Let's Talk Windmills

Discussion in 'Energy & Electricity' started by TechAdmin, Oct 10, 2008.

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  1. TechAdmin

    TechAdmin Administrator Staff Member

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    Anyone done any research on wind energy and DIY building or has anyone actually done it?
     
  2. Jack

    Jack ExCommunicated

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    G'day Dean

    Friends here and around and myself have been playing with this for 20 odd years

    its a big feild so if you have specifics just say em and i'll help you where i can or can get the others to assist

    I'm good with wind hybid systems but not photo volteic's

    i'm pretty good with alt fuel gens but not all ( i prefer methane and natural fuels) but friends are into gasifiers and similar

    ask away

    we did build a few systems one did 220 KW on solar gen wind with passive thermal as a secondary here in Australia

    but agaun its a awful big feild and specifics would help

    cheers

    jack
     

  3. carnut1100

    carnut1100 Well-Known Member

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    I've done a fair bit of reading, and I have some plans for a small home built turbine around somewhere, but I think it is a poorly executed design.
    I am looking at buying a block of land right now, and some of the places I have looked at are off-grid and I want backup power anyhow so this is a subject I will be delving into further soon.
    the thing I don't like about a lot of small home build ones is that they rely on you to know strong winds are coming and turn the tail to shut them down.
    I want one that will detect strong winds and shut itself down or preferrably feather so it can still generate.
    There are a number of ways I can do this but I want to do it as cheaply, simply, and reliably as possible.
     
  4. JeepHammer

    JeepHammer Well-Known Member

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    I've been messing with 'Alternative' power since I was very little, and I've been messing with water and wind generators pretty regularly for the past 20 years or so.

    Your question is so vague it's hard to tell what you are asking about, so I'm going to assume you know very little, and cover a bunch of different issues very superficially, and then you can get a feel for things, and ask specific questions.

    Since I don't know specifically what you want, please don't get upset if I review below your knowledge base.
    --------------------------

    Wind generators will come in three basic types,

    1. Commercially made wind generators that all have something specific to them, but are all mostly low and medium wind units and are usually all 'AC' or Alternating Current output.
    Some have built in Rectifiers that convert the AC to DC or Direct Current.

    2. Publicly sold, or home built AC generators that are usually made from old car alternators.
    These almost always have the rectifier left in the case so the output DC instead of AC Voltage.

    3. 'Home Brew' generators that are made out of everything from old car alternators to plywood, and everything in between.

    4. Vertical Wind Generator,
    [​IMG]

    OR,
    Bowed Blade Wind Generator,

    [​IMG]

    OR,
    Front Windmill Bladed Generator (most Common)

    [​IMG]

    OR,
    Rear Bladed Wind Generator.

    [​IMG]

    5. Or do you want the 'Wind Mill' to do Mechanical work, like pump water or turn a saw?
    -------------------------

    As stated before,

    Some have the rectifiers in the wind mill head, some have the rectifiers in the wiring somewhere else, like on the pole or near the inverter or charge controllers for batteries.

    Some are old generator types that have commutator rectified voltage or they are made from Permanent Magnet motors that will be commutator rectified...
    ----------------------

    Now, if you don't know what a 'Rectifier' or 'Commutator' or 'Slip Rings' or what 'Field' means,
    Or you don't know the significance of Permanent Magnets over wound magnets is, you need to ask those questions so we can bring you up to speed.

    You might also need to know about 'Tail Yaw', blade 'Swept Area' and 'Air Stream Deflection' when you discuss blade types and ways to govern the unit when strong winds come up and try to spin it too fast.

    We can cover any and all of these subjects you don't understand, and you can do searches to find out any information you don't understand also.

    Just let us know what you want to talk about, and we'll go there!

    Do a search for 'Wind Generator Plans' and see what pops up! You might be surprised!

