Experimental wind turbine prototype 4 is flying!

[reinoud]

Dear folks,

as some of you might have read in an earlier post of mine, i'm working on an experimental wind powered generator that uses no proppellor type blades. Its still without alternator as seem on the images but building one, thats my next challenge

The design is of course inspired by older designs and some company once sold look-a-likes that are based on the same concept but apparently they are now out of business. I haven't seen home made versions though and wondered how well it would/could work and decided to build one. After a three simple tryouts, here's a glimpse of the 0.25 m2 prototype 4 :

Testing it at winds speeds of a reported 4-5 meter/second (no wind speed meter yet ) results in an rpm between say 50-70 and 120 at gusts. It also got quite a torque! Even at very low wind speeds to virtually no speed like at walking speed its allready turning with a torque. Now the construction is sure not weather-proof having used MDF but for a first functional one thats not really an issue.

From what i understand of the physics, it can't spin itself up to death since it will get flooded due to the limited outlet and will then behave like a flat surface in the wind. A second of third layer of `scoops' could allow it to `eat away' more wind though... haven't tried a second layer yet! (labour intensive... waiting for a nibbler-tool to speed things up significantly)

As of electricity generation, i hope achive some 20 watts at higher wind speeds but that might be optimistic due to the small size. A one m2 or two m2 would make a lot more sense for a real one.

The price-tag of this exprement was around say 50 euro, but i learned a lot of it constructing it. On for my first home build alternator and then likely a new bigger one Watch this space

[zubbly]

reinoud!

thats definately different.  sort of looks like a huge pinwheel.  i hope your efforts pay off and find a place for it in wind generation. i think the key if you find that the speed is on the low rpm side and torque is very good, may i suggest you try and design your genny with a corresponding cut in rpm.

experimenting is good for the soul and helps us to use a little more than the 10% of brain capacity that scientists say we use.  LOL!

have fun,

zubbly

[TomW]

 reinoud;

Please allow me to congratulate you on grabbing the mill by the tail as it were and building something totally different than anyone I have seen post here at least.

I did some pinwheel type blades and they spin up easy but i never got them to make any power. Those were made from aluminum newspaper printing plates the size of a sheet of a regular size newspaper and 4 blades. See my diaries for some of that stuff I did awhile back.

Be very nice to hear how these work they sure look different.

I truly enjoy these posts from people doing things and sharing the experience. Thanks.

Cheers.

TomW

[Ungrounded Lightning Rod]

Looks like a lift turbine, using curved-sheet airfoils (like a hang glider).

Have you measured the unloaded TSR?

[Norm]

  Maybe either a cone to divert the wind to the

blades or a spoked rim to support the blades

and allow the wind to pass thru...I like bicycle

wheels for this....and old (free take one) cd

disks for blades tho' not as efficient...cheaper!

  Small ones don't make as much electricity but

they make it when the big ones aren't even turning.

Nice job !

                 ( :>) Norm.

[powerbuoy]

Nice approach. Even if it should not perform, it'll be an eye catcher.  

[reinoud]

thanks for the nice comments and encouragements!

I'll try to explain some of the workings as far as i understand them. Its basicly converting energy from the turbulence that gets created when the wind hits an fixed object and gets around it; thats why the back plate needs to be solid. Also the wind gets diverted into a radial wind stream over the plate into the curved metal blades. These then direct and extract energy from the various rotations in the air and then delivers the wind in the wake of the sheet. A cone is in the planning though i dont know how much it would actually matter in its performance.

Interestingly the Betz power coeficent constant (16/27) is not valid for this design and the power efficiency can get higher since there is no bulb of slowed down air behind the rotor but rather a wake that needs filling up. We'll see if this is really true!

Nice note for the neighbours: its noise-free

For the alternator i got myself some 40 (minus one, broken) `toy' NbFeB magnets, 20mm x 20mm x 3mm though strongly magnetised at 45M. I was planning to build two rotors each having 16 or 18 magnets. Only how many coils should i take? I've got plenty of 0.5 and 0.6 mm insulated copper wire ('magnet wire') to make the coils from.

With a desired cut-in speed of around 50 rpm i guess thats going to be a lot of turns

I wonder if there is electronics around that can convert whatever voltage it generates into the charge-voltage of my battery and let it trickle whatever mA's it gets out into the battery. Ought not to be extremely difficult though i haven't seen it around.

[ghurd]

A very small AC motor conversion can make charging volts at low speeds.

Very small, like 50W, has a lot of turns!  It also means very low power out, 50mA?

G-

[kenl]

Low RPM high torque, hmmmmm been looking for a design to convert to pumping water.

[finnsawyer]

If you put a disk up crosswise to the air flow you get get a force on it.  The air on the windward side must build up pressure to change the flow direction to make the radial flow.  The air on the back side has no such requirement.  It could be still.  however still air has a higher pressure than moving air.  Since there is a net force pushing the disk backwards the air must be moving faster on the backside on average.  How is this possible?  On the windward side the air at the center has no velocity at all.  This gives the highest pressure.  As you move toward the rim the pressure drops and the radial velocity increases with the maximum being near the rim.  On the back, however, a circular airflow is set up, also from center to rim.  But in this case, while the flow may be zero at the center it may reach a maximum well before it reaches the rim.  This turbulent flow on the backside is caused by the effect of the lower pressure high velocity air flowing around the disk.

This whole thing leads to the basic question of how important is the radial flow at the rim anyway?  The pressure distribution may be such that the component of air velocity in the direction of the incident air may very quickly become larger than the radial component as the radial distance moves away from the rim.  If that is the case then the pressure distribution acts like a cone anyway, and one would be better off putting a hemisphere over the disk to eliminate the radial component entirely and design around that.  Keep in mind that nature is trying to move the air past the obstruction and that a radial velocity is not its preferred direction.  In fact, it is Nature's trick to speed up the air passing an object in order to keep the air in the entire air stream moving.

"Pressure Matters".

[JF]

Dear Mr Reinoud and other friends

This is a very well made machine - congratulations.

A small booklet - "Building a Domestic Windpump"

by James Barr ISBN 1 870653 29 7 UK 1994 -

Gives full plans and discusses these interesting

small turbine-type units.- However not quite as

elegant as yours.

With greetings and best wishes to all - JF

[reinoud]

I tested prototype 4 with higher wind speeds, probably around 7-8 m/s.  I got rpms of over 200, peaking at around 250.  The structure held well.

We also tried another larger prototype model.   This one was made by my friend Boris.  This 8 blade model has about 1 m^2 area.  It is made of chicken wire lined with plastic garbage bags, with some bent metal strips for sturdiness.  The blades are rolled up at the edges to ensure they stay in shape.  

While no-one would believe this floppy thing would fly, it did quite well, and reached over 100 rpm in this wind.  

[dinges]

Hallo Reinoud. Nog 'nen Hollander, hi.

Interesting looking devices. Don't know whether they will produce much electricity, but only one way to find out: build an alternator as well.

At least those contraptions look a bit like lawn-ornaments, so you shouldn't get too much complaints from the neighbours. I don't think they would be as pleased with a 17ft Dan-design on a 15m mast, giggle. Or maybe you should gradually work your way up.

Looking forward to updates on the project!

Peter.