Hawts and Vawts
 

One or two points from one not greatly endowed with wind power knowledge. Bob McGovern's two posts on small wind power seemed full of good sense to me. I have n't been very impressed with much else I've read (Hugh Piggott also seems pretty good) in an subject area which seems to be fashionable and therefore full of charlatans out to make a quick buck .As B Mcg says of the many small wind power systems "..what a poor lot they are.." .I would extend this description to 90% of whats written on small wind systems.

To get to my points, I have a sneaky preference for Vawts somewhat modified by B McG's comments which seemed pretty sensible to me. However Vawts definitely win on aesthetics. Bob mentions the downwind blades are in the wind shadow of the upwind blade. Presumably this point would not be true for the most aesthetic version with helical blades ?

Secondly due to 1/the possibility of at least two bearings to the Vawt rotor , with a third easily added centrally.
2/ Some balance of rotor stresses by using helical blades and extending these above and below the top and bottom bearings.
3/ Potentially stronger blades supported at at least two points for a vawt.
4/ A much lower TSR

..I feel instinctively a Vawt should be able to stand much higher operating wind speeds than a Hawt and therefore be able to extract larger amounts of power from high wind speeds at exactly the time a Hawt has to furl to avoid damage. Less maintenance should be an additional bonus.

Surely these points must be significant in narrowing the gap between Hawts and Vawts. Any comments anyone. Big Al.

From the research I've done, HAWTs win hands down. VAWTs have been tried many times in the past and have all either failed or not been able to compete with HAWT.

If you're dead set on a VAWT, the Lenz2 is a reasonably effective unit you can build yourself. Lenz2 turbine

Patrick , many thanks your response and ref to Lenz. With all due respects to Lenz this looks to be a drag turbine and a "science fair project " 63 Watts indeed !! If I ever get round to it (too many projects !!) I would build a helix bladed lift Vawt and would n't think it worth the effort unless I could get 2-5 KWhr a day.
This might sound pie in the sky but I have the metal working machines to build this and a lucky bonus in that I've just completed a tree house for the grandkids with a lookout tower extending to 10 metres above ground level. Climbing to the top of the lookout tower I noted I have nothing between the top of the tower and the Gargunnock hills 5 miles away to the south west which is where the prevailing wind comes from in Scotland.
I don't dispute your and Bob McG's point hawts win but the point is , is it better to have a reasonably quiet and attractive vawt producing say 200W @ 6 m/s wind speed or an ugly, potentially noisy and more dangerous (more RPM ) Hawt producing say 600W at 6m/s but which has to shut down as soon as the wind reaches real power producing speeds? I don't know and am attempting to find out just what the gap between Helically bladed Vawts and Hawts is ; given the points on blade strength and potential operation in higher wind speeds for Vawts (lower TSR for a given wind speed plus extra bearings and better blade support I made in my post. Rgds Big Al.

Hi, Al. This guy claims his carbon fiber blades will withstand up to 90 mph winds. He doesn't furl the generator because he says in higher winds you will really start to make the power. Home Page

If you do make a VAWT, please keep us posted. Sounds like an interesting project.

Have always liked the look of savonius rotors VAWTs, problems exist with bearings, one bearing at the bottom needs to be pretty big to take the side loading, and if you have a bearing at the top it needs to be stayed, unless you are using a substantial axis. Then you will need a gear drive, where in a horizontal axis you can put the blade right on the generator shaft. Blade design is interesting, because you cannot have washout the way you do with aircraft style blades, so you wont get start up until the wind is cranking a bit higher than for horizontal blades. Efficiency will be lower, but they sure look nice.

Wood blades will withstand high wind speeds (lots of aircraft use them) if well engineered, carve your own, I will happily look over your virtual shoulder for design.

