My First Vawt Project

[tjm2000]

Regarding the self starting, The turbine is only a few meters off the ground and surrounded by rocky terrain, so that probably helps it start.

For the next set of blades, I decided to trim the trailing edge slightly to make it possible to wrap fiberglass around. The original blades ended in a sharp point and were very fragile at the trailing edge as the fiberglass did not overlap. I was worried about them delaminating at that point and letting water in.
How much is this likely to affect aerodynamics? From what I have read, an infinitely sharp trailing edge is best so not sure If i have made a big mistake...

[Adriaan Kragten]

The geometry and the aerodynamic characteristics of many airfoils are given in report R443D: "Catalogue of Aerodynamic Characteristics of Airfoils in the Reynolds number range 10^4 - 10^6". This report can be found on my website: www.kdwindturbines.nl at the bottom of the menu KD-reports. All airfoil geometries are given for a chord of 100 mm. The thickness of the tailing edge is given for x = 100 mm.

There is a large difference in thickness. For instance the Gö 623 has a thickness of 0.3 mm for x = 100 mm. The Gö 711 has a thickness of 1,4 mm for x = 100 mm which is rather large (for both see page 3 - 76). For the symmetrical airfoil NACA 0018, two values are given for x = 100 (see page 3-94 table on figure left under). One gives the upper and the lower y-value with respect to the zero line. The smallest y-values are zero so this is a sharp tailing edge. But the other values are + 0.189 and -0.189. This means that the thickness is 2 * 0.189 = 0.378 mm for a chord of 100 mm. So for a chord of 350 mm you will find a thickness of 3.5 * 0.378 = 1.323 mm. If you make the thickness much more than this value, you will introduce some extra drag but I think that a thickness of about 3 mm will give no problems.

[SparWeb]

Not a big deal.  Closing the fiberglass trailing edge is more important than small fractions of drag.
Today your goal is to get a machine operating.  Later you can improve. 

[DamonHD]

"Do it"

THEN

"Do it right"

AND ONLY THEN

"Do it better"


Rgds

Damon

[Mary B]

You can build the trailing edge up with chopped fiberglass and resin and and sand it back to smooth it being careful not to sand thru the fiberglass mat wrapped around the trailing edge profile

[Adriaan Kragten]

"Do it"

THEN

"Do it right"

AND ONLY THEN

"Do it better"


Rgds

Damon

Study all available literature which you can find before you do something. If not, you will make the same mistakes which have been made by others.

Adriaan Kragten

[Bruce S]

"Do it"

THEN

"Do it right"

AND ONLY THEN

"Do it better"


Rgds

Damon

Study all available literature which you can find before you do something. If not, you will make the same mistakes which have been made by others.

Adriaan Kragten

Making a mistake is okay so long as you learn from it. I'm a "Kinesthetic / Kinaesthetic <-sp(s)" learner and some of my best outcomes have been from the mistakes.  Making the same misteak over and over is a different aminal all together.

Bruce S

[tjm2000]

MKII is up! No wind today so have not seen it spinning yet.
This time I changed the L brackets that hold the wings on so I can adjust angle of attack +-10 degrees. It is currently set at 0 degrees.

[DamonHD]

Well done!

Rgds

Damon

[SparWeb]

CONGRATULATIONS
 

Great photo, too, I gotta say.  That is one hell of a site for it.

[MagnetJuice]

That looks RRREALLY nice.

10 m/s wind, where are you?

[Adriaan Kragten]

To my opinion, a blade angle of 0° is the optimum for a H-Darrieus rotor with a symmetrical airfoil. For this angle, you have an angel of attack of about 9° if the blade is at the front side and at the back side of the rotor, if the rotor is spinning with a tip speed ratio of 4.2 and if the wind speed in the rotor plane is reduced up to 2/3 V (see KD 601 figure 2 and table 1 for positions 1 and 7). For these angles, the blade is nowhere stalling, so the average Cd/Cl ratio will be low and the rotor will have a high maximum Cp. If you give the blade a positive blade angle of for instance 5°, the angle of attack will become 4° at the front side and 14° at the back side. So now the blade will stall at the backside. The starting behaviour will also not improve because a blade at the front side will now get a positive torque but a blade at the back side will get a negative torque.

