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Forum Index : Windmills : Concepts on Blade Designs
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MrDelanco Senior Member  Joined: 12/11/2011 Location: United StatesPosts: 101 |
Common Misconceptions I have seen many others use propellers. Propellers are used to pull an airplane or push an air-boat or be driven by a motor like in a fan to create wind. They are not intentionally meant to capture the power of the wind. This is a common mistake made by many. It would help to rethink the blade design to allow the wind to power the unit. Please Post here Thought's, Idea's, New Blade Design's ; MrDelanco:Project Videos It is not only too know what it does but to understand how it does what it does. |
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Rastus Guru  Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi MrDelanco, Welcome to the forum!I'm wondering if it is possible to exstract power out of the nose cone area of a windmill rotor.A propellor type shape would allow the air to flow over/through and when furled may cushion the rotor slow down.What is your opinion?Cheers Rastus see Rastus graduate advise generously |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
So, you are saying that all those gigantic wind generators all over the countryside got it wrong? You're kidding, right?  Klaus |
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| MrDelanco Senior Member Joined: 12/11/2011 Location: United StatesPosts: 101 |
Hello Rastus; I may not be understanding your post completely, are you referring to the stream tube affect that travels over the turbine’s rotor, decreases in volume some of the energy so that air flowing out behind it moves even more slowly causing the air behind the turbine hub to slow and expand so new air flowing in would not have anywhere to go? This would allow excessive pressure to build up behind the blades and decrease the efficiency of the propeller type blades. MrDelanco:Project Videos It is not only too know what it does but to understand how it does what it does. |
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| MrDelanco Senior Member Joined: 12/11/2011 Location: United StatesPosts: 101 |
Hello Tinker; I am not debating that I do feel there is a better way. I am saying it's time to rethink the blade design for higher efficiency in extracting the power from the wind. The force in the wind is equal to and opposite the thrust force as the wind passes the rotor and slows down. Then if a larger blade surface area and smaller circumference-diameter can be used to contact that force, a higher efficiency can be extracted from the turbine and lesser wake affect's will be formed behind a wind turbine unit. I am asking for others thought's and idea's on improving the design of wind turbine blade's on HAWT's or VAWT's to be more efficient in capturing the energy from the wind. Do you Tinker have any thoughts on new blade design's you would like to share? MrDelanco:Project Videos It is not only too know what it does but to understand how it does what it does. |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
A read of this article on efficiency might help. Wind Turbine design I am in the process of making some blades that I hope will perform well, the use NACA 2142 airfoil, 3 blades and a TSR of 7. At a 1.3 radius the tips are only 65 mm wide and 7 mm thick. I see others have built similar blades on here and where tested by Glenn and reported to have worked very well. At the moment I am half way through making the fibreglass mould so can't tell how they will perform but all my research tells me this is the way to go. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yes, a propeller is not suitable for a wind turbine. It does work, but not very well. Wind turbines are made differently to propellers, the foil faces the other way. The 3 blade wind turbine you see used in wind farms is pretty well as good as you can get. They are typically close to 40% efficient, not bad considering they are also designed to run quietly. Slight improvements have been made over the last few years, but only slight, and the people that build the turbines know their stuff. It costs a few hundred thousand dollars to make a big wind turbine, so if they can make them more efficient, they would. There is also the Betz limit, which is the max theoretical power limit that can be extracted http://www.thebackshed.com/Windmill/articles/WindPower.asp Rastus the area of the nose cone is very small compared to the whole turbine area. In fact the center 1/3 of a turbine, which is a pretty big hole, only covers 11% of the total area, so a nose cone would be much less, like <5%. So while you could improve its shape to guide the air through the turbine, the gains would be almost unmeasurable. http://www.thebackshed.com/Windmill/articles/SweptAreaofHAWT .asp Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| MrDelanco Senior Member Joined: 12/11/2011 Location: United StatesPosts: 101 |