Done a lot of reading since my last post (H.Piggott, and the back shed website-full of useful info.These antipodeans mean bizness !!-plus a lot of other websites).
In a maze of projects have at least gone as far as purchasing a Wind Predictor which I should have mounted on my 10 metre look-out tower this week. Things will then go quiet while I measure wind speeds for a month or two-at my age I don't build anything until I have checked out the potential !!
Am struck by the similarities between wind power and metal working (another hobby of mine ) in that the Americans get things done and are very unselfish in publishing helpful info. , the Aussies and Kiwis even more so , and in the UK we now seem to rely on commercial ventures with most inputs coming from people out to make a quick buck , and with very little practical experience . Hugh Piggott , and the Home Workshop site are among the few noble exceptions.
The Backshed site I found amazing , full of good advice , and full of projects producing real power using all the technology tricks you could imagine. However they seem to love Hawts much more than Vawts. I do think however that in the UK where we have less land than the "colonials" and where neighbours and the Nimby syndrome is so strong that Vawts may be the way to go . My reasons are:-

1. Vawts have a better defined footprint , in theory should n't need such high towers, and with a lower TSR (bad )have less chance of impaling a neighbour with an absconding blade(.Mainly good)

2. From my reading so far I'm not convinced that Hawt performance is that much better for the same horizontal footprint. Admittedly Vawts need a higher vertical profile to achieve this-however we do have in the UK as much air above us as the US, OZ and NZ.

3.Most of the objections to Vawts seem to be based on older technology and don't seem so applicable to helically bladed Vawts.

4. The BIG problem of effective electrical generation at lower speeds surely does nt apply to Vawts where the space under the bottom bearing can be used to make a large radius generator , albeit expensive on magnets, WITHOUT blocking the wind path , this space could also be used (altho I doubt I'm clever enuff ) for variable pitching and for centrifugally swithching in of extra, speed-limiting, coils . This again gets rid of a host of problems and is almost impossible to do with Hawts due to windpath blocking..

5.Hawts seem to have a long history of small wind DIY development , most of the new money seems to be going into more advanced Vawts.

Anyway , enuff of my prejudiced ramblings , got a Power predictor to install. Watch this space . While my PW logs data I'll keep reading and don't be surprised if my next post is a diatribe against Vawts !!!

Big Al

A thought about starting a Vertical Axis mach popped into my pumpkin while reading your thread. If the generator you use will also motor, you could use a sail switch to start it spinning.
I will bet you 20 pushups (honor system) that a horizontal machine will be the most efficient.

My brother has been working on some VAWT designs. He is doing it as a test project, not a working design. He does not report large amounts of power available, but his VAWT is on the ground so he can test different blades, so efficiency is low. However he has been trying a lot of different designs and is improving efficiency and buildability as he goes.

Caleb Engineering, LLC - Home

The latest thing he is working on is a Kline-Fogleman airfoil. This is significant because one could use easily use the wonder material of the future to build airfoils: coroplast.

Kline Fogleman airfoil - Wikipedia, the free encyclopedia

http://upload.wikimedia.org/wikipedi...criptions3.jpg

In particular KFm-3 looks like an easy to build airfoil with coroplast. There could be some heat applied to the coroplast to bend it as well (as in KFm-5A), to try for an even more efficient foil. Bending would also add stiffness to the airfoil.

Skyl4rk-Thanks your input. I'm in UK where getting suitable airfoils difficult compared with US and OZ/NZ and even then most of what is available is Hawt directed rather than Vawt.Two points of which Caleb ? may be unaware
1/ There is on web what I thought a very good thesis on small wind by Claude Guillaume , Sandra Algazze and Emmanuel Duc on home wind . They favour Vawts and recommend S2027 airfoil which they measure as giving significantly increased O/P over the other airfoils tested-they are also very good on solidity and aspect ratio.
2/ The backshed website is full of really useful information and technical ingenuity to increase O/P . This is mostly Hawt directed but a lot of it particularly on the generating and control side is applicable to Vawts.

I had n't come across KFm foils or coroplast so thanks for the reference.

