Trying to find what my vawt is doing

[thefinis]

Is the blade swept area on a vawt measured from the blade's outside edge or from the leading edge where we measure the chord length from?

I had a 2 blade vawt up and changed it to a 3 blade but my tip speed ratio to wind speed seems to be higher am I crazy? I used a blade vawtman had designed for a 2 blade with 4 foot arms. Thinking I knew how to increase the tsr by lowering blade solidarity I made the arms 6 foot but it never seemed to fly right especially in high winds and had a tsr of around 2 in low winds. Wanting to go to a 3 blade design I added one more blade of the same size increasing my blade area to swept area ratio which should have lowered the tsr but instead tsr went up to about 3. I understand that with more wing area I should be making more torque but more rpms too? Is running this unloaded causing some of my strange results?

Any suggestions on how to measure the wind speed from a handheld anemometer in a turblent area? My readings tend to change a lot over 10 to 30 secs and all I have been able to do is make a good guess at an average wind for calculations from the readings.

Can an old generator not an alt from a tractor run through the regulator from the same tractor to a low battery be used to measure power output? If the regulator is left off isn't it like shorting it out? The ones on some of my old tractors would pull start and charge with a dead battery or even no battery.

Finis

[Norm]

   Hardly anyone would know what the blades

look like a picture would be nice....

   Now it's true that in the case of a hawt

when you increase the blade area to swept area

ratio you usually get more torque less speed,

but I have the idea that in the case of a vawt,

things figure out a little differently....maybe

maybe not...

   To get the average windspeed make an anemometer

with 2 ft.arms a heavy disk of particle board for

the hub....very good bearings ....make a device

a little piece of wire on one arm that clicks

on each revolution even in a good average windspeed

of 20mph you should be able to count

the number of clicks per minute.

             ( :>) Norm.    

               

[thefinis]

Are you saying that the one you suggest will even out the gusts? I have a fine little german made handheld anemometer that is very sensitive works fine. I need to know if there are any tricks to evening out the reading. I may have readings of from 2 mph to 6 mph in the span of a minute or less.

Vawts seem to not follow the hawts as well as one might expect.

stole your pic vawtman

Finis

[Norm]

  Mighty fine looking piece of machinery...Finis !

  I've never had a real good handheld anemometer,

the one I have doesn't register until 7mph.

  So I know of no tricks or tips for yours...

  I built one like the Dans easter egg anemometer.

only with larger aluminum cones and 1 foot arms

the particle board hub is a kind of flywheel to

smooth out the gust of from 2-6mph in a minute or

less (in my case too)....put a magnet and a

reed switch hooked up to a bike digital speedometer

9 function that gives you your average speed...

             ( :>) Norm.

born and bred in Illinois 25 years,

last 50 years in NE Ohio.

 

[vawtman]

Hello Finis

 I would just add the blade width to your rotor length thats your radius square that x 3.14 x 8ft(height)and that the swept area.So roughly 6.5x6.5x3.14x8=swept areaft.

 Be back in a minute gotta run.

[vawtman]

Im back

 What rpms are you seeing with that diameter?

 How do you stop the beast if you wanted to?Lotta freakin torque.

 Hows your test tower responding to 3 blades?

 I would think the additional lift created by the 3rd blade could cause increased tsr values, not sure but a good thing.

 If you know the weight of the machine and rpms along with windspeed theres a torque calculation cant think of it maybe others will chime in.

 Now you see why im struggling with the gen.A good thing.

 Has far has aneometer goes im going to wait till i butcher some trees and get the tower done.My current location is worse than yours the wind can go south to north in a blink of the eye but the turbine is happy and doesnt care.

 Lets keep plugin along and thanks for your efforts Finis

[thefinis]

Outside edge of blade is what I have been using making it 13 ft diameter.

