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Wind Generators- pros & cons

Discussion in 'Renewable Energy' started by tcmtech, Nov 18, 2016.

  1. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    ~40 - 45 F for many hundreds of feet down and the well drillers here are greedy as all get out.

    The wind tears all but the most over built wind generators to bits here.
    I've played with the AE stuff all my life and when it comes to the energy levels needed for winter heating the numbers for most AE based energy sources don't pan out favorably. Direct solar thermal capture dumped directly into the ground loop is the only thing I have found that ever worked out by the numbers as being plausible but even then the winter time electrical power consumption to run the heat pumps itself still adds up to being less favorable than burning wood coal or used oil.

    It will work if you don't mind having a cold wet slimy floor all summer. You will have a hard time keeping your floor surface temperature at a level that's good enough to provide cooling effects but not produce condensation everytime the weather and local humidity levels change. :p
     
  2. spec

    spec Well-Known Member Most Helpful Member

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    Hi all,

    The early posts on this thread have been transferred here from http://www.electro-tech-online.com/...-soil-temp-testing.149492/page-2#post-1279384 by admin at my request, and with the agreement of TCM and FL, because we were getting a bit of topic (my fault).

    I started this thread to get members views on home-made wind power, especially, horizontal turbines, mainly because these do not seem to have been used successfully by home constructors and I imagine that they have a lot of potential. But comments on vertical wind generators would also be much appreciated.

    Because the early posts have been moved the flow of this thread is a bit askew, and my opening post has been lost, but the information is still there and that is what counts.

    spec 2016_11_20


    Yes, there does seem to be high winds in North Dakota TCM but, consequently, the wind thus contains a vast amount of energy and it is a shame, in view of what you say, that that energy can't be tapped.

    I have next to no practical experience of wind generators, but it is my understanding that there are ways of dealing with high winds.

    spec

    PS: I am particularly interested in this area at the moment- perhaps a subject for a new thread.:)
     
    Last edited: Nov 20, 2016
  3. fastline

    fastline Member

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    Having a reasonable amount of experience and design work in wind gennies, there is always a way but IMO, vertical axis or VAWT units hold the most promise for lower scale units. There is an efficiency drawback running vertical (wind can't strike the back side) but these units manage turbulent variable winds better and do not require any pitch and yaw tuning to work decent. Yes, you could probably add that stuff BUT what hurts wind is all the costs! The machines are not cheap, battery backs are not cheap, etc, etc, etc.

    Another issue with VAWT is they don't mate to the grid as well due to not staying at constant frequency. Would need an inverter. HAWT has that fixed by simply using yaw and pitch to keep rpms perfect for the grid and will just go offline if outside of spec.

    This starts making solar look much more appealing. I personally spent weeks designing some solar collectors that have yet to be constructed. Hopefully soon.

    So really, all this stuff comes down to making it cheaper!! You just cannot afford to spend $50K on this equipment and see it return in 50yrs. I think we can do better.
     
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  4. dave

    Dave New Member

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  5. spec

    spec Well-Known Member Most Helpful Member

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    Hi FL,

    Thanks for info.
    Don't think I am arguing, just interested. The sticky on the ETO section on renewable energy says the exact opposite. That is that horizontal turbines are the best approach. http://www.electro-tech-online.com/threads/wind-generators.94505/
    A solar approach requires both storage batteries and inverters.:)
    To me the huge drawback of solar is that, by definition, solar can only be productive for 12 hours a day and then thre are clouds to worry about and the seasons.

    spec
     
  6. fastline

    fastline Member

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    true, pros and cons all over this road map. Thermal solar is what I was referring to. Banking hot water for heating applications.

    Regarding VAWT, I was not referring to them as being "the best approach" but rather have the best possibility of becoming simple and cheap. They will NEVER achieve the efficiency of HA BUT no one said the VA cannot be just a little bigger to compensate for its lack of efficiency. So you use up a little more air space.....you won't miss it.

    Remember that for a HA to work well, it really needs yaw and pitch. However, that pitch feature can be really slick to protect against overspeed as well. With VA, you can typically design one to become so turbulent at high speed that they mostly max out. There are pitching VAs coming down the line.
     
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  7. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    That added complexity for blade pitch control is the primary killer behind DIY wind power. The commercial stuff has it but they typically want 15 - 20X what a single unit costs to build which puts the realistic ROI so far away into practical.

    The best and most reliable DIY wind generators I have ever built just use a single 2" x 6" carved to match the old 1930's wind charger and similar genset blades of that era. Dang hard to kill a 6' long hardwood 2" x 6" by spinning it! Still the service life here is about 4 - 5 years before the wood gets so wind scrubbed it losses all its aerodynamics. :(

    I've tried many different supposedly commercial fiberglass blade sets over they years and everyone had at best a few months service life before they either just came apart or flew apart. Same with the last set of all metal blades I tried. Worked great for ~ 3 - $ months then stress cracked to bits and folded over one day.

