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Forum Index : Windmills : Big Als Mill
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Big Al Newbie  Joined: 06/10/2010 Location: United KingdomPosts: 38 |
My ! My! You colonials have got us Brits sussed . No wonder you got away. Regarding mill I am still at the wind logging stage. Using a Power Predictor which needs at least 30 days logging b4 I can analyse wind speeds , directions , and gustiness factor ( it also logs solar-but remember I'm in Scotland , altho English (even worse ). My initial thoughts are a Vawt (for site reasons ). Helically bladed. My initial plan was 6 MegaW from a shoebox sized unit , regulation by covering and uncovering pin holes in the box . The few sneaky peaks I have had at what my PP is recording leads me to believe I ain't gonna get winds of sufficient speed (maybe a blessing )so I've downgraded my ambition slightly to 300W from a Vawt hopefully about 2M diameter by 2M high or not much bigger and without a box round it. This seems to be a difficult target. There is a twin rotor design on Youtube which looked good but was n't helically bladed but used two part-shrouds to give a Bernoulli effect in the centre to give the blades a low pressure return path. (It eventually crashed due to a battery fault and overspeeding despite what looked like outstanding build quality and design). I don't know whether helical blades would have saved it.I think the video from memory was posted by bigdbez but I'll check that. Other thoughts I have is that a vawt enables a larger diameter generator (gets over the lower TSR problem but expensive on magnets and coils ))under the bottom bearing without impeding wind path and would also give room for a centrifugally operated device 1. to gradually load increasing inertia into the rotor to keep it going in lulls 2. Variable pitching , but this is very difficult as the upwind blades need pitching inwards and the downwind blades outwards. Even if I could do this reliably how the H would I keep the rotor balanced ?so variable pitch is probably out 3. to switch in extra load coils to limit overspeed electrically (and increase o/p)4. the larger diameter bottom bearing disc could have thickness (streamlined )and weak springs could pop out vanes for self starting which would retract automatically under rotation wind pressure Theres one like that on the web somewhere ) I don't fancy kicking it with a motor giving up hard won electron flow back to the wind so if poss would like it to be self starting without adding significant drag once it gets into lift mode. I think but can't prove it that a Vawt which almost must have two bearings (with xtra bearings in the middle easily incorporated) should be buildable that will keep generating even when the wind really gets some power in it. I'm still thinking and planning which I've got time to do while my PP works away. One things for sure my target won't be easy and I'm going to need every trick in the book plus hopefully some advice from you experinced guys if I'm going to get near it. Two things which might help me are an article on the web by some French guys which implies a S0027 airfoil gives up to 16% extra efficiency on some of the usual NACA foils and another guy has put me on to KFm foils which might give some advantages-don't know yet. I'm aware a reliable centrifugal device is a complication that may be difficult or impossible to realise. Meanwhile my PP works and I've got a tower in that I just built my grandkids a tree house 18 feet high with a strong lookout tower on top of that another 20 feet high which pokes through the top of the tree. The look out tower has a platform at the top so I can self erect to 10-11 metres pretty easily and I hope safely. Rgds. Big Al Every Day is a school day (even at 67) |
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MacGyver Guru  Joined: 12/05/2009 Location: United StatesPosts: 1329 |
[Quote=Big Al]My ! My! You colonials have got us Brits sussed . No wonder you got away. I left a little note for you on a reply down near the bottom: Here! Also, I'm pleased to see your "PP" works so well! 
. . . . . . 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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| Big Al Newbie Joined: 06/10/2010 Location: United KingdomPosts: 38 |
Saw the reply Mac. don't write us off . remember its not so long ago we conquered the Falklands again. THAT PP meant Power Predictor , the other one is a "Power Loss". rgds. Big Al Every Day is a school day (even at 67) |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Ah but its only because we came from good stock 
Though, I do think we should rename the Commonwealth Games to the Australian Games, since we always win
Have you looked at the Lenz windmill. Ed Lenz did a lot of research into different VAWT's and even built his own little wind tunnel. I built one and was pretty happy with it power, but was having problems scaling it up. Another unfinished project. 