    One of the best references I can give you is a magazine called 'Home Power', it's EXCELLENT in covering the basics of 'Alternative' energy including wind electric generators.
    http://www.homepower.com/home/

    Good articles,
    http://www.homepower.com/article/?file=HP122_pg28_Woofenden&pdf=1
    http://www.homepower.com/article/?file=HP106_pg104_WordPower
    http://www.homepower.com/article/?file=HP116_pg52_Woofenden
    http://www.scoraigwind.com/axialplans/
     
    Last edited: Oct 13, 2008
  5. JeepHammer

    JeepHammer Well-Known Member

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    The 'Front Bladed, Horizontal Axis' wind generator is the most common by far, and they are used on everything from,
    Micro-scale,
    [​IMG]

    This thing is nothing but a few PVC pipe fittings, a computer fan blade, and a CD for a tail to keep it facing into the wind.
    It will light a small Light Bulb or string of LED's according to the inventors.
    Great kids toy project or learning tool for beginners.
    ------------------------

    To small-Scale,
    [​IMG]

    This is a real teaching tool, and one not much larger than this is what I use to top off, or 'Finish Charge' the batteries in my Electric Conversion pick up.
    The smaller amount of current the wind generator provides at night is EXACTLY correct for 'Finish Charging' the batteries after the solar (PV) cells have given them 95% of the charge they needed....
    ----------------------------------

    To Large-Scale,
    [​IMG]

    This is much bigger than I'll probably ever have, but in a windy area, this could easily supply all the electrical energy needs for several households!
    -------------------------------------

    To MASSIVE SCALE!,
    [​IMG]

    In case you haven't seen the massive wind farm generators, this should give you an idea of what 1.5 MW generator looks like!
    I won't be owning anything like this very soon!
    --------------------------------

    Anyway, these Front Bladed, Horizontal Axis generators have some pretty common features for some pretty basic reasons....

    Front blades face into clean air flow.
    The air isn't disrupted by the tower since the blades see it first.

    They will have a 'Pivot' or 'Yaw' point so the generator can turn to follow/face into the wind.

    Since the blades are in front, the natural tendency of aerodynamic drag would be to pull them around backwards to there pivot point,
    SO,
    They require some kind of device to keep them facing into the wind.

    Smaller units usually have a 'Tail Blade' that stands off some distance behind the pivot point.
    The stand off distance is to multiply the leverage force created by the tail fin.

    Larger models, like the super large commercial models, will have a computer that controls the Rotation of the generator body, and with input from a small weather station and computer on board, keeps the blades facing into the wind via servo motors.

    'Blade Over Speed', or blades moving too fast in a storm or gusty winds can be handled in a few different ways, but there are just three or four common ways that MOST builders use to control blade speed...

    I'll cover those in a different post, since I'm only allowed 4 images in a post.

    Blades can be covered pretty quickly, and the name of the game is 'Swept Area'.
    The more surface area the air flow pushes on, the more 'Torque' the center shaft is going to create.
    The more Torque the center shaft has, the more 'Work' you can do.

    Again, I'll cover that in a different post since I only get 4 Images per post, and I've already used up those four on this post.
     
    Last edited: Oct 13, 2008
  6. JeepHammer

    JeepHammer Well-Known Member

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    Blade Speed Regulation is a big deal!
    If a storm comes up, or just high winds from a weather front,
    Your wind generator can over speed, and make more current than your wiring can handle.

    Besides that, the blades can spin fast enough to exceed the mechanical limits of everything from the fasteners on the blades, to the strength of the shaft, to the bearing speed limits!

    Over speed can be a REAL problem, and if you are designing a wind generator that is intended to have a long, constant service life, you MUST address this problem in one way or another!

    1. Yaw The Windmill.
    Since the earliest wind mills went up in in the Netherlands, this has been a time tested way to deal with shaft speed and over speed.

    The principal is simple, you simply turn the blades out of the direct wind path to slow the shaft speed.