[tjm2000]

So there was some good wind today, around about 10ms.
I have a few issues though, this set of blades seems to be noisier than the old set. There is now a pretty noticeable swooshing sound.
There is also a some minor vibration when running at high speeds, especially when gusty. Im not sure how to balance it better as it would be very difficult to turn the turbine on its side.
Self starting is also hit or miss. Sometimes it will start fine an other times it gets stuck at 10-20 rpm.
I am also having issues with the charge controller. I get an overvoltage alarm which then disconnects the generator completely, which is not good at all. I have emailed the manufacturer to see whats up. When this happens it will run at ~250 rpm , which is well above the 150 rpm maximum I intended and pretty scary to be around.
I have seen up to 900 watts during gusts, which I am pretty happy with.
If the wind gets any stronger I am going to manually shut it down until the charge controller issue is fixed.

[SparWeb]

Those are great early results. 
As I said before, you're on the path to success so what I'm really concerned about is not being ready to harness that success. 
My intuition is that you were told to do something that you should not do with that charge controller.  The likelihood of a disconnect that coincides with strong wind is very high - almost guaranteed - meaning that I hope you can deal with this quickly.

Can you tell me more about your charge controller and why it has any business disconnecting your turbine?
Make, model, how it's connected?

FYI, my system is typical of a battery-charge system, where the output of the generator is rectified from 3-phase AC to DC, then directly connected to the batteries.  For battery charge control I use a controller in diversion mode only.  It will discharge excess energy through a resistor bank but only when the batteries are fully charged and don't need extra.  Shut down is accomplished with a manual switch which shorts the AC leads.  I don't use the shut-down switch very often.

The whole idea of permitting the charge controller to disconnect the generator only works when using solar panels.

The vibration will not go away until you make the arms to the blades more rigid with a diagonal strut.
The noise can come from any moving components, not just blades.  If the strut tubes are round, if the blade tips are rough, if the fittings have bolts sticking out, they all shed a vortex. 
IMO the noise is a low priority.  You don't seem to have a lot of neighbours... just sayin'...

[tjm2000]

I changed some settings on the charge controller and that fixed the disconnection issue. It has been very windy here for the last few days and the turbine has been running non stop. So far so good. I have also done a lot of testing, so here are
some basic numbers:
3ms 50 rpm, no usable power
4ms 65 rpm 50 ish watts
5ms 85 rpm 100w
6ms 100 rpm 225w
7ms 125 rpm 300w
8ms 132 rpm 450w
9ms 148 rpm 620w
10ms 155 rpm 900w
11ms 160 rpm 1020w
12ms 169 rpm 1200w
After this the turbine will brake. Bear in mind this is measured using a cheap handheld anemometer, a bike computer and the readout on the charge controller, so accuracy is not guaranteed. Below 6ms it will not self start, It needs a push to get going. Anything above that and it starts fine.
I am generating more than I can use at the moment, so my garage has been getting pretty warm from the heat of the dump load. I cant decide what to do with the power. I will either get a grid tie inverter or use it to heat hot water to save on gas.

[MattM]

You have winter coming just around the corner so that dumpload heat may be a blessing in a few months.

Styrofoam has interesting harmonics in wind.  I bet your blades ends are bending in & out at those high RPMs.  There has to be some scary howling as the styro foam vibrates.

[SparWeb]

Matt,
I think TJM lives in New Zealand, and has lots of sunny warm days to look forward to, yet. 

TJM,
That's very impressive!  I was pretty sure this was going to turn into a success, and excited to see it, now!
So this is what I meant about preparing for success.  You've got a lot of energy coming in, and there are details you can now focus on that weren't important in the "get started" phase.  What to do with the energy, what to optimize, tuning things like the blade angle, and so on.  I suppose I should harp on the same business about a diagonal brace in the arms.  That can be deferred for a bit but not very long IMO.

Do you have an effective method of stopping the turbine at will?  For the next few months I hope you will be able to bring it to a halt and examine the arm joints and the blade surfaces in detail every few weeks.  Wind turbines run a lot (yours even more so it seems) so the gut-feel you get about bearings and bolts and other mechanical stuff that comes from buildings that don't move and cars that operate for only 1 or 2 hours a day will tell you the wrong things - by a factor of 10 or more.  With a bit of a track record (next year) you will have an excellent idea what are the strong and weak points in your machine (barring any accidents).  Just think of the even more awesome machine you can build with the knowledge you'll have then!

I hope you will be willing to stay and share more details of what you built and how.  There are plenty of folks here who will enjoy it.

