This page describes an idea I had for a vertical axis wind turbine. The main concept is to keep flat paddles oriented so that they are flat to the wind on one side and edge-on on the other. At the front and back (with respect to the wind) they also end up oriented at 45° such that they push in the direction of rotation in both cases.
This isn't meant to be a be-all end-all design, just an idea I had that I hadn't seen described before.
I have since then found another wind turbine design where the blades are pivoted back and forth via a linkage depending on where they are in the rotation cycle. This may appear similar at first glance, but actually operates quite differently. The blades are edge-on to the wind on both side and power comes from the front and back phases. Since the blades get pivoted back and forth as apposed to continuously rotate, they do not need to be at 45° at the front and back. This means they can be flatter to the wind and move sideways faster than the wind. In other words, this is a lift design whereas my idea is a drag design.
I hope the picture explains the mechanics well enough so that additional description is not needed. The important part is that the paddles pivot at half the speed and in the same direction as the center gear driven by the wind vane. Large spur gears are shown with one tooth marked to better illustrate the relative rotations. In practise a chain drive would be more appropriate.
It may help to see the device in action. Click on these links to see different animations:
This information came from Dave Reffin who lives near Orere Point on the North Island of New Zealand. He came up with the idea independently and found this web site in the process of looking around to see what similar might be out there. Dave has built a working unit, and has provided pictures and a animation. Click on the pictures below to see the originals as he sent them. The last one is a animation of the windmill in action.
Edward has put up a web site about this same general concept. He shows a basic diagram, but has a good collection of references to prior art and patents.
I found this paper while looking around on the web. This link is to a copy on my web site since I don't know whether the original might move or be taken down. The authors and their affiliation are shown in the paper, so hopefully they won't mind. Unfortunately there is no date on this paper, but it must be after June 2004 since that's the latest reference.
It is interesting to note the high aspect ratio of the blades. I suspect that squarish blades are more efficient, but haven't tried to prove that.
Several people have asked how I made the image and animations. This was done with our own "slide making program" called SLIDE. It started out in the early 1980s to write text to computer images that would be written to slides via a film recorder. It has gone thru two major rewrites since then. It is now essentially a full programming language that sits on top of RENDlib, our 3D graphics library. It has the normal constructs of a programming language, like variables, subroutines, arithmetic expressions, loops, and the like. It also has some features specific to 2D and 3D graphics built in, like transformation data types and operators, color, polygons, visual properties like emissive, diffuse, and specular, and a few other things. Since it is a RENDlib client, it has access to full software rendering, anti-aliasing, ray tracing, image file generation, and many of the other RENDlib features.
The SLIDE program has been added to the "everything" software release at the software downloads page. After installing the release, you can read the SLIDE.TXT documentation file in the DOC directory.
The SLIDE source code, W.SL, for making the pictures
here is only a bit over 300 lines long. It is a text file and can
be viewed with an ordinary text editor. If you install SLIDE, it
can also serve as an example. The command
slide w -dev screen -frame 18will render the picture above on your screen although it will be Z buffered. The command
slide w -dev screen -frame 18 -raywill render the same picture as above live on your screen, including the ray tracing.