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Windmill Design
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Vegita
Level 3

Join date: Apr 2003
Posts: 7516

So I have been thinking about making my own personal windmill for supplemental electricity generation and came up with a new little design. I think it should create more torque than a traditional windmill. The energy is transfered directly to the rotor instead of it beng directed traversely in another direction.

The little half circle thing is a guard so that the wind is only hitting half the blades. The fin in the back will make sure the thing is pointing into the wind instead of it hitting it sideways. The whole device will swivel around on a pole. See attached rudimentary image.

I should be able to make it mostly out of wood. I'd start out with a small device maybe using those wooden paint stirrers for the blades. Couple thin peices of wood for the shielding and a wooden fin on the back.

V

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Vicomte
Level 4

Join date: Mar 2008
Posts: 4993

"Whatcha doin'?"

'Buldin' a windmill.'

"Oh."

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Bill Roberts
Level 5

Join date: Mar 2003
Posts: 8669

It appears to me you are trying to make an air-driven paddlewheel.

This is not as efficient as a turbine design.

Not that analogy is the best way to reason, but for illustration:

A conventional windmill is like a modern day propeller.

Your design is like a steamboat's paddlewheel.

(If I understand your intent correctly.)

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conorh
Level 3

Join date: Sep 2004
Posts: 2713

I would try this before I would try what you've drawn up:

http://www.mdpub.com/Wind_Turb...

The wind only hits half your rotor, so it defeats the whole purpose, doesn't it? I mean, you're essentially choosing half of a rotor exposed perpendicularly to the wind versus an entire rotor at some oblique angle. Intuitively, this doesn't seem optimal to me.

Plus, at high wind speeds/rotor velocities I think you're going to have balance issues. Think about the old fashioned over/under water wheels, they weren't designed for high speeds and as soon as we had the technology to do so, we switched to turbines.

Interesting project though, and best of luck.

-Conor

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Vicomte
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Join date: Mar 2008
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Vicomte wrote:
"Whatcha doin'?"

'Buldin' a windmill.'

"Oh...


"You're doing it wrong."

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Vegita
Level 3

Join date: Apr 2003
Posts: 7516

Bill Roberts wrote:
It appears to me you are trying to make an air-driven paddlewheel.

This is not as efficient as a turbine design.

Not that analogy is the best way to reason, but for illustration:

A conventional windmill is like a modern day propeller.

Your design is like a steamboat's paddlewheel.

(If I understand your intent correctly.)


I'm not so sure, what would the advantages be? To me it seems like I could "catch" a more direct energy than using a blade with a tilted angle to the wind. My blades would be getting the wind straight on so the torque should be higher. And if I am setting up an electromegnetic generator, there will be resistance in the device from the electrons pushing back against the magnets, so i need the most torque as possible.

V

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Bill Roberts
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Besides all this, it's based on an errant premise.

In the conventional design, the aerodynamic lift of the blades is indeed in the direction of providing torque. Whether talking about the top, bottom, left, or right of the windmill.

It's not that the force is in the wrong direction: it is in the correct direction to power rotation.

EDIT: hadn't seen your reply when posting before, but see it now.

I believe you are trying to have the wind push the blades, just as a paddlewheel pushes the water.

In contrast, a wing design generates force, excluding drag considerations, at 90 degrees to the direction of airflow across the wing. Thus, a helicopter rotor, for example, generates upwards force from the blades rapidly moving horizontally.

If you instead had a wind blowing from the bottom up through a helicopter rotor, then power would be generated.

Wind pushing the blades like a paddle, or for propulsion having a paddle push the air or water, though more intuitive, is not as efficient.

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Vegita
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Join date: Apr 2003
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Bill Roberts wrote:
Besides all this, it's based on an errant premise.

In the conventional design, the aerodynamic lift of the blades is indeed in the direction of providing torque. Whether talking about the top, bottom, left, or right of the windmill.

It's not that the force is in the wrong direction: it is in the correct direction to power rotation.

EDIT: hadn't seen your reply when posting before, but see it now.

I believe you are trying to have the wind push the blades, just as a paddlewheel pushes the water.

In contrast, a wing design generates force, excluding drag considerations, at 90 degrees to the direction of airflow across the wing. Thus, a helicopter rotor, for example, generates upwards force from the blades rapidly moving horizontally.

If you instead had a wind blowing from the bottom up through a helicopter rotor, then power would be generated.

Wind pushing the blades like a paddle, or for propulsion having a paddle push the air or water, though more intuitive, is not as efficient.


Well here is what I'll do, as an expiriment. I'll build two systems trying to keep the scale and costs similar and see what blade setup produces more electricity. I think my idea will work at lower wind speeds better than the modern turbine design. The house I am buying is in a valley not a hilltop, so I won't get the consistantly good 20-30 MPH winds like we do around here up on the hills. I can probably excpect 5-15 MPH on most days.

BTW I understand where you are coming from, I just think having the wind deflect off a turbine blade isn't going to transfer the energy as cleanly as my design will. It is all going to boil down to torque and rotational speed, and while I think probably the rotational speed of a modern turbine would be increased, I think the torque on the "paddlewheel" will be higher. Only a scientific expiriment will answer these questions.