Hello; I don't know how we got on large turbines. Could we concentrate on the small home units ? I see many blade designs out there on small home units. Do any of you have any thoughts on new blade design's for the small home units, you would like to share ? Have any of you seen whats out there and have any thoughts on how good or bad they work ? There are all kinds out there share what you have seen. MrDelanco:Project Videos It is not only too know what it does but to understand how it does what it does. |
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mac46 Guru Joined: 07/02/2008 Location: United StatesPosts: 412 |
Hello MrDelanco, The forum is full of just exactly what you are asking...the folks here have been working on just this topic for several years. Basicly speaking, the type/style of blade depends on you'r local wind speed, and size/type of generator...among other things such as tower height, obstructions, ect. so we know what you'r asking, but are'nt sure how to answer. Kind reguards, Mac46 I'm just a farmer |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Glenn, Thanks for the reminder about swept area.A passing comment about timber mill blades with twisted trailing edges was "to make the inner blade aproach angle as large as possible,to assist light wind start up".This prompted me to consider exstending it around the nose cone as a helix,to get the last straw to break the camels back.I do accept there is "little" to gain,but done well it could be most of the little bit.As you can see I'm drawing at straws!!Cheers Rastus Hi Mr Delanco, Thankyou for your knowledgeable reply.Glenns comment about the Betz law is pertainent to your description.Cheers Rastus see Rastus graduate advise generously |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
I see I have a little language problem here. What you call a "propeller" on the front(or back) of an aircraft is in my mind a device that converts rotational energy into thrust. Now, if the thing is engineered to work in reverse (as on wind mills) and converts wind thrust into rotational energy I still call it a 'propeller'. You obviously don't  so I beg to differ here. I do agree that one can't interchange one application for the other and expect similar efficiency.Klaus |
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| Eddie Newbie  Joined: 16/10/2011 Location: United StatesPosts: 25 |
I can give you my ideal blade for a small home wind generator.after lookimg up everything I could that was written in laymans terms for my small 125 watt turbine I settled on ( I'm talking about pvc) Three blades 19 1/2 inch long cut 7 degrees off the center line towrds the leading edge.This is susposed to make them like a rifle spiral and therefore more effiecient? So far they have worked better than the original blades that came with it and several other designs I tried. |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi All I notice a lot of different Ideas on turbine blades and increasing their efficiency, also the reference to the commercial giants in wind farms, but I think we need to be more size specific for our size mills as we tend to keep our blades less than 3.5 meters. Over the last three years I have tried a number of blades and find that they all do a reasonable job, providing there is 5 MS + wind. I have tried the poly pipe blades both home made and a set I bought from a blade maker, above 5 MS they are OK but leave a lot to be desired. If you are short of funds and want to get something going OK but in reality a trip to Bunnings or a timber supplier of your choice and purchase 3 fence palings round the front edge and taper the back over the last 50% of cord is a better choice. I have one mill with conventional professional made 3 blades 8 ft diameter for a 1KW mill I refinished and balanced them and they perform well at 7+ MS but not good starters. I also have a work in progress of a 1 KW mill driven by a set of Gyro copter blades cut down to 12 ft diameter, I will let you know how it goes when finished. I have also tried multi blade high speed blades from 3 to 10 blade 60 inch dia they start well 2 MS and produce good power above 8 MS but the small diameter limits low down power, I am going to extend the blades by 24 inches and then I think they will be useful. By far the best blades I have tried are the GEO 222 alloy blades, they are not a high speed design but the torque produced and power capture is outstanding, I have just purchased 3 more sets to add to my mini wind farm, and also a set to make a 8 meter diameter blade for a 5+ KW machine I am gathering parts for. If you want a set of cheap blades do the fence paling thing and it will run a 500 watt turbine in 5+ MS wind, I wouldn't waste the time making a set of poly pipe blades unless for trial purpose. Do not make the mistake of comparing our little blades with a large commercial turbine, as that is like comparing a runabout with a ship. On the center of the blades there is very little power collected so it is possible to extend the center to get more swept area with little or no loss in power extracted as the blade near the center is travelling much slower than the wind speed, and is therefore less effective, this area does have some effect on start up speed. Sorry to stir the possum in the discussion but this is based on my own testing. All the best Bob Foolin Around |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Mr Delanco, A forum member,Rinaldoparaipan,was very inventive and posted his individaul, concept blades a short while ago.I think most of us rely on more qualified people in this field for help.I get what seems to me,to be a basic idea,then try to develope it with others input.Cheers Rastus see Rastus graduate advise generously |