My initial thoughts on airfoils of the S2027 type was to build it out of 2 thick aluminium strips Rivetted or welded together ) and machine it to the required profile. Altho I have metal working facilities I'm not sure they would easily cope with modifying the profile for a helical blade or the subsequent bending.This is also an expensive approach. My second thought was to use my Hydraulic press and a die to bend thinner sheet to most of the required profile and bonding or riveting this to wood to make up the rest of the profile . Again I suspect not easy. The backshed guys don't seem to worry too much about profile and still get amazing amounts of power but to get Vawts up near Hawt performance I think I'll need to use every trick in the book ( and even Hawts can hardly turn their nose up at a 16% increase in power by using a simpler and more efficient airfoil )

I shall be measuring and logging wind speeds for the next two or three months but will try and move my thoughts along and maybe even do a few experiments over the winter. An initial thought is to make the bottom blade support , a thinnish discus shape (low drag ) with weak spring loaded vanes popping out of this at rest to give a savonius starting effect , the vanes retracting automatically(to cut drag) under wind pressure as the rotor accelerates. I also believe this bottom plate would allow the mounting of a variable pitching mechanism which could do a lot to improve efficiency altho making this simple and reliable is a challenge. However some of the the revered Jacobs turbines had variable pitching on Hawts (much more difficult ) and are reputed to have been reliable.

While I'm logging wind don't expect any great technical progress but will post anything I find of interest. Rgds. Big Al

Skyl4rk Have had a look at caleb's site. V. interesting as a potential problem for me is manufacture/procurement of suitable Vawt airfoils (aerofoils to me ).
coroplast looks interesting and speaking from a viewpoint of vast inexperience (i.e none) I would have thought lining mould with thin foil (baking foil ? grease proof paper ? ) or spraying with the right compound (WD40 ? ) would ease extraction problem.
His technique of using foam laminates also looks good. He seemed a bit disappointed at lack of rotational speed using these but IMHO the Savonius type (Lenz ?) foils he has incorporated are giving tremendous drag . I like the idea of a Savonius type starter but think it has to be decoupled from the rotor (tapered track ball ratchet ?) once the lift rotor has started. Even better i feel are automatically retracting vanes as per my last post as they would have less effect on wind profiles thro the turbine--unless the Savonius starter can be designed to contribute to a more effective wind profile which ourweighs the drag it contributes once lift forces give a TSR >1.
A final thought -I hate building things I have to spend hours maintaining and would need to convince myself that coroplast or plastic foam would stay the course. How ever at worst they give good ways to produce blades for testing.
My internet skills are limited and I was n't clever enuff to work out how to contact Caleb directly. I will continue to post anything of general interest on ecorenovator but if you want to pass my email alanfrost43@btinternet.com to Caleb it my be easier if he contacts me directly.
Rgds. Big Al

Nibs-I'm pretty ancient-- 5 push-ups might be more appropriate. I don't think I can build a Vawt to be more efficient than a Hawt altho based purely on instinct I 'm not sure its impossible given the technical ingenuity of some of the newer designs , and some of the down to earth ingenuity of those guys on the backshed web site. All I'm hoping is that it will be possible to narrow the gap to the point where the other advantages of vawts make them worthwhile. Was n't aware of sail switches but not fond of the idea of giving back hard won electron flow to motor the rotor up to speed. Reminds me of those poor people who invested in lousy hawts and vawts only to find they generated negative amounts of electricity-there are loads of those stories on the web !! Thanks your offer to peer over my shoulder-I really need help with the aerodynamics , the mechanics and electrics I'm probably OK on. For next 3 months or so I will be logging wind speeds -I ain't building a watermill until I've checked I've got a river !!-so expect a period of hibernation. Rgds.

This page has some good info on VAWTs: Darrieus wind turbine analysis - Home

Why all the interest in exotic materials for the foils? It is really hard to beat wood, except for abrasion resistance. When I made wooden aircraft props, we used to offer a self adhesive (peel off backing) thin stainless steel leading edge cover, took care of much of the abrasion problem.
You can laminate wood into any curved shape & carve the foil using hand tools. Wood in tension is almost indestructible, and will flex to within 90% of its modulus of elasticity an infinite number of times, I do not think there is another material which can make that claim. We used to laminate 1/8" maple for our aircraft props and use a solid piece of 1/4 sawn fir for our wind blades, both worked very well.
Cheers, Tony

Nibs -I don't know if you've read the Daox post on the jet turbine windmill but from that article I see the germ of an idea to save me push-ups. That is if I can get a " series B funding of $25M " It also occurs to me ,again from that post that maybe I'm more of a disrupting Ecorenovator than a lurking one. Come to think of it I'm not sure I 've had my series A funding yet-no wonder I'm always doing push-ups !!
Suppose you'll claim the jet turbine job as a horizontal as even a persistent b----d like me can't see a way of making it work vertically. (hey wait a minute -isn't that pole its on vertical )
Take the point on wood, I tend to have enthusiasm at the build stage and less for the maintenance stage and ally seemed a better prospect but I'll look at wood again.