http://www.thebackshed.com/windmill/articles/Lenz2.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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| Big Al Newbie Joined: 06/10/2010 Location: United KingdomPosts: 38 |
Thanks for i/p Glenn . Yes I had looked at this but it seemed more Savonius than a lift type-I'm looking for a lot of power for the size I want to build and think a lift type essential (although I'll need Savonius to start ) Trouble is I need to get the Savonius to stow itself to reduce drag once it starts "lifting " I'll have a closer look at the Lenz but I don't think the airfoil shape is good for high efficiency. Big Al Every Day is a school day (even at 67) |
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| Big Al Newbie Joined: 06/10/2010 Location: United KingdomPosts: 38 |
Had a look again at the twin rotor job I mentioned in my first post. If anyone interested you'll have to google bigdbez as I 'm not clever enuff yet to give you a straight referral link. If you have n't seen this or one of his several videos IMO the build quality and design are excellent and it really looks to be knocking some power out. The crash has n't deterred bigdbez and he's now building an improved model with 3 sections on the mast in case he gets hit by another big blow with his battery not loading itI suppose most of you guys being Hawters this model might appeal as it uses all that empty mast below a hawt. Rgds. Big Al Every Day is a school day (even at 67) |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
[Quote=Big Al]I 'm not clever enuff yet to give you a straight referral link. Sure you are; it's easy. Just look down at the "Post Reply" box. Under it is a blue "Forum Codes" link. Click on it and it'll take you to a listing of several codes you simply copy and then paste into the body of your reply, replacing pertinent information and it's a done deal. To set an active link, choose the code that has http= and so on. Copy and paste the code, then replace the URL information with that of the page URL where you want to direct the traffic and replace the "My Link" with whatever you want to call the link. If I can figure it out, anybody else is a shoe-in! . . . . . 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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| Big Al Newbie Joined: 06/10/2010 Location: United KingdomPosts: 38 |
Hey look I'm learning . I've now got one of those nifty little slogans at the bottom. If I could have gotten enuff characters I would have listed all the former colonies but you know who you are.Incidentally I'm seriously impressed with how good this website design is. Big Al Every Day is a school day (even at 67) |
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Perry Senior Member  Joined: 19/11/2009 Location: Posts: 190 |
Hey Big Al, Welcome to the forum. They even let us Yanks in. Look forward to your posts but for now you get the all too standard greeting for people that see a VAWT on youtube and get all fired up to build one....Don't build one.... You seem sharp enough to figure this out but I have never seen any compelling data that shows they deserve to exist in any way shape or form. Maybe someday but for now they are the domain of Youtube garage builders that don't understand power vs. voltage and slicksters looking for easy venture captitalists that don't perform due diligence. Welcome friend, Perry |
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| Big Al Newbie Joined: 06/10/2010 Location: United KingdomPosts: 38 |
Perry and others. Appreciate your inputs while I'm still at the planning and thinking stage and don't disagree with most of your comments as things stand at the moment, Having read a lot of this site before joining , other sites , and most of the gurus I should by now be a Hawter. However I've got a stubborn streak and can't get the following thoughts out of my head. 1. I was trained as an engineer (not aeronautical ) and know you can't argue with the Physics. However we are all trying to "couple" fluid power (pity the fluid is n't a bit chunkier like water - maybe if the almighty does a redesign he could give us an air atmosphere with big chunks of turbine-seeking water flying about in it-similar to Scottish weather )) to Mechanical motion to generate electricity, AS far as Big Wind goes a slowly rotating 4oo feet diameter propellor , which has to shut down when the wind gets really powerful ,looks wrong to me instinctively-It seems to be extracting the energy by brute force instead of quietly sucking the power out in a more underhand British way. 2.For small wind new Vawt designs with helical blades such as QR5 , Turby etc. look good , are much quieter ,are probably safer and are n't producing that much less power than the same footprint Hawts. Whats more the design looks inherently to have a longer life. These guys are telling the venture capitalists they basically have a 25 year life. They probably lie like an Aden watch but looking at the designs I don't see why this should n't be true. True the Vawts have to be taller (not higher necessarily )but in the UK where we don't have those wide open spaces (except between the ears maybe ) a small defined footprint is good and going up is n't bad as we've got the same amount of air over us as you guys. There are a couple of a site factors for me. I think my site will be gusty especially in summer with leaves out and I'd hate to waste the 10-12 metre look out tower I.ve built on the Grandkids tree house and I believe that a Vawt would be a less effective Grandchild decapitator . This may become a reverse argument in favour of Hawts as they become older. 3.Its easy to build Vawts with 2 or 3 or more bearings , triple or more blade attachment points, and less stresses (safety, lower maintenance ,extra ruggedness , higher wind speeds b4 shutdown -or collapse !!) 