Hm, I've never kept a diary before, we'll see how it goes !
My name is Jacques Mattheij, I'm currently (and have been for almost two years now) busy with the construction of a 5 m (15ft) variable pitch windmill. We - my wife, son and myself - live in rural Canada and have been off the grid for two years now. Because the solar panels we have are not producing enough power to supply both the house and the workshop we have decided to add a windmill.
The type of windmill I want (>2 Kw, <5 Kw, variable pitch) does not appear to be for sale so I have decided to roll my own. <P>
So far so good, after all this time I have little bits of results to show for all the effort and a whole pile of 'failures' (or lessons if you prefer to look at it that way).
I started out with buying some magnets from forcefield (1 x .5 x .25 ") and to try to convert various existing 'squirrel cage' motors and car alternators, all with varying degrees of success in making power. Over time the output of the designs has steadily improved and the required RPM's have dropped.
The first time I crossed the 100 W barrier was with an all wooden wheel with a bunch of magnets glued to it and some hand wound coils. About a year ago I built an alternator with 16 1.5 x 1.5 x .375 " magnets and a stator made out of laminations salvaged from an industrial electrical motor. Output was about 4500 watts@540 rpm (powered by the PTO of a farm tractor, the only thing I could think of that would not stall out, I did not have the big lathe then yet), but it cogged like crazy and was very noisy so I decided to do it the right way.
For the next 6 months after that we built - toghether with a dutch friend called Johannes van den Dop - a computer controlled plasmacutter to cut laminations and other parts to our own specifications. A small (scale model) prototype (500 W) was built, but the local winding shop could not get all the copper in there so we ended up with less than the projected power (about 200 W) at 600 rpm. The unit is really small click here for a picture (about 6" across), if I rewound it properly I'm pretty confident it would produce the 600 W that I intended.
6 weeks ago we started the work on 'the real thing'. My objective is to make the whole machine from scratch, without any store bought items other than the unavoidable magnets and bearings. All the rest of it is to be made from raw materials. (well, to a point, I don't make my own copper wire out of ore
The magnets are 18 2x1x.5 " neos, revolving around a 54 slot steel laminated core. I bought a whole pile of them last year, we were joking that anybody ordering any videos during that shipment was going to be pretty disappointed at receiving tapes with nothing but noise on them
The airgap is not optimal, it's a little on the large side, but I was not confident enough with the welder to dare to bring it any closer. Material warp during the welding could easily cause the whole thing to go out of whack. The next rotor I make will be a lot better, and I'll be able to reduce the airgap quite a bit, right now it's about 2.5 mm (a little under 1/8").
I briefly experimented with casting the core in resin loaded with iron powder, but I could not get the flux density high enough to make enough power (about 30% as compared to the steel laminations).
There are two layers of coils, 3 phase wound, so that's 6 x 18 coils two layers thick. Winding the stator was an 'interesting' experience, and I owe a lot to Daniela and Nathan, who helped with the winding until they had blisters.
The machine puts out impressive power, so much so that my 'Meusser' lathe, an old German industrial beast can not push it past 350 RPM without blowing breakers or stalling out (or both). At that point it's making about 3 Kw into a set of 4 12 volt batteries. A picture of the test set up is here.
This whole experience so far has been an interesting mix of going back to school (boy there is a lot of math in building a windmill!), shop class (the place where I live has an amazing array of craftsmen/women that are willing to spend time with me to teach me their trades, from welding and machining to a friend that came over from the Netherlands to help ironing out some vibration issues in the plasmacutter). Laurence McKay, the owner of 'Norhtern Lights Energy' has been an invaluable resource during this time, he has been building alternative energy systems for the last 20 years or so.
Right now I'm busy writing some software that will help with desiginging the blades (in python) I'll post the code when it's done (not very pretty but it does the job).
The plan is to use the plasmacuttertable with a spinsaw to mill blade blanks (in 3d) out of styrofoam, then fibreglass over that to give strength. We'll see how it goes
When I'm done I intend to post all the cad files and part numbers for bearings so other people can duplicate this without spending the time I did.
Comments and feedback very much appreciated, some pictures of the machine in progress at www.greenbits.com. The governor was a tricky bit to do, I'm not entirely happy with linkage yet (too many wear points there), but right now I want to get the machine finished, I'll revisit the governor when it's winter here.
I'll try to keep this diary up to date, but no promises !