Now I see that the first post has shown up, I will leave this one because it is a bit different.
MOD feel free to delete if you think it redundant.
Darn, a couple of nights ago I wrote a few paras on this but must not have pushed the post button.
The main thrust of my unsent post was - Why all the interest in exotic blade materials?
Wood with the exception of abrasion resistance is an almost perfect material. Wind turbine and wooden aircraft blades will obviously withstand wind speeds of hurricane force, they can be laminated into desired shapes and carved with hand tools. We used to sell a thin self adhesive stainless steel leading edge cover for our aircraft props, but abrasion was never a problem for our turbine blades.
Buckminster Fuller claimed that wood can be flexed to within 90% of its modulus of elasticity an infinite number of times without failing. There may be another material that equals this, I do not know of it. Wood is tremendously strong in tension, the fastening usually breaks before the wood fails. The greatest amount of stress on high speed turbine blades is radial. The big guys are different, they are not spinning fast so their main load is wind pressure.

Vertical axis blades pass through the wind shadow of the other blades and of the axis column, as they rotate, so I think the downwind argument is a bit thin. I have read that a downwind horizontal machine can set up harmonic vibrations as the blades pass the tower, under some conditions. I have no experience with downwind machines, so cannot comment.

It is late I must go and get rested up in case (not likely) for the pushups Al thinks he will win.

Al, if you get round one financing, I shall expect a handsome retainer and consulting contract, as the expert from afar.

Of course , Provided I've enough strength left from push-ups to write a cheque. I have some hope now that Flodesign have received $35M they will ,in the spirit of true ecorenovators , pass on the spare $10M to me for the ongoing development of my Megawatt Vawt in a shoebox.
A short technical input-I've been interested to observe that sod's law which states among other things " any newly erected turbine will immediately suffer no wind conditions " also applies to anenometers . My newly erested wind monitoring power predictor is just sitting looking at me.Al.

Hey Big Al, I was driving in Jacksonville today when I saw these 3 VAWTs at the side of the road. I thought they were just eye-catchers to get people to come into the nearby car dealership, but a Google search found the linked article saying they are real power generators. They were spinning like crazy and I would say the wind was about 10 mph. Wind: Eye-Catching Alternative Energy on Atlantic Blvd | Firstcoastnews.com | Top Stories Video: http://www.firstcoastnews.com/video/...id=51741642001

Patrick. Was aware of these windspires but many thanks for input. For some reason they and Mariah power have a bad reputation. One of the gurus Paul Gipe, wrote a very sarky article about them. Looking at them my only comment would be they look a bit flimsy. Unless the central axis is pretty strong I would n't see them standing up to strong winds. If they were spinning fast in 10mph wind they ought to be reasonable generators given a good design and I don't entirely understand why Gipe was so critical unless torque is very poor, altho this would n't alter the "flimsy" argument.
I'm hoping my several MegaW Vawt in a shoe box will be so efficient that it can be totally enclosed in the shoe box except for one (or at most two ) pinhole (s) on each side to allow limited amounts of wind through. In which case Nibs will have to do so many push-ups we won't need turbines. We'll just wire him up to generate a significant portion of the worlds' energy needs. Big Al

Well supposedly it costs about $10,000 per turbine and the output is about 2000 kWh/yr. At my rate of 12.6 cents/kWr that's a savings of $252/yr. 10,000/252 = 40 years for them to pay for themselves. So maybe that's Gipe's complaint. But it's not cost-effective for me cuz I won't be here in 40 years.

Hey Big Al, how's that VAWT coming along? You got me hooked on the idea and now I want to build one (a very simple one, that is). :-) Have you seen the discussion on vawts.net?

Are you talking about this project:

5 Watts For 25 Dollars - windgen.org discussion

It is coming along nicely.

Not particularly. Mine will probably just be a "wind spinner," unless it looks like it has a lot of potential, then I might try to hook an alternator to it.

I have a HAWT that I got on Ebay that I will use to generate power. It would be interesting to do a side-by-side comparison, though. Hmmmm . . . .

