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76 Responses to Contents

  1. esualdo says:

    Hello, I would like to manufacture a vertical wind generator that powers the 5 computers in my business and the lights.

  2. Roger says:

    Hi Hugh
    I have built a 9kW micro-hydro system and am struggling to find an insurance company that will cover it for theft, vandalism or moorland fires. I cannot get it added to my household policy and all the renewable energy and farming brokers I have contacted say it is too small for them to consider. Can you recommend anyone?

  3. Paul says:

    Hi Hugh,
    I have a 5 KW turbine and have recently re balanced the blades, but I am expereincing tail bounce still, any ideas on how to rectify it, thanks as always in advance,

    • hugh says:

      Hi Paul,
      There are a couple of things that can cause oscillation even when the static balance is perfect. First thing to check is the tracking. Do the blades follow each other in space or is one tip forward and one tip back? Measure the distance of each tip from the tower as it passes. Another thing to check is whether the blades all have the same pitch angle.
      I hope this helps.

  4. bessonneau sylvain says:

    Hi Hugh,

    First, thank you for sharing your knowledges.
    I have built a generator with 12 magnets per rotor and 9 coils following your advices.
    So, I have 2 circular rotors with 12 permanent magnet surrounding a stator with 9 coils. I am wondering why, instead of surrounding one stator by 2 rotors, we can not do the contrary and surround one rotor by 2 stators. Indeed, when I look at “professionnal” generator, the coils are not surrounded by 2 magnets on both side and this is still working so that should produce electricity in the coils with the variation of the magnetic fiels. This way, we would optimise both sides of the magnet. Indeed, in the current configuration, the side of the magnet far from the stator is not used. I hope this is enough clear. That mays be stupid but I just wanted to ask. Maybe, to make it work, we should use iron core in the coil to “spread2 the magnetic fields in all of the coil.

    Anyway, if you have an opinion on this idea, I would be curious to know it.

    I have an other question : to optimise the generator, what can I play on? I thinked about the size of the wire, the gap between the rotors and the stator, the kind of connection : stars or delta, what else?

    For information, in my city, the wind is a bit slow.

    Thank you for every thing you shared.

    Hope to hear from you

    Sylvain from France/Germany

    • hugh says:

      hi Sylvain,

      To understand this you must first study the magnetic circuit. The rotors have steel disks outside the magnets, and the flux at the back of the magnets connects with low reluctance to the next magnet. All of the force of the magnet is used to throw the flux across the gap, and through the stator. So the magnets are used very well. Yes you can create a smaller air gap by putting iron in the stator coils, but then you will start to have iron loss, and also problems with startup, and difficulties with manufacture. I have built alternators with iron cores but for small wind turbines that must work in light winds I prefer to use the axial flux design with no iron in the stator. It is easy to build and it is very efficient at low power when it really matters.
      I hope this helps.

      The design of the winding is based on getting the correct voltage at the correct rpm for the battery and the blades. I suggest you look at page 54 of my Recipe book. If you then have questions I am here to answer them.


      • Sylvain says:

        Hi Hugh,

        Thank you for your answer.

        Indeed, I have forgotten the steel plates that “spread” the magnetic flux so it was a bad idea.

        About the design of the alternator, I have checked in a translated version of your book. It is explained that the design is made to get a TSR a bit bigger than the most efficient TSR (around 125% of the most efficient TSR) to reach the battery’s voltage in order to reach the most efficient TSR with the most frequent wind speeds. That is correct if I use a classic charge controller.
        If I use a MPPT charge controller, the TSR will always be constant more or less. Maybe I can try to design the alternator in order to reach the battery voltage at the best TSR in order to have the best TSR at low wind speed. In practice, for the 2F wind turbine, instead of reaching the battery voltage at 220 rpm (TSR=7,5), I would reach it at 172 rpm (TSR=6).
        I agree that this optimisation won’t be revolutionnary because at low wind speeds, the production is low. At least, do you agree with my reasoning?

        Other question : Does the cut-in wind speed depends on the design of the alternator? In your translated version book, it is said that the cut-in wind speed is always around 3 m/s for those design of wind turbine. My conclusion is that the cut-in wind speed depends only on the design of the blades and whatever rpm I choose to reach the battery voltage, it would be at a wind speed of 3 m/s, is that correct? Of course, like it is said in the book, if we choose a rpm too low or too high the blades won’t turn.

        I hope it is clear.