    In the Netherlands, operators of the large grain grinding and pumping windmills simply turned the blades of the tower out of the wind, Up to 90° to wind travel direction to control blade speed.

    Later working windmills Yawed the tail to move the blades up to 90° to the direction of the wind.
    (ever notice on the old water pumping windmills how the tail sometimes doesn't seem lined up with the windmill?
    That's so the blades are only turned partly into the oncoming wind at an angle and won't over-speed!)

    Some wind mills and wind generators use a the size and angle of the tail to control shaft speed/over-speed...
    The tails would sometimes have a curved back edge,
    An exactly sized tail at an lower angle to shaft speed will keep the blades facing into the wind most of the time, but when the wind gets to a certain speed, the tail will have much more effect and move the shaft out of air flow a little, controlling shaft speed.

    Another type of 'Yaw' tail is purely manual.
    The owner simply comes out and uses a hand crank or other means of Yawing the tail more or less to compensate for wind conditions.
    .......................................

    2. Self Speed Governing or 'Automatic'.

    Then we get into automatic Yaw mechanisms...
    Some tails are equipped with a Drag Device of some sort.
    When the wind gets to a certain speed and overcomes weights or spring pressure, that force works to Yaw the tail and take the blades out of direct airflow.
    I'm not a big fan of this, since so equipped wind mills tend to oscillate back and forth in the fast wind, load and unload, and the hubs/blades/shafts are over stressed due to gyroscopic forces created by the spinning blades.

    Another type of 'Automatic' yaw control is a pressure simple set of 'Fly Weights' like in old time mechanical governors.
    These are still in use in everything from vehicle distributors to automatic transmissions, and they have been around since the beginning of the machine age, so they are understood, simple, reliable, cost effective and easily built & maintained.

    The idea is, when the rotor or rotating hub/shaft reaches a certain speed, weights held back by gravity or springs overcome their weight and move outward in an arc relative to their mounts.

    This movement is translated to mechanical energy and used to Yaw the blades out of the direct air stream path.
    When the air speed slows, the spring or gravity takes over, and the shaft/blades will come back inline with the air flow path.
    ......................

    3. Rotate Blades To Control Speed.

    This same 'Flying Weights' arrangment can be used to rotate the blades of the windmill, changing the angle of attack, so they loose lift.

    Anyone with aircraft are familiar with 'Feathering' the prop, and that is what the movement from the 'Flying Weight' arrangment does.

    When you get into much larger wind generators, the blades are simply rotated so they are not producing little to no torque by the computer and servo motors....
    (I don't have 12 million for one like that!)
    ........................

    4. Brakes.

    Some home built units use a brake of some kind to slow the rotation speed.
    I don't like this idea one bit...

    Some of the 'Brakes' are electronic, they use extra current to the stator windings to slow the rotor down.
    This can result in burned connections and melted regulators.

    Others use a physical mechanical brake, like a vehicle disc or drum brake to slow the rotation speed.
    There are two basic problems with that,
    The first is an application mechanism to apply the brake,
    The second is wear, mechanical brakes are friction devices and they simply wear away and need to be adjusted and changed as they wear.

    To a lesser extent, even with a brake being applied to the main shaft, the blades are still having large forces applied to them by the wind.
    Blade stress is an issue and should be address in this situation.
     
    Last edited: Oct 13, 2008
  7. telegramsam

    telegramsam Member

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    I recently saw a thing about a new wind energy device, it operates as if you took a piece of really light fabric about 1 foot long and 1 inch wide and strap it between two poles, the wind makes it "flap" around... this energy is harnessed by mini magnetic generators at the ends of the fabric or whatever material is used... this could survive substantial winds...
     
  8. JeepHammer

    JeepHammer Well-Known Member

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    Just a quick dissertation about blade design.

    Many of us are used to seeing two, or three long blades with lots of square inches of 'Swept' or surface area the wind can act on.
    OR,
    You are used to seeing lots of short blades with lots of square inches of 'Swept Area' the wind can act on.

