





Now take a bunch of the structures depicted in the last step and connect them together with arcs to form a giant circular wind dam:


Drive System
Notice that since a given “Totem Pole” of HAWT rotors are stacked one on top of another, they can share a common drive chain. This common drive chain ultimately drives a sprocket that drives the generator shaft. The generator is located in a small compartment on the ground, beneath its “Totem pole” of turbine rotors.
Does This Turbine Require a Yawing System?
I can think of two variations of the I Dream of Genie Wind Dam as regards the yaw drive. The first version would always have all of the rotors turning, regardless of which direction the wind is blowing in. This would be easier to explain if I could draw a nicer 3D model, but I’m not much of an artist, so bear with me here. All rotors can rotate simultaneously because some of the high speed wind moving around the outside of the dam seeks the “smallest radial path”, meaning it will eventually force its way through a rotor to the inside of the wind dam. The wind outside the dam that does not manage to find its way into this smaller radial space will instead shoot off the bowed out end of one of the wall sections (much like the wind shoots off the trailing edge of an airfoil). This will create a low pressure region in the smaller radial locations that “suddenly appear” next to this high speed air at the moment it shoots off that bowed out edge of the wall. This low pressure sucks low speed high pressure air from the inside of the dam through the rotor that is near the high speed air that is shooting off the bowed out end of the wall.
In the variation just described, the rotors do indeed need to assume one of two yaw angles, each separated by 180 degrees. (Alternatively, the blades may have variable pitch so that they can accommodate the flow of wind in either direction through the rotor.)
The other variation would have doors that can block the “hole” that is occupied by the rotor. In this variation, all the rotors that pass wind from the outside of the dam to the inside of the dam (given wind direction) have their doors opened, while the doors of all the other rotors are closed, rendering those rotors inoperable. Or you could do it the other way around, allowing air to be sucked out of the inside of the wind dam, but not to be forced from the outside of the wind dam to the inside. In this case a yaw system is not required. This is so because the door will always be closed when wind has a tendency to flow through the accompanying rotor in the “wrong direction”.
Third World Variation
Think of how easy it would be to build a low cost variation of this machine for the developing world! Imagine that instead of building a circular dam, we’ll build one that is polygonal, with an approximately circular shape. Maybe the circle has 10 or 12 sides. So we put concrete columns or telephone poles up in the shape of the polygon. We have one set of telephone poles for the “smaller radius” polygon, and another set for the “larger radius” polygon. Now we string cable between the poles. The following diagram shows just one side of the polygon, and uses blue to represent the cables connecting the “larger radius” polygon, and green to represent the cables connecting the “smaller radius” polygon:

Now take some of that beautiful multi-colored fabric like they have in India and wrap it back and forth around the cables to imitate the I Dream of Genie Channels:

When wind flows around sharp edges, it tends to create turbulence. To avoid this tendency, we might like to use something with a larger diameter than cables. How about we use cheap PVC pipe? Then we can string the cables through the inside of the PVC pipe. This way the cables can provide a great deal of strength and stiffness to the structure, yet the cables will have no adverse affect on the aerodynamics.
For More Information on Wind Dams

For further information related to this idea, see the earlier Salient White Elephant post: Circular Wind Dam.






This turbine produces power in pulses. Each time two blades that are traveling in opposite directions pass each other, their generator components (permanent magnets and coils) pass close to each other as well. So a pulse of power is produced when two blades pass each other. Obviously, it would be better for a turbine to produce power at a smooth constant rate. This is desirable for many reasons. For one thing, producing power in pulses applies a cyclic fatigueing load on the mechanical components, and this is obviously bad news. For another, the electricity is easier to process and manipulate if it is produced at a smooth regular rate. But I am hypothesizing that the design proposed here may be a good one because it allows blades to be supported at both blade tips, even as both tips travel at high velocity! This is a tremendous advantage. But the main advantage of this design is that although it allows blades to travel long distances guided only by slots that are cut into blade guides, it does not require for these long distances to have generator components (magnets and/or coils) distributed along these long portions of the blade guides. Instead, the generator components are compact, and are attached to the ends of the airfoils. You can think of all of the airfoils that rotate (say) clockwise as comprising the generator “stator”, while all of those rotating counter-clockwise comprise the generator rotor. Of course, another disadvantage of this approach is that slip rings would be required to get the power away from the blades and into the electrical system. But there’s another advantage as well – the fact that the generator’s rotor and “stator” rotate with equal and opposite rpm’s effectively doubles the relative speed with which the coils and magnets pass each other.
Now Cut a hole in the top, and cover the hole with a shroud that can yaw in order to keep its opening pointing upwind. Also add vents near the lower part of the dome can than be either opened or closed:
The variation depiced above has air flowing into the hole at the top of the dome and out of the vents below. I’m not sure this is the best arrangement. The alternative would be to have air flowing into the lower vents and out of the hole in the top. In this variation, the shroud over the top hole in the diagram would be yawed (rotated) 180 degrees, and (I’m guessing) the left two vents in the diagram would be open, while the other vents would be closed. I guess one of these ideas is probably aerodynamically superior to the other, but I don’t know which is which. It’s worth noting that the real low pressure should be at the top of the dome, since this is where the wind has been accelerated the most. Seems like it might make sense then to let the wind flow in to the lower vents (where pressure is naturally higher), and out through the hole in the top. I don’t know much about the theory of fluid flow, so I’ll leave the rest to those of you who have the academic background to model and solve a problem like this.
Powered Bicycles in the City
Soft, pastel colored cotton ropes move through the city driven by pulley wheels. If you get tired of pedaling, you just grab on to the rope and it pulls you along. This would be particularly useful in places like San Francisco where lots of people want to ride a bike, but the hills are just too steep. A person could pedal on the level areas, coast downhill, and hold the rope to go up hill.
Of course, you don’t actually grab hold of a rope, because that would make it hard to balance. There’s a mechanical device that is easily flipped over that grabs the rope and transfers the force in a way that doesn’t throw you off balance. And this also allows you to have both hands on the handlebars.
One of the nicest things about China was its bicycle transportation system. Of course, I don’t guess there’s much left of it now, thanks to the magic of capitalism and its ability to turn every corner of life into the dullest and most discouraging of chores. I believe this is what Adam Smith was referring to when he coined the phrase “the invisible butt of the free market economy”. But let me tell you something – you haven’t lived until you’ve traveled to your destination anywhere in the city alongside young girls that just stepped out of a fashion magazine and wise old leather-skinned men and women with impenetrable facial expressions that have seen hardships you can’t imagine… everybody cruising along at about 15 miles per hour, no diesel smoke stinging your nostrils, birds chirping, and the nicest widest bike path you can imagine meandering through the city. There wasn’t a road you needed to travel that didn’t have one of these cadillac bike paths, for in 1990s China, the bicycle was the mode of transportation, and everything else had to get out of the way. And as for those wise old men and women and the emotional burdens of past hardship they carried, seems like most of them usually had the most calm and content aura, impenetrable though it was. How could that be? I don’t know, but I think it had something to do with the magic of riding a bicycle, the healthy bodies that bike riding produced (you couldn’t find an obese person in China in those days), the chirping birds, and most of all, the fact that you were king of the road.
… old stogies I have found,
shooooort, and not to big around I’m a…
maaaaan o means by no means,
King o the Roooad!