Fixed v Floating Power Output

Wind & Water Structural Analysis
1

Hi Jason, all,

Just wondering if anyone has compared generator power output for fixed and floating OWTs and could share any findings?

I ran a quick test case as follows:

  • IEA 15MW turbine
  • Wind speed above rated (16m/s)
  • Turbulent wind modelled (TurbSim Kaimal spectrum with NTM normal turbulence model)
  • Challenging sea conditions (Hs 9.8m, Tp 14.1s)
  • 10 minute simulation
  • Fixed (platform motions disabled) and Free cases

Time History

image
image1618×954 89.7 KB

Statistics (ignoring the initial transient period)
Fixed Model
Mean : 15.015
Std : 0.132
Min : 14.56
Max : 15.46

Floating Model
Mean : 15.017
Std : 0.514
Min : 13.33
Max : 16.89

So it looks like the mean power is almost identical in both cases. The floating model shows more fluctuation in peak power and standard deviaiton. Also max power is abut 11% higher than rated power, so this may cause issues for turbine safety, possibly triggering shutdown

I should also stress that I’ve just run one quick test case, I haven’t looked at different wind or wave conditions, or mis-alignment etc.

If anyone has any comments/insights, or can recommend any technical papers to read, it would be interesting to learn more…

Kind regards,
Aengus.

2

Dear @Aengus.Connolly,

I can’t point to a specific paper that summarizes this effect across different metocean conditions, but your results are what I would expect for such a severe sea state for a turbine without a safety system shut down.

Best regards,

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