        Many thanks


        • hugh says:

          hi Sylvain,

          Yes the tip speed ratio can be kept constant using a DC-DC conversion device with suitable software. i am not sure that solar MPPT software can find this optimum rpm on a wind turbine with changing winds because the wind turbine has inertia. Normally it is better to use a table of voltage and power for the control software. If you are using a buck converter then you will need to have a higher voltage than battery voltage at the target rpm so yes you would use a higher voltage in this case (in principle).

          Power in the wind below 3m/s is very feeble and we run into problems with turning the bearings in the hub and suchlike. There is not much to gain, and it is hard to say whether is will even work below 3m/s. With larger turbines I find they often will produce power at lower windspeeds than 3m/s if the design is clever but it’s not really that practical to try this with small ones.


      • tj oneill says:

        hi ,
        i have a 6kw wind turbine with windy boy inverter.The display on the windy boy is blank any ideas what could be wrong

  5. Sean Thrasher says:

    Dear Hugh,
    I am a huge fan of your work, and you have inspired me, so thank you first of all 🙂
    In your Wind Turbine recipe book, you say that working at a constant voltage is like working at a constant blade speed. I am confused by why that is the case? I am wondering if the mechanism is that if the angular frequency of the blade is increased there is increased resistance, and so there is effectively a mechanism which corrects deviations from the blades turning at a constant frequency.
    I was told that this has something to do with Zener diodes.
    Finally, I seemed to get the impression that changing the cut- in speed will change what the frequency which the blades rotate at. is this true?

    Many thanks
    Sean Thrasher

    • hugh says:

      hi Sean,
      Blades are designed to run at a certain tip speed ratio and this together with the diameter of the turbine will set a relationship between blade rpm and windspeed that you should try to achieve. Blade rpm should vary in proportion to wind speed for best results.

      My statement about voltage was based on the fact that the open circuit voltage produced by the turbine is in proportion to the speed (rpm) of rotation and hence frequency of the alternator. Actual open voltage can be adjusted in various ways during design, but it will vary with speed in direct proportion. This is open circuit voltage or EMF. There is a mitigating effect due to internal resistance (resistance in the wires in the coils) which calls for more EMF when on load. So the blades do have to run a bit faster when the turbine is loaded, but nothing like as much faster as they should as wind increases.
      If you want to cut in at 200 rpm and reach full power at 600 rpm for example this this will not achieve that ratio.

      Zener diodes are devices that conduct current at a certain voltage which makes then suitable as voltage references but they will not help.

      The low tech solution is to accept a that the blades cannot operate always at their best speed in relation to the wind. Allow for some overspeed in low wind and some stalling (too low rpm) in stronger winds. Keep the range of windspeeds tight. Trade off some losses in the wire run against gains in efficiency due to increased rpm. Even use some of the extra voltage to produce heat in series heaters so as to keep the turbine close to its maximum power point. I do that in my house and it works nicely.

      Or the high tech is to use a programmed MPPT controller such as the Midnite Classic.


  6. Drew Meakin says:

    Hi Hugh,

    Just seen your amazing work on Positive Energy programme on Nat Geo. Do your books cover micro wind turbines as I live in suburbia, well small town in West Lothian but think building one would be a great project.

    Any initial advice?

    Kind Regards,


    • hugh says:

      hi Drew,

      The smallest that I have designed is 1.2metres diameter (each blade 60cm long). It’s important to put any wind turbine in a windy spot and raise it about surrounding obstacles or you will be disappointed. And larger ones give you a lot more back for what you put into them. But it can be fun to build something, even if you don’t have an ideal site or ideal size of machine.

  7. Morgan says:

    Hello, I would like to connect a wind generator 48V type Piggott of 2m40 to the electrical network. Do you have a brand / model of regulator + shedding resistance to advise me to place before the inverter? (I do not put batteries) Thank you in advance

    • hugh says:

      hi Morgan,

      You can use a windmaster with a 48-V winding in the turbine. This is a popular choice actually.
      I do recommend you also connect a protection circuit. I can supply an LDR 96-15 if you need one. This is what a lot of people use for this inverter. What country are you in?


  8. Eric Lotz says:

    Hi Hugh,

    Been looking at your designs since 2007. Am in Haiti and got busy with the earthquake back in 2010. Finally slowed down enough to revisit and actually build something. I bought your US version E-book a couple of days ago and have read through several times along with numerous other resources. I am putting together a shopping list to build either the 12′ or 14′ turbine. Have to ship in the magnets, wire, rectifiers, etc. Looking at magnets, how much of a production difference is there between N42 an N52 grades in your experience?

