Comparison NREL 5 MW Land vs FOWT platforms

Wind & Water
21

Dear @Jason.Jonkman ,

I would be very grateful if you could tell me your opinion about the planning of simulations I have.

My target now is to compare the energy production and fatigue damage in the 5 MW wind turbine atop the OC4-DeepCwind and OC3 Hywind. I have a temporal series of data from 20 years in hourly resolution about wind speed, Hs, and Tp.

According to IEC 61400-3-2, I have organized all the data in bins of 2 m/s for the wind and 0.5 for the Hs and Tp. In total there are around 900 combinations of bins. I managed to count the occurrence of each combination of bins and computed the mean value of each bin in order to simulate that condition. I have something like this:

U90 Hs Tp Occurrence
1 0.75 8.25 100
3 0.75 10.75 50
3 0.75 10.25 6000
3 0.75 11.75 1
5 0.75 10.25 200
5 0.75 11.75 1
7 0.75 5.25 5000
7 0.75 6.75 2000
7 0.75 6.25 1

My doubt is that I don’t know what to do with the combinations of U90, Hs, and Tp that have a very low occurrence, like the ones in the table. Should I consider them and simulate those conditions, or is their contribution to the total negligible?

I’m not sure if they can really matter in an energy production and fatigue damage study like mine, and if I can save time and space in my computer storage, it would be better

PD: I am writing my own scripts to execute multiple simulations in parallel (I have a CPU with six cores so I am doing six simulations at a time).

Best regards,

22

Dear @Ignacio.Lopez,

If there are gaps in your data, it may be better to fit a probability distribution to your data rather than use the raw data directly.

Best regards,

23

Dear @Jason.Jonkman,

My problem is not related to gaps in my data; it is quite the opposite. I have a lot of data, and I’m having trouble managing it. That’s why I am asking for the best practice.

The table on the last post was just an example. Let me break it down in another way. My idea for the simulations is to fix a bin of U90, and analyse the values of Hs and Tp for that bin. I wanted to do that with every bin of wind speed. For example, for the bin [10-12) m/s I have this combinations of Hs and Tp.

BIN [10-12) m/s
U90 (m/s) Hs (m) Tp (s) Occurrence
[10-12) [0,5-1) [10-10,5) 5
[10-12) [0,5-1) [11-11,5) 1
[10-12) [0,5-1) [14,5-15) 1
[10-12) [0,5-1) [2,5-3) 113
[10-12) [0,5-1) [2-2,5) 9
[10-12) [0,5-1) [3,5-4) 1732
[10-12) [0,5-1) [3-3,5) 571
[10-12) [0,5-1) [4,5-5) 1061
[10-12) [0,5-1) [4-4,5) 2643
[10-12) [0,5-1) [5,5-6) 29
[10-12) [0,5-1) [5-5,5) 140
[10-12) [0,5-1) [6,5-7) 16
[10-12) [0,5-1) [6-6,5) 28
[10-12) [0,5-1) [7,5-8) 5
[10-12) [0,5-1) [7-7,5) 2
[10-12) [0,5-1) [8,5-9) 1
[10-12) [0,5-1) [8-8,5) 1
[10-12) [0,5-1) [9-9,5) 5
[10-12) [0-0,5) [1,5-2) 5
[10-12) [0-0,5) [2,5-3) 40
[10-12) [0-0,5) [2-2,5) 21
[10-12) [0-0,5) [3,5-4) 22
[10-12) [0-0,5) [3-3,5) 21
[10-12) [0-0,5) [4,5-5) 7
[10-12) [0-0,5) [4-4,5) 10
[10-12) [0-0,5) [5,5-6) 5
[10-12) [0-0,5) [5-5,5) 6
[10-12) [0-0,5) [6-6,5) 1
[10-12) [0-0,5) [7,5-8) 1
[10-12) [0-0,5) [7-7,5) 1
[10-12) [0-0,5) [8-8,5) 1
[10-12) [0-0,5) [9-9,5) 2
[10-12) [1,5-2) [10,5-11) 1
[10-12) [1,5-2) [10-10,5) 3
[10-12) [1,5-2) [11,5-12) 2
[10-12) [1,5-2) [11-11,5) 2
[10-12) [1,5-2) [5,5-6) 268
[10-12) [1,5-2) [5-5,5) 27
[10-12) [1,5-2) [6,5-7) 539
[10-12) [1,5-2) [6-6,5) 470
[10-12) [1,5-2) [7,5-8) 188
[10-12) [1,5-2) [7-7,5) 201
[10-12) [1,5-2) [8,5-9) 1
[10-12) [1,5-2) [8-8,5) 38
[10-12) [1,5-2) [9,5-10) 3
[10-12) [1,5-2) [9-9,5) 9
[10-12) [1-1,5) [10-10,5) 9
[10-12) [1-1,5) [11,5-12) 2
[10-12) [1-1,5) [11-11,5) 5
[10-12) [1-1,5) [2,5-3) 2
[10-12) [1-1,5) [3,5-4) 31
[10-12) [1-1,5) [3-3,5) 1
[10-12) [1-1,5) [4,5-5) 2861
[10-12) [1-1,5) [4-4,5) 661
[10-12) [1-1,5) [5,5-6) 1312
[10-12) [1-1,5) [5-5,5) 2534
[10-12) [1-1,5) [6,5-7) 100
[10-12) [1-1,5) [6-6,5) 350
[10-12) [1-1,5) [7,5-8) 16
[10-12) [1-1,5) [7-7,5) 12
[10-12) [1-1,5) [8-8,5) 10
[10-12) [1-1,5) [9,5-10) 1
[10-12) [1-1,5) [9-9,5) 17
[10-12) [2,5-3) [10-10,5) 4
[10-12) [2,5-3) [7,5-8) 73
[10-12) [2,5-3) [7-7,5) 8
[10-12) [2,5-3) [8,5-9) 32
[10-12) [2,5-3) [8-8,5) 82
[10-12) [2,5-3) [9,5-10) 9
[10-12) [2,5-3) [9-9,5) 71
[10-12) [2-2,5) [10,5-11) 1
[10-12) [2-2,5) [10-10,5) 5
[10-12) [2-2,5) [13-13,5) 1
[10-12) [2-2,5) [5,5-6) 2
[10-12) [2-2,5) [6,5-7) 83
[10-12) [2-2,5) [6-6,5) 38
[10-12) [2-2,5) [7,5-8) 245
[10-12) [2-2,5) [7-7,5) 78
[10-12) [2-2,5) [8,5-9) 16
[10-12) [2-2,5) [8-8,5) 197
[10-12) [2-2,5) [9,5-10) 5
[10-12) [2-2,5) [9-9,5) 42
[10-12) [3,5-4) [10-10,5) 7
[10-12) [3,5-4) [9-9,5) 4
[10-12) [3-3,5) [10-10,5) 7
[10-12) [3-3,5) [7,5-8) 1
[10-12) [3-3,5) [8,5-9) 1
[10-12) [3-3,5) [8-8,5) 11
[10-12) [3-3,5) [9,5-10) 5
[10-12) [3-3,5) [9-9,5) 14
[10-12) [4-4,5) [10-10,5) 2
[10-12) [4-4,5) [11,5-12) 1
[10-12) [5,5-6) [11-11,5) 1
[10-12) [5,5-6) [12-12,5) 1

