View Full Version : darrieus wind trubine blade shape

12-22-2009, 06:16 PM
Anyone know a good forum to ask about wind power stuff ?

I am considering making a small darrieus wind turbine and have a question about the shape of the blades. Everything I can find seems to show symmetrical blade shapes, but I am not sure how you get any lift out of that. I'd like to ask someone who knows.

I've been searching for DIY wind power forums but most of the ones I have found aren't very active, like the last posting was Feb 2009, or is really people talking about commercially purchased wind turbines.

Thought someone here may know where there is an active wind power Do It Yourself forum that I could ask about blade shape for darrieus style wind turbines.


12-22-2009, 06:32 PM
Try a search of this forum as the topic has come up a few times recently. As I recall the only way to go is the standard-prop-blade design on a tower at least 50' tall...

Wikipedia doesn't like the Darrieus -
The Darrieus type is theoretically just as efficient as the propeller type if wind speed is constant, but in practice this efficiency (http://en.wikipedia.org/wiki/Energy_efficiency) is rarely realised due to the physical stresses and limitations imposed by a practical design and wind speed variation. There are also major difficulties in protecting the Darrieus turbine from extreme wind conditions and in making it self-starting.

Some of the other early designs are also not worth messing with for generating power, my fave being the Savonius -

Phillip Allen
12-22-2009, 06:46 PM
there's a lot of wind power right here in the bilge

12-22-2009, 06:55 PM
Symetrical air foils. How about a NACA 0015?


Also, the OtherPower.com site is pretty active. They'll steer you (with good reason) toward horizontal axis machines.


12-22-2009, 07:00 PM
Tylerdurden was up on this kind of stuff.

12-22-2009, 07:07 PM
Efficiency as a pure engineering spec or amps per $ .There can be a lot of difference .

12-22-2009, 07:13 PM
I live in a horseshoe canyon and the way the air masses drop down from the mountains into the valley the air is very turbulent. The HAWT would be zippin around like crazy trying to stay properly positioned. I know I am loosing some efficiency, but it seems appropriate due to the turbulence factor.

Also, I am looking at a pretty small one I'm not trying to power the house by itself.

I'll checkout otherpower.com

12-22-2009, 07:48 PM
This is worth a look .Very simple and efficient in the $ per amp scenario .I'd use nylon fabric for vane material .



12-22-2009, 07:52 PM
Nope. Anybody with a savonius rotor on the cover, talking about generating electricity, is not competent. They are pretty simple though and that makes them useful for water pumping, where you need the high torque.

Try this book instead:


12-22-2009, 07:58 PM
Dan ,the step up is pretty damn simple .The main challenge is limiting overspeeding .

12-22-2009, 08:11 PM
That NACA foil is alright but use half of it...then make the blades flexible so that they twist under stress and de power....you want them to turn at low wind speeds and to maintain a fairly constant speed as the wind increases.

12-22-2009, 08:20 PM
Savonious is good for starting a Darrieus.

12-26-2009, 04:45 AM

12-26-2009, 06:47 AM
The last time I was down in Jacksonville I saw three vertical turbines spinning away in front of a shopping center. At first I thought it was just an installation to catch your eye, the way car dealers are prone to do with balloons and other colorful devices. But these turbines looked just like ones I had been reading about.

I stopped to examine them closer and was surprised at the size and shape of the blades. Three blades were mounted vertically. They were no more than four inches wide and probably 3/8 inch thick. As best as I could tell (they were moving) the foil shape was symmetrical. They did not appear to be angled in or out. I'm still wondering why only three narrow blades on the circular turbine about 33 inches in diameter. Why not four? Why not ten? Why not many closely spaced blades as on a squirrel cage blower?

I believe the turbines are the model shown here: http://www.treehugger.com/files/2008/08/windspire-vertical-wind-turbine-video-clip.php

12-26-2009, 08:01 AM
Some explanation here (http://www.google.com.pk/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/9/9e/Darrieus.jpg&imgrefurl=http://en.wikipedia.org/wiki/Darrieus_wind_turbine&h=451&w=675&sz=55&tbnid=7jjSwRXy7sfGzM:&tbnh=92&tbnw=138&prev=/images%3Fq%3Ddarrieus%2Bwind%2Bturbine&hl=en&usg=___rbY3jzSX1XdQpCKMKGbWyfT_2U=&ei=8gc2S-CMCoLs7AP69ZGhDg&sa=X&oi=image_result&resnum=5&ct=image&ved=0CBoQ9QEwBA);


12-26-2009, 08:54 AM
The twitter pated here in the bilge. no one likes vert generators cause they seem to think its cool to spend 200 times the money for a little whirly gig on the roof.

the lift on a symmetric wing might not be to great but its enough for variable airs. the idea is to generate power no matter the wind speed and we are talking high winds cause they wont work well in low. you want a low lift wing profile so in the higher wind loads you don't develop to much force on the bearings. this is the problem with a sevonious system the huge loads carried on the bearings on the other hand the fella o know out your way with one is sitting down slope of a glacier and his works fine and constantly. IIRC its been in place since 1980 or so. you cant figure efficiency these days cause folks like there illusions of high tech.

