Vertical wind turbine with two concentric rotors

Summary
I am not an engineer, just a guy who knows some CAD and has some experience with a 3D printer.

I want to build a wind turbine with two concentric rotors that would allow this device to effectively adjust itself to any wind speed, to gusty winds, to storms and to gentle breeze, and to work quietly.
Hello.
For a long time, I wanted to build a wind turbine prototype that would have two concentric rotors.

The design was inspired by an automotive torque converter, used with automatic transmissions.
This device would have an external rotor that would be coupled to one generator and an internal rotor that would be coupled to another generator.

By adjusting the load on each of the two generators, I am looking to achieve a very smooth, consistent "power curve" that would allow me to charge a battery bank at different wind speeds/types, effectively using all the energy of the wind, while reducing the cost by minimizing the requirements for precision parts.

A wind that is fast and gusty would be utilized by allowing one combination of loads that would allow the turbines to rotate and produce optimal output. A gentle breeze would be utilized with a different ratio of loads on the generators.

One of the turbines can be coupled to a pump that would lift water into a water tower, while another blade would be loaded in such way as to keep the main turbine rotating at the optimal speed for the pump to operate, by using an electric generator with a variable electrical load (charging system).

Such configuration can allow a wind turbine to power a mechanical load directly over a wider range of wind speeds, reducing the electrical power conversion/transmission losses. I can already see many applications for such systems.

The external rotor would also offer a simple mechanism that would allow all the blades to be rotated sideways, so the outer turbine would remain stationary, trail with the wing like a weather cock and protect the inner rotor from damage by extremely high rotation speeds.

In my original design, the blades of the internal rotor redirect air vertically, along the axis.(Is this useful?)

An interference pattern between two concentric rotors would minimize the drag, produced by the wind, as the blade is traveling against the direction of the wind, on the opposite side of the vertical wind turbine. (a drawback of a conventional vertical wind mill design)

I had a dream about this wind turbine once, a vision stuck in my head since.

I see that this approach may allow for a very cheap wind turbines to become available.

One of the major advantages of building such wind turbine turbine that I perceive is that the central rotor would be a higher precision, smaller diameter part that would rotate at faster speeds, while the outer rotor would be a less precise, the blades would be made out of stretched vinyl banner fabric, directing the wind at higher velocities to the inner turbine. This, by itself is not a unique idea.

The turbine would generate electricity while also bringing revenue through billboard advertisements.
However, at lower breeze speeds it would be allowed to freewheel and to capture slower winds.

I don't know what the optimal load ratios on each turbine would be for each wind speed.

The adjustment of load for each individual turbine would allow the generator to achieve the same effect that the angle of change of the blades achieves in a conventional horizontal wind turbine, yet at a lower cost with a smaller number of precision parts that require balancing.

I also see that such wind turbines can phase out commercial billboards.
The outer blades would be designed so advertisement can be readable at low wind speeds.

With appropriate strobe lighting, synchronized to illuminate a specific vinyl fabric turbine blade with a design, such device could become an impressive advertisement for green businesses, an animated advertisement, consisting of several frames, with each frame printed on a vinyl banner, resembling a blade.

If this idea has a practical application, I would like it to remain in the public domain.
I would like to ensure that all profits generated from such advertising would go towards research and development of renewable energy systems and sustainable living products.

I have some drawings in my notebook and some 3D models of the internal rotor that are not very presentable.
I would like to build everything with straight blades and experiment with generator loads before I consider anything else.

I would like to print it on a 3D printer in segments that would fit inside the 3D printer. Possibly, I would like to make the inside rotors so each has its own bearings and so that they interlock, once I slide them onto a shaft.
The stator would be built

The experimental design that I intend on building would vary from the concept design since 3D printing offers its limitations.
I am still not sure about how I would construct the outer squirrel cage of the outer rotor and how I would couple it to it's generator.
It is very likely that I would use the motors that are sold for electric bicycle conversion, as generators since they seem to offer very desirable characteristics.

I would like to read some pros and cons of this design before I move ahead with building this project.

Thank you.
--Vladimir Tolskiy
 

anorlunda

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Why begin with the complexity of the generators? Why not start with small 3D printed wind vanes as an experiment? Measure their properties and their efficiency.

By the way, there is a theoretical limit to the efficiency of wind turbines that applies to all designs, including yours. See https://en.wikipedia.org/wiki/Betz's_law
 
I am aware of the theoretical limit of the wind turbine's efficiency.
I am also aware that the outer turbine/blade set would increase the wind velocity for the inner turbine.
The main parameter that I think about is cost.

Perhaps I am going to build a small toy at first.
A DC motor and a stepper motor with a rectifier will serve as my generators.
 
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IIRC, there was a vertical-axis design some years ago that had the inner and outer rotors contra-rotating.

An 'amateur' crafting, it was, IIRC, intended for 'off-grid' use, with the faster inner producing electricity, and the slower but torque-rich outer either pumping water or running simple machinery. I've never seen such since, as the remarkable mini-turbines designed for yachties seem to have cornered the market.
YMMV.
 

Baluncore

Science Advisor
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You need to produce drawings or sketches to show what you are actually considering.
A verbal description is insufficient.

There are many simple commercial designs of wind turbine available today. The cost and payback time of those is less than the cost of designing and building any new design. If you need an economic wind turbine, buy an existing design.

As long as it remains a dream, it will be perfect in your mind. That will not change until you wake up to the reality of the thousands of complex engineering decisions that must be made before it can be built. Only once it is built can it begin to pay back it's design and construction costs. If you have time and resources, study engineering for 3 years.
 

berkeman

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Summary: I am not an engineer, just a guy who knows some CAD and has some experience with a 3D printer.

I want to build a wind turbine with two concentric rotors that would allow this device to effectively adjust itself to any wind speed, to gusty winds, to storms and to gentle breeze, and to work quietly.

One of the major advantages of building such wind turbine turbine that I perceive is that the central rotor would be a higher precision, smaller diameter part that would rotate at faster speeds, while the outer rotor would be a less precise, the blades would be made out of stretched vinyl banner fabric, directing the wind at higher velocities to the inner turbine.
It seems that nesting the turbine blade structures will create shadowing, which will reduce efficiency significantly compared to using two separate turbine blade structures. Why design something on purpose that starts out life with a built-in efficiency degradation?


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cjl

Science Advisor
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Do you have a drawing or something to show what your concept is in more detail? I'm having a hard time visualizing it. Also, it's worth noting that if your large rotor is crude (you describe fabric stretched over a frame), you're giving up a tremendous amount of the potential power. Most of your swept area comes from the blade tips, so you really want your most efficient airfoils out there.

It's worth noting that modern horizontal-axis wind turbines can regularly achieve power coefficients of 0.45 or higher, so they're already approaching the Betz limit, so there's really not much to be gained there. A drastic cost reduction would be very significant, but I don't see how your design would achieve that.
 
Thank you. Perhaps my design would not work and is not worth it.
I made several attempts to draw it and none of my designs considered things that you mentioned.
 

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