I am seeing 2.5 to 3.4 on tsr so I am missing my averaging on wind speed when I take the rpms. I can't do them at the same time and the wind is so erratic right now during the day. There is around a 20% drop in a 5 mph wind inside of the turbine. I am seeing around 3 rpm at 1 mph  13 rpm at 3 mph 20+ rpm at 5 mph and 25 at 6 mph but it is just an average after many readings. I have only had one good chance since they went up to see what they were doing in around 15 mph winds but by the time I moved the tractor out of throw range and tightened the guy lines the storm front had passed and the wind dropped.

To stop it in low winds less than 5 I climb a ladder and slow it by grabbing the arms near the hub till it slows. If I have near 5 mph I drive a pickup under it and stand on the truck and grab the arms near the hub till it slows. If I have very good winds I stand back and watch cause it will knock you off the truck. Even in light winds the arms out near the edge and blades can hurt you if they hit you. Prony brake did not work on vertical shaft for brake hp measurement.

Tower is fine but for so short a tower 11 ft I thought that 3+ ft in the ground with a sack of sackcrete poured with four guys at top would be fine. The 2 blade would shake the ground and make cracks out about 3 ft from the base. The 3 blade is doing better but in the 15 mph wind (guessing) it was shaking a little and showed that the tower is not based well enough. It needs to be deeper and more concrete plus the rachet ties streach with loading so for anything but testing the guys need to be cable.

Hey you are running out of summer better get the next model up or at least some kind of shack around the base cause cold weather is coming. I would go with a small gen if I had to just to see how it does and maybe make a little free heat.

Finis

[vawtman]

Finis i noticed when inside the turbine at high rpms all you could feel was little pulses Even though outer winds where around 20.We need to harness that.

 I noticed something this summer during the 4th of july fireworks i light off.

 There was no wind at the surface but at about 30ft the smoke rolled away.I live on a nice little hill after viewing the surrounding landscape after 15yrs living here.

 Need strong towers to contain this energy.I think

 

[thefinis]

While one nice thing about vawts is usually little or no tower the H rotor works well on a tower. You could go with your original tower design only taller twin highline poles and use a 4" well casing in the middle hinged and pinned to raise and lower the turbine if you wanted to get up to 30 ft. Size of turbine would show how many guys are needed. I made C brackets out of all thread and a piece of channel iron for mounts for my bearings. The top one had a plate welded on that fit over the top of the pipe so it could not slip down. I think that the drive shaft could run down the pipe if you want the genny on the ground.

Finis

[vawtman]

Finis thats a clever idea never thought of that.I have the launchpad 12x20 slab and would like 4 towers steel since i can get it free from a job im doing so far got enough for 1 leg.Lotsa welding needed.Trying to design without guy wires.Could still use that method. Awesome thanks

[Countryboy]

vawtman,

  That is the formula for calculating the volume of a cylinder.  That does not give you swept area of a VAWT.  It just tells you how many cubic feet of air are contained inside the path of the VAWT blades.

  A 13 foot diameter VAWT, with 8 foot tall airfoils, has a swept area of 52 square feet.  6.5 X 8 = 52.

  For comparison, an 8 foot diameter HAWT has a swept area of 50 square feet.

HAWT A=3.14 X r^2

VAWT A = r X h

[vawtman]

Hello Countryboy

 I checked with wind4regs rotor caculator and it uses DxH=104.

[Countryboy]

104 is not swept area.  Swept area is the square footage of wind that power can be extracted from.  A VAWT doesn't extract power all the time during the 360 degrees of rotation.  It only extracts power during 180 degrees, and the VAWT uses the power gained in the first 180 degrees of movement to move the other 180 degrees.

Yes, there is 104 square feet of wind hitting the VAWT.  However, the VAWT extracts power from 52 sq feet, and the other 52 sq feet adds wind resistance.

This is why VAWTS tend to be so inefficient compared to HAWTS.  The power obtainable with this VAWT is the power in the 52 sq feet, minus the wind resistance of the other 52 sq feet.

A VAWT improves its efficiency greatly if you build a cowl or air dam which prevents the wind from hitting one side of the VAWT.  However, this limits the wind directions the VAWT can extract power from.

