and the mechanical magnet to steel attractions in this wide configuration, is too much to live with on small machines), but it's your call in the end. There is a possibility that the lure of faster magnets on a larger diameter may remain out of reach as the rewards may not justify the more difficult build for these low power levels... ask Vawtman, he is doing the same kind of thing. Whatever you do with it, have fun. ..........oztules (Glenn, if you want me to write less just say so, I have a tendency for long posts) Oztunes thats fine, write to your hearts content, its all good informative stuff.  Glenn.Village idiot...or... just another hack out of his depth |
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vawtman Senior Member  Joined: 14/09/2006 Location: United StatesPosts: 146 |
Hi Oz Nice work on your axial.My opinion is alot of people that build vawts don't understand the inner workings of making power from them.So much comes into play thats why most just give up.To this day i'm not sure i got it but think this latest thought will even give me options to adjust the airgap between the dual rotors since only the inner rotor will have mags.If it works smaller radials could be built for smaller vawts. The stator insertion and design is buggin me yet but have thoughts. Sorta a halfbreed between an aircore and the dual magnet rotor. |
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Tinbender Newbie  Joined: 03/02/2008 Location: United StatesPosts: 14 |
I live on about a half acre lot and the city wont allow a tower and prop for my propety because of the danger, but they say it is ok to have a plastic barrel savonius. I have 13 mph average wind speeds here. I want to grid-tie and do net metering and need to figure out what inverter I'll need to be able to do this. I found this inverter that looks like it should work..The OutBack GTFX and GVFX series I don't need battery back up, just need to feed it to the grid for credit, but if I need a small battery bank to feed it thats cool. I know that for example a 55 gallon drum savonius stacked 2-3 high may not put out enough to match my grid usage, but I am sure I could add how ever many separate turbines it would take to match my grid usage. I want to build a dual-axial flux alternator for the Savonius. I found stators already made that I could purchase here. I need to know if either the 12,24 or 48 volt stators would be compatible to grid-tie, what inverter to use, and also if these stators could be wired together if I wanted to add another and another until I matched my grid usage. Any suggestion would be much appreciated. This is my power usage. Brian 
VAWTs Up Doc? VAWTs Happening? Is that VAWT you vant? VAWT vere you thinking? |
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Brian, You have a tall ask there. An average of 20kWhr per day. You get an average 13mph wind. Do you know the approx wind velocity distribution and at what height was it determined? You would probably need multiple units. Maybe best to just build one and see what you get and then duplicate till you balance the usage. The grid connect is another can of worms. Some systems are available here in Aus. Not familiar with 110VAC 60Hz. I was able to interface my windmill to a solar grid connect inverter, currently using a battery as buffer, as I use about 1kWhr free energy with AC inverter to reduce my daily grid consumption when there is little wind. There is an SMA WindyBoy. This is a higher DC voltage unit. My preliminary estimates of wind power gives approx 100W per square metre of wind section at the average wind velocity you provided. Extractable energy could be around 1/3 of this. This gives 0.8kWhr per day per square metre of capture area. You could need over 25 square metres of capture area. At the average velocity you have given, there is a relatively low amount of energy. I hope this info helps. cheers Gordon. become more energy aware |
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