Modelling an 18MW turbine with OpenFAST

Wind & Water Structural Analysis
1

Hello,

I am interested in modelling an 18MW turbine with OpenFAST. I cannot find a reference turbine of this size so I was thinking about scaling up the IEA-15-240-RWT turbine which is publicly available. I noticed that NREL have published a power curve for an 18MW version… [2020ATB_NREL_Reference_18MW_263 — NREL/turbine-models power curve archive 0 documentation]. Apart from increasing the blade lengths and changing the hub height. I am wondering what other changes would be required to the OpenFAST model of the 15MW turbine.

  1. The individual blade span lengths could be scaled according to the blade length ratio, therefore moving the aerofoil profiles further away from the hub (I am assuming the same aerofoils could be used).
  2. Blade and hub masses could be upscaled similarly. Blade stiffnesses also.
  3. Would the chord lengths of the aerofoils need to be scaled also?
  4. Would the same ROSCO controller also work for the larger turbine? If not, would a new DLL be required or simply some changes to the .IN input file?

I would appreciate any advice from NREL or indeed any contributor who may have some experience in upscaling OpenFAST models.

Kind regards,

2

Dear @Oisin.Conway,

A similar question regarding scaling was discussed in the following forum topic: 2.5 MW WT.

Regarding your specific questions, I would say “yes” to 1-3, and for 4, I would say that the input file of ROSCO needs to be changed, but the DLL does not need to be changed.

Best regards,

3

Thank you @Jason.Jonkman.

4

Hi Oisin,
I am doing an upscaling from 15 MW to 20 MW. We can keep contact for some doubts we have. About the blade stiffnesses, did u find any relation to upscale stiffnesses? I am saying this because i have not found any relation. Plus, are u upscaling your turbine linearly or based on statistic methods?

br

5

Dear @Alberto.Utrera,

If you are referring to pure geometric scaling of the blade cross-sectional bending stiffness (E*I), this would scale with the length^4 (keeping the material properties the same).

Best regards,

6

Dear @Jason.Jonkman, when you say that bending stiffness scales with length^4, what would it be in terms of mathematic expression?

I suppose what you are referring to is as follows: Let’s suppose we want to do an upscaling from 15 MW to 20 MW, so the scaling factor would be sqrt (20/15)=1,1547. Is it correct if i say that the bending stiffness for the 20 MW wind turbine is going to be the 15 MW stiffness multiplied by (1,1547^4)?

Thank you very much.

7

Dear @Alberto.Utrera,

No, I meant that cross-sectional stiffness would scale with the length ratio to the fourth power, e.g.:

( bending stiffness for 20-MW turbine ) = ( bending stiffness for 15-MW turbine ) * ( ( blade length for 20-MW ) / ( blade length for 15-MW turbine ) ) ^ 4.

Best regards,