Designing, Building and Testing a Darivonius VAWT

[MagnetJuice]

I downloaded and installed SMATH. It looks a bit too complex for me.

I thought that there would be an equation similar to the one for a HAWT, where you plug in the turbine dimensions or the swept area to get an approximation of output power.

It would have been nice to have that information but I don't really need it. I think that the best way to find out the output of the turbine will be to build and test one. I will continue with the construction.

Ed

[SparWeb]

It would have been nice to have that information but I don't really need it.

I don't doubt the sincerity with which you say that, but I'm still disappointed to read it.

Imagine what would have happened if the Wright brothers had taken that attitude.

I think that the best way to find out the output of the turbine will be to build and test one.

Because you're giving up the chance to try hundreds of combinations in the time it would take to build one.  And the insight that doing the math would give you.

I know that some people say "do the math" as a way to insult others or make them quiet.  I wish people didn't have it in for mathematics that way.  Math is beautiful, practical and creative.
But I don't know a better way to say exactly that and mean the opposite: if I encourage you to work it out mathematically, not only will it give you a chance to build your first machine better, but also to improve it more quickly if you want to build a second.

[MagnetJuice]

SparWeb, I truly appreciate your encouragement and enthusiasm for the benefits that the SMATH software could bring into this project. I agree with you that working out some problems mathematically could be very helpful. If I could quickly learn to use that software, I definitely would try it. The problem is that I am unfamiliar with that program and could take months for me to learn to use it.

Some people are naturally good at some things and some are good at others. For example, one of my hobbies is designing and building high fidelity speakers. I work with a program where I plug some numbers (the Thiele/Small parameters) into a speaker design program, and the program tells me the volume and the dimensions needed to build an enclosure for a particular woofer. I can do that in less than 2 minutes. A program like that could take someone else months to learn but it is very easy for me because I have been doing it for over 20 years.

I would love to learn to use SMATH, but for now, building a design platform for testing different blades and configurations seem to be my best choice.

Ed

[SparWeb]

I think you're smarter than you portray yourself.

A piece of paper would do just as well, but I'll stop there.

[MagnetJuice]

I think you're smarter than you portray yourself.

OK, I take your word for it 

I am not that smart, I just have some talents. With the technological advances of the last 20 years, it is easy to pick-up knowledge if we are willing to learn.

Here is a picture of some of the parts that I plan to use to build the turbine. The large sprockets I will use to build the alternator. They are 9.62 inches in diameter. The 16 magnets are 2 x 1 x ½ N42 Neos.

[electrondady1]

those sprockets look ideal for mag rotors. what thickness?

[Lange1975]

Here are three images of H-Darrieus Rotors. How would the shape and positioning of the airfoils affect their behavior during operation?

(Attachment Link) (Attachment Link) (Attachment Link)

I know it is a difficult question, if it was easy I would ask in another website. 

Thanks,

Ed

Hi Ed,

Is this question already solved? I'm working also on a VAWT an Darrieus H type with GOE-222 airfoils just as in picture B and C.
I have seen working ones with this airfoil and the foils are placed in the circumference as in the picture below. So I think the answer is B.


Regards Sander

[MagnetJuice]

those sprockets look ideal for mag rotors. what thickness?

Those sprockets are .283 (7.2 mm) thick. What I really like about them is that they are machined flat like a mirror.

I also have two others that are larger. They are .46 inches thick (11.7 mm) and 14.5 inches (368 mm) in diameter. I plan to use those for a big alternator. Here is a picture of the bigger ones:


Ed

[MagnetJuice]

Is this question already solved? I'm working also on a VAWT an Darrieus H type with GOE-222 airfoils just as in picture B and C.

Welcome to the Forum, Sander.

That question has not been fully answered. There has been CFD simulations that indicate that a straight symmetrical profile would work best. Also, there have been other simulations that claim better performance when a positive camber is on the outside of the VAWT blades. I have also seen pictures of some VAWT's that have the negative camber towards the outside of the VAWT.

People that have a good understanding of aerodynamics lean towards the idea that a symmetrical airfoil would work best.

There are many opinions, but I have not been able to find anyone that has done tests on a real VAWT. I have more faith in actual testing than in computer simulations.

That is one of the reasons that I decided to build a testing platform. That way I can try different configurations under the same conditions.

Ed

[Lange1975]

Thanks Ed.

So it's still ongoing the debate.

I'm designing one with an asymmetrical airfoil (GOE-222) with the positive chamber on the outside as in the picture that i posted above. I have seen movies of people in Germany were I'm in contact with who built one and it spins very fast.

Sander

[MagnetJuice]

That is good to hear Sander.

I love to see people designing and building. When you start building it, post pictures if you can.

Ed

[Lange1975]

I will Ed. But as I said it's still in the design phase.

I'm also struggling how to setup the grid tie connection.

In the picture below you can see how it will look. The support base shown is a temporary test support.

Sander

[MagnetJuice]

I have been reading through some of the more than 800 PDF files that I have acquired since I started this topic. I want to find out which blade profiles work best concerning the self-starting and performance of a VAWT. I found some CFD simulations that indicate that some asymmetrical profiles work better than symmetrical profiles like NACA 0015 and 0018.

These are some profiles that have performed better than the symmetrical ones.



According to some CFD simulations, these profiles started the turbine spinning at lower wind speeds and produced higher Cp.

I wonder why these profiles seem to perform well?

Ed

[Lange1975]

Hi Ed,

Maybe you can do some simulations with the software from Q-Blade.
It's freeware.