    I will be running the turbine into a midnight classic either 150v or 250v before my batteries. I am thinking I would be better to wind coils with more turns of a slightly smaller gauge to increase voltage and keep amps down, as the controller can handle higher voltage. This will reduce my cut in rpm considerably I believe and give a larger range of operation. Any thoughts on that approach?

    Still working out dump load and controller, slip rings if I think it is necessary, tower, etc. I have a lot of experience with inverters, batteries, PV, AC coupling, 3-phase and single phase power systems, fabrication, etc. Am ready to dive into this if for nothing more than the experience, but would be great to add some kWh to my production!


    • admin says:


      I recommend N42 magnets but if you do use N52 then you can use a much larger air gap and this can be reassuring. or you could design a winding with slightly fewer turns of thicker wire, but the AWG wire sizes are a long way apart so I do not find that easy to do in north america.

      Using a classic is interesting. You will need some sort of clipper. You can make one. This is to protect against over-voltage. The one they sell is really expensive. Chris Olsen did some interesting stuff with Classics that you can read about on the Otherpower Board.,146180.msg1000687.html#msg1000687

      You can use a Classic to increase the usable range of wind speeds but it does increase the cost and add an element of vulnerability and complexity.

      Have fun and keep in touch

  9. Brian says:

    Hi Hugh. I just bought a couple of ampair turbine heads at the Andrew graham/ ampair auction. One is a 300w and the other is not marked but a bit heavier so might be a 600w. There is a pitching hub on the 600? . I wonder what to do for blades? And would value any comments or ideas. Have you any experience of the plastic blades on eBay ?. RGDS Brian

    • admin says:

      hi Brian,

      It’s a real shame that Ampair had to go bust. Ideally you ought to try to get 600w blades for the 600w turbine but maybe you can try some of the plastic ones on ebay and just see. The weight is important as is the stalling properties of the blades. I thought the 300 was pitch controlled also.

      Have fun

  10. lamberti says:

    Hi Hugh , everything is ok.
    A big thank you for your valuable help.
    see you soon

  11. lamberti says:

    hi Hugh,
    if rpmx60 is revolution per second. I don’t see why you use “divide by 30”. I understand 2,72.
    A big thank you for your explanation.
    Sincerely .
    Jean -luc

    • admin says:

      “the average voltage = 2 x total flux x number of turns x revolutions per second”
      follow the logic and this 2 changes the 60 into only 30.

  12. lamberti says:

    Hi Hugh , the problem is that I don’t understand why you use 0,44T while for other turbines use you 0,62T . However, they are made ​​with the same type of magnet and also a double rotor.
    Indeed the number of magnets and the number of coils change. This value 0.44 is calculated or measured ?
    Indeed the number of magnets and the number of coils change. .
    A big thank you for your explanation.
    Sincerely .
    Jean -luc

    • admin says:

      hi again
      There are magnets on one side only on the 1800. On the others there are magnets on both sides. That is the reason for the difference in flux density. The number is effectively measured and not calculated exactly.

  13. lamberti says:

    hi Hugh,
    by the way I don’t understand this :
    n=(udc+1.4) x 11/(…)
    I don’t understand why eleven x11 ???
    thank to your help.

    • admin says:

      OK this 11 times follows from the lines above. Turn the equation around.

      “DCV = (A x B x n x rpm x 2.72/30) – 1.4
      To find the number of coil turns required for a given
      rpm one needs to turn this equation around thus:
      Total series turns n = (DCV + 1.4) x 11/ (A x B x rpm)”

      30/2.72 = 11


  14. lamberti says:

    Hello Hugh,
    I’m studying the construction of the alternator in your document Auto build his wind turbine. French translate Tripalium September 2010.
    I can not find the coefficient of induction 0.44 (1800) on page 54.
    thank you to enlighten me.

    • admin says:

      hello jean,
      I am not sure what you are asking me but maybe you are asking Why I use 0.44 Tesla for the flux density in the 1800? The reason I use 0.44 is that the 1800 has magnets on one side only and on the other side it has a steel disk. In that case I find that the flux density is around 0.44 when I am using NdFeB magnets grade 42 or similar.

  15. admin says:

    hi David,

    In the menu bar for this site there is an item “wind turbine plans” and under it the best option to choose is probably “all books“. You want the North American edition which is available as an ebook for 9.99 from smashwords (choice of file format, can be amazon kindle style) or if you want hard copy you can buy it for $26 using the paypal button.