[Adriaan Kragten]

Self starting is also hit or miss. Sometimes it will start fine an other times it gets stuck at 10-20 rpm.

This is just in accordance with that what I said earlier. If it is turning only slowly, it is mainly working as a drag machine so the tip speed ratio is low. It needs a strong wind gust during which it speeds up. If this strong wind gust is then followed by low wind speeds, it comes in the region for which the Cq-lambda curve is positive and then it accelerates until it reaches the normal tip speed ratio.

[topspeed]

"Do it"

THEN

"Do it right"

AND ONLY THEN

"Do it better"


Rgds

Damon

Study all available literature which you can find before you do something. If not, you will make the same mistakes which have been made by others.

Adriaan Kragten

I know I should have done that...now I am learning the hard way !

BTW great Project tjm2000 !

My problem has been extreme shaking first....how is/was yours shaking ?

Are the blades really 4,5 kg each ...as I have only 2400 gramms each ?

[tjm2000]

There is some vibration at around 130 rpm. It is not too bad, you can only tell if you put your hand on the tower. It is fine above and below that.
This is not ideal as it sits between 100-130 rpm most of the time and I am not sure how it will hold up long term.
Im not sure if 4.5kg is heavy or light? I does take a while to accelerate so lighter blades would be better. How are your blades constructed?
These blades are pretty strong, it has been up to 250 rpm with no damage to the blade. The tips did start to bend outwards though.
This has been a fun project. I cant decide if I should build a variable pitch Vawt next, or build a horizontal axis machine.
I have some ideas of an arduino/servo motor controlled variable pitch vawt, But on the other hand I just brought Hugh Piggotts recipe book (which I should have done before I started this project) and I would like to try build one of them.

On a different note, has anyone on here brought neo magnets from aliexpress? They claim to be n52 which is almost certainly not true, but the are a lot cheaper than magnets in New Zealand. 50x25x12.5 magnets are about 25usd each here, and aliexpress is a whole lot cheaper.
Or does anyone know of a website that will ship magnets to me? most wont ship to NZ
[/quote]

I know I should have done that...now I am learning the hard way !

BTW great Project tjm2000 !

My problem has been extreme shaking first....how is/was yours shaking ?

Are the blades really 4,5 kg each ...as I have only 2400 gramms each ?
[/quote]

[topspeed]

There is some vibration at around 130 rpm. It is not too bad, you can only tell if you put your hand on the tower. It is fine above and below that.
This is not ideal as it sits between 100-130 rpm most of the time and I am not sure how it will hold up long term.
Im not sure if 4.5kg is heavy or light? I does take a while to accelerate so lighter blades would be better. How are your blades constructed?
These blades are pretty strong, it has been up to 250 rpm with no damage to the blade. The tips did start to bend outwards though.
This has been a fun project. I cant decide if I should build a variable pitch Vawt next, or build a horizontal axis machine.
I have some ideas of an arduino/servo motor controlled variable pitch vawt, But on the other hand I just brought Hugh Piggotts recipe book (which I should have done before I started this project) and I would like to try build one of them.

On a different note, has anyone on here brought neo magnets from aliexpress? They claim to be n52 which is almost certainly not true, but the are a lot cheaper than magnets in New Zealand. 50x25x12.5 magnets are about 25usd each here, and aliexpress is a whole lot cheaper.
Or does anyone know of a website that will ship magnets to me? most wont ship to NZ

My construction is a regular wooden wing structure...ribs and spars and covered with 1 mm plywood.

I have a short cutting lever in the system which brings it to sudden stop instantly. How do you stop your system ?

Seems that you and I both run the blades against the Coriolis effect..thus loosing some momentum.

[bigrockcandymountain]

I would try CMS magnetics in the usa.  They shipped to canada, so maybe they would to New Zealand.

I went with them because I wanted countersunk magnets, and they were the only place where you could select N or S countersunk.  I needed half N and half S.

They were good quality and well packaged. 

[tjm2000]

There is some vibration at around 130 rpm. It is not too bad, you can only tell if you put your hand on the tower. It is fine above and below that.
This is not ideal as it sits between 100-130 rpm most of the time and I am not sure how it will hold up long term.
Im not sure if 4.5kg is heavy or light? I does take a while to accelerate so lighter blades would be better. How are your blades constructed?
These blades are pretty strong, it has been up to 250 rpm with no damage to the blade. The tips did start to bend outwards though.
This has been a fun project. I cant decide if I should build a variable pitch Vawt next, or build a horizontal axis machine.
I have some ideas of an arduino/servo motor controlled variable pitch vawt, But on the other hand I just brought Hugh Piggotts recipe book (which I should have done before I started this project) and I would like to try build one of them.

