Not sure how I found this (I think Reddit technology) but an OffGrid World article on a new wind tower configuration looks very odd but seems to work up to 6X(?!) better than most others that are deployed today. The new wind tower is being built by SheerWind.
The tower has what looks to be a set of funnels around the top (checkout the picture) that funnel wind power and vent it downward into a long duct out along the ground.
Inside the ground duct lies a Venturi effect tube section which constricts and speeds up the wind coming in from the top. After the Venturi effect component lies a small wind turbine power unit.
Bby placing the wind turbine on the ground, it becomes a lot more accessible. Also, the wind turbine blades can be much smaller due to the increase in wind speed. Finally, the tower is not nearly as tall as current wind turbine towers.
Sheerwind says that the new wind tower can generate electricity from wind speeds as little as 2MPH and will generate, on average, 3.14X more electricity from the same wind power as standard turbines do. These statistics are from some field data they published from their testing.
Still, the thing is huge, the down duct exit funnel has a diameter of twice the man standing next to it.
Couple of potential Improvements
Here are a few thoughts that came to me on some improvements to the tower configuration. One thing I noticed in the field results data is that the turbine speed (wind speed?) seems to be somewhat faster in certain directions than others at the same intake funnel wind speed. From this I would surmise that wind flowing in the direction of the ground duct works better than wind in the opposite direction.
As such, I would suggest that they do away with the long ground duct all together and just place the Venturi valve and the wind turbine somewhere in the down ducting. This would eliminate one curve which should boost effective wind speed at the turbine, at least and should eliminate any direction sensitivity to the turbine speeds.
Below the turbine I would have a sort of reverse funnel with a cone at the bottom of it to push the air out along the ground in all directions.
Also, as the wind speed ratio (incoming speed to wind speed at turbine) averages out to be a factor of 1.8, I would think a second turbine downstream from the first with perhaps two blades could extract some more useful power from the air stream before it’s dumped into the atmosphere.
Finally, as wind speed is often different depending on the height off the ground, I might consider lifting or lowering the top of the tower (the funnel section) to supply the optimum wind speed available. You’d need to have the down duct and its support superstructure to be expandable or contractable and you would want to lesson the weight of the flexible part of the top of the tower. You could do this with an array of electronic wind sensors and servo control logic and motors which would take wind speed samples at various heights and cause the servo motors to raise or lower the tower height. But I believe letting the wind power passively move the top up or down would be more effective in the long run and potentially cheaper to boot. How this would work I have no idea.
Also I would be interested to understand the exit wind speed after all the above, there may still be some energy to be gained from the airstream.
Photo Credit(s): From SheerWind.com’s Website, © 2014 SheerWind