Patrick , things are moving. I should now have 30+ days of windlogging data and will post details of this asap so we know what sort of wind regime I have. meanwhile I've been reading sites and booke to get up to speed on whats necessary. I don't know what the etiquette is between various wind sites but have been reading a lot of the backshed.com posts and posting with my big mouth there quite a bit ( this site was down ).

Result of this so far I have 3 possibilities depending partly on what my wind logger throws up

1 The unexciting route is to build (I hope competently ) a good hawt > this route would practically guarantee the o/p I'm looking for but may give me planning problems , and neither myself or the neighbours would be aesthetically as pleased as with a Vawt. That matters to me.This route does n't sound very exciting and won't add anything to anyones experience and knowledge. Cleverer folk than I have done it all before and its too easy.I am also anti hawt for I think a good reason-I don't like maintenance. Spin a bicycle wheel held in both hands by the spindle/axle at say a low speed 10 rpm. and feel what it does when you try to change the plane of rotation. hawts have to do this all the while especially in the average domestic wind regime ,and altho they can be designed to stand this stress you are better off without it. The excellent Danish wind power site on big wind (excellent except" like the oil lobby" it only admits to hawts existing ) if read between the lines is paranoid about bearings. I'm not surprised-- they ought to be. This week I went to the UK Renewables conference and exhibition in Glasgow. What's in the really big Hawt nacelles is mind blowing in the sense its all unnecessary and very, very expensive . And have you read some of the blade replacement figures for big Hawts ? Anyone think replacing a blade on a 150m tower is cheap or safe ?

2. Slightly more exciting is to aim for the same o/p from a fairly standard Vawt, helically bladed and with sufficient solidity to be self starting . I think this may be possible but is difficult and may take a better man than me. However this is my fallback route.

3. The exciting route , having read up the Peter Allan Sharp and Bayly-Kentfield patents is a revolutionary state of the art Vawt . This is potentially a long route with much experimentation and maybe disappointment at the end. My opinion is that if I was n't 67 this would be the route to go and given time I don't think would end in disappointment , but I am 67.

4. I have a couple of revolutionary (maybe ) ideas of my own regarding Vawt design. Before shouting my mouth off , over the next 2-3 months I want to model these and see if I think they are possible. I also have a couple of revolutionary ideas (maybe ) on energy storage for home builders but again I would like a bit more time before deciding on these.

Route 3 has thrown a spanner in the works in that I have been watching for a while progress on the Cranfield college Vawt. I have a highish regard for Cranfield. This has now surfaced as Aerogenerator X and involves Arup, Windpower , and Rolls Royce and a lot of other high power names. If you google Aerogenerator X I'll think you'll find enough data there which if its half true (I believe it--- they've wind tunnel tested a 15KW version and if Cranfield are good at one thing its aeronautics-I don't see Rolls royce, Arup and some of the other names involved failing to exercise due diligence ) will consign Big Hawts to one of technology's dead ends. Just imagine an Aerogenerator X at 20MW with another 10MW unit concentrically inside it and maybe even more inside that . At 3 rpm the blade replacement guys should be out of business and if a say 30MW unit is possible (again at 3 rpm these things on land could be interwoven which kills Hawt o/p but can enhance vawt o/P if done cleverly ( "drafting" ) and you could MAYBE envisage several GW windfarms on 1% of the land required for Hawt windfarms without the fleets of large trucks, cranes and repair bills and without the Hawt associated environmental concerns. I would n't see this happening before 2025 but it could end up being the way we go. Then we'd really be getting green. ( I don't know , as a new boy , how green this site is but we need renewables IMHO and we also need nuclear -this is a no-brainer-interesting channel 4 evening of programs this week on "what the greens got wrong " .At the moment with Hawts getting bigger and bigger the cost per KW hour paradoxically goes up and up. Its getting like the oil lobby situation.

To come down to earth one things for sure, mine's going to be a vawt. If my progress seems slow that's OK by me. I always have several projects ongoing ( at the moment I' m renovating a Fritz-Werner H-V mill , two engraving machines and a tool and cutter grinder. On top of that my Grandkids generate a lot of projects for them. I'm also trying to mend a shaper for a lady in Poland (by email) and get a new telescope into commission.