Kind regards,
Sander

[MagnetJuice]

That is interesting. I will give Q-Blade a try.

Thank you Sander.

Ed

[Lange1975]

Hi Ed,

Let me know how it works? I still have not find the time to play with the package!

Sander

[MagnetJuice]

During the last few days, I have been working on the final dimensions for this VAWT.

It is difficult to decide on a certain size because I want to use parts that are readily available. I do not want to do any welding or machining to keep it simple and easy to assemble. The final design and dimensions were mostly dictated by what parts I could easily find. Overall, I am happy with the shape and with the dimensions.

Here is an image of what the final design should look like.



The image only shows two blades, but it will have three. The image also shows the center shaft to be 48 inches long, but I am hoping that the final product can be constructed using a 36-inch shaft, because that size is more common. I am using the 48-inch shaft because I want a larger area in the center so I can try different sizes for the central Savonius blades. Ultimately, I want the Savonius to be as small as possible so it doesn't interfere with the H-Darrieus blades.

A turbine of this size could produce about 400 watts with 22 MPH winds (10 m/s). That estimate is assuming that it has a well-designed set of blades. That is going to be the major challenge, building a good blade profile with simple tools and materials.

Originally, I had wanted to build a taller turbine to get more power. But a taller turbine would have to be supported at the top. That would have required a frame around the turbine and complicate things. I want to keep it simple.

Because this turbine is smaller, I can build an alternator using 12 magnets instead of the 16 that I had in mind. The alternator will have 2 rotors with 6 magnets each and a stator of 9 coils. It will be a 3-phase alternator with 3 coils per phase. By using 9 coils I can make them thinner so the air gap is smaller.

This alternator could easily put out about 550 watts.

Today I placed a couple of orders for the rest of parts that I need. I will take a break from this to work on other projects until the parts arrive.

Ed

[MagnetJuice]

The parts that I ordered should be here by the middle of next week. It is taking a long time, maybe because of the Thanksgiving holidays. On top of that, one of the bearings was back-ordered and I might have to order it from a different supplier.

In the meantime, I have been making room in my garage for the turbine. It is too cold and wet to build it outside.

There is a lot of stuff in the garage, “valuables” from my wife and kids.

One quarter of the space in my garage is taken by recyclables. Shuffling bottles cans plastics and cardboard has become Canada's main pastime. It used to be hockey. 

Building this turbine is number one priority, so I have to make room. Maybe I accidentally take some of the “valuables” and donate them to the second hand store. 

Ed

[topspeed]

I have been reading through some of the more than 800 PDF files that I have acquired since I started this topic. I want to find out which blade profiles work best concerning the self-starting and performance of a VAWT. I found some CFD simulations that indicate that some asymmetrical profiles work better than symmetrical profiles like NACA 0015 and 0018.

These are some profiles that have performed better than the symmetrical ones.

(Attachment Link)

According to some CFD simulations, these profiles started the turbine spinning at lower wind speeds and produced higher Cp.

I wonder why these profiles seem to perform well?

Ed

S1046 looks pretty symmetrical to me.

[MagnetJuice]

You are pretty smart Juke. It took you a while but you caught that.

Ed

[topspeed]

You are pretty smart Juke. It took you a while but you caught that.

Ed

I tought there was a catch there Ed.

That foil seems to be very thick...and thus can be made very durable without extreme weight penalty.

[MagnetJuice]

For my application, I am contemplating a profile that has 2% camber at 50%. Something like this:



Ed

[MagnetJuice]

I finally have all the parts that I need for the turbine, including all the bearings.

Now, for some reason, all I want to do is PARTY!!! 

Oh well, I guess that the construction has to wait until after the Holiday season.

I'll continue to juggle different construction techniques and materials for building the different blades that I want to try.

I found an online calculator to calculate the centrifugal forces of a given mass at a certain RPM. Very handy to find out the effective mass of a blade of a known weight.

For example, a blade that weights 1 kg (2.2 Lbs.) spinning on an H-Darrieus turbine that has a radius of .76 m (30 inches) at 250 RPM will have an effective mass of 54 kg (119 Lbs.)

That is the reason that the blades have to be constructed of light materials. They also have to be strong so they can sustain the flexing as it gets hit by the wind from both sides many times per minute.

So I'll be partying, but also working on this.

Comments and suggestions on how to build strong light blades will be appreciated.

Ed

[DanG]

This is a peek inside an Enercon monster turbine blade, the picture is one I posted here from 2009 - layers of balsa wood as honeycomb, gaps between the blocks filled with resin providing stiffening - likely a tubular spar 'spine' buried under the foam fillers, everything bedded in resin and the covered with the flavor of the month fiber reinforced resin & gel coat.

Those 60, 80 meter blades have to stay lightweight and be stout - that cheat of an analog honeycomb versus the aerospace metal ribbons laid up in composite bedding just struck me as particularly clever. Laminating a few sheets of large core but 'thinner' lateral-grain (ultralight) plywood together then form & coat might* be worth the trouble?

[MagnetJuice]

I just came out of hibernation today and it is a beautiful sunny day here in BC. Outside temperature is 8 degrees (46 F)

It is time to continue with the construction of this turbine. Because I have to do the building outdoors and I have to do gluing and painting, I need to wait until the temperature is a bit warmer.

Here is a video that shows that the wind can also be used for moving beautiful art.

It would be nice if these wind sculptures could generate some power too.

https://www.youtube.com/watch?v=T5bDXGJ13XY

Enjoy,

Ed