T Nation

Windmill Design


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.



"Whatcha doin'?"

'Buldin' a windmill.'



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


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.



"You're doing it wrong."


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.



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.



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


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

Check out this design.


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


This topic blows.

ba dump bump.


hey guys whats up.


My Boner?



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.


Im totally useless in this thread


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.



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.



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.


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.