V

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Bill Roberts
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Yes, that is excellent that you plan on trying both and comparing.

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Yo Momma
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Posts: 4729

If you want more efficient energy transfer, use vertical rotation, not horizontal.

Check out this design.

http://www.bsi-global.com/...y/Wind-turbine/

It's optimum for where you live, where the wind flow is turbulent and gusty.

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lostinthought
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Posts: 2391

This topic blows.

ba dump bump.

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schultzie
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Join date: Oct 2007
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hey guys whats up.

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Vegita
Level 3

Join date: Apr 2003
Posts: 7516

schultzie wrote:
hey guys whats up.


My Boner?

V

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SkyzykS
Level 2

Join date: Apr 2004
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You should also look up some designs for commutators to transfer the electricity from the generator to where ever it is going to go.

Even if the generator is attatched to the shaft of the prop, it will still be rotating around the base, and you don't want a wire snagging up and limiting the range or rotation of the head.

Most of them are relatively simple brush/commutator designs made of brass. Once you have a design, you can have one machined to specs prety cheaply.

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MangoMan305
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Im totally useless in this thread

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DoubleDuce
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There is probably a reason no one makes a paddle wheel design. Efficiency arguments aside, you are limiting your air power collection to the area of 1 single blade.

It is true that turbines need higher wind speeds for maximum efficiency but that efficiency curve can be adjusted with design.

If you want efficiency as lower wind speeds with lots of torque, go with an old fashioned rotary design.

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Vegita
Level 3

Join date: Apr 2003
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DoubleDuce wrote:
There is probably a reason no one makes a paddle wheel design. Efficiency arguments aside, you are limiting your air power collection to the area of 1 single blade.

It is true that turbines need higher wind speeds for maximum efficiency but that efficiency curve can be adjusted with design.

If you want efficiency as lower wind speeds with lots of torque, go with an old fashioned rotary design.


Interesting. I see where the point is made that having all blades in contact with the wind at once could be better than only a few of the blades at a time. Well it will be cheap to do both anyways, The most expensive part is probably going to be the testing device to test the electrical flow from them.

V

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Vegita
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That old fasioned rotary design looks like it could really grab some wind! I wonder why there isn't many of them in use? What would be the downside?

Also Just thinking about an airfoil design, This may make the blade over time spin much faster than is possible from a regular balde. I think you would need sustained winds for this design to be effective though, And heavy blades would probably help to keep momentum up while winds temporarily die down or change directions.

V

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conorh
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Vegita wrote:
That old fasioned rotary design looks like it could really grab some wind! I wonder why there isn't many of them in use? What would be the downside?

Also Just thinking about an airfoil design, This may make the blade over time spin much faster than is possible from a regular balde. I think you would need sustained winds for this design to be effective though, And heavy blades would probably help to keep momentum up while winds temporarily die down or change directions.

V


Heavy blades also increase shear forces on the rotor shaft, exacerbating balance issues, increase frictional losses and decrease the life of bearings. Obviously, they also require greater wind speed to generate any power at all.

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conorh
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Honestly, if you're serious about doing this, I would follow the instructions on that link I posted. That's what I'm going to do at some point, because I have a couple hookups for old DC motors.

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Bill Roberts
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Join date: Mar 2003
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I am missing the difference between "rotary design" and turbine?

Unless one is using different words according simply to the number of blades or their aspect ratio (chord, that is to say width, versus length.)

??

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zImage
Level 1

Join date: Mar 2009
Posts: 16

Rotation about the vertical axis is much more efficient at low altitudes.

See the link that Yo Momma posted.

I've worked on these in the past, but probably at a much bigger scale than what you are moving towards.

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bushidobadboy
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There are a few domestic wind turbines in the UK. They generally look like this, which I assume is because this is the most efficient design.

BBB

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BigJawnMize
Level 4

Join date: Jul 2008
Posts: 338

Vegita wrote:
That old fasioned rotary design looks like it could really grab some wind! I wonder why there isn't many of them in use? What would be the downside?

Also Just thinking about an airfoil design, This may make the blade over time spin much faster than is possible from a regular balde. I think you would need sustained winds for this design to be effective though, And heavy blades would probably help to keep momentum up while winds temporarily die down or change directions.

V


V

I am an architect. I actually work for the government on energy conservation projects. I have seen design similar to what you are proposing, they are installing them as micro generators on buildings. I wish I could find a website. This design works well on smaller scales for the reason it takes less torque to move the generator because the assembly is rotated as you mentioned. Once you get to larger scales the construction is unruly.

This is also a design used in fan boxes for large builing applications.

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DoubleDuce
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Bill Roberts wrote:
I am missing the difference between "rotary design" and turbine?

Unless one is using different words according simply to the number of blades or their aspect ratio (chord, that is to say width, versus length.)

??


What I ment by that is blade shape. Essentially airfoil vs. angled flat surface or sail-like cloth.

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