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| MrDelanco Senior Member Joined: 12/11/2011 Location: United StatesPosts: 101 |
Hello: Rastus Most of the discussing has been about Hawt type blades, with several good points and inventive idea's. I would tend to listen and consider that member's and the other members inventive qualifications in the field and share concepts on improvements and theories with that member and other inventive members that are building and sharing their idea's. I have done testing and building of several styles and will be sharing ideas on both the Hawt and Vawt as the discussion progresses. From my testing I favor the vawt style so I can allow the blade's to start strong and stable. Then design a compatible extraction unit to work with the output produced by the blade design and this process will work for both styles. You really don't know what you have until you build a prototype and do some testing. The theories of yesterday were developed with the sciences of yesterday. With the new sciences of today, those past theories may be enhanceable. Cheers Bob. MrDelanco:Project Videos It is not only too know what it does but to understand how it does what it does. |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Hi Bob... I do not think the theories change very much over a decade or so, oh yes they did change quite rapidly at the end of the century before last but I dont believe much has changed in the last half century. What has greatly changed though is the tools and materials that have become available to us to implement those theories. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yeah I agree with John. HAWT wind turbines today are pretty much unchanged for over 50 years, and thats because they have been engineered to as good as they can get. There are a few laws that dictate how much power we can extract from the wind, and the modern wind turbine is a good balance between performance and economics. There may be a gain of one or two percent in the future, but nothing more. VAWTS are the same, there are different designs popping up every 2nd week, but again there is not going to be any massive jump in performance, because they are already as good as the laws of physics allow. A great deal of research was put into VAWT's in the 70's, most of us are familiar with the egg beater looking Darrieus VAWT's, but in the end, a 3 blade HAWT proved the best commercial design. Its like the modern aircraft. They basic shape and control hasn't changed since the war. In 70 years little has changed, because its a proven design that works. The engineering done at the beginning of last century is sound, and there is little we can do to improve it. In my lifetime the only noticable change in passenger aircraft is the fitting of a TV screen in the headrest! Small wind turbines like those we build follow the same rules as their big cousins. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
[Quote=MrDelanco] I see many blade designs out there on small home units. Do any of you have any thoughts on new blade design's for the small home units, you would like to share ? Welcome to the 4m. Here, try THIS on for size. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| MrDelanco Senior Member Joined: 12/11/2011 Location: United StatesPosts: 101 |
Welcome to the 4m. Here, try THIS on for size. . . . . . Mac Hello Mac; Very nice work. I have used a similar material with aluminum cladding but had some whistling from the holes along the edge. How does the Coroflute you used hold up to strong winds and does the material breakdown when exposed to prolong sun-lite ? Regards Bob. 
MrDelanco:Project Videos It is not only too know what it does but to understand how it does what it does. |
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| MrDelanco Senior Member Joined: 12/11/2011 Location: United StatesPosts: 101 |
Hi KiwiJohn I agree as I stated with the new sciences ie" tools and materials that have become available" today, those past theories may be able to be enhanced. I do feel that with today's materials available for capturing a driving force from the wind, and modern technology implemented into the Pma's. Betz's theory can be enhanced with the implementation of modern technology "design materials" then wind power could take a big step into this century. Say for instance one pma being driven by a windmill that is being used to power a 2nd pma built as a motor generator through enhancements in the electrical circuit. Could this allow the 2nd pma to operate at a steady speed even if the wind force slows for a time ? Cheers Bob. MrDelanco:Project Videos It is not only too know what it does but to understand how it does what it does. |
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