    I put up a 20' tower near my old house so that I can put a smaller wind generator up some time soon but until carve a new set of blades it's just gonna have to wait. I've got a 1500 watt PM three phase servo motor for the generator and the steel for the frame so that could go together at any time but I have other priorities now like my new mini used oil fired boiler I am putting together. :cool:
     
  8. spec

    spec Well-Known Member Most Helpful Member

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    Thanks for info TCM: always illuminating to hear from people with practical experience.:) The twenty-feet-high tower sounds impressive: you don't mess about.:D

    Once again I am not arguing, but what I can't understand is that there are aeronautical propellers that stand much more stress and have to be much more reliable than any wind generator propeller, so why are wind turbine blades such a problem? Then there are helicopter blades which have even more stress! For example, can't wooden propellers be clad in stainless steel?

    Also variable pitch aircraft propellers are widely used without problem, so why is variable pitch a problem in wind generators, I ask as a novice in this area.

    One question: if you had a fixed-pitch propeller and it was braked would the fixed-pitch propeller survive OK, even in the strongest wind?

    spec
     
    Last edited: Nov 19, 2016
  9. spec

    spec Well-Known Member Most Helpful Member

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    One of the major problems with wind generators appears to be the life and size of the blades so I have been considering an array of smaller propellers which would have a lower tip speed.

    While I appreciate an array of small propellers would not be as efficient as a single large propeller, is there any merit in this approach from the home constructor point of view?

    spec
     
  10. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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  11. spec

    spec Well-Known Member Most Helpful Member

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  12. cowboybob

    cowboybob Well-Known Member Most Helpful Member

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    I've mentioned before that I've built and deployed various Savonius rotor driven PM generators (not a big fan of propeller driven systems).

    The biggest advantage I've observed is that they are omnidirectional, i.e., no need for a rotating base. They are also relatively immune to over speed problems and are pretty torque-y; they are frequently used for irrigation pumps and pond aeration. And, compared to prop types, remarkably easy to construct.
     
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  13. spec

    spec Well-Known Member Most Helpful Member

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    Thanks CBB

    How big were your wing generators? Do you have any links?

    spec
     
  14. cowboybob

    cowboybob Well-Known Member Most Helpful Member

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    By "wing" do you mean "prop" types?

    If so, only once tried to build that type - gave up pretty fast because of the degree of expertise (airfoil calcs) needed. By comparison, I could put together a (crude but working) Savonius from a 50 gallon oil drum (biggest I've made) in about an 2 hours. Smallest from a beer can.

    Here's a pretty good example (not mine):
    http://www.thebackshed.com/forum/forum_posts.asp?TID=889
     
  15. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    I've been playing with wind power since my mid teens nearing 30 years ago now. The #1 problem I have ran into with the DIY or any other system in my area is durability of the blades.
    Making a genset and frame that can take a beating is easy enough but finding a reasonable blade set that will take gusty winds with 70 - near 100 MPH peaks is not and around here if a wind generator is placed on a good hill using wind ramping effects makes hitting those wind speeds pretty easy.

    My general approach has always been to build a unit with a generator systems that can keep a blade set loaded down to a reasonable RPM (just under supersonic tip speed is where I shoot for ;)) in any wind we have which to be honest meant most of what I have ever built ended up being system with 6 foot rotors and 1000+ watt generators with nonlinear loading systems which in every case obviously that was not enough to hold things together.

    For my preference I have never been one to try and get energy from light winds and have always designed for high output hammer down winds for my energy production. I don't consider anything under 10 MPH worth going after for any realistic power production numbers. Doable but not a primary design goal. Why bother going after 500 - 1000 WH a day production on light winds when a good high wind day here can do 20 - 30 times that?

    I don't bother with hanging out on the AE forums anymore given there at too many goons who need to take the OCD pills and step into reality over what it is they are working with and toward for what level of realistic time, money and effort they are investing.
    To me it makes no sense to spend 10's hours on designing and making a blade set to get X amount of power from say a 6 foot rotor in a 15 MPH wind when a less efficient but far simpler, cheaper, more durable and far faster to manufacture (< 3 hours from a common size board) design can put out the same power if you made it 6.5 feet long. :rolleyes:

    But that's just me.
     
  16. spec

    spec Well-Known Member Most Helpful Member

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    Yes, in my (air force) terms a prop comprises N blades and blade is one of the blades in a prop. Sorry for not using the standard terms in this field. And, yes again, I do mean a horizontal turbine.