    The lesser number and longer blades get cleaner air flow, and the longer blades are 'Torque Mulitiplers', like using a breaker bar to turn a stubborn bolt, the longer the handle, the more torque at the center point is produce with the same amount of force.

    Long, thin blades are usually much lower weight, or less Mass to be turned, and they have the torque leverage factor going for them, so they start turning at MUCH lower speeds.

    Shorter blades have less torque leverage at the same air flow, so more of the blades are used to get the same amount of torque at the shaft.

    Shorter blades use a larger number of blades, so the blades don't always get a 'Clean' air supply.
    The air is disrupted by the blade before it traveling through it to a certain extent.

    More, and shorter blades are more efficient at turning mechanical loads, like running water pumps, grain grinding machines, or things like woodworking or metal working tools.
    Much like the older 'Windmills' you see on farm lots to this day.

    Generators are a light load compared to that, and generators will benefit from faster shaft speeds and don't require an intense amount of torque, so they are usually longer, thinner and number two or three blades.

    One other note about blades,
    The reason for the usually odd number of blades, three instead of two, is three blades are self balancing to a large extent.
    Differences in weight, differences in pitch, differences in rotational mass, differences in alignment are all magnified in a directly opposed two bladed prop.
    They are directly opposed to each other, and magnify each others differences with speed.

    Add in a third blade, and these differences aren't directly opposed anymore, so they are lessened a great deal, and in some cases, negated entirely.
     
  9. JeepHammer

    JeepHammer Well-Known Member

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    Good idea, but needs a LOT of work to be practical.

    Electrical current is generated by moving a magnetic field through a coil of wire.
    (or to a lesser extent, moving a coil of wire through a stationary magnet field)

    Either way, there won't be any current production unless the field is MOVING.

    The idea you are talking about is simply a piece of light weight fabric with a magnet attached to it, and when the fabric 'Flaps' in the wind, the magnet moves, or vibrates between two coils of wire.

    I guess the 'Flapping' of the fabric could be equated to holding a piece of grass between your thumbs on both ends, and blowing on it to make a whistle...
    Attach a magnet to the blade of grass, and mount two coils of wire on your thumbs, and you could generate a tiny current as well as making sound.

    You can produce more current by yelling into a speaker cone, which moves a coil of wire up and down around a magnet, again, Electromagnetic induction at work.

    I like the idea, but it's really nothing new, since we've had cone speakers for well over 100 years, and they work on the same basic principal.

    With the advent of 'Super Magnets' and 'Super Conductors', I'm watching these old ideas to see if some application of new materials will breathe new life into old ideas!
     
  10. svenhammermon

    svenhammermon Member

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    wind power

    I worked in the field of energy alternatives back in the 70's when there were government rebates and incentives trying to encourage folks to invest in these systems. After 30 years I can tell you without a doubt that you will never live the life you are now with wind or solar energy alternatives. If you are willing to completely change the way you live then you can glean enough energy out of a hybrid system to accomplish the obvious electrical needs of running a computer, some LED lighting, occasional water pumping if your well isn't too deep. Mostly peripheral luxuries. If you invest in a system that is large enough to live the life you're used to in the modern world, you'll have a huge investment in machinery and control systems, not to mention maintenance. A local system I was involved in from the 70's has had to have major work done it several times over the years and considering the investment the owner has in it, he has broke even at best. Argue if you like, but wind and solar are the alternative for off grid folks who want to be able to run their computers and a few rudimentary electrical luxuries.
     
  11. StillStanding

    StillStanding ...despite the fall

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    +1

    Wind systems are maintenance intensive and pose a safety problem due to the possibility of falling debris in the event of a blade, hub, or bearing failure. They are also noisy.

    Yes they will work if you live someplace where the wind blows and can build a tower that clears obstructions sufficiently.

    Overall the people with solar are happier, in my experience.