direct drive wind turbines? 2

[alehman]

Siemens recently announced availability of a 3 MW direct-drive turbine. Their web site is severely lacking in any technical details however. Makes me wonder if it's real.

GE's acquisition of ScanWind (Norway) last year should put them in the direct-drive business, but I don't see anything about Scanwind products on the GE web site. Does anyone know the status?

The only other large direct drive design I know of is a 2.2 MW machine that Northern Power has had under development for some time. They have had a 100kW direct drive machine for several years.

It seems direct drive would have a lot of advantages in simplicity, reliability and maintenance. Can anyone shed any light on when any of these products my start appearing in the real world?

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[BigInch]

They have been out in the real world for awhile now. 5% of the wind turbine market today is direct drive. Enercon is the largest supplier of these types, having almost all of that 5% themselves.

Big advantage is removal of all the drive train and gearbox weight and inefficiency at the top of the tower, which comes at the apparently only slight disadvantage of adding some roughly equal voltage matching device inefficieny.

GE seems to be adsorbing Scanwind, supposedly to enter the direct drive market, but with GE's heavily vested interest in drive train-gearbox technology, and their relentless touting of their expertise in gearboxes as their main marketing gimic, I have some suspicions that they may delay implementation of Scanwind's direct drive until they are absolutely forced to move to it by Enercon and other rivals, as they gain a larger market share.

No matter what GE says about gearboxes, I believe that direct drive will capture the market. Enhanced reliability and the weight savings in the tower, reduced size of nacelles and reduced wind loads at the top of the tower are all important advantages that will force the change towards direct drive soon enough.

The next improvement to direct drive, or actually any PM generator, will be a significant reduction of the weight and size. A potential startup I know of right now is proposing a reduction in generator weight of 40% making a target size of 5 to 7 MW an economic possibility, especially advantageous for an offshore market.

**********************
"Being GREEN isn't easy" ..Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

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[Sparweb]

It seems GE is in the direct-drive WT business now, given the cover-page they got in Popular Science last month. Apart from Enercon, only a few major players have tried direct drive. It is much more common in smaller wind turbines, but I think you're interested in the giants instead.

The first thing that comes to mind is the grid's frequency (50Hz in Europe and 60Hz in North America). Large WT's like the big Vestas and GE's only turn the rotor once every second or two. There are two solutions to that. One is to gear up the rotor 50x-100x so that the generator can spin at 1200 or 1500 RPM. The other is to build a generator that works at really low speed - like 60 RPM if you're going to put it on a 30-40 meter rotor.

Motors and generators have a certain number of magnetic poles that correspond to their speed of operation. For instance, a European generator with 4 poles will turn about 1500-1600 RPM - this corresponds to the generator needed in the geared WT system. To make a generator work at 30 RPM, it will need 200 poles! This can be done with the new "rare-earth" magnets, but the amount of material required to make 200 of these big suckers is quite a feat of procurement and material science. Very expensive, fragile, and vulnerable to to corrosion and high temperatures.

All of these factors can be dealt with in the design, and I have no doubt a corporation in GE's class can deal with all of it. The process of getting all that to market, however, does take time, and some of it is "new technology" so I don't blame them for starting slow, gaining experience first.

They may not be thrilled with the fact that 100% of the entire world's supply of rare-earths for magnets is mined in China, subject to export taxes, and a Chinese government-set price that goes up a few % every year!


Steven Fahey, CET

 

[alehman]

Thanks for the replies. Just curious what others are thinking. I believe direct drive is the likely way of the future for these machines, but the technology seems to be slow getting to the market. I have wondered about the permanent magnets, but one manufacturer told me that procurement has not been a significant problem to date.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[BigInch]

http://www.enercon.de/en/_home.htm

http://www.greentechmedia.com/articles/read/wind-tubines-the-next-generation/

**********************
"Being GREEN isn't easy" ..Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/