[vawtman]

I could see that for the sav not the darrius type.

 If you block off part you will still have drag and it would need direction to the wind taking away one of the many advantages these have.

[windstuffnow]

  The frontal area would be height x width ( or diameter ) for any VAWT either drag or lift.  The difference would be in how the output is calculated.  Drag machines only use the downwind side to extract power and the upwind blade tends to steal some of that power.   Lift machines utilize primarily the upwind side although all the blades are producing a small portion of lift during the rotation.  On a strictly lift machine you could say your only extracting from 2/3 of the area exposed to the wind and on a drag machine your collecting slightly less than 1/2.

.

[vawtman]

Hello Ed and Thanks for your expertise.

 Just a curiosity here

 If the blades tsr is 2 wouldnt that mean that the blades are creating lift throughout the entire rotation?Thus 3/3

[windstuffnow]

  If the blades are running 2x faster than the wind there is some lift on the downwind side but very little.   Think of it this way...  it very much depends on the angle of the blade at any given point in the rotation with the relation of wind direction.   If the blade is running 2x faster than the wind say in a 20mph wind the blades are running 40 mph, the upwind sees 60 mph and the downwind sees only 20 so the lift generated from each wing will be considerably different at any given point.  For the most part the upwind blade is giving you the most power the others are reduced.   So it's probably 2/3's at best.   Most darrieus type turbines have their greatest efficiency at a tsr of 4 or more.

.

[vawtman]

Thanks again Ed

 But from my experience there comes a point where the blades dont know whats going on.Im not making this up.When the blades look to be going backwards everything is swept.

 Your turbine was designed to get the best of both worlds tsr less than 1 but much better than the sav and at that time no blowing apart.

 Its tough to figure whats going on at the furl point.The wider chords and more blades seem to set this point.I believe you can build these to max out at certain rpm and did that with the little guy.

 The poster has seen this also.

 Who would have thought awhile back to let these run free in winds greater than 45mph.

 Even to get them to start was a major hurdle.And was for me early on. My best day is when the rotor 2x2 with shelf brackets bent in a 10mph wind before i could get back to the shop 30ft away.

 Im havin fun!

 Interesting how Solwind and the Chiness people have added blades to the so called hrotors.

 Do you still think im crazy?If so i understand.

 Ive posted this many times before and maybe its time to move on.

[windstuffnow]

  I never said you were crazy vawt man, we're tinkerer's we're all a bit eccentric at times.  Some might call it crazy or something else but come on... some of the greatest minds that brought us to where we are today were probably called every name in the book.   Hey we can fly, watch moving pictures through the air and now beamed from space.   Our job as eccentrics has been made much easier by those wacko's before us.  

  The self regulation is the cause of disrupting the airflow through the blades after a certain speed, as the windspeed goes up the efficiency goes down.   Mine works similar because of the fat wing but I wouldn't call it self regulating as it will still exceed 500 rpm in a stiff wind.  It starts out in the range of Betz and looses efficiency as the winds pick up.   In a 30 mph wind the wing efficiency is down to around 35% and in winds around 40 mph its down in the 25% range... In a 50 mph wind it's doing less than a savonius in regular winds.  The dampening effect is limiting the shaft output but still puts a heck of a load on the tower.  In high winds I've let it run with the alternator shorted but it still wants to go 300+ rpm and lately I've simply locked the rotor during a storm.   The little roof top unit has pushed as much as 450 watts into my battery bank although most of the time it runs happily along at 2-10 amps.   I really need to get it off the roof and up in the air, its actually in the middle of a multitude of obstructions including trees shrubs and buildings.   As far as continuous charging it beats the heck out of my 500 watt turbine.  I'd like to put a data logger on the two but I'd bet I get more watt/hours from the little one than the larger one on the tower, it's a little work horse.

.