    I recommend using rectangular magnets 2″ x 1″ x 1/2″ that you can buy at magnet4less.

    hav fun

  16. David Hodgson says:

    Thanks for replying so soon. All this over unity stuff is very interesting and I think with permanent magnets it is possible but has a long way to go for it to prove itself practical.The best thing I have found so far is the Howard Johnson magnet motor and the Perendev magnet motor. These motors run solely on opposing forces of magnetism but are very difficult to replicate.
    I would like to purchase the “Recipe book” ASAP. I noticed Amazon. com sells it for $5.00. however it is the metric version. Where can I purchase the English version from?
    Also, since I have not progressed very far with building the axial flux PMA I started building from your earlier plan book would it be better for me to start over again from the “Recipe book”? I would definitely want to do so especially if it would be considered an upgrade from your previous plans. For example if the “Recipe book” indicates using more powerfull neodyium magnets, different AWG, improve mold desighn techniques
    Do you think it is better to use round magnets or rectangle one? I would think it would be better to use round since they have the most surface area.


  17. David Hodgson says:

    Hi Hugh,
    Several years ago I built the Ford F-250 brakedrum wind turbine. Unfortunately I have not been able to put it up because of where I moved to has ordinances and variances preventing me from doing so. I have decided to sell it for $200.00 to whoever I can get to buy it. I figure since it is such an old desighn being made with ferrite magnets it is a fair price. Half the fun is building it and the other half is putting it up and watching it work. Experiencing the first half and learning what I learned from it is better than nothing.
    A few years later I purchased the ” How to Build a Windturbine” the axial flux desighn. I bought a spool of magnet wire that the plans call for and started to make the plywood mold and that is as far as I got.
    I am still very interested in axial flux PMAs,magnet motors and anything else that runs on magnets and copper wire.
    While looking at some of inventions patented by Tesla I ran across a coil he invented called a bifilar coil. I started wondering what the result would be if I were to make an axial flux PMA with bifilar coils instead of regular wound coils. I did some research on the Internet to see if there is anybody out there that has done this and what the result woul be. It turns out I did find something at koalas-magnetics-workbench/30.
    A quote from Michellinho states ” In an alternator, the bifilar coil will give the same voltage but twice the current over a regular wound coil with the same length of wire. I just finished building an axial flux alternator with bifilar coils, my son-in-law both coil versions before I started winding my coils and that is what he saw as output under the same condition of testing.”
    What do you think about this idea? Is there any advantage to it? If you are not familiar with what a Tesla bifilar coil is just google it and you will see it.

    Since the writer claims “In an alternator, the bifilar coil will give the same voltage but twice the current over a regular wound coil with the same length of wire” then since volts x amps equals watts would the alternator put out twice as many watts being made with bifilar coils instead of regular wound coils? Sounds to good to be true.Am I missing something here?

    • admin says:

      hi David,

      Don’t believe everything you read on the internet 🙂

      Many of my alternator designs in my Recipe book use bifilar coils in the sense that they are would with 2 wires “in hand”. The result is you can use thinner wire which is easier to handle but it does not mean that you can get twice as much current. One thicker wire gives exactly the same performance as two thin ones do. It’s done in my case for reasons of practicality and do-ability.

      The power you get depends on the wind and not on an tesla hocus pocus. The alternator converts this power to electricity. It needs to be well made to match the correct speed and power of the blades, but you will not double your output by doing some magic trick.


      • Dave B says:

        The fact that you call Tesla’s work “hocus pocus” indicates that you are arrogant and disrespectful to an incredible electrical genius. Now, I will agree that an overunity post may well (and likely is) “hocus pocus” with their claims. Tesla’s patent on bifilar coils, however, is not.
        Tesla deserves your respect, you of all people should know that.

        • hugh says:

          Hi Dave,
          Yes I admit that was an arrogant statement, which I regret when you point it out, but I stand by my statement that the output current depends on the wind and not on the alternator. I took the trouble to google it just now and I cannot see any justification for the claim that a bifilar winding can “double the current” which I suspect is a simplistic misunderstanding. I will try to be kinder in my skepticism in future. Tesla was obviously a genius, but his work is not always easy to understand.

