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Forum Index : Windmills : VAWT and F&P recomendations
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Gill Senior Member  Joined: 11/11/2006 Location: AustraliaPosts: 669 |
Sorry folks, Had another look at my idea and it's not so good after all. Still seeking that right combination though. Back to start & try again. was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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martinjsto Senior Member Joined: 09/10/2007 Location: AustraliaPosts: 149 |
does the cam tilt the blades? it looks like only the top is cammed, i have seen similar designs on a smaller scale or does it just offset the blades at a set point around the circumference creating a escentric rotation, if so, surely there must be alot of vibration at higher speeds. i havnot built a vawt yet, but i am planning to start on in the new year, i need all the advice i can get, thanks heaps guys. i havnt done any sailing so not quite sure of the wind thing and how to capitalise on the conditions i can get acces to a few scrolls from industrial a/c, a good start i guess, wont be untill i start to experiment for me to understand things better im a hans on man, work things out as i go lol. make a lot of mistakes but. trial and error. its good to see others have tryed and are willing to pass on info from there experience. this will probably be my last post for a while as im off to my farm for the xmas break. happy christmas to all and seyas in the new year martin free power for all McAlinden WA |
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| KiwiJohn Guru  Joined: 01/12/2005 Location: New ZealandPosts: 691 |
I saw a design for a variable geometry vertical axis wind turbine which seemed quite interesting. The blades were mounted to form a letter 'H'. The blades were attached to the horizontal spar by a hinge that was not at exactly right angles to the spar in such a way that as the blades moved from the verticle their angle of pitch changed. The example that was shown had three blades and they were weighted at the bottom so that as RPM increased the blades tilted out at the bottom due to the action of the hinge the pitch changed for better efficiency at that speed. |
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vawtman Senior Member Joined: 14/09/2006 Location: United StatesPosts: 146 |
Hi Gill and others, Back in the day(3yrs ago)i got the itch to build a vawt. Back then the Darrius would not selfstart either needed a starter device or be cammed to change blade pitch but took away the major advantage of the vawt. Some things i tried early on with a 8ft rotor, Flat blades with little curls on each end and using mags with simular poles facing each other and the thinking was that the mags would force the blades out on the downwind and compress on the upwind. Total flop no go. Another thought was a v/shaped blade with an opening on the tip of the v Total flop no go. Yet another test was plastic barrels cut in half attached to the ends of the rotor. Not a total flop it did spin but no usealble rpm. Another thought was to use an airfoil like others have tried and soon discovered the problems they had with the indecision of rotation. Then this crazy thought popped in my little head,why not design the foil to the rotation. BANGO The blades were 8ft long and the rotor was only a2x2 with shelf brackets attached to the blades.After i installed them not thinkin much would happen,my daughter who was in the pool at the time, hollered and i looked back and saw it spinning like crazy in the light winds and knew my brackets were going to fail. Needless to say i did a backflip in the pool. But then the struggles were'nt over.NEED POWER and beefiness. The 5hp motor conversion i did cogged just slightly and revurberated through the blades and starting became an issue again. No go even though the turbine played with it 15 mph winds using hand dryer elements geared 1:3 only a couple hundred watts but the gearing and motor idea was a flop. So now im at where i am today. Rebuilding the tower. Builing the 32in 54pl dual rotor radial alt(ice fishin and thinkin now) Building 2 more blades(done) Rebuilding the tower to accept the blades. Its all in fun for me. |
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| Evil Roy Slade Newbie  Joined: 14/01/2008 Location: AustraliaPosts: 11 |
I am confused about something. If the power in wind is proportional to velocity cubed why is it that all power to wind velocity curves I have seen are linear? Is the limitation in the generator? BTW: I am new here. Hi to everyone! ERS |
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| Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
G'day Evil Roy Slade, And welcome to the forum. Good observation there ERS. You seem to have an inkling of the dynamics when you refer to the generator. Many approach this subject from different ways so I can only give you one of mine. The power is related to it's velocity as you say but the prop speed is related more to velocity than power. Not only by the fixed Blade Angle as derived from a fixed ratio of Tip to wind velocity but also by the relatively linear resistance loading of the generator in relation to the rpm. In short there are two primary ways to overcome this discrepancy between wind power curve and generator power curve, one is to alter the blade angle and the other is to alter the generator loading as they relate to shaft rpm. Always keen to hear reports of efforts in these areas. Variable pitch props are not a popular approach due to their engineering complexity, but with generator loading we have a few new ways to approach this and I for one only wish I had the ability to explore them. But that's another story. Hope that's answered your question and made you more curious. was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| Evil Roy Slade Newbie Joined: 14/01/2008 Location: AustraliaPosts: 11 |
