Deployed my mini VAWT

[ffoegw]

Woke up at 3:00am and heard the wind gusting.

Immediately got up and deployed my mini VAWT.

I am very pleased / excited with the results. I estimate it reached rpms just over 100 but was unable to measure.

If this is a different technology to anything previously done with a vawt then I think it needs a name.

How about "ffoeg vawt"  or "ffoegw turbine". Any suggestions?

I am going to post the photo's here but also have some video.

Not certain how to put video up in the forum or even if it can be done.

Any advice appreciated.

These photos were taken in the dark with a flash I also took some video as soon as it got light.

The fence which I strapped the vawt to is about 10ft away from the bottom of a 3 story house.

Probably the worse place for a windmill, it is very turbulent.

If I can leave work early I might take it out somewhere more in the open.

Regards

Geoff Wright

Here are some photo's:

If you want to see the video send an email request to ffowgw@hotmail.com or please explain how I can put it on the forum.

Regards

Geoff

[ffoegw]

Spelled my email wrong:

If you want to see the video send an email request to ffoegw@hotmail.com or please explain how I can put it on the forum.

Regards

Geoff

[Slingshot]

Geoff,

I can't tell for sure from your photos, but are the vanes hinged to somehow reduce drag when they come upwind?

[ffoegw]

Slingshot,

I prefer to call them rigid sails rather than vanes or blades.

Yes they are hinged at the front and attached with elastic at the back.

I have not concerned myself with drag coming upwind. I have reckoned that any drag on one side is balanced by the other.

Instead like a sailboat sailing into the wind there is forward (rotational) power obtained by allowing the wind to move the sail against the load provided by the elastic.

The elastic is extended to some amount for almost all the 360 degrees of rotation.

If you see the elastic extended then rotational power (pull) is happening on the spoke.

I am now convinced to go the next step and build something on the rear end of a truck using 4 x 8 sheets for the rigid sails and some very strong bungee.

I had to wait for a calm period this morning before I was willing to get close enough to take it down.

The video is very impressive.

Maybe try and upload like a photo and see what happens.

Regards

Geoff

[ffoegw]

Gonna put my video here:

Hope this works.

Geoff

[zap]

Very nice video and an impressive VAWT!  Congrats!

Any idea of the wind speed at the time?  Judging from the tree in the background and the wind sound on the mic I'd say gusts in the 10-15mph range?

[TomW]

Geoff;

You can upload a video to your files area then just post a link to it. They will not display in the page like a photo.

Cheers.

TomW

[ffoegw]

No idea of the wind speed but think you are about right.

Estimate from the video that RPM is reaching just over 100.

What do you think?

Also when I go to my post above all I see is a red x and no video.

I guess some can see it and not others.

Geoff

[ffoegw]

Thanks Tomw.

Here is the ling to my files:

Have fun

http://www.fieldlines.com/user/ffoegw/files

The one with the avi extension is the video.

Regards

Geoff

[coldspot]

Pretty cool vid

Just have to click it to watch it.

[windstuffnow]

  Thats a different but interesting machine!  Nice video... I counted 9 turns on the video and it runs for 9 seconds which comes out to about 60 rpm.   What wind speed was it running in?  Very interesting...

.

[ffoegw]

Windstuff,

If its running at 60 rpm and the sails are each 1ft x 1ft and the spokes are 3ft do you still need the windspeed to calculate HP?

Or can you still calculate it with one of those fancy looking formula's you have on your site?

Geoff

[ffoegw]

The weather link which follows shows that at 7:00am (a little after sunrise) at the Toronto Airport the wind was 41kph.

The Toronto Airport is about 1 hr east of Georgetown, Ontario where I live.

http://www.theweathernetwork.com/weather/24h/pages/YYZ.htm?CAON0258

Geoff

[ffoegw]

From examining the video footage I have determined that centrifugal forces are having an effect on where I expected each sail should be through the entire 360 degree rotation.

