Multi Micro/nano VAWT assembly

[profp]

Random Friday thought...

Suppose one built an array of VAWT (or horizontal axis, for that matter) turbines, with each set of blades driving a small, lightweight PMG. The mental picture I have is of say a 16x16 grid of VAWT, each about the size of a coke can (or if that's too small, say the size of a 2litre or 5litre paint can). The small generators would start generating at lower wind speeds than conventional ones, the components might be cheaper to manufacture too, and of course it scales in a nice lego-brick way.

There must be a reason why this approach doesn't work - what is it? That you can't achieve a sensible power output vs. overall size?

[martin]

 stumbling blocks are the fact that VAWTs need higher windspeeds than a HAWT to get up and boogie, and that all turbines need to be high up above the turbulence around at low levels (particularly in urban areas), so you have to picture your array of coke cans atop a 100' or taller tower............

(there's also the turbulence and "shading" induced by a "grid" of turbines........)

[profp]

stumbling blocks are the fact that VAWTs need higher windspeeds than a HAWT to get up and boogie, and that all turbines need to be high up above the turbulence around at low levels (particularly in urban areas), so you have to picture your array of coke cans atop a 100' or taller tower............

But both of those are generic issues to all VAWT, not specific to my suggestion?

(there's also the turbulence and "shading" induced by a "grid" of turbines........)

If the grid is in the vertical plane, I don't think there'd be any shading issues at all. Turbulence issues are harder to quantify - where's an aerodynamacist when you need one?

[martin]

Cetainly they're intrinsic with all VAWTs - if the grid's vertical you shouldn't get "shading", but you'll still need the very tall pole!

Suggested reading - http://www.wind-works.org/articles/small_turbines.html (from the bloke who wrote many of the text books)
superb resource -  http://wiki.windpower.org/index.php/Main_Page#Welcome_to_the_Guided_Tour_Wiki
from the chap who wrote some of the other text books - http://scoraigwind.com/

[mespilus]

- where's an aerodynamacist when you need one?

They are all still lying down in darkened rooms....

still recovering from the swindlesave fiasco.

[djh]

(there's also the turbulence and "shading" induced by a "grid" of turbines........)

If the grid is in the vertical plane, I don't think there'd be any shading issues at all. Turbulence issues are harder to quantify - where's an aerodynamacist when you need one?

The main selling point of VAWTs is that they're insensitive to wind direction. If you have a vertical grid, you reintroduce the problem that HAWTs have; you have to steer them to face the wind. So you would need a barrel of micro turbines; about three times the number.

I guess the main evidence that this is not a good idea is that wind farms are made of ever larger turbines, not rows and rows of small ones.

[wyleu]

Whilst looking at the displays in Blackpool of pictures made up of arrays of metal discs, it was speculated that perhaps one could use a magnetic disc adjacent to a coil for each element of the grid and by suitable ( there in lies the rub) diode steering one could generate from any vertical surface in pretty much any wind condition. Probably not very efficient overall but I'd love to try it ...

[profp]

The main selling point of VAWTs is that they're insensitive to wind direction. If you have a vertical grid, you reintroduce the problem that HAWTs have; you have to steer them to face the wind. So you would need a barrel of micro turbines; about three times the number.

Good point...

I guess the main evidence that this is not a good idea is that wind farms are made of ever larger turbines, not rows and rows of small ones.

Yes, but at the risk of sounding like a petulant 5 year old, why?

[profp]

Whilst looking at the displays in Blackpool of pictures made up of arrays of metal discs, it was speculated that perhaps one could use a magnetic disc adjacent to a coil for each element of the grid and by suitable ( there in lies the rub) diode steering one could generate from any vertical surface in pretty much any wind condition. Probably not very efficient overall but I'd love to try it ...

Nice idea!

[martin]

"Yes, but at the risk of sounding like a petulant 5 year old, why?" - not least "economies of scale" - with the usually more "useful" HAWTs being used, the bigger they are, the taller the tower has to be, geting them up and out of all the problems of "roughness" and turbulence low down

[profp]

"Yes, but at the risk of sounding like a petulant 5 year old, why?" - not least "economies of scale" - with the usually more "useful" HAWTs being used, the bigger they are, the taller the tower has to be, geting them up and out of all the problems of "roughness" and turbulence low down

I think you misunderstand, Martin. I fully understand why HAWT is preferred over VAWT in general, what I don't understand is why an array of smaller VAWT doesn't offer an advantage over a monolithic design from a theoretical/engineering standpoint.

[martin]

as DJH pointed out, you'd lose one of the few advantages of VAWTs - it'd have to "track" the wind or it would suffer acute "shading" and turbulence problems (which'd be great fun atop a far taller tower than a HAWT would need....)

[smegal]

"Yes, but at the risk of sounding like a petulant 5 year old, why?" - not least "economies of scale" - with the usually more "useful" HAWTs being used, the bigger they are, the taller the tower has to be, geting them up and out of all the problems of "roughness" and turbulence low down

I think you misunderstand, Martin. I fully understand why HAWT is preferred over VAWT in general, what I don't understand is why an array of smaller VAWT doesn't offer an advantage over a monolithic design from a theoretical/engineering standpoint.

Carbon/financial payback.

The larger the machine the more ability it has to capture the available energy, coupled with the fact that this system is unlikely to be placed in an area with a worth wile wind resource. The energy out is proportional to the cube of the wind speed.

[petertc]

Check  out these systems.

http://www.motorwavegroup.com/new/motorwind/index.html

[Richard Owen]

I guess the main evidence that this is not a good idea is that wind farms are made of ever larger turbines, not rows and rows of small ones.

Swept area.

Double the size of the blade (radius)

Square the amount of power available (area)

Thank you Archimedes, and Good Night.