Thanks for the reply Gill. Modifying the generator load was exactly what I was thinking. My solution is to use some electronics between the generator and load to maximise the output current for any wind speed. A high output generator would be used which would be current limited at low wind speed to reduce generator load and hence required torque. This would allow some power to be extracted instead of the turbine grinding to a halt. I wanted to make sure the theory was correct before starting on the circuit design. I am building a 'short and fat' high torque, low rev VAWT. I came up with the load control idea to take advantage of the high torque instead of a mechanical high loss gearing mechanism. Sort of new at this so forgive me if I am covering old ground! ERS |
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| Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
I don't think a low speed high torque VAWT would be my choice for power generation. Still, an electronic technique for adjusting the generator loading to suit a wide range of ever changing wind speeds could possibly be applied to any generating system? Keen to hear further details as you feel appropiate. Your ideas may be similar to systems used by some and boardering on discussions in the 'MPPT project' thread. was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| Evil Roy Slade Newbie Joined: 14/01/2008 Location: AustraliaPosts: 11 |
Hi Gill, I read through the MPPT thread last night and found it most interesting as it is along the lines of my ideas. However it ended rather adruptly. Is this tact being continued on another thread somewhere? ERS |
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BartHermans Newbie Joined: 19/01/2008 Location: BelgiumPosts: 10 |
Hi everybody, I've just joined this forum. I've made a couple of days ago a savonius (90cm high, 3m long). It's my first attempt... It's turning in the wind already at my parents house, because my garden is not big enough (not windy enough). There's no alternator attached, and now I'm experimenting with the blades. I'm covering the blades with plastic. I've already noticed that the blade design is not realy correct. Because when covering 3/4 of the blade, the results are better. In heavy wind it takes 3 sec/turn. In slow wind is takes 7 sec/turn. I detached the savonius when there's heavy wind. I want to test the following in the near future : I want to put little flaps in the little holes on the wings. Flaps that only opening in one direction. So the flaps are closing when the wind is blowing on it, and they open in the other way... I think it's possible because the windmill is not making a lot of turns/minute. So the flaps have time to open and to close. Something I don't know is what noise the flaps are going to make. It's not that I need the electricity, it's just for fun. Greatings from Belgium. Sorry about my poor English.  |
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| Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
G'day BartHermans, Welcome to the forum and thank you for sharing your project so far with us. Your English is very good so no need to worry, it is easy to understand. That is quite a large construction you have there. I like the idea of stacking another on top but at 90deg rotation. I imagine a more even applied power when turning a generator, but it makes the structure more complex. I have a few questions if you don't mind, What are the little holes in the wings you are going to cover with flaps? At 20 rpm what type of generator do you plan to use? Will it need gearing to higher rpm? With these large diameter, high torque low revving drivers such as savonius and water wheels, I think they would suit a very large diameter homegrown generator. Perhaps using low quality but many magnets and small but many coils. I have not seen any reports of this being done though I feel sure someone will have tried it by now. I wonder what the results were? Look forward to an update on your wind generator as it develops further. was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
Sad to say ERS there has been no furtherer discussion of this subject. Too few were able to contribute to the work and assess it's progress. As you'd have read, personalities started to clash and though the work may continue, no one has felt inclined to share any details with the forum. However, there are many who would like to see a renewal of this topic leading to the development a viable project. If nothing more than to bounce ideas off the group, please initiate a new topic that we can assist if possible with developing your ideas further. was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| BartHermans Newbie Joined: 19/01/2008 Location: BelgiumPosts: 10 |
Jill, In Belgium a lot of people are living in a relatively small country. HAWT Urban windmills can't be used because of noise and danger. In fact there're as good as no urban windmills in Belgium. I've choosen to test a windmill who makes not much turns/minute because people don't like to see fast rotating devices in their garden (or neighborhood). And something that makes no noise, even with high windspeeds. I know that this type of windmill does not produce a lot of power compaired to a VAWT. But a VAWT is out of discussion because of the mentioned reasons. The first thing I need to do is attach the Savonius on a strong concrete plate because even with 60Kg of stones, the wind blows the windmill on his side. After that is done, I'm going to use a little software to count the turns/minute and the windspeed. Before I want to make (or think about) generating electricity, I'm gonna test, play and measure (statistics) the performance after modifications on the original design. This is a hobby, so this will take some time. I think that I can make the concrete plate in a couple of weeks. In my parents garden the device is already turning, so that motivates me take the next steps. In the picture below I show you the 'holes' I was talking about. (A couple of hundreds holes...). I've found some sheap rubber thin elastic plastic. I need to cut some hundreds little flaps out of the plastic and attach them to the green wire. The program to measure the turns/minute is written in Qbasic and communicates with a parallel port of a computer. It's also possible in .NET program code, but I loose to much time to learn the code. With 'Microsoft Virtual PC' I created a little disk and with the free operating system 'Freedos' I'll get the I/O from a little program written in good old QBasic. What am I planning to measure : I need two sensors. One for the speed of the big Savonius windmill (who will measure the time that one turn takes) A second one for the speed of a very small savonius windmill. This little devices will be my reference to get the windspeed. Thanks for your reply. Bart.  |