    My main interest is home-built horizontal turbines, only because they have not been as fully exploited as vertical and my feeling, rightly or wrongly, is that a home-built horizontal turbine should be successful. But I speak from a theoretical point of view and do not fully appreciate the practical aspects.

    spec
     
    Last edited: Nov 19, 2016
  17. spec

    spec Well-Known Member Most Helpful Member

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    Hell TCM, you have a busy life. I would love to have some of your facilities, but then I do not have your drive.:)

    Very illuminating information. Traditionally in the UK small local wind turbines have been used for electricity generation and pumping (irrigation or water flow). The prop is horizontal with a vane, so an upwind design. Probably about 10 of 3 feet blades are used with a stabilizing ring around the blade tips.

    You mention about the blades being torn to bits in a high winds. But isn't it a simple matter to limit the blade tip speed to any value you like. This is the bit I do not understand.

    spec
     
  18. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    I wouldn't call my life busy or driven. I tend to avoid being both as much as possible and my facility are still a dirt floor shop I started building some ~15 years ago and have yet to ever get closed in and finished of to where its a heatable year round work place. It was intended toe be a well equipped facility within the first 5 years after I started it but life took me in a whole different direction putting such a goal well outside of my capabilities to achieve in both time and financial investment.
    To be honest my life didn't start gaining traction enough to even consider such things again until the last few years and even then most of that last few years was dedicated to married life and all the pain in the ass money sucking inconveniences that went with it. :(

    Anyway, Yes. A lot of the blade issues come from tip speed which in itself come from not being able to either load them down hard enough to keep the sped down or not having a pitch control or some sort to feathering system.

    That's the main problem with DIY designs. Having some sort of self governing system that is simple, rugged and reliable. So far I have never came up with one that worked very well in our area given our conditions. Offsetting the whole unit on its pivot point so that it would yaw out the wind never worked. Nature just always seems to find that perfect combination of wind speeds and gusts to get the units oscillate to the point that the centrifugal forces of the spinning rotors would stress the blade roots to the point they would eventually tear out.

    Many years ago, ~20+, I aquired a old original condtion Paris-Dunn 32 volt 1000 watt unit that was in workable condition. http://www.windcharger.org/Wind_Charger/Parris-Dunn_Corp..html They were a very well built and designed unit that would simply tilt the whole rotor and generator up to reduce its speed and kepe the system under control. It worked great most of the time but ultimately we had enough days where the wind would hit it hard and tilt it up then drop dead letting it slam down which eventually broke the heavy frame castings that the generator pivoted on and once that was fixed it eventually just broke the blades off. I have been considering restoring and improving it now being my skills plus fabrication resources have came a long way in that time. The first improvement would be to add some sort of shock absorber systems to it so that when it tilts up it can only drop down in a slow controlled fashion.

    The people I got it from are good friends of mine an they have a second 1500 watt unit still up on the tower in their yard from back in the 1940 - 50's from the days before rural power came to their place. They said they would sell it to me but I cant get them to get off their butts and get a buddy of theirs to come over with his boom truck and pull it off the tower. :mad:

    Now as for my most recent designs, ideally I would like to design a blade pitch control system like the commercial units use but to do so is not a simple easy task to do. Even with full on CNC milling and machining equipment making a reliable design takes time and resources. I don't have any CNC machining capabilities but I do have a good Smithy 1340I lathe mill combo unit that could make such a device. The problem is to do so is still a very long drawn out process just to do the numbers behind the layout before a cutter so much as touches metal for a single piece of it. And that's just to make a single prototype to see if a design even works once. :(
     
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  19. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Commercial designs feather the blades and shut down totally in high wind speeds.
     
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  20. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    This thread got me thinking about a couple of retired aircraft propellers I have sitting around here... If I mounted these on a tower as a giant wind-driven piece of yard-art using a DC generator as a dynamic brake, would they produce any usable power?

    One is a fixed-pitch, two-blade, 74inch tip to tip, solid aluminum prop from a Cessna 172. Tipping this one up would be the only way to stop it. Dynamic braking could slow it down...

    The other is a variable-pitch, two-blade, 82inch tip to tip, solid aluminum prop from a Cessna 182. It is used as a constant-speed prop (meaning that a servo senses the engine crankshaft rpm and the blade pitch is automatically adjusted, varying the load on the engine, to keep the rpm constant). Varying oil pressure (0 to ~ 50psi) inside the prop hub is what actuates (using pistons/springs/gears) the angle of attack of the prop blades. Unfortunately, this is not a full-feathering prop; the blades rotate about 40degrees.
     
  21. spec

    spec Well-Known Member Most Helpful Member

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    That sounds like an interesting approach Mike. I had similar thoughts. So you can get fully feathered props from what you say. What sort of weight are your props?

    spec
     

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