Commenter Godfrey makes some good points over at the bd site:
Chetwood Associates’ sail-like ‘wind dam’ lands on Lake Lagoda - Building Design
Godfrey 15 November, 2007 Looks nice but unfortunately the idea is completely flawed and demonstrates a total lack of understanding in fluid dynamics (amongst other areas of physics). 'Dams' work because of the difference in potential between one side and the other. In a water dam, the differential is the gravitational potential energy of the water on one side vs the other. The size of the dam is unimportant for electricity generation, only the difference in altitudes. The energy harnessed is the potential energy lost moving water from higher altitude to low altitude. A wind turbine of the type here is exactly like the ones in the fields. What this 'sail' intends to do is increase the wind velocity over the blades and hence generate more power. However, as with water turbines, the power generated comes from a loss of potential energy. Here the potential is pressure. There must be a higher total air pressure on the inlet side of the turbine than at the outlet otherwise the air wouldn't flow. Sails are not used to generate pressure differentials, they are intended to generate force. The pressure difference on either side of a yacht sail is not much. But bigger sails deilver more motive force than smaller, because the small pressure differential is over a larger area. All a bigger sail will do in this design is create bigger forces, not larger flows through the turbine. And by the way, turbines (which are NOT propellers) work because air 'escapes' around them, not in spite of the fact. Sorry to party poop, but there are very good reasons why this hasn't been done before.
Looks nice but unfortunately the idea is completely flawed and demonstrates a total lack of understanding in fluid dynamics (amongst other areas of physics). 'Dams' work because of the difference in potential between one side and the other. In a water dam, the differential is the gravitational potential energy of the water on one side vs the other. The size of the dam is unimportant for electricity generation, only the difference in altitudes. The energy harnessed is the potential energy lost moving water from higher altitude to low altitude. A wind turbine of the type here is exactly like the ones in the fields. What this 'sail' intends to do is increase the wind velocity over the blades and hence generate more power. However, as with water turbines, the power generated comes from a loss of potential energy. Here the potential is pressure. There must be a higher total air pressure on the inlet side of the turbine than at the outlet otherwise the air wouldn't flow. Sails are not used to generate pressure differentials, they are intended to generate force. The pressure difference on either side of a yacht sail is not much. But bigger sails deilver more motive force than smaller, because the small pressure differential is over a larger area. All a bigger sail will do in this design is create bigger forces, not larger flows through the turbine. And by the way, turbines (which are NOT propellers) work because air 'escapes' around them, not in spite of the fact. Sorry to party poop, but there are very good reasons why this hasn't been done before.
Sails are not used to generate pressure differentials, they are intended to generate force.
It may be true though that a spinnaker is more toward the force directing mode since it is used when running before the wind, but that is not what the commenter said. Yet, even being right about that, the conclusion can be wrong...there would be difference in potentials where the turbine is driven.
The first concept that I had when I saw this was the small wind catching sails that we would place over the hatches on hot languid nights in the Caribbean. I'm betting on Russia on this one. Never underestimate their intelligence, always underestimate their knowledge.
Frank Delaney ~ Ireland
this looks like a water-type dam for a lighter fluid (air) where the ambition as with any dam for power -- a weir and mill, a megadam and turbines -- is to increase the psi at the point of capture by having a wide "bucket" to funnel water into the turbine.
mainsail of a yacht is a very different kettle of wind, using the aerofoil effect.
a spinny is a big bag of wind not using the aerofoil effect (downwind only), so somewhat similar, but it still doesn't collect air in order to drive it through a narrow opening at high velocity. what this app is most like, imho, is the old trick of using a balloon to make a rude noise. The difference between theory and practise in practise ...
Fluid mechanics is a bit tricky and there might have been some good modeling I do not know about involved, but from the look of it, I would expect that structure to have more force acting on it (increased risk of damages to the structure) but not that much higher output. Imagine if you like a big wave (water being the fluid we are generally most acquainted with) hitting that thing. Supposing it holds, how much of the water will pour through the turbine and how much will spill on the sides?