[thefinis]

Hey Ed I see a drop in wind speed inside the turbine even in low wind conditions(power is extracted by slowing the wind duh) and with the power formula that means a big drop in power for the downwind side. Lift may be generated all along the path on a lift machine but drag is too and it is the L/D ratio at each point that determines net power effect. Not quite the point you were making but close and for your figures shouldn't it be with the wind and against the wind. <Grin> I know picky picky. Does the lenz have a wind speed increase or decrease in the center or is there a way to tell. When you first started with them I seem to remember that it was creating a vortex in the middle.

Here is a page on a pretty helical vawt that they are making in London.

http://www.quietrevolution.co.uk/qr5.htm  I need to try and make mine artsy as wind turbines are quickly lossing the novelty appeal and some are protesting the big ones as unsightly now.

Finis

[vawtman]

No ED you never called me crazy i was just referring to past comments and was directed at myself.

 Your website was the first i visited maybe a year ago and became hooked on this it must be in my blood.Same has at work when theres a problem i dont give up but find a solution.

 Im glad that you see the self regulation aspect of these.If the effeciency goes down who cares at least it doesnt become a bomb like others beleive.

 What do you think will happen when you increase height and diameter has planned.

 I know the tower loads trust me If anyone thinks they can put an 8ft or whatever lift based vawt on the same tower has the other ones think twice.

 Im leaning in the direction with the 16 using fluid controls and gridding.

 If anyone can bust betz you can GIVE HER

 I need to do some hacking around the yard myself.

 The other tinkerer Thanks Ed

[windstuffnow]

  Your right, the calculations can be quite elaborate on the Darrieus type machines as the wing angle and aparant wind is changing all the time.

  The original Lenz used a venturi effect creating a low pressure zone behind the turbine.   This was to increase windspeed through the wings and drum thus increasing lift.  When I was building experimental and ultralight aircraft I designed a wing for very slow speed lift.   The plane would lift 900 lbs off the ground, flying, at 24 mph.   Great for low speeds but draggy as can be at higher speeds.  Basically a fat wing, single surface open bottom wing.   I decided to make a clumbsy copy of that design for the wind turbines since most of the energy collected was in the range of 0 to 25 mph.  The highest lift in the lowest winds.   Similar wing shapes are used in STOL aircraft with a few additions such as slats and drooped ailerons.   Even large jets change the shape of the wing when taking off and landing.  Its the only way they can get reasonable lift at slow speeds ( 60 tons of steel, aluminum, people and cargo ).

Anyway, I was getting in the range of 38% efficiency from the venturi model with smaller Lenz wings but couldn't seem to break that mark and was at a stand still.   I tried a few models with larger wings and removed the drum and things started to click.   I'm still running at or around 42% in winds under 20 mph, not where I want to be but it's quite reasonable for a VAWT.  It will match the Betz in winds less than 10mph, I just need to shift the efficiency a bit to the higher side.

.

[vawtman]

Finis Has you know inside mine and yours with the wider diameter but 3 bladed there is a point where all you can feel is little pulses probably unreadable with a aneometer.

[thefinis]

"It will match the Betz in winds less than 10mph,"

It doesn't get better than that congrats on a job done right. What is the biggest Lenz built so far? Not sure that the self limiting factor is a bad thing. For most trying to design for the power from 40+ mph wind is like designing for a 100 year flood. You try and design to survive it but you build for the normal range. Arrrggghh I am going to have to try a set of Lenz wings from your design but first my fabric airfoils.

You know sometimes I get a little jealous of other folks knowledge/experience. I envy you the fact that you have all that previous experience with wings and aircraft. Thanks for sharing some of it with the rest of us. There are so many here who do the same it does my heart good. I use your wind page a bunch just to double check my old memory.

I am getting close to doing what I have experience in, turning energy into work. If I can make an old combine run which takes one motor and turns its output into a myrid of energy forms and operations with some varying and others staying constant then I can do the wind to electric. To quote a current campaign slogan for Texas governor by Kinky Friedman "How hard can it be". Ah Texas politics where we ALWAYS take it to a whole new level.

Finis