Looking into small DIY wind turbines.

Solar, wind, hydro and other non-fossil sources of electricity.
Logic11   100 mW

100 mW
Posts: 40
Joined: May 02 2022 3:16pm

Re: Looking into small DIY wind turbines.

Post by Logic11 » Jun 16 2022 6:29am

I would advise anyone looking at wind power to google:
whale fin tubercles wings fans wind turbine

Image

https://newatlas.com/bumpy-whale-fins-s ... mics/9020/

https://www.windpowerengineering.com/wh ... ne-design/

If making fan blades the old main spar, ribs, fabric covered trailing edge, way;
Getting passable tubercles may be as simple as rounding the (many) ribs and covering the leading edge (top only?) with fabric too..?

ynot   10 W

10 W
Posts: 94
Joined: Mar 05 2022 3:52pm

Re: Looking into small DIY wind turbines.

Post by ynot » Jul 29 2022 10:19am

Logic11 wrote:
Jun 16 2022 6:29am
I would advise anyone looking at wind power to google:
whale fin tubercles wings fans wind turbine

If making fan blades the old main spar, ribs, fabric covered trailing edge, way;
Getting passable tubercles may be as simple as rounding the (many) ribs and covering the leading edge (top only?) with fabric too..?
Realize that this is an old thread, but the subject is near and dear to my heart.

On a small wind turbine, (under 6ft diam) there is little point in putting the work into complicated tip design.
The goal of any turbine that small, is to get it rotating fast enough to "fill the circle" ie spinning fast enough so that no air can pass through the circle without imparting its energy to the blade.
The energy to begin accelerating the blade(s) is generated at the root (center) of the blade, I built and sold many blades for wind turbines, and spent many hours on design. In practice we made the angle of attack as steep as the material would allow at the hub, and at the tip of a 4ft blade had an angle of around 0.5 degrees. You could see on an ammeter jump the moment that the blade filled its circle. Above that wind speed much of the design work was to get as much of the blade out of its own way, so that the blade could spin faster due to reduced drag.

There is virtually no advantage in trying to squeeze energy out of the tips once the circle is filled, as drag becomes the limiting factor. This is very different from the huge wind turbines that never attain "filled circle".

PS. It is very difficult to exceed the cost benefit analysis brought about by photovoltaics.

Logic11   100 mW

100 mW
Posts: 40
Joined: May 02 2022 3:16pm

Re: Looking into small DIY wind turbines.

Post by Logic11 » Jul 31 2022 3:38pm

ynot wrote:
Jul 29 2022 10:19am
If making fan blades the old main spar, ribs, fabric covered trailing edge, way;
Getting passable tubercles may be as simple as rounding the (many) ribs and covering the leading edge (top only?) with fabric too..?
Realize that this is an old thread, but the subject is near and dear to my heart.

On a small wind turbine, (under 6ft diam) there is little point in putting the work into complicated tip design.
The goal of any turbine that small, is to get it rotating fast enough to "fill the circle" ie spinning fast enough so that no air can pass through the circle without imparting its energy to the blade.
The energy to begin accelerating the blade(s) is generated at the root (center) of the blade, I built and sold many blades for wind turbines, and spent many hours on design. In practice we made the angle of attack as steep as the material would allow at the hub, and at the tip of a 4ft blade had an angle of around 0.5 degrees. You could see on an ammeter jump the moment that the blade filled its circle. Above that wind speed much of the design work was to get as much of the blade out of its own way, so that the blade could spin faster due to reduced drag.

There is virtually no advantage in trying to squeeze energy out of the tips once the circle is filled, as drag becomes the limiting factor. This is very different from the huge wind turbines that never attain "filled circle".

PS. It is very difficult to exceed the cost benefit analysis brought about by photovoltaics.
[/quote]

Tips..?
Ah! from the pic. :)
Ye the whole wing should have tubercles.

You rely on the lift created by each blade/wing to turn your turbine.
Wings/blades stall when the angle of attack is greater than around 12 deg.
Making variable pitch a must, or for some less than optimal blade designs to get them turning.

Here the angel of attack can be a good bit higher and the wings/blades stall much more gradually.
ie: some lift even at low wind speeds where the blade is not at the rpms reqd for a good angle of attack.
In a turbine that translates into fixed pitch blades that start spinning at lower wind speeds, handle a wider range of wind speeds without any variable pitch and IIRC around 20% more electricity in tests.

That's quite a step up from: 'less tip vortex'
These tubercles on the leading edge are evolution's answer to whales stalling in the tight turns reqd to herd fish, not some wanna be bright spark selling the latest fad to the gullible...

ynot   10 W

10 W
Posts: 94
Joined: Mar 05 2022 3:52pm

Re: Looking into small DIY wind turbines.

Post by ynot » Aug 02 2022 4:26pm

Logic11 wrote:
Jul 31 2022 3:38pm
ynot wrote:
Jul 29 2022 10:19am
If making fan blades the old main spar, ribs, fabric covered trailing edge, way;
Getting passable tubercles may be as simple as rounding the (many) ribs and covering the leading edge (top only?) with fabric too..?
Realize that this is an old thread, but the subject is near and dear to my heart.

On a small wind turbine, (under 6ft diam) there is little point in putting the work into complicated tip design.
The goal of any turbine that small, is to get it rotating fast enough to "fill the circle" ie spinning fast enough so that no air can pass through the circle without imparting its energy to the blade.
The energy to begin accelerating the blade(s) is generated at the root (center) of the blade, I built and sold many blades for wind turbines, and spent many hours on design. In practice we made the angle of attack as steep as the material would allow at the hub, and at the tip of a 4ft blade had an angle of around 0.5 degrees. You could see on an ammeter jump the moment that the blade filled its circle. Above that wind speed much of the design work was to get as much of the blade out of its own way, so that the blade could spin faster due to reduced drag.

There is virtually no advantage in trying to squeeze energy out of the tips once the circle is filled, as drag becomes the limiting factor. This is very different from the huge wind turbines that never attain "filled circle".

PS. It is very difficult to exceed the cost benefit analysis brought about by photovoltaics.
Tips..?
Ah! from the pic. :)
Ye the whole wing should have tubercles.

You rely on the lift created by each blade/wing to turn your turbine.
Wings/blades stall when the angle of attack is greater than around 12 deg.
Making variable pitch a must, or for some less than optimal blade designs to get them turning.

Here the angel of attack can be a good bit higher and the wings/blades stall much more gradually.
ie: some lift even at low wind speeds where the blade is not at the rpms reqd for a good angle of attack.
In a turbine that translates into fixed pitch blades that start spinning at lower wind speeds, handle a wider range of wind speeds without any variable pitch and IIRC around 20% more electricity in tests.

That's quite a step up from: 'less tip vortex'
These tubercles on the leading edge are evolution's answer to whales stalling in the tight turns reqd to herd fish, not some wanna be bright spark selling the latest fad to the gullible...
[/quote]

Increasing the angle of attack will only make the blade begin spinning in lower wind speed, and will slow the blade at higher wind speed.
Comparing the design of a whale fin to a turbine blade is apples and bananas, water is 256 times more dense than air, and the whale never approaches the relative speed of a small turbine blade.
Wind turbine blades must be designed to suit the generators characteristic output. If you are going to decrease the rotational speed of the blade by increasing its angle of attack, you will have to use a larger diameter generator to optimize the slower speed.

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