The Vawt by the way is supposed to be just part of a larger project (before it took over my life !! ) for a heatpump system using my garden as a heat source and I'll be using A.C.Hackers excellent thread and work on this site for that.

(groan) However did I find time to go to work for a living !! By the way I have been following avidly the vawts discussion--its a site with very open minds IMO.

Edit addition. One of the things that came out of the Glasgow trip was an input from the Proven guys who make one of the best Hawts in my opinion and who did n't have an axe to grind as they were n't involved in Zeeland, is that the Zeeland tests were crap. I always suspected something very fishy in those figures. The Proven engineer made a point in saying it very loud in front of the Skystream stand who were next door . He did n't get any takers.

Every Day is a Schoolday.

Rgds. Big Al

Couple of comments on VAWTs. First, none of the currently available units actually produce usable amounts of power, and typically have a payback of decades to centuries. The blades in a VAWT are stressed as beams, and need lots of support at high RPMS or they will break just like an overloaded beam. HAWT blades are stress along their length, along the radius of the rotor, and are much stronger in that direction. And third, a VAWT is much harder to put on a tall tower where the powerful winds are located. Putting any kind of turbine at ground level or near ground is not getting it up where the winds are powerful. No matter what kind of turbine, it needs to be up high!!!!

a couple of points to past posts,
re: helix,it doesn't matter what shape of blade is downwind, it is still down wind, or in the shadow of the blade in front of it. With a lift blade though you get some power from the down wind side depending on the tsr and profile you use.
you can find a lot of usefull info on builds at this site for vawts and mills in general: www dot vawts dot net this is where 5-25 and the caleb I know lives

Progress ??? Of a sort
 

Well, the plan for the several MW Vawt in a shoebox has hit a serious problem. I've now got 3 months of logged data and what it tells me is I have n't got enuff wind. About 1 m/s average. This I don't fully understand as from my windlogger in a straight line with no obstructions in the way are 3 or 4 large commercial Hawts. Were those guys crazy too ?? Only thing I can think of is that so far we have had a freakily cold winter with most wind from the North and NE which it is not where it is supposed to come from. Its supposed to come from the SW which would suit my little wind logger and the big commercial Hawts a lot better. So I shall continue logging ( raising my logger another few feet and possibly improving its siting slightly )-I ain't giving up yet.

Will try and get some photos posted of my site and maybe one of the knowlegeable guys can tell me why both me and presumably the guys who paid to put the monster ones on the hill are n't getting the wind we should.

Incidentally , driving around the area I have come across 2 Proven mills (I think from looking at them from about 40 yds ) . One in a valley on about a 15M tower which seemed to be defying the law of conservation of energy , spinning fast on what seemed to me a pretty windless evening.

I saw another one near Cumbernauld last week ( about 6 metres diameter on about a 11M tower) which seemed to be spinning a lot faster than it had any right to , although it was on a small hill and there was some wind.

Anyway rgds for now. Got a data logger to move and some photos to take.

Big Als Update
 

Been a while since I posted progress on the "megawatt in a shoebox project". Well things are moving. You might remember that the vast quantities of power generated were part of a larger project to put in a heat pump a la A.C.Hacker and I certainly did n't envisage paying a power provider to power my pumps. Meanwhile I have n't been letting the sheep cuisine grow under my feet , no sir.

Firstly I now own two excavators for putting in the ground loop. A small towable digger (a Powerfab procured in Ireland where they still go for reasonable prices ) which is in excellent nick and will do the digging. Secondly a Thwaites Tusker , much more powerful , but this needs restoring. Why two ? Well I got fed up with the rapid escalation of prices on Ebay during the last few hours and bid on two and won them both. When my 4 yr. old grandson asked why two? My reply was "Well , you want one don't you " He certainly did and the 18 month old also thinks "diggas " are the best thing since chocolate biscuits. The granddaughters are almost as keen.