12-26-2009, 10:47 AM
Take the illustration above, make a limited swing bearing assembly as in the lead/lag hinges on a helicopter, ake the blades more low speed friendly and slightly flexible for depowering.....no more work, and a helluva lot more better range of energy recovery....and it takes some stress from the overall structure.

Captain Blight
12-26-2009, 01:59 PM
Yeah but doesn't that "stress on the overall structure" come from lift and therefore potential work? I suppose one could install springs on the swash plate so it so that it wouldn't start to work that way until wind loads got above a certain point.

12-26-2009, 02:22 PM
Illusion of high tech? Well, that would be the vertical axis machines. If this is about being cutting edge and designing your own turbine, then by all means, do whatever trips your trigger. But if you want to build a proven design for cheap, out of fairly readily obtainable components, then go here:


..and build one of these, like lots of others have already done:


Savonius rotors are so aerodynamically inefficient that even if you gear them to whatever RPMs you need for the generator (losing even more power in the process) you still waste huge amounts of power. For the same capital outlay and personal effort, you can have a horizontal axis machine that actually works.


12-26-2009, 02:36 PM
We've installed a grid-tied PV setup, which has been trouble free for the last five years.

While our general area is in theory good for small wind power, our place is in a narrow valley with a pronounced venturi effect: the gusts can be stunning, and switch direction very quickly. In winter when the wind picks up dry snow, one can also see wild little eddies and swirls: snow-devils. It's a difficult environment for small windpower devices. With quick wind-shifts and shears, the side-loading on the bearings can be pretty bad.

While the horizontal axis turbines (SkyStream, Bergey, etc.) are less $ per kWh, they also require quite a lot of maintenance. Talking to people who have them, one hears of bearings destroyed and blades breaking loose and flying for considerable distances. When one goes down, it can be a month or more to get the parts and install them. Those who've had good luck with HAWT setups tend to live on the plains where the airflow is closer to laminar. That's also where the huge windfarms are sited.

I've been watching the Vertical-Axis field for a few years, waiting for a breakthrough. Pac-Wind has some interesting designs, now sold by WePower: http://www.wepower.us/products/

Here's a forum with a discussion of Pac-Wind VAWT turbines: http://www.wind-sun.com/ForumVB/showthread.php?t=1493

A "green-alternative" business in downtown Laramie recently installed a grid-tied 1 kW Tangarie Gale VAWT on the roof. Here's a link: http://www.tangarie.com/products/gale_vertical_axis_wind_turbine.php

Last I checked, he hadn't gotten much power out of it because his system requires that the windspeed be not only a certain minimum (6-8 mph?) but that it remain steady for a matter of minutes to kick the inverter on. His downtown rooftop has taller buildings on both sides and there's considerable turbulence: seems pretty obvious that it wouldn't work.

I'm thinking about making him an offer (on the low side) to get the thing for tinkering purposes. It'd be smart to try a small one for durability before laying out for a 5 kW unit.

Interesting thread. You'd think sailors would be pretty keen on wind power, and more knowledgeable than average.

12-26-2009, 03:51 PM
I initially used a Hamilto Ferris towed system...then added a wind generator. I also had strategically located 4 solar panels on the coach roof where normally there would be empty space...I never had a want for more power.

12-26-2009, 07:19 PM
I think most are keen on wind power but i also think folks get stuck in the whole "new Tech" idea. the Savonious is a good example; heres a thing that works made from farm junk and time. its been around for a while but like all vert systems it gets put down cause a propeller in an air stream is better.... kinda.....sorta......if you squint and ignore most of the down sides like the burnout from wind, throwing blades, compound rotating joints so it can keep its nose to, fairly intricate profiles for the blade shapes. and fine bearings.

