Wind generator voltage

ChacabucoChacabuco Registered Users Posts: 1
So i'm building a wind generator from scratch, and realized the following thing. So I will have a wind generator, a Xantrex c-40 as divergence controller, and some batteries connected with an inverter. What happens if the generator is turning, but not enough so that the voltage in the generator is not as much as the voltage in the batteries. I was thinking about using some diodes to make sure current doesn't go up the generator, but for that time being the kinetic energy of the generator won't turn into electricity until the battery's voltage goes down. So it will just be turning and doing nothing else. Any ideas on how to address this issue?


  • BB.BB. Super Moderators, Administrators Posts: 32,924 admin
    Re: Wind generator voltage

    Welcome to the forum Chacabuco.

    What type of wind generator do you have? Do you have a true "generator" with an armature and brushes:

    Attachment not found.

    Or an alternator with a fixed stator, and either permanent magnets or slip rings and field coils in the armature:

    Attachment not found.

    A generator would need a blocking diode to prevent it being powered like a motor from the battery bank (the old fashion generator regulator would disconnect if generator was not running).

    For an alternator, you would need a diode bridge circuit or rectifier--Typically three phase AC power (three wires) connected to 6 diodes.

    Do you have a "cook book" that is helping you to design the wind turbine and tower system? (good forum for DIY Wind Power)
    Hugh Piggott - Scoraig Wind Electric site for tons of info (from mike90045)
    Scoraig Wind "Recipe Book" for DYI Turbines (added from "russ"--Like here but more wind/less solar)

    There are many different wind turbine designs out there--So getting a good book/web site on the subject is very helpful.

    Also having a good tower and lots of wind (and no obstructions/trees/etc. up wind) is important. Turbulent air has almost no useful energy for a wind turbine to collect.

    A diversion load (resistor bank) + diversion/shunt controller is the common method for controlling battery state of charge.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Wind generator voltage

    So unless you live in an exceptionally windy location, you will likely find that most of the time, except during wind storms, your wind turbine will indeed be spinning but not fast enough to produce any usable electricity. So anytime it's not spinning fast enough to produce voltages higher than the battery voltage, no charging takes place and there's nothing you can do about it other than lay back in the tall grass, meditate and enjoy watching the blades spin against the sky. Welcome to the world of wind turbines. Been there, done that, took it down, gave away the blades and tail, but kept the alternator which for the last 5 or more years has been faithfully turning running water into electricity. :D
    Moral of the story - - - - - don't get your hopes too high and you won't be disappointed.
  • bpolitobpolito Registered Users Posts: 6
    Re: Wind generator voltage

    The fixed relationship between RPM and open circuit voltage in alternators and generators is a challenge in designing an efficient home-built turbine. If you wind too low a voltage (few turns of fat wire) you will freewheel in light to moderate winds and lose a lot of energy, but if you wind too high a voltage (lots of turns of little wire) your load won't be well matched to the blades in higher winds. The Piggott designs that Bill linked to do their best to find a happy middle ground.

    In designing a manufactured turbine it makes sense to invest the time to build a more sophisticated controller that can vary the impedance of the load and draw the optimal power at each RPM (kind of like an MPPT for solar). In the case of the Pika turbine we intentionally wind our alternator to run below bus voltage (+/-190VDC) and then use a boost converter to push the desired power onto the bus. You can also take the opposite approach and wind higher voltage, then use a buck converter to step down to battery voltage. I believe that Midnite Solar makes a programmable buck converter that homebuilders have successfully used with Piggott-style machines.

  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Wind generator voltage

    the piggot machines are wound high voltage to work with mppt. In the end the point being made is there is no power in a 6 or 7 mph wind no matter what your windings are and if that is the type of wind you have lot of time the tare losses of an mppt will probly ruin your battery before the next big storm. For wind to work even close to solar, you would need to live where it is dark half the year and you can't go outside without carrying something heavy to hold you on the ground. If however you want to see things spin and don't care what it cost (like me) wind will probly be perfect for you. I might be a bit harsh, but only a bit.
    Look at what real people get in real life and not what the person promoting the turbin says.
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