Windturbines + Jet engines.

[fields2grand]

This is going to sound crazy and likely has been tried but I couldn't seem to find it on this board.  WHAT IF.....Your blades facing the wind are connected to a shaft (N1) spinning your magnets.  You have a second shaft with your stator butted up near your magnets and on the back of that second shaft you have blades that pick up residual wind spinning the stator in the opposite direction with sliding contacts to pick up the resulting power?  Sort of an N1 and N2 version of jet engines.  The Blades on the second shaft (N2) would be far enough away not to interfere with the wind for the first shaft (N1).  I don't know how to make diagrams on this board but imagine an axle split in half pointed towards the wind, the first brake hub spins counter-clockwise and the downwind brake hub spins clockwise with your rotor and stator in the middle.  I'm a complete noob in this stuff but if N1 can harness approximately 50% of the relative wind, would N2 harness about 50% of that?  I think this is an interesting discussion likely already brought up at some point.  Yet I'm eager to hear your thoughts.  

[brokengun]

Sounds like a lot of moving parts and added complexity to me. I am not sure how well it would work. It would definitely add some new challenges to designing. In theory it sounds good but who knows. I would try to look into it and see if anyone has tried it before. Seeing their results might encourage or discourage you.

Also, I am not certain what the airflow is like behind a spinning windmill blade. I would assume it is very turbulent and this might cause some loss of power in the second set of blades.

Interesting though.

[tanner0441]

Hi

If the two magnet discs ar spinning in oposite directions, what happens when the north pole on one disc is oposite the south pole on the other.  Surely the one would canel the effects of the other, result no magnetic field, no induced voltage in the coils.

just a thought......

Brian

[fields2grand]

I probably explained it wrong.  I guess what I was trying to say is that in a regular wind turbine the blades spin counterclockwise while the coils or stator is stationary.  So what if we could spin the stator clockwise or opposite of the rotor and utilize the extra wind flowing past the rotor?  This would essentially increase the RPM of genny.  THANKS FOR THE REPLIES!

[ghurd]

The 59.3% is 59.3% of the area.

If more than that is extracted, then the air behind the turbine piles up, and no more air can enter the front.

If 59.4% of the power is extracted, then the air behind the turbine is in the way of the in coming air and part of the incoming energy is used to move the stagnant air away.

It would be theoretically possible to get 50% of the remaining 50% (really under 40%), ignoring all losses.

Except that is past 59.3%, and every stage adds losses.

Things do not pass through air without friction.  More stages add more losses.

Imagine 100% of the energy is removed from the moving air.

The wind speed at the rear is 0.

And then the wind speed of the air entering the front is 0, because it can not enter if it is not leaving.

There is NO air moving through the turbine.

The energy in unmoving air is 0 watts.

Somewhere in between is the maximum available extractable power, which Albert Benz proved as 16/27ths.

G-

[joestue]

A 1:2 gear box is cheaper than a second set of blades, and slip rings, as the both rotor and stator are spinning.

[fields2grand]

So what you are saying is that 59.3% can be harnessed period.  Theoretically (assuming no losses) if the front blades harnessed 59.3 % then there would be no way for the back blades to harness 59.3% of the remaining 30.7% because the rear blades would cause a backup not allowing the front blades to operate at 59.3%.  So at best you could get 59.3 percent combining the two but then there would be no point.  Is this what you are saying?

[electrak]

unless you have the blades far enough apart so that does not happen, look for Salsen of something as such, he did something with a bunch of small blades on a long shaft, think 6 or 7, 12 inch blades spaced 2 to 3 feet apart, seams a bit unwieldly but he claims it works,

Using a counter rotation thing might work better with VAWT as rpm is a big issue,

May be a fun project, if I was to build, I'd go tryed and true first, then work from there.

If you want something done right, have a lazy person do it,

never lift what you can drag,

never drag what you can roll,

never roll what can be left.

[dnix71]

If you get 20% of the available power consider yourself to have done well.

There are long shaft designs (all the blades spin the same way). This increases to effective area. If the blades are small enough and the distance between them far enough, they do not interfere with each other.

There is a picture of one here. It also looks like difficult to build and maintain.

http://www.speakerfactory.net/wind_old.htm

[fields2grand]

That thing looks unbelievably unsafe.

[jaketheironhead]

I'm new to most of this however alway the simpler the better if u want more power build a bigger ginny or more of them

[Flux]

It's an old idea, the last attempt I can remember was by Trimble windmills nearly 30 years ago.

It works ok but is rather complex and there seems no good reason to do it when it is simpler to do it the conventional way. I don't think the aerodynamics works out any better you still only get something over a Cp of 0.4 and the mechanical complexity and the need for slip rings makes it more expensive than a bit more magnet and copper.

Yes it does work if you really want to try it.

Flux

[fabricator]

Wow! Thanks for that link, that is some really cool stuf those guy are doing, that's the first time I've seen anything like that.

[Norm]

yes....either a 1:2 ratio or double the coils and

magnets would work just as well....I'm thinking.

[whatsnext]

Why? His blades are very very light so there isn't much energy contained in the rotating assembly so even if something goes wrong there isn't a bunch of residual energy to tear things up. Mass is the enemy of power production and Greg knows this. Look through his site and you'll see him holding blade assemblies with one hand. I think they look safer but not as easy to build for the DIYers.