How to Build a Windmill

Admit it, if you’ve ever been surprised by a big electricity bill you’ve fantasized about generating your own power at home. Be it solar or wind or whatever. Electricity’s expensive! The sun shines and the wind blows every day. Why not?

Well, because it’s really hard:

At this point we took a 6 month detour in the wonderful world of sheetmetal fabrication. This was a lot harder than it seemed at first. Finally we settled on using a plasma cutter to cut the stator elements from standard sized sheets of metal (a special kind, which is low on carbon and has very good electromagnetic properties). Die cutting was impossible due to the cost of the dies, but if this were ever produced in volume that would be the way to go).

Actually, maybe this guy is looking or something a bit more serious than I had in mind:

The design parameters of my homebrew windmill are: 2.5 KW of output at a windspeed of 10 m/s, variable pitch blades, rotor diameter 5 meters (about 16’). The total weight of the machine is about 85 kilograms (or about 170 pounds). It has survived numerous storms and worked very well supplying our house with reliable power, far more reliable than the solar panels we had used exclusively up to the point the windmill was finished. The plan was to open-source the design and to make available a list of parts. I really should get around to that one of these days, the fact that I finally had the time to do this write up means that there is hope 😉 If you bought a machine with those specs commercially it would have cost about $10,000, but that would not be a variable pitch one. This machine cost a (fairly) large multiple of that, not counting our time, tooling and so on, but it could be reproduced well under that $10,000 mark if you already had all the tools and the knowledge and you didn’t have to go through a prototyping stage. Prototyping is very expensive and time consuming.

Designing a machine that size was a lot harder than I ever thought it would be. What was intended to be a one summer project turned into a two year tour of technology including magnetic theory, power generation, mathematics, mechanical engineering, woodworking, metalworking, meteorology, CAD/CAM, computer programming, electronics and aerodynamic theory. If you feel like acquiring some real world skills, go build a windmill! I never ever realized how much knowledge goes into making one of these until I tried it for myself.

The most demanding bit in my spec was that the windmill should be super reliable and should not require maintenance other than a lube job once every year or so. The place where it was put up has some of the harshest climate conditions on the planet, winters with days of -40 celsius and summers of +35 and sometimes even higher. Taking the windmill down during the winter was absolutely not an option (too much snow and no grip for the tractor used to raise and lower it) so reliability was extremely important, being without power meant that our house would be inhabitable almost instantly (no backup power grid, we did have a stand-by diesel generator which was used quite a bit before the windmill was installed).

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