  18. David love says:

    I am looking for parts for a 6kw Eoltec wind turbine can anyone help Bearings etc

  19. Frank Secretan says:

    I purchased your book and love it. It answers many questions, but raises one that I would like your response:
    Your model 1200 turbine uses only one rotor . Your model 1300 turbine uses two rotors, but the 2 nd rotor is merely a steel plate without magnets. My question is this:
    How does the magnetic path get completed through the stationary coils in the 1200 model without a second rotor to complete the magnetic path?
    Thank you far the book and hopefully for an answer to my question.

    Sincerely, Frank

    • admin says:

      Hi Frank,

      Glad you like the Recipe Book. The 1200 diameter is the smallest and it has a simplified alternator with only one rotor. The magnetic flux has to jump through the air rather than having a second disk, so it is weaker as a result, but this is factored into the design of the coils. The 1800 is the next smallest and it just has a steel disk to complete the magnetic circuit more effectively. The flux is therefore a bit stronger but the cost is still low as it only has 8 magnets. With 16 magnets you can increase the flux density but if the stator is carefully made you do not need such strong flux.
      Having the magnets all on one disk is a good use of magnet material but it would start to become very large in diameter if I applied it to the larger turbines, so instead I use magnets on both disks and this increases the flux density although not the number of poles.
      I hope this helps.

      • Frank Secretan says:

        Hello Hugh
        Thanks for your very timely response.
        If I build a single rotor alternator, can I increase the magnetic flux through the stator coils merely by bonding a steel plate to the back side of the stator?
        Or, are there eddy currents induced into this stationary steel plate that defeat this idea?


  20. Maik -Nighit says:
    wind generator in korinthos Crecce ..

  21. gill harrington says:

    Hi Hugh, do you ever visit sites to give advice. We live at Ardnarff, south shore of Lochcarron so not far from you. We have no mains electricity and at present run on a generator with batteries. We are looking at ways of cutting down on dependence on generator and would be grateful for advice

    • admin says:

      hi Gill,

      I can do site visits, but mostly prefer to stay at home and advise by email or phone as much as possible. Looking at your site I’d say you need a hydro turbine! I can also supply batteries and an inverter so you can have 24 hour power, and make best use of the hydro energy. If there is no water (seems unlikely, but then again you should not dry the burn out completely or you will kill off the organisms of one sort and another…) then you can use the generator intermittently to keep the system working full time.

  22. Haseeb says:

    Dear Hugh,

    i am planning on building 1kW stand alone HAWT using 3phase Radial flux PMG from the market, i have some confusions , hope you can give me some suggestions:
    1. The electric braking system is not clear to me , from some literature, we can use Dynamic braking resistor. is this braking system included into the PWM controllers or inverters available in the market or do we have to separately connect it ?
    2. can we use furling together with electric braking system ? the MPPT settings done directly from controller or inverter or is there any other device for this ?

    • admin says:

      hi Haseeb,
      1. The simplest brake is to connect the AC wires together into a short circuit (using a 2-pole switch). This is done before the rectifier. You can find such a switch in the Midnite Clipper, but not in the MPPT controller itself. You can easily find a suitable switch and do it your self.

      2.Furling is for automatic limitation of maximum power. The brake is for parking. Both are useful. You can brake it while it furls of also when it is not furling in lower winds.
      3. You may need a computer to connect to the MPPT controller or inverter so as to program the best setting for you wind turbine. YOu will also need to think about how to protect the MPPT device from the wind turbine open circuit voltage.


  23. Maik -Nighit says:

    Good morning from Greece
    I bought your book and I have built three generators have a gap in construction please me I want you to tell me what material put around the wooden mold to not leak the polyester in the second building and I use only polyester with glazes, while you put and other material in the mix beige and white should be strong I drink ice sir Piggott answer to these questions thanks Maik ..

    • admin says:

      hi Maik,
      i am sorry I don’t understand this well but I do suggest using caulk (silicone or something) around the borders of the mould to reduce overflowing of the resin. Gaps in the casting don’t really matter too much. If you want you can fill them with body-filler paste (polyester filler for car bodies). I don’t really drink much ice so I can’t help you there. try
      have fun, Hugh

  24. Maik -Nighit says:

    Good morning from Greece
    I bought your book and I have built three generators have a gap in construction please me I want you to tell me what material put around the wooden mold to not leak the polyester in the second building and I use only polyester with glazes, while you put and other material in the mix beige and white should be strong I drink ice sir Piggott answer to these questions thanks Maik ..

