1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Looking to build a backyard windmill

  1. Feb 1, 2016 #1
    Hey all. I'd like to build a small windmill in my backyard. Small is I'm going to guess maybe 5 foot blades or so. I do CAD work so I can design most of the parts I need EXCEPT the blades. I have no idea where to start. I understand the basic shape, but I'm unclear where to start to get one going in the size range I need. Does anyone know of any good resources to get me going? Book, website or something? I don't have a CFD program, but would like to take a stab at the design so I can make it myself. Any advice is appreciated. Thanks!
     
  2. jcsd
  3. Feb 1, 2016 #2
    note, I want this to be functional, i.e. generate power. Not for decoration. Thanks!
     
  4. Feb 1, 2016 #3

    anorlunda

    Staff: Mentor

    Google "marine wind generators". Some of the brands are Airx, and Kiss. You can buy spare blades for them. You can even buy a complete wind generator.
     
    Last edited: Feb 1, 2016
  5. Feb 1, 2016 #4
    Thanks, I'm hoping to get some dimensions and design it from scratch if possible. I will check that search out.. thank you.
     
  6. Feb 1, 2016 #5

    anorlunda

    Staff: Mentor

    They break down frequently. You may be able to get a broken one free and use it as a template.

    Owners of such windmills must learn to be windmill repair technicians pretty quickly.
     
  7. Feb 1, 2016 #6
    thanks for the leads. I see some blades sets for not all that much. That's a good idea. I'll keep an eye out. Thanks!
     
  8. Feb 2, 2016 #7

    jim hardy

    User Avatar
    Science Advisor
    Gold Member
    2016 Award

    many hobbyists cut blades from pvc pipe. A quick search turns up plenty of youtubes and instructables.
     
  9. Feb 9, 2016 #8
  10. Feb 10, 2016 #9
    I have seen a very good, well designed and completely home made windmill it was constructed using an alternator from a car, a homemade center hub cut from diamond plate aluminum and an old ceiling fan. He just used the ceiling fan blade (brackets) and scaled up the length of the blades, he used plastic or Plexiglas he purchased from home depot to make the blades and they had to be 6' across. He had made it so it would pivot 180 degrees and used it to supplement a solar charging station he had build with a few car batteries an inverter and voltage regulator. He was able to power one Green outlet per room in his home.

    Note he only used these outlets for lights (lamps) and a couple tvs but it worked
     
  11. Feb 10, 2016 #10
    I think unless you have a high tower, the ground turbulence would take away any advantage
    of complicated blades. I have seen some Savonius Turbines made with 55 gallon drums, that would help this.
     
  12. Feb 10, 2016 #11
    About using an automotive alternator... I tried to make a water turbine with one, and found I was getting a disappointing amount of power from it... I was feeding it enough water to get about 300W, but was coming up short at about 100W... My turbine was not an efficient one, but it caused me to look into it deeper.

    The alternator needs about 7A to generate the field, this 7A is taken away from your final power output, and that's about 100W @ 12V

    Unless you're going to be operating it near it's rated power output (120A/1400W in my case) they really lose efficiency at lower outputs since the 7A field must be maintained.
    If you can find a permanent magnet brushless generator you will probably realize better efficiency at low power outputs
     
  13. Feb 10, 2016 #12
    I'm not sure how this guy had his rigged, but it had been modified it had a steady output at 12 volts when turning, BUT he also had several solar panels wired up to this inverter In fact the alternator was wired up to something different and run straight to the battery bank if memory serves me correctly.
     
  14. Feb 10, 2016 #13
    He probably had a controller that varied the field current that would cut out above a set voltage.. an alternator with a built in regulator would do that automatically.

    If you took the alternator rotor apart and replaced the field coil in it with a large permanent magnet you may improve the efficiency at low speed at the cost of having to use a different regulator setup and some loss of peak current capability... I haven't tried it, I wasn't involved enough on the project, but I would give it a shot.
     
  15. Feb 11, 2016 #14
    If someone could figure out the methods he used for this (to get the steady 12 v from the recycled alternator) then the applications of this could be used to make working generators out several power sources, water wheels, windmills, old lawn mower engines, even old bikes (motorized or peddle powered) All out of old recycled material. I'd have to think that you'd need to put a capacitor in the line somewhere that only discharges at a steady 12 volts if the alternator spins at variable speeds. And it would probably need an alternate source of charging like solar and maybe a back up gas generator. But seems possible if you have the know how.
     
  16. Feb 11, 2016 #15

    jim hardy

    User Avatar
    Science Advisor
    Gold Member
    2016 Award

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Looking to build a backyard windmill
  1. Windmill Generators (Replies: 1)

Loading...