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Wind Generators

Discussion in 'Renewable Energy' started by bryan1, Jun 24, 2009.

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  1. bryan1

    bryan1 Well-Known Member

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    WIND GENERATORS(version 0.01)



    As the world is becoming more concerned with global warming wind generators are becoming a more common site. The large megawatt downwind turbines do look impressive to some and an eyesore to others, however with the growing need for renewable energy those large megawatt downwind turbines are here to stay.

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    This article will focus on the smaller wind turbines one can build themselves if the need is there to harvest the wind for power.

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    TYPES OF WIND TURBINES

    Wind turbines come in 2 types Vertical AXIS (VAWTS) or Horizontal AXIS (HAWTS). Within these two group there are many different styles and in the RE DIY world, VAWTS are considered a waste of time as for the work involved to make one the harvested power is alot less than a HAWT.



    VERTICAL AXIS (VAWT)

    The vertical axis wind turbine come in 2 distinct types which are Saviuonous(Savvy) and Darrius. Where the Savvy will self start in a gentle breeze the Darius turbine wont start by itself. The darrius turbine usually has a small motor to initiate the start of even a small Savvy turbine in the centre to enable it to self start.




    HORIZONTAL AXIS (HAWT)

    The horizontal axis wind turbine come in 2 types, upwind and downwind.

    A good example of a downwind turbine are those huge megawatt turbines and one can easily tell the difference as a downwind turbine doesn't have a tail.

    There are many ways to make your own HAWT depending on your need for power.

    A small stepper motor based wind generator will be good for charging some nimh or nicad batteries or light a few led's but not much more.

    DC motors are also used for wind generators with many mixed results. A 1800rpm 12 volt DC motor won't make much power at all as voltage is dependent on speed when using a DC motor as a generator.


    A 3 phase motor can make a very successful wind turbine, however, it isn't a project for the faint hearted. First you need to either machine the existing rotor down to take Neo magnets or make a machine a new rotor from steel stock. The Neo magnets are placed on the rotor either on a skew or by using the offset method. On some 3 phase motors it is OK to use the existing copper windings but what you read on the name plate will be a good guage on what you'll get out of it. Totally rewinding a motor to suit the voltage, current and cutin speed is a big job but the results will speak for themselves if the job is done correctly.

    The Dual Axial Flux Wind Turbine is a great DIY turbine to build but once again it isn't for the faint hearted. Mr. Hugh Piggot and the Dan's at Otherpower are the main guys who have helped to make the dual axial flux what it is today and any person thinking of building a dual axial flux turbine would be well advised to buy either or books both guys have written as they are considered the best written guide on the subject of DIY dual axial flux turbines.

    Basically a Dual Axial Flux Turbine is 2 metal disks which hold Neo magnets and a cast stator that hold the coils. Generally people make a 3 phase AC unit, however, if you wanted to make it 4,5,6 of even 12 phase theres nothing stopping you.



    TOWERS FOR WIND TURBINES

    This discussion is for guyed towers that one can build themselves.

    One cannot stress enough a wind turbine tower MUST be built properly and be suited for the turbine. Too many people (even myself) have seen a tower fail and a set of turbine blades in tatters and burnt in the fire over a cold beer.

    For a wind turbine to have clear wind there should be no interference from trees, dwellings hills etc. A good rule of thumb is 10 metres at least above any obstruction to get clean wind.

    The base of the tower should be a decent concrete pad with re-enforced rio bar or suitable bracing in the concrete slab. Although the base doesn't take too much stress when the tower is vertical, raising and lowering will cause considerable stress on the base.

    Guy wires also play an important part in keeping the tower upright, also in the raising and lower of the tower. The general rule is a minimum of 4 guys is to be used and the 2 side guy wires are used to steady the tower on raising and lowering. On tall towers lower guys are also used to stop the middle of the tower oscillating in strong winds.

    Guy wire anchor points also need to be well built as they will take all the thrust of the guy wires. If the ground is very rocky and deep holes are unable to be dug a 'deadman anchor' is used. A channel is dug as deep as possible in a 'T' configuration and steel bracing is secured in the trench with the anchor point which takes the guy wires well braced to the bracing. The trench is then concreted in and left to set over several weeks.

    In order to raise and lower the tower a 'gin pole' is used. This pole is attached to the base of the tower and rule of thumb it should be 1/3-1/2 the length of the tower. The gin pole takes most of the weight of the tower in the early raising stage and stop the tower from buckling.


    SUMMARY

    The DIY wind turbine is a great feeling when the owner/maker gets the genny in the air for the first time and see's the current flowing.


    In future updates more content will be added as seen appropriate.


    Regards Bryan1








     
    Last edited: Jul 4, 2009
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