I now plan to build a new set of sails, spending time to carefully balance them so that centrifugal forces should have little effect.

Excited to see what happens.

Geoff

[Stonebrain]

Hey geof,

Nice vawt,what's funny about vawts is that they never look the same,

unlike hawts.

I like the sail idea.

Typical of a sail is that it's not rigid.

But off course call it as you want.

Why not try real sails of real cloth,triangular with an elastique inthe down-behind corner.

The good thing about non rigid lol sails is that they

take the form of an airfoil in the pressure of wind.Just have to find an elastique

of the right strength and length.

Might be more performant than a rigid lol sail,but that's just a speculation

of mine.

I look forward to the ffoegw2

cheers,

jaap

[vawtman]

Good job Geoff,I coulnt figure out how you where planning this.What would you estimate the start wind speed is?Ive flown a lot of different blades but none like that.Good luck and I think you must really have this bug bad to get up at 3am to fly it.

[hvirtane]

Really, really nice.

I hope that you will

put up a small generator

with it to see, how much

power you can get out of it.

By the way. There is a drawing

for a quite similar machine

from 1970's by an Irish company:

Low Energy Systems

3 Larkfield Gardens

Dublin 6

Ireland

As far as I know the design

should be available

on the AT Library CD about

wind energy.

I some time ago told

about that drawing

to one friend of mine

hoping that he would

like to build it.

Maybe your example would

put him at work...

- Hannu

[Stonebrain]

Geoff,another remark

"I now plan to build a new set of sails, spending time to carefully balance them so that centrifugal forces should have little effect."

With this conception,there will be allways some inbalance,because the "sails"

move outward downwind and inward upwind.The heavier the sails are and the

longer the amplitude of their movement,the bigger will be the inbalance.

Another argument for real sails who can be really light.

I feel I have to build a sailvawt too...one day.

cheers,

Stone  

[windstuffnow]

  Hi Geoff

    You would need a way to get a torque reading from the machine while it was running...

torque x rpm / 5252 = hp x 746 = watts

    You can sort of guess by using the area of one flap ( 1 sq ft ) in a 40 mph wind to find the pressure against it minus the speed in which it was traveling away from the wind, you would also need to assume a loaded speed...

Something like...

.00492 x area x ( windspeed - rotor speed )^2 x Cd = Force on the flap in pounds.

Windspeed in mph

rotor speed in mph

So if we loaded the machine to run at 30 rpm in a 40mph wind...

Pi of the diameter ( 6ft ) = 18.84 ft x 30 rpm = 565 ft/min x 60 = 33,929 ft/hr / 5280 = 6.42 mph

.00492 x 1 x ( 40 - 6.42 )^2 x 1.2 = 6.65 lbs of force on the wing

6. 65 x 3ft arm = 19.97 ft lbs
   
30. rpm x 19.97 ft lbs / 5252 = .11 hp x 746 = 85 watts
    
    

As you can see in the formula as the rotor speed reaches the wind speed there is no power being extracted.   As well this doesn't include the drag that is taking away from the overall output on the upwind side.  To find the drag on the upwind side you can use the same formula but you have to add the windspeed and rotor speed since its traveling into the wind ( 40mph + 6.4 ).  The cd would be much less on the upwind side depending on the actual area exposed to the wind.  Just guessing maybe a cd of .4 with the wing closed fairly well and the drag of the tubes.  So you could calculate the losses...

.00492 x 1 x ( 40 + 6.4)^2 x .4 = .09 lbs x 3ft = .27 ft/lbs x 30 / 5252 = .0015 x 746 = 1.16 watts.  

It's probably a little higher than that but it gives you a basic idea.  You'd have to measure the area of the tubes as well and the cd of a tube is I believe 1.2 as well.  