    Καλημέρα από την Ελλάδα
    Έχω αγοράσει το βιβλίο σας και έχω κατασκευάσει 3 γεννήτριες έχω ένα κενό στις κατασκευές μου παρακαλώ θέλω να μου πείτε τι υλικό βάζετε περιμετρικά στο ξύλινο καλούπι για να μην διαρρέει ο πολυεστέρας κατά το χτίσιμο και δεύτερο εγώ χρησιμοποιώ ,μόνο πολυεστέρα με υαλόπαγο ,ενώ εσείς βάζετε και κάποιο άλλο υλικό στο μείγμα χρώματος μπεζ λευκό και πρέπει να είναι πιω γερό θέλω κύριε
    Piggott απάντηση σε αυτές τις απορίες ευχαριστώ ..

  25. Marc Stevens says:

    I am building a 2400/8′ turbine from your Recipe Books. I had purchased some 2″ x 1/2″ N50 disc type Neodymium magnets awhile ago (I see the price has gone up) for another project. If cost was not the issue is there any advantages at all in going with N50. I was wondering what your thoughts were about using them in the 2400. Would you do anything different with the coils or air gap.

    Peace, Marc
    Chadron Nebraska

    • admin says:

      In my opinion the 8 footer is already over-endowed with alternator power. Using stronger magnets will stall the blades unless you widen the gap between rotors. No downside other than cost, but I see no reason to do it.


  26. hemant says:

    i have built my vertical axis wind turbine . i m facing problem with generator . which one shuld i prefer. i want to eliminate the gear arrangement rather i would prefer the chain shaft arrangement. it’s a kind of prototype. plz suggest one.

    • admin says:

      I’d need to know the power and speed of the turbine to suggest a design. also the battery voltage. I really don’t like vertical axis and suspect you will not be able to tell me the power and speed of it. I recommend you follow one of my standard recipes to have a good outcome.
      Best wishes and have fun

  27. Brit says:

    Hello Hugh,
    Is there any preference for a particular type of weave when selecting fiberglass cloth?

    Thank you,

    • admin says:

      Fibreglass cloth is woven unlike the usual fibreglass ‘chopped strand mat’ that is just a sort of mess of fibres. I like to use cloth because it is tidier and also a bit lighter weight than mat. My preference is for a tightly woven cloth that does not fall apart easily. But to be honest I doubt if it matters that much what you use.

      Avoid using the normal weight of mat because it is un-necessarily heavy and wastes space. A thick layer of glass and resin on the stator inhibits cooling and makes it harder to get the optimum spacing between magnet rotors without them rubbing on the stator. I don’t ever remember a stator failing due to inadequate fibreglass strength.

  28. Tony says:

    Hi Hugh, I was wondering if you had any thoughts on a turbine that furls vertically rather than horizontally. I have made a 1800 model to your designs which works beautifully and was toying with the idea of a furling mechanism that tips the hub and blades back with a counter weight and a damper. Maybe you have investigated this and discovered some major obstacles to get round or a flaw in the concept?



    • admin says:

      Hi Tony,

      Yes this is a valid way to furl and I have built and worked with several machines that furl like this. I built one that had the cable on the back end of the furling rocker so that it could be furled by simply pulling on the power cable, which was neat, but of course manual furling is not really necessary in most cases.

      You can use the weight of the alternator in place of the weight of the tail, but the centre of gravity is not in the ideal place as it tilts back over top-dead-centre and furls too easy at the top. So it normally needs a spring to correct the restoring action and get constant output in stronger winds.

      This type of machine does tend to dance about a bit in turbulence due to the interaction of diving torque and yaw bearing as it approaches pointing upward. It needs a robust rocker bearing and a spring, that tends to fail eventually. Otherwise it works pretty well.

      have fun, HUgh

  29. owen brookes says:


    I am embarking on an MSc project, a feasibility study for a small / medium wind installation for the Ingram Valley community. Can you give me any advice or do you have any top tips? I shall be looking at the Achitibuie community wind turbine developments with interest, good luck!

    • admin says:

      I’d say the main thing to check is that there is a good site for wind and not put the turbine in a place where the wind is inadeaute or too turbulent. bear in mind too that microhydro is often overlooked and has potential to be a lot more effective than wind because of it’s high capacity factor. It works all the time (nearly) whereas wind turbines often average less than 25% of their rated output. Other than that, good luck and have fun!

  30. Thank you so much hugh…

    i understand all the things, that whats going on….!!

