The main thing that keeps you from pulling more energy out of the wind is that after a point the air starts to move around the blades, spilling over the tips of the blades, so a ring like that is going to help "trap" that wind, the more you can keep that high pressure air from spilling over the tips of the blades the more force the blades are going to see and the back side of the blades is going to see a lower the pressure.
but my point early on was, if we just make the turbine a little bigger we also see a big jump in power output because you are collecting more energy from a larger area and however you look at it, the generator at the hub is going to have to increase in size at some point as well.

Larger wind turbines are more efficient. The biggest development recently is direct drive -- older turbine have a step up transmission, which adds a lot of complexity, and was the most trouble prone part, and increased the weight a lot (~17 tons!). Direct drive is much more reliable, cost less, weigh less.

Land turbines are low cost -- less than most other sources. Ocean based turbines cost more, but they are more productive, too.

"Ocean based turbines cost more" is also very expensive to get installed around here.
Since the 'Beautiful People' who have places on the Cape (and also own sailboats),
don't want anything detracting from their view of the ocean.

I'm not to sure about the ring but check out Wind from Cleveland State University (PDF opening in google Docs) In the paper they are using 2 to 4 smaller turbines that are connected to a turn table on top of a water tower. Since wind speeds up when it goes around an object it can take advantage to lower speed winds.

Right, that's what I meant -- that the overall cost of ocean based wind turbines is higher. Those beautiful smoke stacks and cooling towers are not visible from the same places as the turbines, I guess?

That's right Neil, poor people get to look at smoke stacks and cooling towers, while rich people have the weight to stop wind turbines from obstructing their view.