4, Vawts have one advantage you don't often see listed . The area under the bottom bearing lends itself to centifugal switching to switch in extra generating coils (speed limiting and power increasing ) , vary pitch (probably not practicable ) and maybe retracting self start vanes and adding moment of inertia gradually as speed builds-- All WITHOUT significantly impeding the wind path BUT more expensive and technically demanding. Generally a good Vawt seems to me to be harder to build, despite the constant blade profile , and almost certainly more expensive than some of the great home brew hawts on this site, However once we Brits get the Boston Tea party , the Chinese Boxer rebellion , and Ozzie bodyline batting reclassified as war crimes we ain't going to be short of a bob or two . Until then we have been keeping a daily log of what the US and China will eventually owe us despite our motto of "Forgive and forget" After all these dastardly events were only a few hundred years ago. We have n't forgotten either the rumours of a Continental ( we think German ) T. Rex crossing the land bridge and eating some of our plant-eaters although even I admit proof will be difficult here. 5, That twin rotor TRV posted by bigdbez on utube looked to be pushing out a bit of power before it crashed (battery problem ) and the design and build quality looked to be a tribute to N. American savvy. Hey you hawters it was using the pole of a hawt as its axis-waste not want not Anyway I.m still studying, looking to do a few a few experiments while my wind logger plods away , and I'll probably end up as the guy who warns newbies about Vawts. Even hawters rely on VERTICAL poles to hold them up.Cheers Big Al Every Day is a school day (even at 67) |
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| bluffit Newbie Joined: 08/10/2010 Location: New ZealandPosts: 1 |
hi Big Al Greetings from an Englishman who used to live in Scotland, and ended up in one of the windiest spots in NZ. Have just stumbled across this site, but your post inspired me to register and say hi. I'm not really into electronics so read in awe of the knowledge here. However, I'm a half decent software hacker; love a bit of risk taking; and never say die. My VAWT plans are similar to yours, but a little larger. I can't see what the fuss is about though. Basically you'll never get much more than 50% efficiency, so with that in mind, my view is simple - build it big enough to work; strong enough to sleep at night; and quiet enough not to annoy the neighbours. Take 3 x ~3-4M x 300mm sheets of ~4mm thick alloy. Press them into simple aerofoil sections. Connect them to a truck axle with ~2M radius struts. At the end of the axle is a simple truck diff at 1:10 (with one axle closed off). Bolt the whole thing onto the side of a shipping container, and connect the drive shaft to a 3kw 240v alternator wired straight into a few hot water tanks (adjust load based on RPMs ~100RPM ideal). Hope to have the thing up for a $2-3k kiwi (but could be dreaming here). Anyway, this is the crude spec, and no doubt things will change as we get closer. The shipping container is in place; the power is cabling done, and I've tought myself to program one of those PLC things (ugly ladder logic). Wish me luck! |
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| Big Al Newbie Joined: 06/10/2010 Location: United KingdomPosts: 38 |
Hey -someone newer than me. The official welcomes will no doubt come from the Ozzies -they seem a good bunch and even the Yanks seem to be the better kind. As an Englishman who lived in Scotland you'll probably thick skinned and tuff enuff to make your generator take off. A word of advice .Don't come the old colonial "my vawt plans are similar but BIGGER than yours" bit . My original Vawt plan was a 10megaW job from a shoebox sized unit involving titanium, carbon nanotubes but I had to change that (could n't get the Krytonite I needed ).
Hope your neighbours are n't too close . Even if your truck axle is quiet the whole installation does 't sound like a thing of beauty although a couple of union jacks painted on the shipping container may do the trick. Watch those Kiwis . They are a good bunch but nearly got into bed with the French (spit spit ) some time in the 1800s at Akaratoa (?) near Christchurch. They were pulling the old Dutch Manhattan trick. "take these beads and mirrors and we'll just have this useless land in exchange " Luckily we got onto it sent a warship down and said "P**s off !! This is ours " A technical point which may encourage . the rule of thumb quoted on the home page that any newly erected turbine immediately suffers from no wind also applies to anenometers . Having risked life and limb erecting a power Predictor on my site in a high wind it then just sat looking at me for three days. Although from the sound of your site you'll be more concerned with surviving the wind than measuring it. Best of luck .You've ended up in a great coutry although like the Scots God did penalise them with their neighbours I like the style and scale of your plans. If they work out you could pipe some of your hot water up to Rotorua and increase Kiwi tourism.Big Al Every Day is a school day (even at 67) |
