Efficiency of wind power plants

Mike ODELL mo at ccr.org
Sun Apr 29 20:11:47 CDT 2012

An excellent illustration of why all the design effort these days is focused on direct drive generators.
The thesis is straightforward, which is not the same as "simple". Direct drive turbines 
Have no gearbox and the alternators are usually permanent magnet with lots of
Poles and phases. The power is bulk rectified and then big inverters make what you
Want from the raw material.  Replace the transmission with transistors. You need
Something Big in there somehow, might as well make it small and light by
Comparison with a gearbox that can handle a million foot pounds of torque.

All the new turbines are in the 5-7 MW range and most of them are all direct drive
Or at least have much less gearing than the 2MW class machines.

Boulder Wind Power is an NEA company that is a pioneer in direct-drive PM
Generators using axial flux geometry and windings fabricated using PCB
Technology. Solves a number of efficiency problems like turn-ends and flux path length.
The generators also come apart in sections so you don't have to transport the whole thing
Assembled. That is a big issue, too.

 the Boulder Wind machine driveline also has 1/12th the number of bearings
Of its geared competitors and the nacelle weights only about 30%. This  means
Much smaller yaw drives and bearings. The main bearings are also very near
The vertical centerline so the precession forces have a much shorter moment arm.
Those are the forces the try to rip the nacelle off the tower 90 degrees
To the wind when the big rotor (a huge gyro) yaws in the wind. So a  great
Many things come from direct drive turbines, although being rid of the damnable
Gearbox makes it worth the trouble all by itself,


Sent from my iPad so please excuse the jammy fingers.

On Apr 25, 2012, at 9:50 PM, Andre Kesteloot <andre.kesteloot at verizon.net> wrote:

> http://www.electronicdesign.com/article/power/dont-expect-large-wind-plants-provide-lot-energy-73713?cid=ed_newsletter&NL=1&YM_
> 73
> André N4ICK
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