More Power From Less Wind
Shrouded Wind
Wind power is currently limited by the fact that there is a minimum wind speed required for a wind turbine to begin operation. We could harvest a lot more energy from the wind if that minimum speed was lower. Plus it would help a lot if the wind passing the turbine was speeded up to make generation more effective. There is a new design for wind turbines which does exactly that.
FloDesign Wind Turbine, a spin-off from the aerospace company FloDesign based in Wilbraham, MA, has developed a wind turbine that could generate electricity at half the cost of conventional turbines. The company recently raised $6 million in its first round of venture financing and has announced partnerships with wind-farm developers.

The company's design, which draws on technology developed for jet engines, circumvents a fundamental limit to conventional wind turbines. Typically, as wind approaches a turbine, almost half of the air is forced around the blades rather than through them, and the energy in that deflected wind is lost. At best, traditional wind turbines capture only 59.3 percent of the energy in wind, a value called the Betz limit.

FloDesign surrounds its wind-turbine blades with a shroud that directs air through the blades and speeds it up, which increases power production. The new design generates as much power as a conventional wind turbine with blades twice as big in diameter. The smaller blade size and other factors allow the new turbines to be packed closer together than conventional turbines, increasing the amount of power that can be generated per acre of land.

The idea of enshrouding wind-turbine blades isn't new. But earlier designs were too big to be practical, or they didn't perform well, in part because the blades had to be very closely aligned to the direction of the wind--within three or four degrees, says Stanley Kowalski, FloDesign's CEO. The new blades are smaller and can work at angles of up to 15 to 20 degrees away from the direction of the wind.

One of the questions that will have to be answered is does the turbine wind up sounding like a jet engine? If so it will limit the places it can be deployed.

There are other problems as well. Like how will the rig stand up to 100 mph winds? Still it is a promising development.

H/T Helius at Talk Polywell.

Cross Posted at Power and Control

posted by Simon on 12.23.08 at 05:45 AM


It's intuitively wrong.

rhhardin   ·  December 23, 2008 6:41 AM

Actually, the benefits of this kind of design have been known almost since the invention of propellors in the 19th century. The newer American subs use ducted fans for propulsion.

The basic problem of wind intermittancy, however, is not solved. Every kw of wind power requires a kw of backup coal/nuclear/oil/gas/hydro, and the intermittancy poses severe problems to the stability of the transmission grid.

Sorry, I know you're a fan (no pun intended), but you are wrong about wind power.

Bob Sykes   ·  December 23, 2008 8:36 AM


Wind will extend our supplies of natural gas. It has its place. In fact wind is a hedge against rising natural gas prices.

And the intermittancy declines as lower speed winds become useful for electrical generation

In any case I'd like to see more work go into storage. A very neglected part of the equation.

Still wind is at 2% of the electrical supplies and can go to 10% without imperiling grid stability.

And yes - wind requires backup. Natural gas turbines are the obvious choice due to their lower capital costs.

The question is: what mix of wind and natural gas provides the lowest cost of electricity?

One thing to consider is that wind output is greatest in winter when the preferential use for natural gas is heating. Seems like a good balance to me.

M. Simon   ·  December 23, 2008 8:57 AM

I think the question missed in your comparison, M, is about nuclear.

At what point does nuclear become cheaper per MWh than wind? Is the cost to build, say, 100 standardized design reactors at 1000 MW more or less than the comparable wind farms? And that's assuming grid and transmission capacity.

The problem with the 'Pickens Plan' was always one of transmission cost. Does the cost of transmitting all that energy from tornado alley exceed the cost of putting reactors closer to the point of use?

At the risk of being flippant, wind power is the wave of the future, and always will be.

brian   ·  December 23, 2008 10:38 AM

Even if wind is ultimately not the way to go a 2 MV DC grid backbone would be a boon to national electrical energy reliability. It would allow power generation across several time zones. While demand in one area is peaking another area would be declining.

And I agree with you about T. Boone - He is a crook. If he was proposing a 2 MV DC backbone I might have more respect for him. But he just wants more HV AC with all its problems.

BTW wind is expected to be cheaper than coal or nuclear once turbine size goes above 8 to 12 MW peak. To get there faster subsidies for wind must decline - to zero.

With 345 KV AC, power transmission is limited to about 500 mi. A 2 MV DC backbone would extend that to about 2,000 mi.

M. Simon   ·  December 23, 2008 11:14 AM

This has been around, in reverse, for a long time. As My. Sykes notes, current US SSN designs use ducted props to improve propulsive efficiency. For the past few decades, US torpedoes have also used ducted propulsion systems. And Kort nozzles have been a standard feature on landing craft and other shallow draft vessels for at least a half century.

It still seems to me that wind power might be most effective in small scale applications, in home use for example. I'm not sure how long it will be before it could be scaled up to provide significant power over a large area, if ever.

Steve Skubinna   ·  December 23, 2008 11:57 AM

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