help/advice for small wind turbine

Discussion in 'General Electronics Chat' started by Kiki_00, Sep 20, 2016.

  1. Kiki_00

    Thread Starter New Member

    Sep 20, 2016
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    Hi Everyone,

    I'm not very experienced in electronics, but I'm very eager to learn more. I watched a lot of the video lectures on this website, which is very helpful, but at the moment I'm doing a quite specific project where I could use some help with.

    I'm building a small installation/sculpture which is powered by wind. I think it could work pretty simple, but maybe I'm wrong about that.

    The idea is that a couple of small toy windmills (I'm making ones that are a bit bigger and stronger that average) power the installation. Every windmill is connected to a different part of the installation that starts moving when the windmills turns (see attached file). These small windmills will not generate much energy, but it should be enough to let an other small thing turn right?

    So my first question is: Do you think it could work?
    Then I need to know what I need to let it work; what kind of motors would you recommend? What components do I need in between the two motors?

    It would be great if someone could give me some tips to help me out!

    Cheers,
    Kiki
     
  2. Sensacell

    Well-Known Member

    Jun 19, 2012
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    Could work, but you must set your expectations VERY low for the amount of energy to be generated.

    1) Wind must blow HARD in the area.
    The piece will have a distinct wind speed threshold below which nothing happens. You will be disappointed how high this threshold is.

    2) A small wind generator can create a few watts at best.

    3) The loads driven must be very low power.
     
  3. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    If you're driving mechanical devices, wouldn't it be better to drive them directly from the windmill? If you convert the mechanical energy to electrical energy and back again, I would be surprised if you get even 25% of it back. You would be starting off with barely enough useful energy and then throwing most of it away.

    The best thing to do is to build a test rig so that you can try different motors and windmills and then assess just how much useful energy is available. If you use brushed DC motors, they can be connected together without any other components.

    Could it work? Yes, but the windmills are likely to be much larger than you expect.
     
    Last edited: Sep 21, 2016
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The "Best" designed windturbine can get 50% of the kinetic energy of the air that passes through the cylinder created by the blades. Best = airfoil blades that look like those on modern wind turbines which have become an industry standard. Efficiency falls as you implement something like an old dutch flat-panel windmill blade.

    After that you can work backwards to calculate the current/voltage of the motors you plan to power. (100mA at 12V, for example) and then assume that the motor you plan to use (70 to 90% efficient as motor) is much less efficient as a generator working at low speeds (cogging and static friction from stop) lets say 50%.

    Now, you are down to 25% of the incoming wind as electrical power at the motor. The generator is producing AC so you need to rectify it - (another efficiency drop as you lose 1.2V).

    Cogging effects can be reduced by using a coreless motor and/or gearing the wind turbine output to the generator so the generator spins faster.

    Also, if you want 100 mA to the toy you are powering, then put a static load (Resistor) on your generator motor that represents this 100 mA and you can immediately see how much more difficult it is to turn that "generator". That is how much wind force you will need.
     
  5. hp1729

    Well-Known Member

    Nov 23, 2015
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    Enough for theory, build it!
     
    DNA Robotics likes this.
  6. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Get a small 12 volt battery and a small 5 watt solar panel.
    Use this as your power to the wind activated devices.
    Put a 5 volt relay between the battery and the devices.
    Trigger the relay coil with the voltage from your wind generator.

    When the generator makes enough voltage to operate the relay the devices will come on.

    :)
     
    ronv likes this.
  7. wayneh

    Expert

    Sep 9, 2010
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    I second the discouraging comments that "small wind" is difficult. There's a reason those commercial windmills are enormous - there are large benefits of scale. Height of the blades above the ground is part of it.

    @blocco a spirale said in #3 the same thing that came to my mind: Drop the conversion to electricity and use the mechanical motion directly. It's more efficient and more interesting to look at as well. I also like @Kermit2's idea to use the wind to switch on the other devices, not relying on the wind to power them.

    If you want to continue pursuing the electrical approach, you need to define how much power you need for the load you want (lights, motors, whatever), and the minimum wind speed you want it to work at. Those things will combine to dictate the size of the windmill you need.
     
  8. Kiki_00

    Thread Starter New Member

    Sep 20, 2016
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    Thanks for all the tips guys!
    I'm gonna build a prototype this week and see how it goes. I will let you guys know if I encounter anymore specific questions. If it doesn't work Kermit's option sounds also interesting and if that not work I'll do in mechanical.
     
