Toroidal Propellers on Wind Turbines?

Well in one case you have the wind pushing the blades, and in the other you have the blades pushing the water, so what works in one case may not work in the opposite...and we must consider density and speed as well...you can't just reverse the rotation on a fan blade and expect it to work as well...

As an HVAC worker I have seen fan blades reversed many times, leading to reduced cooling, it's a problem I've fixed many times...I have a window fan that reverses rotation to exhaust or supply air into or out of the room, it works better one way than the other way, this seems to always be the case...Now I suppose it would be possible to design a blade that changed shape for use in either direction, but I've never seen one...

Fan blades can change shape through various methods to optimize performance or adapt to different operating conditions. One approach uses shape memory alloys (SMAs), which can deform when heated or cooled. Other techniques involve flexible blades that can passively adapt to airflow, or blending techniques that modify the shape of individual blades to affect overall aerodynamic performance. Elaboration:

• Shape Memory Alloys (SMAs): SMAs, like those found in certain automotive fan blades, can be designed to change their shape in response to temperature changes. This allows for a morphing blade that can adjust its geometry to optimize airflow at different speeds or operating conditions, as demonstrated in research on heavy-duty automotive cooling fans.
• Flexible Blades: Some designs, like those inspired by boat sails, utilize flexible blades that can passively adapt to the flow field. This allows the blade to change its shape based on the airflow, potentially improving efficiency in reversible axial fans.
• Blade Blending: Blending techniques, used in turbofans, involve modifying the shape of individual blades to alter aerodynamic loading. This can affect the performance of both the blended blade and the adjacent blades, as shown in studies on the aerodynamics of blended fan blades.
• Blade Twist: Fan blades are often twisted to account for the varying rotational speed of different points along the blade. This twist helps ensure that the angle of attack (the angle at which the blade meets the incoming airflow) is optimized for each part of the blade, improving efficiency and performance.
• Adaptive Aerofoils: Adaptive aerofoils are designed to change their curvature in response to airflow conditions. This can involve sections that rotate or deform, allowing the blade to adapt to different flow velocities and pressures.

As the conventional Wind Turbine blades are up to 107 meters long (351 feet), if you were to convert the 3 bladed fan to a Toridal design, the structure would be ernormous, not to mention the lifting capacity required to get it from a horizontal to vertical position and mount it ! It would be impossible to assemble in Offshore locations.
Modern Blades have been redesigned to reduce wind noise, I live in a very quiet rural area about 1 km (0.62 miles) from 7 large Wind Turbines and on a perfectly quiet day I cannot hear any noise.
The use of a Toridial designed Fan for private Wind turbines used on domestic houses is quite common as are vertical axis turbines using other blade designs, but for large commercial designs we seem to be stuck with the 3 Blade design as we know it.

<...would it be feasible and profitable to do so?...>

In the context of "they exist", the answer is clearly positive.

The way I am looking at it is that the toroid propellers "thread" their way into the wind, or water, whereas a normal prop "chops" it's way into the medium. Of course, the "chopper" will make more noise than the "threader" and reduce efficiency.

There might be a way to hybridize the two, which I am pretty sure has been tried, but you never know. Lots of discoveries have been made by accident, and afterwards people would say "That was simple, Why didn't I think of that?"

Curious, is it not, how the toroid props look like the paper fans we made in elementary school.

I would like to see wind tunnel tests of air flow of wind in both directions, with smoke traces.

Any links to this?

I have seen many yootoob videos of toroid boat propellers compared to more common screw props.

A search for water with dye should get more internet hits than smoke in wind tunnel. Certainly not the same, but may be similar enough.

The scale of things ... makes a lot of differences.

The wind travels at very different speeds as it is measured from the surface of the earth for the first 1000 ft or so in elevation. Large wind turbines that I have been involved in the design of ( their controls) ... vary each blade's pitch - independently, within each revolution- to optimize power extraction at the top of the arch (faster wind) vs the bottom of the arch (slower wind). Most people are unaware of just how much wind speed changes over 100 ft in elevation change near the earth's surface. This known condition (wind gradient) is very hard to reproduce in wind tunnels.

of course.. wind turbines with blade diameters in excess of 500ft.. their rotational speeds are quite slow.. to keep the blade tips from exceeding the speed of sound - which would create some real noise.

... vary each blade's pitch - independently, within each revolution-

Sort of like the cyclic control on a helicopter. That's a good point.

Maybe a wind tunnel could be designed with a swash plate cyclic fan to create a wind speed gradient—just a thought.

Wind turbines are so yesterday, today it's all about geothermal, a dependable on-demand clean energy source...