I Why is it claimed that Betz's limit is a law?

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Betz's limit, which states that no wind turbine can capture more than 59.3% of the kinetic energy in wind, is often mischaracterized as a law despite being a theoretical maximum. Large wind turbines operate efficiently near this limit but are designed to stop in high winds to prevent blade damage due to bending stresses. The discussion highlights the potential of piezoelectric systems to double the power coefficient if they could fully convert mechanical stress into electricity, although this remains theoretical. The conversation also explores the dynamics of forces in wind turbines and sailboats, emphasizing that the efficiency of energy extraction is not solely dependent on wind speed. Ultimately, while Betz's limit is a valid theory, it has not been universally accepted as a law in scientific literature.
  • #31
normandajc said:
For Darrieus type turbines, the stresses vary during each turn. You do have a notion of time. It is possible to transform constraints into additional energy recovery.
Time varying stress still isn't energy.

I agree with @Arjan82 ; at best, you are trying to use the same energy twice, and glossing-over it.

Since evidently this is your own unpublished "personal theory", it is not appropriate for discussion on PF. If you get it published in a reputable journal we can discuss it further, but I don't think publication is likely since it appears to suggest a violation of conservation of energy.
 
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