  9. Kiki_00

    Thread Starter New Member

    Sep 20, 2016
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    So I attached some different windmills to a 12V motor. The most energy I got from it untill now was 0.5V.. Which is very small as you guys predicted. Anyone maybe still any idea's how I could get this a bit higher?

    If that really isn't gonna work I'm thinking of using the windmill as a switch instead of a power source. So when the windmill turns it will switch a battery run motor on (see attached file). It would be cool if the windmill could still also charge the battery, but maybe that will make it a bit too complicated for now..

    Do you think that could work? Any tips for how to proceed?
     
  10. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    Unfortunately, 0.5V is not even a measure of energy and if you were to put a load on the terminals of the motot it would probably stop spinning. I agree with the earlier suggestion of charging a battery from a solar panel but use a contact-less (so as not to stop the windmill from spinning) optical or magnetic sensor on each windmill to detect the rotation and trigger a timer to switch the battery power to some other device.
     
  11. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    0.5V seem almost too low for a bare motor (unloaded circuit). Was your meter on AC or DC voltage? It should be AC unless you added some type of diode rectifier to make DC.
     
  12. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Trouble with small motors is they run FAST. To get 12 volts out you need the wind to spin them very fast as well.

    Larger blades for more wind power and a pulley system with a 10 to 1 ratio or more, will get the motor up to a proper RPM and get you more voltage from it. Visit a modeller/RC hobby shop and ask or google/amazon for it.
     
    GopherT likes this.
  13. hp1729

    Well-Known Member

    Nov 23, 2015
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    Do you have only one windmill? Could you put a bunch in series to build up the voltage?
     
  14. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Gentlemen,


    Have you checked what type of "windmill" the OP had in mind? Please read the .pdf he attached.

    Used to deal with real-windmill parts I started to wonder how I should handle one of those but of indusstrial size :D
     
    Last edited: Oct 2, 2016
  15. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    https://www.amazon.com/XOAR-Electric-Airplane-Propeller-PJM-E11x6/dp/B015GVDGZ8/

    https://www.amazon.com/URBEST®DC-6000RPM-Magnetic-Motor-Smart/dp/B00NN2YUWQ/

    drawing.gif

    This is the general idea with a large rim pulley about the size of a paint can lid driving a small pulley on the motor. Should get you about 40 or 50 to 1 speed increase. so if you can get 100 rpm on the propeller you would get 4000 to 5000 rpm on the motor, which is near its 12 volt operating speed.
    Even with this set up you may find the propeller to be to small to move the motor when it is loaded electrically.
     
  16. Kiki_00

    Thread Starter New Member

    Sep 20, 2016
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    If been very busy with other things, but now I have finally time to continue with this project.
    I made a quick pully setup (see pic), with a 12V motor. I made it out of things I could easily find which makes it not very efficient. At the moment it creates to much friction for the windmill to turn by wind. Do you guys think there is any way what this could work with a better setup or maybe a smaller pulley system? I'm gonna spend a couple of more days trying to figure this out and then I'm gonna try alternative things with batteries and such..
     
  17. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    And then what do you think will happen when you add a load to the motor output? If this is to work at all, you need to use a different kind of blade. The one like your using is not meant to do any type of work, it's a child's toy.
     
  18. dendad

    New Member

    Feb 20, 2016
    17
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    I've uses a fairly large model airplane propeller (for a rubber band powered model) on a stepper motor from an old printer. Then 6 x small diodes for a 3 phase bridge rectifier, and an electrolytic cap. This then was used to drive some LEDs and it worked quite well as a garden ornament but it is doubtful you could do much else. A good propeller shape is important, and it was about a foot diameter.
    Another way is to build a "real" wind turbine to power it all...
    Have a look at these links...
    http://www.thebackshed.com/Windmill/articles/GettingStarted.asp
    http://medicalandscientificservices.com.au/?page_id=281

    A good starter is a Fisher and Paykel Smart Drive washing machine motor, very popular in home made wind (and hydro) turbines.
    Search for "Fisher and Paykel wind turbine" or something like that, and you will see lots of info.

    Moderators note : replaced link, please do not use bold characters in links.
     
    Last edited by a moderator: Nov 7, 2016
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