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Big Al, I commend a persistant group of readers persuing with VAWT designs. I myself have no interest in them though. I have seen U-tube videos of VAWTs in operation and I have not been inspired. I have a few HAWT windmills of my own design and these have survived whatever comes by. 100kph + is not that uncommon where I live. I believe the HAWT design superior, as it places as much of the active component possible in the best air. The windspeed increases with elevation above the ground. A high speed VAWT typically is tall and narrow. This presents differing windspeeds at different heights. This poses engineering difficulties with airfoil designs to work in harmony across all parts of the turbine. In contrast. With a HAWT, The designs are well understood and the designs lend well to the creation of a strong active airfoil. I use side furling of my own HAWT type mills to limit output in severe winds. I have seen feathering blades and stall limiting work equally as well on a HAWT. Any issues with danger associated with a HAWT is most likely an outcome of a poor design. Any mechanical design can fail if an aspect is not strong enough for the expected loading. To design a HAWT to have strong mechanical and electrical qualities is more economic and is a better use of resources compared to a VAWT. I have experience with "Skystream" windmills. These are downwind HAWT type, with active stall limit electronic braking for maximum power and rotor speed limiting. I would expect the mechanical aspects of these windmills to approach 10-20 years between servicing. I would expect that my own windmills should last equally as long, with some regular checks for corrosion and lubrication needs. VAWTs and HAWTs have had an equal time to be tested and HAWTs seem to be the commercially viable outcome. I do not doubt that any high speed object that fails is a danger with the bits that may become projectiles. I would not be comfortable with a large VAWT being located close to my home. There is something about a large, rotating mechanical device with all the active airfoil that is located at the perimeter that would worry me, if something was to go wrong. I suspect this debate will continue as long as there is wind. Gordon. become more energy aware |
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| Big Al Newbie Joined: 06/10/2010 Location: United KingdomPosts: 38 |
Gordon-many thanks your input most of which I agree with. If I do go Hawt (and you guys are working hard on me -I feel a bit like a Christian in a Muslim land or vice versa ) my inclination would be a downwinder. here in the UK we have the Proven Ltd. range who's (Proven 7) power curve (which I think is accurate-they've been around a long time) even beats the Skystream from a slightly smaller rotor , and which keeps generating to a higher wind speed. It eventually limits by the blades "coning " which my gut feel tells me is a good way of doing things. But its pricey. I agree with all your points and would only say that the windshear effect with height is also sufferred by Hawts to a lesser extent , and of course downwinders also get a bit of cyclic stress every time the lower blade passes the mast. I also agree that Hawts and Vawts have been tested an equal time and Hawts have prevailed in the main. However it was a "contest" in which Hawts had a flying start in that the aeronautics industry well understood propellors and Hawts were easier to build.Once Hawts got in front they had a vast amount of money spent on them and all the vested interests pushing and spending. It is also true that Vawts use more materials , and are further back in the development race. Never the less although I'm trained as an engineer and Physics beats gut feel I can't help but think that for Big Wind there must be a better way than up to 400 feet diameter , slowly rotating propellors ,that have to be widely spaced ,and that shut down just as the power starts really coming in.Remember the old "Tall Ships" that used to take the grain out of OZ ? They thrived on gales (although they had their limits and had to shorten sail in the worst conditions-but we are talking Cape Horn.) It just "looks " wrong to me although I don't mind the look of them in the landscape in general. For small wind I don't know , but if I can get a slightly taller Vawt up to giving me 80% of the power a Hawt of the same footprint would give( in my gusty site conditions )then the aesthetics , and I think lower noise and inherently stronger design of the Vawt would keep me a Vawter. Whether I can achieve this I don't know . If calculations and other inputs show that I can't I will probably attempt a downwind Hawt. (with the proviso my wind monitoring finds at least 4.8m/s say or preferably 5.0m/s ). As I've stated b4 "I ain't building no watermill 'til I find out if I've got a river " I'm still reading , testing a bit and thinking and inputs like yours are very helpful , even if I do end up a muslim. Big Al Every Day is a school day (even at 67) |
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| neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210 |
This effect is mentioned quite a lot. Has anyone tried using a different section or shape for this area of the mast? Perhaps something like this? .........| .........| ......../.\ ......./...\ .......\.../ (Just ignore the dots - too lazy to set their colour to white). ........\./ .........| .........| Could also reduce the noise effect as well? OK. Feel free to dismiss it as waffle! |
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| Big Al Newbie Joined: 06/10/2010 Location: United KingdomPosts: 38 |