Looking at the drag coefficients of different shapes a rectangular flat shape has a cd of 1.16 and if it has an aspect ratio of 50 to 1 it will go up to a cd of 2 and a tube has a cd of .99.. thats from the Marks handbood.   A half tube or cylinder cut in half has a cd of 2.4 and thats about as high as it gets.

Hope that helps...

.

   

[ffoegw]

Thanks for all the math windstuff.

It's gonna take me a while to get all this stuff in my head though.

Geoff

[ffoegw]

Hello Stone,

"With this conception,there will be allways some inbalance,because the "sails"

move outward downwind and inward upwind."

What I am noticing though is that when the sail should be moving inward upwind it's not.

I think it's because of the centrifugal force thats throwing it outward.

I'm also thinking that though the centrifugal force is playing a part the rotational pull is still mostly obtained even against this seemingly opposite force.

Hope I explained that right.

Geoff

[electrondady1]

congratulations on your proof of concept proto type.  it works well!

[ffoegw]

Thanks Hannu,

If anyone can find the drawing I sure would like to see it.

Geoff

[ffoegw]

Hello Windstuff,

If I decide to supersize the mini vawt the area and the diameter would change.

So with 4 x 8 sheets extended 12ft out.

Pi of the diameter ( 12ft ) = 37.69 ft x 30 rpm = 1130 ft/min x 60 = 67,858 ft/hr / 5280 = 12.85 mph

.00492 x (4x8) x ( 40 - 12.85 )^2 x 1.2 = 139.24 lbs of force on the wing

139. 24 x 6ft arm = 835.45 ft lbs
     
30. rpm x 835.45 ft lbs / 5252 = 4.77 hp x 746 = 3560 watts
    
    

Not bad for a couple of 4x8 sheets and bungee cords.

Does that make the expense and effort to supersize viable?

Your formula's are extremely usefull for making those kinds of decisions.

If I added two more spokes would that double the output?

 7000 watts.

If I added and extra 4x8 sail on every one of those 4 spokes would it double again?

 14000 watts

If this is correct then 4x8 panels are relatively cheap considering the potential increase.

In an earlier post I had asked the question about how much horse power one of the large tall sailing ships might obtain from the wind.

The person who answered said about 8000 horse power x 746 = 6 megawatts

Reaching those levels now becomes an enormous structural enterprise which I think could eventually be reached with some innovation.

Drag

I had never worried :-( about drag when considering how this design might work simply because if the wing or tube causes drag on the upwind side the same wing and tubes should cause the equivalent in usable power on the downwind side.

It should cancel out.

If I am mistaken please explain.

Thanks again for your help.

Geoff

[windstuffnow]

  Geoff, That formula is a very general outlook on whats really going on.   You also have to consider the torque that is created starts small (wing toward the front) peaks at 90 degrees and falls off as it rotates to the back of the turbine.  The formula would represent peak force on the arm at the 90 degree point.  So the outcome or performance would be considerably lower.   You can install an arm of 12 inches long and a spring scale and measure the torque at various angles of rotation to get an idea of where the torque starts, peaks and ends.  Record your results, add all the data points together then divide by the number of data points... this will give you an average which can be worked into a percentage.   This would be a locked rotor test which would give you higher readings than you would see in normal operations.  A drag based machine will extract the most energy at a Tsr of .33, the highest torque value will be in the locked rotor test and at a Tsr of 1 will be the point where it will no longer extract energy.  

  As to the question of increasing output by adding blades... There is only a certain amount of energy in a given exposed area of the turbine.  Typically the only way to increase that extraction is to increase the efficiency of extraction.  The disruption of air flow from another blade or multiple blades can cause defeating results from a given design, more likely you will notice a decrease in output.  Sometimes the gains, if any, are so small that the addition or complexity of the addition doesn't complement the cost.  Its best to take  the simplest form and work toward improving efficiency with small changes.  With any new design its best to build, test, rebuild it and keep rebuilding it until you get the results you want or determine its time to move on to another design.   As you move forward the answers will become clear but the questions will multiply...