Raised the Power predictor another couple of meters to about 14 meters and got improved figures but still short of a 5 meter/sec average , so I'm going higher. I have a 70 feet birch in the garden (a magnificent specimen and almost the highest thing around.) Plan is to fell a couple of 35 feet straight trees growing on wasteland just over my garden fence , splice these together to give me a 60 foot "telegraph pole" erect these about 7 feet from the base of the birch and construct a working platform between the birch and the erected pole. From this I will erect a third straight and smaller tree to carry , initially the Power Predictor and then my Vawt. This third pole will be raised and lowered from the platform to ensure easy maintenance and experimentation on the Vawt.

Sounds crazy but I think I can do this safely and as a bonus the view from the top of the birch is breathtaking. The birch has stood for decades resisting all winds and the small wind resistance of my "telegraph pole" , guyed and connected to the birch should give me a solid platform at about 60 feet allowing for splicing overlaps, and some " pole in the hole".

A 20 foot pole erected from the platform should give me a turbine at about 80 feet, 27 meters, above ground level , and higher than most things around . If I don't get an average of 5 m/sec up there there's something seriously wrong with the UK wind charts. Also as I will erect my pole on the far side of the birch , any tubine will be largely screened from the view of all residents which will aid planning permission.

Timescales ? I have to paint the house this autumn but hope to get the pole up by the end October and start measuring wind at this height. The megawatt in a shoebox will be designed over the winter, and I'll dig in the groundloop , next spring/ early summer.

Meanwhile its a race between me and aerogenerator X ( only Rolls Royce , Arup partners and others backing this one, so I should be favourite) to produce a megawatt Vawt. Warning to any new readers-the megawatt may have to be slightly scaled back to 5 Kw per day but I only need enough to drive my pumps.

Cheers for now.

Al, have you considered a height of over 70m? Most turbines and farms near me have a tower height of 70-110m. And that's for HAWT turbines rated at 7m/s wind for 1.5MW. Even reviewing a few VAWT designs (mostly Savonius) show that at 5m/s a 4MW design barely makes 0.5MW.

I'm not detracting from making a savonius or darrius VAWT, but I feel you need to get sufficiently above the ground layer into a clean air stream. Even a building 1 mile away will affect the ground layer at your site.

I've a real neat book I picked up for an Alternative Energies class that emphasizes wind energy (something my state has lots of).
Wind Energy Explained
Theory, Design and Application.

It has more math about capturing wind energy than you would want to read or learn. BUT the few equations it does have are what the major wind turbine producers use for building and siting wind farms; in that it would be useful to read it and apply the data to your site and see what kind of turbine design and size would work, if any.

Thanks for input. I've got to go higher and have a plan which won't give me 70m but should give me 30m at which I would expect to see some improvement. My turbine was planned as part of a bigger project which is to install a ground loop heat pump (I can manage about 40m length in trenches ). That won't heat the house totally but should make a very useful contribution. The turbine output I envisaged as driving the pumps so I'm hoping to get enough output for this.
In the UK because we don't have the average plot size and acres of space that the US, oz, and New Zealand have our planning laws are tighter , altho I must admit that I have n't really investigated this yet. This means a 70 metre tower might be difficult (I live in a residential area , altho on the very edge of town. I intend to spend the minimum possible as I'm 68 and payback time is a consideration.
A vawt is more aesthetically appealing and I have some ideas that may help with output. I always have a lot of projects on the go and am quite happy to proceed at a slowish pace but things are moving. I bought a couple of diggers this summer (one goer to do the digging and a beefier one for restoration and then digging if my ground proves as rocky as I expect ). I certainly think boreholes would be difficult (we're pretty regulated on these too ).
To get enough o/p to drive the heat pump system , I'm going to have to use every trick I can with a vawt at 30m and am considering wind lensing (aesthetically ok again) , one or two ideas for efficient self starting, and a few other ideas which I will need to test with models first. I had hoped to do this last winter but other projects keep intruding. I'm pretty relaxed about this however as they are all interesting and I'm not in a race.

On my side I have an extensive metal working facility (some of which generates projects which keep intruding ) , and I think a cheap and easy way to achieve 30 metres altho this will not put the turbine in a clean airstream ,BUT it will be higher than most things around it.

I'm also watching the progress of Aerogenerator X , which you can find if you google it, as this seems a good vawt approach to higher power at a lower altitude, but this is largely unproven . Some of the companies backing it are no slouches so there may be something in it.

Rgds. and thanks for interest