Savonious machines where not meant to be efficient by the standards of today. they where meant to be cheap and use up farm scrap in Oklahoma where the wind blows all the time day in and day out.
your not getting a high end generator your getting a tiny amount of power for a very long time with little or no maintenance. funny part is they IIRC where never intended to run generators they where intended to run pumps.

but i digress all that gonna happen is an argument as the number crunchers try and justify ten grand in new fangled composite tech and a maint schedule of twice a week as a desirable system over the 40 or 50 designs for scrap built that aren't as cool but are made of stuff getting thrown in the trash every day.

12-26-2009, 07:45 PM
If your winds are fluky, the way I see it you can waste your money on a propeller type or accept the inefficiencies of vertical turbines. That horizontal generator is going to be constantly trying to adjust to changes in wind direction, doing very little for you while it's in hunt mode. A vertical turbine doesn't care which direction the wind is coming from.

12-26-2009, 07:58 PM
We have an old fashioned windmill on the property put ther by my grandfather 75 years ago...it still works...blades have been replaced 3-4 times, twice due to tornadoes....very little paint etc... has run a water pump for all that time, and since about 1950 a car generator for the lights in the barn....battery has been replace a dozen times or so...usually every 6-7 years when things start getting brighter and dimmer with wind speed someone will decide we need a new battery. Critters have always had water...even in winter with freezing temps...

12-26-2009, 09:30 PM
Mother Earth News has several books on both wind and solar power, their
address is,

12-28-2009, 11:14 PM
The old "American Farm"- styled multiblade windmills proved themselves reliable, and the 'high-solidity' rotor generated good starting torque , which suits mechanical waterpumping applications. They generally employ 'lift' rather than 'drag' for power and are not inefficient. A two- or three bladed (horizontal axis propellor) design is more efficient , due to a higher 'tip speed ratio' , ie , less blades imply less drag , and more efficient aerofoils go faster , creating more apparent wind , and now the viscosity of the medium (air) is becomming significant. Bergey windmills coupled to electric submerged waterpumps outperform the multibladed American farm designs , for given swept areas.
Bergey windmills have established a very respectable record/history worldwide , in terms of output , survivability , and duration. They frequently endure 15-20 years without maintenance.

The Savonius mills are primarily a drag-operated mechanism, primitive , effective , inefficient. The Darrieus designs were the subject of much attention in the US during the Carter-era research programs ... as they promised potentially a quick scale rollout , employing extruded/untwisted aluminum blades. They inherently incur vast fatigue , since the blades move thru each other's wake... and aluminum's fatigue properties are soon exceeded.

By the mid 1980s NASA's doting on the Darrieus cost them credibility in the growing commercial wind industry... the US research on verticals tapered off soon thereafter, although the Canadians pursued the field for another 5-10 years , to limited progressive effect.
No commercial-scale wind turbines are of the Darrieus design {1995-2008}. All are horizontal , prop-type.

Vertical-axis turbines [darrieus/savonius, gyromill, H-rotor, etc] Are good at accomodating shifty winds.
Keep in mind that Winds are defined as Horizontal air movement , while Currents are defined as Vertical air movements. Turbulence is complex , vorticity 'unflow'.
No turbines available can harness turbulence.
A tower , costing more than the windmill is oft justified by the improved immunity to turbulence in the lower boundary layer (and increasing speed at elevations).
The Darrieus was designed for surface/grade 'mounting' , allowing easy generator access -- but this locates the design in high shear , high turbulence , low velocity wing regime , further depressing the output of inherently inefficient , high-fatigue machines. Tower-mounted Gyromills with (fatigue-resistant carbon fiber blades Might be feasible , but i don't know if anyone ever figured out the optimal blade angle-of-attack(s) !

Locations where Bergey mills have high attrition , are poor sites for harvesting wind power -- hilltop towers may do better. The servicepeople/engineers who work the California winfarms in the Tehapachee and SanGorgonio passes see losses due to gusting...

Otherpower , Dan Bartmann,Dan Fink , and HughPiggott http://www.scoraigwind.com/ are good DIY sites.

AWEA smallwind : www.awea.org/smallwind/
The “small-wind-home” Yahoo! online forum is designed to facilitate discussion of small-scale energy systems that include wind as a component.
To subscribe, visit http://tech.groups.yahoo.com/group/small-wind-home/

Danish wind ...
http://www.windpower.org/en/ http://www.windpower.org/en/knowledge.html

12-30-2009, 08:46 AM
TMny, that was an excellent post.


12-30-2009, 12:26 PM
Spoke to brother last night....and number 2 nephew was there....I couldn't remember where the old windmill was made and when..it was built in the '20's in Ohio, and it was built with flat wooden blades and strictly as a water pump...the kit for the generator was added in the late '40's or early 50's and still works. It's on a 40 foot tower.