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Wind Turbine

  1. Apr 15, 2008 #1
    I have few question about wind turbine and its theory
    for the situation, the average wind velocity is 2m/s

    1. what kind of vertical wind turbine is the best for the design? helix, Darrieus, "S" shape?

    2. for a wind turbine, how to increase it's output current?

    3. what is the relationship between current, voltage, rotor speed, and number of stator?

    thanks a lot:smile:
  2. jcsd
  3. Apr 16, 2008 #2
    1) Depends. How much power are you developing? What are your maintenance requirements in terms of down time and frequency? Is the wind steady or intermittent? Cost of construction?? Desired efficiency. Location, location, location. Way to many factors for a simple answer.

    2) V=IR. To increase the current for a given V, then lower the internal resistance. Otherwise if you have an A/C generator, then pick a transformer that meets your desired output. Note: This will affect the voltage...

    3) Rotor speed depends on the design used. For a simple bucket rotor the speed of rotation can be far below the wind speed. For wing shaped rotors, whatever the configuration, the lift component can increase the tip rotation velocity to exceed wind velocity. (Note that while the velocities increase overall thrust does not past the Betz limit. Something about laws of conservation ... )

    In a nutshell, calculate the force wind in question will develop, ie: velocity of wind squared times the area and then pick a design that fits best within the limits of your scope. Or is this an entirely theoretical excersise?
  4. Jul 9, 2008 #3


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    home made wind turbine

    At home im building a vertical axis wind turbine and i would like somebody's opinion on my method of construction.
    the purpose of this VAWT is to power a small greenhouse outside yearlong.
    the average wind speed is about 5-7 mph. i plan to use an alternator from a car for the generator.
    this is in a suburban area and is expected to be mounted on top of my shed about 15ft off the ground. it is to be about 4 feet wide and about 5+ feet tall

    i've decided to go with the general design of a helix. not only does it work in any wind direction but it is also efficient and kinda 'purdy' i think it would look good on my roof.
    another propose of this device is to find a way so that craftsman such as myself with the motivation to build such a device can have an idea on how they could do this in their back yard or garage with mostly common/ off the shelf supplies.

    i like the helix wind turbine's design http://www.helixwind.com/en/ they've got a pretty good youtube video. just look up helix wind and its the first one..
    if you look closely at their design there are 2 twisted shafts that turn 25 degrees around the center axis as they spiral up the rod. you can also notice that on each "fin" as i like to call them there is a cup shape to them as to kind of "catch" the wind -which makes perfect sense. by observation it can be seen that each side of the helix a "wing" consists of about 10 fins which are (to my observations) exactly the same design, just mounted at the according angle relative to the position on the axis to form the helix.
    the material looks like a weather resistant plastic. probably injection molded or thermo molding technique was probably used in production.

    materials: at first i considered PVC pipe from a local hardware store to use for the main center shaft which would be fitted with cross pieces vertically up the shaft rotated at the appropriate angle according to their height on the axle to form the helix's shape. pvc pipes about 35 inches long would be melted in a crude propane oven hanging vertically with a flame beneath it (this actually works fairly well with pvc pipe- given you dont burn it..) it melts at a couple hundred degrees F. this pipe would be bent to a kind of a Christmas candy cane shape (basic shape) . all of this was designed on Rhinoceros - 3d CAD modeling program. i took the section between the fins (that will catch the air) and flattened it so it was 2D. i planned to cut that design out of ripstop nylon fabric from offline or if im lucky at fabric store. this section between the fins (to catch the air) would be sliped onto the pvc pipes in a way that you could stack them on top of each other. kind of like connecting the dots.

    after messing around with an oven and successfully got a 3/4 inch dia (inside) pvc pipe from a hardware store malleable and let it dry in a form i made at the appropriate shape; then flowing water through it to cool it instantly. this is a great idea and is definitely an option. but it requires a lot of sewing talent to make the fins.....

    another solution besides using pvc pipes is to buy sheet form PVC (often used to make street signs and such) and make my own crude vacuum/ pressure mold system using the malleable pvc sheets as the material to be thermo-molded.
    with this design it eliminates (given the plastic's thickness) the need for support rods on the horizontal axis up the rod. these plastic fins (like used in the helix wind turbine) could be mounted on the axle itself and you would be done. no nasty sewing machine......:yuck:

    i would like someones opinion on which method to use. pvc pipe is a good east method to make a helix from off the shelf materials and after molding them into fins its not that hard. the real trick in that design is the sewing ability. not everyone has that luxury/ talent.
    i was wondering if im not the only one who thinks building a thermo molding system would kind of defeat the whole concept of home-made.... its not exactly off the shelf as you well know..
    although the mold could be made from plaster of paris (heat resistant) or covered in a later of fiberglass (unlikely)

    one of my main oncerns about the thermo-molding process is that you cannot make this shape because it wraps around on itself. can you do that in a thermo molding device? i've never done this before.

    how should i manufacture this turbine if it is supposed to follow the home made guidelines?
    or are both ways acceptable ways to construct this?

    sorry for the lengthy post...
  5. Jul 15, 2008 #4

    I think helix turbine is better since it is a more advanced and modified version of Darrieus, it's got helical blades. Helix has a way better efficiency in energy capture. For the design I'm not 100% sure which would work best.
  6. Jul 16, 2008 #5
    1. All three types will work. The newer helix design looks good, but looks aren't everything. A lot depends on your location. Noise and being bird friendly are two things to consider.