S0027 Foils-Bluffit send private email question on these. Will post where I got onto these asap. Mac has me under his wing to improve my email/posting skills and I will first of all locate where I got onto this foil. (It was a very good article by three French (spit spit ) guys on foil tests , solidity , angle of attack Etc). I will then post the article reference and then where I got the foil profile. Just have to learn how to do it and remember where \I found them (give me a bit of time ). I also have found just the truck axle for you, Buffit, and another truck with so many axles I doubt if the owner would know if you "liberated" one. Will post pics when skills up to speed. Incidentally why is a skilled hacker like yourself using a PLC? Were you given one for free by an archeologist ? What sort of coal do you run it on ? General question--Just how important is the foil profile??? Some guys on this site seem to have achieved amazing results ,just carving a roughly right foil with a chainsaw. My guess is that if I'm to achieve my (maybe impossible) aim of 80% the o/p , say , of a similar footprint Hawt I'm probably going to need the best foil I can get with the smoothest finish possible to delay laminar flow separation. Further question --how well does fibre glass resin adhere to a perpetually flexing wood foil ?? Buffit Might be worth looking at KFm foils . I have no idea how applicable these would be but they may offer some advantages where angle of attack varies and ,in construction. (will also post some stuff on these when I get the skills ). For what its worth neilomacs idea does n't look too crazy to me but at the moment I'm big on words and small on experience (Yeah I Know , typical Pom , and to be fair it was my wife's opinion too ) rgds. Big Al Every Day is a school day (even at 67) |
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| Perry Senior Member Joined: 19/11/2009 Location: Posts: 190 |
Hey Big Al, Don't make it sound so dismal for the modern utility scale turbines. A big rotor way up high is the key to making any real power. As far as shutting down when the wind starts to blow, that's a bit of a stretch. Most capture the energy of the big winds and are only on storm shutdown during only the worst. Any turbine will have to do that. It's not like HAWTS have been studied for longer because of timing or how much money was poured into them. It just became evident early on that there was limited potential in the VAWT concepts. Remember, the first wind mill made was a VAWT. Over time, they were refined into HAWTS. At least that's my opinion. I think I will make one though. They are different and I really just do this for fun, not to make power for my consumption anyway. I aspire to build a downwind turbine as well. Perry |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
[Quote=Big Al]General question--Just how important is the foil profile??? In a word: Extremely. Let's take a look at something that's been around for a bazillion years: a bird's wing. The shape of the wing is usually an undercut airfoil. I'm not going into all the reasons why it works; everybody already knows that and if you don't, Google it. Now, let's switch gears and compare the bird's wing to a sail on a boat. Each of these designs makes possible the use of what's called "apparent wind". As the airfoil, be it wing or sail, is moved through the wind flow by the momentum of either the bird or the boat, it creates an additional flow of air over the foil. This is what is termed "apparent wind" and it allows the foil to do double duty. Not only does the foil have "static" lift, generated by its shape, but other fancy terms like "boundary layer" and Coanda Effect come into play when it is "forced through" an air flow. As the wind is forced over the surface by the apparent forward motion of the bird or boat, the effect on the airfoil causes the "lift" to be more than it would be if not moving. For this reason, in a perfect world (no losses), a sailboat should be able to move across the wind (using apparent wind) at a speed of 8 times the speed of the wind. A drag machine, like a VAWT without a lifting airfoil section or a sail out on a whisker pole "running before the wind" can only go the speed of the wind flow. One can readily see the advantage of being able to cash in on the apparent wind and thus you can now see its importance. Basically, it's all that counts here!! That's why a HAWT spins like the dickens in a stiff breeze and a VAWT hardly exceeds the speed at which you can see individual blades. Now, if your question is more pointed and you are wondering about a "specific" profile, like an Epler profile (glider wings), I don't think it matters all that much. As long as you have something along the lines of a "Clark Y" or to put it more generally, an assymetric-section wing with a flat bottom and a curved top side, feathered back to a thin trailing edge, you're in the money. Hope that answers the question sufficiently. . . . . . 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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| Big Al Newbie Joined: 06/10/2010 Location: United KingdomPosts: 38 |
Anyway , still considering my options . First step for me is to check out I've got at least 4.5 , or hopefully , 5.0M/s wind average. Below that and I don't build and the world loses the first 10Megaw turbine in a shoebox (albeit a shoebox with pinholes in it ) OOps what happened here ignore this-- will have to retype later Big Al Every Day is a school day (even at 67) |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
I would doubt that you have this sort of wind reigime where you live. I know it gets windy in your neck of the woods, but a region with an average this high would be peppered with MW HAWT windmills already, so no room for a VAWT. BTW we don't tend to live where the average wind is this strong. I know a family that does live in a region with winds this strong, and their house is half buried in the hill, and has wind deflectors, etc, to make it liveable. Doorways and windows and eaves are a problem, as well as damage from blown sand and dust. There are no trees as well, as they cannot grow. Their windmill is a "skystream", and they dump 10-20kWh /day. They have problems with tower guy wires. The sand removes the galvanizing, and the wires rust away. Gordon. become more energy aware |
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