Why wind turbines don't have their dynamos closer to ground?

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Discussion Overview

The discussion revolves around the placement of electric generators in wind turbines, specifically why they are typically mounted at the top of the tower rather than closer to the ground. Participants explore various implications of this design choice, including maintenance, weight distribution, and mechanical efficiency.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Exploratory

Main Points Raised

  • Some participants suggest that placing the generator closer to the ground could simplify maintenance and reduce the weight of the tower.
  • Others question the assumption that the generator would weigh less if moved to the ground, pointing out that the overall weight the tower must support is influenced by multiple factors.
  • A participant proposes that frictional losses in the drive system might negate any weight advantages gained by relocating the generator.
  • Concerns are raised about the mechanical implications of using a long vertical drive shaft, including potential instability and torque issues affecting the turbine's ability to face the wind.
  • It is noted that even if the generator were at the base, other equipment would still need to be located at the top of the tower, complicating the weight considerations.
  • Some participants highlight that the wind forces on the turbine blades may exceed the generator's weight, suggesting that a heavier tower could enhance stability against wind stresses.

Areas of Agreement / Disagreement

Participants express differing views on the advantages and disadvantages of relocating the generator. There is no consensus on whether the benefits of easier maintenance and reduced tower weight outweigh the potential mechanical challenges and friction losses associated with a longer drive shaft.

Contextual Notes

Participants acknowledge that the weight of the generator is minor compared to the wind stresses on the turbine, and that the design of the drive system introduces additional complexities that are not fully resolved in the discussion.

kevin_tee
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Why don't the electric generator mount closer to the ground. The advantage I can think is that it is easy to maintain(no need to climb) and reduce weight(reduce tower cost), however the extended shaft will cost more. Does the longer shaft cost out weight the easier maintenance and generator weight? Thanks
 
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Why would the generator weigh less if you put it on the ground instead of up near the top?
 
You make a good point that the tower could weigh less with the generator at the bottom. My guess is that the frictional losses in the 90-degree gear drive must "outweigh" that weight advantage.

If the turbine were on a vertical axis (as some are), that wouldn't be a problem. I don't think that's as efficient though.
 
Drakkith said:
Why would the generator weigh less if you put it on the ground instead of up near the top?
I am referring to the weight that the tower need to support.
 
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Randy Beikmann said:
You make a good point that the tower could weigh less with the generator at the bottom. My guess is that the frictional losses in the 90-degree gear drive must "outweigh" that weight advantage.

If the turbine were on a vertical axis (as some are), that wouldn't be a problem. I don't think that's as efficient though.

I see, so there are quite a lot of friction there.
 
In most designs the actual generator is only one part of the total equipment needed at the tower head . A lot of the equipment would still have to be up there even if you moved the generator to the tower base .

Illustration
 
kevin_tee said:
I am referring to the weight that the tower need to support.

The weight of the generator and what this adds to the tower requirements is minor compared to the wind stresses the tower and turbine have to deal with. The weight of the drive shaft would probably be higher, plus the tower would also have to deal with the reaction torque.
 
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If a long vertical drive shaft was used with insufficient bearings in the tower, it would twirl.

A right-angle gearbox driving a vertical shaft would apply a torque to the tower head that would make the head harder to point into the wind.

The forces on the blades from the wind will probably be greater than the weight of the generator. Maybe more mass in the tower makes the tower more stable and less resonant at some wind speeds.
 

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