    2. At a given wind velocity the only way to increase the output is to increase the physical size of the turbine. Another factor is torque. The old style farm windmills with the many vanes were high torque and great at pumping water at low RPMS. For Electrical generation higher speed is required. That is why most of the commercial units only have two or three blades.

    There is one vertical axis design called the "eggbeater" that turns fast., but It is noisy and definitely a bird hazard.

    3. Here is a good link on the electrical variables.

  7. Aug 8, 2008 #6
    Your most efficient producing design for conversion of any wind resource to electric power is a three bladed horizontal shaft with twisted blades. Birds are of no consequence since they just fly around turbines like they do around speeding automobiles. You can play with the blades design and twist to make them quieter and if you make a trailing curve, a tail whip at the ends it will quiet them. Vertical turbines are OK for hobby but are not going to harness a wind resource as well.
    Last edited by a moderator: Aug 8, 2008
  8. Aug 10, 2008 #7
    Like WG said, if your using this for actual power production, stay away from VAWT designs and go with a conventional 3-blade HAWT. There is no one design that works better than all the others, it varies depending on the conditions. Since the wind is so low in your area you will definitely want to go with a design that is self starting. In other words, stay away from the Darius design.

    Since your average wind speed is only 2 m/s, expect to get about 0.85 W/m^2 with a well design hobby type wind mill. If you want to make this thing worth your time and money, it has to be efficient.

  9. Nov 19, 2008 #8


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    manufacturing wind turbine

    Hi, i need some advice on the manufacturing of my savoronus wind turbine. to make the fins (20 of them, 10 stacked on each side). i cant decide whither or not to make the fins out of plastic or fiberglass.
    fiberglass is very sturdy and weather resistant although it can be messy
    plastic-> polyethylene can be melded and put on a form.

    both methods will be camped/ secured using a home made vacuum bag.

    the basic design can be found at youtube video http://www.youtube.com/watch?v=q9flSPAdOLk
    product website at http://www.helixwind.com/en/

    if any body has any experience with these materials and their manufacturing i would greatly appreciate it if you could help me decide which method to use.

    Thank you very much,

  10. Nov 19, 2008 #9


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    Tropher, can you give me a reference to the graph you just posted? that would be great.
  11. Nov 20, 2008 #10
    I guess I don't understand why you would pursue the least effective design in such a low wind envronment. 5 to 7mph of wind will not even turn 70% of the turbines out there, at all. The design you reference requires about double the start up wind speed as the standard three bladed design. That's why I don't sell vertical or spend time designing on vertical wind turbines... Maybe you just want to see for yourself? It's easy enough to do.

    After the ineffective vertical design you are pursuing, add to that the toils of home made turbine parts and their effectiveness, compatability, durability, then the low wind zone you are in... I have to advise you to take a more conventional look at this and digest the feedback you are getting. That slow wind zone is a challenge with a fantastic turbine. A home made turbine of an innefective design really doesn't stand much chance of being effective for you. Have a look at the RPM requirements of home made junkyard turbines, then compare that to your wind resource. Let me know how it comes out for you. I would like to see you pursue something that would be more fruitful for you in the end.
  12. Nov 20, 2008 #11


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    I would like to add that the area i live in the average wind speed is about 15-20mph. up to about 60.

    I am unfamiliar with the abbreviations 'tsr' and 'Cp' in the graph above. Could someone explain please?

    I appreciate your advice WindGenerator. I do admit that I have put dozens of hours into the design of this turbine. To hear that the savinous turbine design is the least efficient in its game is startling; but then again, that is how engineering projects work. Although the inefficiency would explain why you don't see one anywhere.....

    The purpose I'm building this turbine is to power a greenhouse I am building, but in the bigger picture, it is to be entered in an Alternative Energy competition in hopes of motivating people to either buy a turbine or make their own like the one I would have made. What I am trying to say is, this turbine is to be most efficient as possible with wind conditions in southeast Washington state. This wind speed average is about 15-60mph as stated above.
    Naturally I aim to generate as much electricity per unit area of the wings, but this design is aimed at home power generation to promote alternative energy. The work that goes into making the relatively low intermittent power from a wind turbine to being compatible with 120V outlets is irrelevant in this experiment.

    Can anyone give me more advice towards the design and development of project I am working on?


    Last edited: Nov 20, 2008
  13. Nov 20, 2008 #12
    The graph is from www.windturbine-analysis.netfirms.com

    TSR = Tip Speed Ratio = Tangential Velocity of Blades / Wind Velocity

    Cp = Power Coefficient = 0.5 x density x area of turbine disc x Wind Velocity ^3

    The most efficient watt/m^2 design is the 3-blade horizontal turbine. How efficient you want to make it is up to you. For simplicity a single speed-fixed pitch turbine will be the easiest to build but will only work well in a small range of conditions. For the best efficiency over most wind velocities, a variable pitch - variable speed design with a directly driven PM synchronous machine with direct torque control is the best way to go IMO.

    I suggest you buy some references and get to reading. Getting even a small and simple wind turbine to work (that is actually be usable) is a very difficult task even to those which have an engineering background.

    One more thing. Don't go to youtube to learn how to build a wind turbine or anything at all for the matter.
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