I have tables like the one from above for every bin of U90. My idea was to simulate each row, writing the mean values in TurbSim and SeaState, but, as you can see, in all 20 years, there are some combinations that have a very low occurrence. What should I do with them? Should I simulate the low-occurrence cases or not?

After the simulations, to calculate the energy and the fatigue, I was planning to weight the results with the occurrence of each respective combination of U90, Hs and Tp, That’s why I am planning my work like this.

Is there a better way to do what I want to do, or is this a common practice?

Best regards,

24

Dear @Ignacio.Lopez,

Yes, I would say that what you suggest is common practice, although making larger bins (with larger Hs and Tp ranges) may provide sufficient accuracy to reduce the total number of simulations. Another common practice is to fit a distribution to the data rather than use the actual occurrences directly.

Best regards,

25

Dear @Jason.Jonkman,

The size of the bins I am using is the one recommended in the IEC 61400-3-2. I didn’t see that previously, but it also states that larger bins are possible if the calculated fatigue loads are not less conservative. Are you referring to this?

Best regards,

26

Yes, that is what I was referring too.

Best regards,

27

Dear @Jason.Jonkman,

I have finished the tests to check if larger bins were possible. Now I would be grateful if you could provide me some guidance in understanding the results.

IEC_SPAR_Lifetime_DELS
IEC_SPAR_Lifetime_DELS475×293 5.79 KB

BB_SPAR_Lifetime_DELS
BB_SPAR_Lifetime_DELS479×294 5.87 KB

IEC_SPAR_Lifetime_DAMAGE
IEC_SPAR_Lifetime_DAMAGE436×548 9.51 KB

BB_SPAR_Lifetime_DAMAGE
BB_SPAR_Lifetime_DAMAGE435×546 9.42 KB

To set the context, I chose the wind speed bin with the higher occurrence and simulated all the Hs and Tp combinations for each case. The sizes of the bins in each case are:

  • IEC_bins: U90 (2 m/s), Hs (0,5 m/s), Tp (0,5 m/s)
  • Big_bins (BB): U90 (2 m/s), Hs (1 m/s), Tp (1 m/s)

This way, what I wanted to do was to calculate the fraction of damage and the DEL that produces only this wind speed bin over the lifetime of the wind turbine. I don’t know if this is common practice, but I thought it was a quick way to check if the calculated fatigue loads are not less conservative.

Is it possible to use larger bins according to those results?

Best regards,

28

Dear @Ignacio.Lopez,

You haven’t labled which column is for the IEC_bins and which is for the Big_bins. Regardless, I feel you should be the judge of your own results.

Best regards,