.

[SparWeb]

You could directly measure torque by putting a "prony brake" on the shaft of your turbine.  Take two spring scales, and hook them to the ends of a belt (any belt will do, the one from my pants worked well when I needed one).  Take video while you're doing this so that you can capture, torque and RPM simultaneously.  The difference in the readings on the spring scales, times the radius of the shaft equals torque.  The torque you apply is variable, depending on how hard you pull, so it takes a few tries to get a steady state torque while the RPM's stay constant, too.

Nice work.  My first VAWT was less elegant.

[ffoegw]

Windstuff,

Thanks for your great recommendation.

Will one of those cheap fish weighing scales work?

Also as regards adding more blades or sails I noticed that on sailboats the sq footage of sail seems to play an important role in speed.

Also noticed on many sailboats that not only are more than one sail added they also often seem to overlap.

http://www.edgewoodyc.org/h28/engines.htm

Some of the older tallships had multiple examples of this.

I think with vawt technology the power is more likely to be reaped from the wind as torq whereas in the hawt technology it comes as rpm.

Slowly moving very large amounts of weight as opposed to very quickly moving small amounts of weight.

Like comparing an 18 wheeler truck to a ferrari.

I'm thinking that engineers to date have been trying to make a VAWT behave like a HAWT without a great deal of success.

It's very difficult to make that 18 wheeler do 200mph in 10 seconds from a standng start.

Instead we should be making that 18 wheeler carry some weight.

My not always so humble opinion using some not always very good analogies.

Regards

Geoff

[windstuffnow]

  The fish scales are a bit stiff for that type of stuff.   I've tried a couple of them and it's hard getting a good reading from them.   I ended up purchasing some spring scales from arbor scientific ( http://www.arborsci.com ), they read in grams or newtons and you have to convert to lbs.  Considerably better getting readings from them when your working with small motors and low power turbines.  I forget what they cost, somewhere in the range of 12 bux each.

  Either way you look at it torque or speed it comes in to the batteries as electric.  Hawt's have low torque at higher speeds and Vawt's have high torque at low speeds... either way 1 hp = 1 hp no matter how you get it.

  On the sailboat issue, they usually run in a straight line and the sails don't overlap frequently as do the VAWT's running in circles.  As well, the sails are creating lift to move the boat forward similar to an Hawt or darrieus Vawt.  Your capturing primarily from drag...

.

[hvirtane]

It seems to be the case that the plan is

still available.

If you'll use with 'google' the search:

'Vertical Axis Sail Windmill Plans'

you will find probably find somebody  

selling the plan.

Please see also these links below.

The second link is for the plan

as discussed:

http://www.icajapan.org/virtualtoure/98PeruDIE.html

http://villageearth.org/atnetwork/atsourcebook/chapters/wind.htm#Vertical%20Axis%20Sail%20Windmill%2
0Plans

http://www.ambergriscaye.com/BzLibrary/trust410.html

http://www.michaelbradley.info/lowtech/windmotor.html

If you cannot get the plan from the Net,

please send to me an email.

- Hannu

[ffoegw]

Windstuff,

Thanks for all your help and advice.

I am now building a second model with several what I hope are going to be improvements.

One of the changes I will make is to the sails.

Instead of a rigid panel I will make a flexible one which pulls into an airfoil shape much like a real sail boat.

The formula's provided above seemed to be designed for a rigid area.

Is there some more mathematics or even a rule of thumb to calculate or guess at what the increase should be using aerodynamics on the area of the sail instead of drag?

I have been playing with the flash animation at the end of the page on this link which gives a very good demonstration of how wind direction effect the forces on the sail, centerboard and direction of the sailboat.

here it is:

http://www.seed.slb.com/en/scictr/watch/sailing/index.htm

Regards

Geoff

[Akos]

How about this solution?

Seems he perfected your design...

http://www.youtube.com/watch?v=qg7hxaPAjnw