On a different note, has anyone on here brought neo magnets from aliexpress? They claim to be n52 which is almost certainly not true, but the are a lot cheaper than magnets in New Zealand. 50x25x12.5 magnets are about 25usd each here, and aliexpress is a whole lot cheaper.
Or does anyone know of a website that will ship magnets to me? most wont ship to NZ

My construction is a regular wooden wing structure...ribs and spars and covered with 1 mm plywood.

I have a short cutting lever in the system which brings it to sudden stop instantly. How do you stop your system ?

Seems that you and I both run the blades against the Coriolis effect..thus loosing some momentum.

I also have a shorting switch, which works very well to stop the turbine.

I definitely don’t have the patience to build wooden wings haha. I have built a few wooden rc glider kits, they take a huge amount of work to complete.

Here is a short video of mine running

[tjm2000]

Turns out I cant post videos. sorry

[topspeed]

Turns out I cant post videos. sorry

Try put them into youtube.

Wooden wings I mastered when bulding small wooden fighters in the sport called "Air Combat".

https://www.youtube.com/watch?v=56Gl6Tj3m8o ( nowadays they are all foamies )

Today a lasercutting system shortens the time...I'll try that next.

[Mary B]

Turns out I cant post videos. sorry

You need a few more posts here before links will work unless a mod takes pity on you and makes an exception.

[SparWeb]

TJM,
Send me a private message and I can set it up for you.
Rather than try to remember what the threshold number is, I'll just write in the link if you tell me what it is.

[tjm2000]

If you search 'DIY 1kw Darrieus VAWT' in youtube, it should show up.
Does anyone on here have any experience building the troposkein (eggbeater) style vawts? Or even any links to research about them? Info on them is hard to come by. From what I have found so far, they are not as efficient as the h rotor style, but by far the most successful commercial vertical turbines used this design  (flowind in the 80's)
I think the look amazing and shouldn't be too difficult to build with my method of blade construction.
 

[tjm2000]

Also Sparweb, you will be happy to know it now has a diagonal brace. There is more noise but it is definitely stiffer.

[topspeed]

If you search 'DIY 1kw Darrieus VAWT' in youtube, it should show up.
Does anyone on here have any experience building the troposkein (eggbeater) style vawts? Or even any links to research about them? Info on them is hard to come by. From what I have found so far, they are not as efficient as the h rotor style, but by far the most successful commercial vertical turbines used this design  (flowind in the 80's)
I think the look amazing and shouldn't be too difficult to build with my method of blade construction.

Real cool.


https://www.youtube.com/watch?v=Alf6EOTmlHM

System is soundless.

[SparWeb]

Let me see if I can find some old reports from Sandia Labs.  They studied them in detail in the 70's and 80's.

[SparWeb]

A lot of WT research you will find these days will have serious flaws and look like this:

https://www.researchgate.net/publication/235235830_Experimental_Results_of_a_Vertical_Axis_Wind_Turbine

On the face it looks technical and methodical, but it's useless.  The authors do not honestly face the horrible wall effects in either their CFD model or the tunnel test.  Sure, they say it's there, but then they present test & model results as if there's any point in looking at it.

The only truly valid sources of WT testing information I've been able to rely on are Delft and Sandia/NREL.  They post results from real machines and they let you know where the warts are.

[SparWeb]

They keep changing the databases.  All my 5-year-old bookmarks don't work.

Try this:
https://www.semanticscholar.org/paper/Aerodynamic-performance-of-a-5-metre-diameter-with-Sheldahl-Klimas/3518171a4dca7e92356b27968170e4027b14f041?p2df

which leads to things like this:
https://prod-ng.sandia.gov/techlib-noauth/access-control.cgi/1980/800179.pdf

Also, you may have luck with this:
https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/SAND800179.xhtml

...and this:
http://nrel-primo.hosted.exlibrisgroup.com/primo_library/libweb/action/search.do?mode=Advanced&ct=AdvancedSearch&vid=Pubs&dscnt=0&dstmp=1600032067479