  31. Bill Kraft says:

    Hi Hugh,
    I took the 8′ axial-flux 12 volt 3 phase out of service due to one burnt coil. It’s been up about 2 years. I saw it perform in some fairly high winds > 40mph and generate 100 AMPS at 15 volts. As I became more relaxed with the high winds and neglected to run out and brake it, I think that coil (weak link) failed.
    While winding the coils originally I thought there was one that missed some turns. While testing the stator I noticed one of the phases was lower in output by almost a volt. I plan to do a postmortem on the stator. Curiosity and knowledge is driving this effort!
    Would I be correct in suspecting the failed coil is the one with less turns? Any thoughts?

    • admin says:

      hi Bill,

      sorry for taking so long to reply – this one slipped through the net. If one coil fails in a 12-volt stator then the usual cause is a diode that has failed short-circuit. This puts a heavy current through one coil but not heavy enough to stop the turbine. Symptoms would be poor starting and vibration.

      If the machine is routinely producing 100 amps then the tail is too heavy. Try using thinner plywood (best quality stuff though). Or a smaller vane.

  32. sunnysri says:

    hi hugh

    Can i use pp on Teflon or PTFE sheets for rotor or stater in wind mill

  33. sunnysri says:

    hi hugh

    i have 36 ferret block magnets (20mm*20mm*3mm) also have 24 swg wire, i want to build 4kw generator , how many turn i will wind for low rpm. which connection is best (star or delta) please give me suggestion.

  34. HUSSAIN ALI says:


    I have a question about certification. I have made a spreadsheet which uses the Rayleigh distribution of any site depending upon the average wind speed of the site.

    During the Durability element of certification, the average wind speed (Vave) attained over the 6 month period, establishes what Class, be it 1,2,3 or 4, your wind turbine is classed as.

    What I dont understand, is that to attain Class 1 status, the average wind speed over the 6 month period would need to be 10m/s. But Vave at Myers Hill is only 7.7m/s yet they still are able to certify turbines and classify them as “Class 1” so i think I must not understand something regarding the Classing of a turbine and the average wind speeds seen during the durability tests.

    The Classification of a wind turbine into Class 1,2,3 or 4 can’t solely be decided upon the “windiness” of a test site can it?

    I’d appreciate any knowledge you can bestow on me 🙂

    kind regard,


    • admin says:

      hi Hussain,

      I am not an expert at this subject but I can pass on some comments.

      A turbine can be designed to one class and tested to another. It can be for example designed to Class 1 but due to the opportunities of the test site it might only be tested to Class 2.

      If the test site mean windspeed is lower than the windspeed of the class it may take a lot more than six months to clock up the necessary high wind hours but Myers Hill can still test to Class 1 given a long enough test.

      That’s the gist of what I can pass on and I hope it helps. The UK standard will include a clearer wording of the difference (between design class and tested to class) in its next edition.


  35. hello hugh piggott..

    first i speak thanks to give vary useful imformation about windfarm in your documents. i made up windfarm with the base of your free download 2003 edition “How to build a WIND TURBINE”. i made up stator and rotor as you mantion as in above document. but i face one problem regardless to stator.

    i use 18 gauge wire for made 10 coil to make 5 phase generator to generate 24 volts and make star connection as you mantion in document. it has one ring which short all coil start point and all end point taking outside called one to ten.when i measure AC voltage between two terminal for example terminal one and two .i get 5 volt at 100 rpm. same way for other coil point.after connecting rectifier i get output of rectifier DC. but when i connect rectifier all (+) terminal and (-) togather as you mantion in above document (page no. 21 and 37 ).i get only 7 volt rather than 25 (addition of 10 coil 2.5 volt each). so please give me solution for this problem sir…

    bhargav shankhalpara
    from india.

    • admin says:

      Hi Bhargav,

      The voltage between AC finishes depends on which coils you choose (in the 10-wire, 5 phase situation) and it can be quite low in some cases. But the DC output for the 2003 design should reach 24V at quite a low speed around 140-150 rpm. This is actually rather too low because it will cause a stall problem as described in my update page for the year 2004 All of this is a long time ago, and my recent work is much better but all the same you should get plenty of voltage output at 150 rpm. Too much actually.

      If the voltage is only 7 volts at 100 rpm then there is a problem with the way it is wound or the way the magnets are installed or suchlike. It should have 160 turns per coil. There should be 12 magnets 2″ x 1″ x 1/2″ of neodymium (grade 35 in those days). The air gap must not be too large or the speed will be very high. I wondder what the problem is but there are several possibilities.