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| Evil Roy Slade Newbie Joined: 14/01/2008 Location: AustraliaPosts: 11 |
Hi Gill, I am currently building a prototype VAWT on which I can test my theories. After some testing I would be happy to throw it on the table for discussion on a new thread. Starting a new thread now is a little premature for me as I would be talking through my axxx not having anything in the real world to work with. Now I have the wind power itch...gotta scratch it! ERS |
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| Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
ERS, No problems mate, good to see you giving it a scratch. Look forward to your future reports of world beating, ground breaking success. was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
Bart, Like most of us, time is not such an issue. I can understand that 60kg of stone is not enough to anchor that to the ground and the higher you go with it, the more secure it will need to be. I'm thinking for safety at least 2 meters to be clear of children and people? And for wind as high as possible yet this will not be simple. Would it not be better to sheet over all the holes rather than do each one individually? Or is the flaps an idea to reduce drag as the wing rotates up-wind? I don't know the dynamics involved so it's too difficult for me to guess the benefits if any. No doubt your prototype will give a good indication. You may be aware that free-running will be vastly different to the running under generator loads especially if step-up gearing is to be used. For your sensors, there are several ways of doing it. I like the simplicity of several small magnets on a disc rotating past a magnetic reed switch. What method do you like best? Are you using Linux as your operating system? It seems like you are all organized in that area. Good luck with your project. was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| BartHermans Newbie Joined: 19/01/2008 Location: BelgiumPosts: 10 |
Jill, Exactly, the flaps are an idea to reduce drag as the wing rotates upwind. But the blowing wind inside the windmill is affecte too, so maybe I'll have to cover only the upper side of the wing full of flaps. And let the wind only pass through the lower side of the wing to get out of the S-shape windmill. I can't wait to see the results, if any 
At this moment the savonius is mounted and turning on an inefficient recuperated axis. I do not care about this because it's causing some resistance like a little generator would do. I wanted to use some optical switches (optocouplers) as sensors, but a 'reed switch' will indeed reduce the complexity of the circuit. I think a little resistance of 1K-Ohm in combination with the reed relay will be enough. Thanks for the advice. I do not use Linux but (also free) 'Freedos' as operating system. I know it's outdated, but for this little project it serves me well. I'm active for years in the IT business, and it's the first time I really post something on the internet that has nothing to do with informatics 
Some of my friends are looking strange when I talk about my new obsession but once we're going in technical discussions about the windmill, the subject is getting their heads to think about the complexity of it. And obviously they get to the point that making electricity is much more difficult than (ab)using electricity the way we all do (at least in Europe). See you. |
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vasi Guru Joined: 23/03/2007 Location: RomaniaPosts: 1697 |
Hi BartHermans, Linux need special configuration for realtime projects... freedos is great for this. Also the good old languages for him. I don't like the way the new software is evolving . Why you don't try Lenz turbine? Hobbit name: Togo Toadfoot of Frogmorton Elvish name: Mablung Miriel Beyound Arduino Lang |
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| BartHermans Newbie Joined: 19/01/2008 Location: BelgiumPosts: 10 |
Vasi, I red about the Lenz turbine. It's much more efficient than a Savonius because it's using (just like a HAWT) a lift effect. This means that it will turn faster than the speed of wind and that implicates that it could make some noise. In an urban environment, noise (at night) is not recommended (at least when it's not in the bedroom  )
Is my information correct about the Lenz ? About the software preferation : I prefer to use a Microsoft .NET or VB(s) programming code. There's a freeware DLL who can handle I/O port communication over RS232 and LPR (or LPT) ports. There're some examples for .NET, Pearl etc... on the internet and they're working correct and fast. But I don't have the time to investigate and learn the code yet. I'll post the link to the freeware DLL in another 'Post Reply'. Have you some experience with a Lenz turbine ? But one more important question : I like nature but also want to test a windmill. I saw on your website that you like pigeons. How does a (slow) turning Savonius in a garden affects birds ? Bart. |
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| vasi Guru Joined: 23/03/2007 Location: RomaniaPosts: 1697 |
No, Glenn is the expert here. He can tell you about noise... I want to make first a HAWT because it looks great and I want to make the blades from wood. But I think VAWT is the best solution in my area. And for now, the best design is Lenz turbine. Hobbit name: Togo Toadfoot of Frogmorton Elvish name: Mablung Miriel Beyound Arduino Lang |
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