      Ideally you would be better off getting a 24V cut-in speed around 200 rpm for best performance. Try adjusting the air gap so as to get this performance. If you can’t then tell me more about the magnets size and type and layout and the turns you had in each coil and hoe thick is the stator and suchlike. We can sort this out.

      have fun


      • hi hugh

        thanks to reply..

        you suggest me some of the criteria for low voltage output in my wind of them is to “magnet of 35 grade neodymium type”.but in my country INDIA it is very costly. one peace price is $10. so in my projects 24 such magnet require so total price will be $240. which make my generator very costly.

        so do you have any other idea for making generator. or i hear that DC MOTOR can be use as a generator if we rotate its shaft by wind blades. plz tell me that to get 500 watt power which rating motor can i use….??

        • admin says:

          Hi Bhargav,

          If you are not using neodymium magnets then of course the numbers will not be correct. I am not sure what magnet type you are using but it’s quite possible to use ferrite/ceramic type magnets instead. These are much less costly but you do need a bigger alternator with more turns in the coils to achieve the same performance. Or you can settle for a low power unit which will work well in low winds.

          It’s easy to build a small turbine because it can produce a higher rpm but if you want to catch power in low winds then you will need to get useful power at low rpm and for that the best is to build your own alternator not to use a motor. Don’t worry too much about the maximum power – what matters is the average power and even just 100 watts average is a lot of energy each day.

          I am happy to help you if you tell me what size machine you want to build.

          • Hi hugh…

            after long time i again start work with my wind-farm project. but my problem is still not solve and it is…

            By reference of your “2003 edition How to build a WIND TURBINE” after building generator as explained in your book. when generator start rotation and i measure voltage between two of terminal i get around 5v. as shown in book page no. 21 and 37. but when combine its all output than i can’t obtain addition of voltage. please tell me what is actually problem. is this happen due to not proper sequence of magnet or other…??

            -bhargav shankhalpara

          • admin says:

            hi Bargav,

            Of course I wrote that 10 years ago, and I have spent a lot of time writing better stuff in between, but I can still remember what happened back then. The only problem with the 2003 design might be that it produces too high voltage at too low speed and this could stall the blades if the battery voltage is low.

            Anyway returning to your questions, The AC voltage that you measure will noly be about 70% of the DC output although the DC output will loose about 1.5 volts from that higher due to the diode losses and this 1.5 volts is a bigger chunk at lower voltages. So if you see 5 volts then the DC will actually be 7 – 1.5 = 5.5 volts. However if you see 10 volts then the actual output of the rectifier will be more like 12.5 volts DC.

            Now when you combine the wires together in the rectifier box you are adding more current sources but you will not add more voltage. I am guessing this is a 12-volt machine and in that case the ideal will be to get about 12 volts output DC at about 200 rpm. It may be that you will get it at lower rpm for the 2003 design and if so then I suggest you use more washers to make a wider gap between the magnet rotors.

            I don’t think there is a problem from what you have told me so far. The output voltage is not increased by connecting more circuits in parallel. However the output current is shared between all of the circuits and all of the coils and that way you can produce a lot more output when the wind is strong enough.

            best wishes,


  36. Shats says:

    Helllow , hows your day at this moment, a want to konw how to make a homemade alternator because our house is far from the source of current , almost 50 kilometer from the source, that’s why i want to learn on how to build alternator, and diagram
    Thank and more power hope your techniques become success….
    i really appreciate your help us…

    • admin says:

      Hi Shats,

      You will find plenty of help with building an alternator on my web site. Look for example at the Free Downloads (the link above to and you will find some pdf documents of my older plans that are available for free.

      If you want the latest plans then you have to pay for them but they will be sent to you as a book which is handier for reading in the workshop. See ‘buying my books’ above.

      I hope this helps


  37. admin says:

    Hi John,

    I appreciate that the diagram on page 35 is not completely clear since it shows the coils arranged in a line. So I have done another diagram here with an explanation of the logic and the procedure. Have a look at it and tell me what you think.

  38. John Dempsey says:

    I purchased a book, A Wind Turbine Recipe Book. And from this I decided to build the 14 ft 12 volt turbine. There is one aspect I’m not clear on, is the parallel connections on the coils. Is it possible you can give me a more clear full drawing on how the connections are done? As I am fitting the rectifier box up at the turbine.

    Hope to hear from you.

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