Some manufactures supply sets of power- and thrust-coefficient curves for different conditions, and then you type both curves into the WAsP turbine editor. However, I have also noticed manufactures who supply the same thrust-coefficient curve for different power curves. I think the argument is that the power curve is the most important one, as it influences the AEP more directly. The usually wake loss is only 5-10%, so a modified thrust-coefficient curve will not have as significant an effect on the AEP as a modified power curve.

Cheers,

Morten

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I am not fully sure if I understand your question, but WAsP can give you an AEP for a given input wind speed distribution. It cannot give you a 10 min timeseries of power production of each turbine.

Regards

Rogier]]>

I'm very happy to hear that Morten's clever workaround was what you needed, Windfrosch.

We have just made some changes to the wind farm in the soon-to-be-released WAsP 12.3, but there was no opportunity to implement support for your requirement. We will keep in mind for the future. It would be interesting to know if this is something that many users need.

Best wishes, Duncan.

]]>It is a standard deviation of the extreme wind estimate associated with the uncertainty of the fitted statistical model for the extreme-wind distribution. There are actually alternative models, see the post at http://www.wasptechnical.dk/forum/viewtopic.php?id=1060

When running the script you mention WEng will use the model defined by the selected extreme-wind-climate object, either annual maximum (AM), peak over threshold (POT) or spectral correction method (SC).

Cheers,

Morten

1) The extreme wind in WEng may be calculated by three alternative methods called the

annual maximum (AM), peak-over-threshold (POT) and spectral correction (SC) methods.

The theory differ for the three methods, but to generalize we could say that they

first fit a statistical model for extreme events and then used that model

to estimate the level of the extreme event with a fifty year return period.

The uncertainty of the 50-year extreme wind estimate depends on the uncertainty of the fitted model. Read more in the WEng help file section 'WAsP Engineering modelling| Extreme winds', specifically in the subsections called 'Extreme wind estimators' for the AM method, 'Extreme wind POT method' for the POT method and 'Spectral correction' for the SC method.

2) The footnote in IEC 61400-1 Ed.4 expresses the coefficient of variation (COV) by the alpha and beta parameters of the Gumbel distributions. Thus, COV depends on the fitted model and not directly on the uncertainty of the fit. However, the uncertainty is closely related to the Gumbel alpha parameter, so you could say that there is an indirect relation. Unfortunately, WEng no longer reports the fitted alpha and beta parameters, but if you look in the 'WAsP Engineering modelling| Extreme winds| Extreme wind estimators' section of the WEng help file you will find an easy way to calculate them by yearly maxima exactly as in WEng when using the AM method. Alternatively, you can read the 100-year event from the graphs in WEng showing extreme winds as function of return period and then use the formula in the footnote of the IEC standard.

With best regards,

Morten

in my test case for for one wind farm in "Windfarm overview -> Flow conditions" I see that all WTGs have a problem regarding Iextreme,amb.

But in the "Reports for selected site -> Eff. turb. table" in the defined wind speed range, all the Iex,site values are below ETM values.

I assume Iextreme,amb is the same as Iex,site.

Is this perhaps an issue that has not been updated after final release of 61400 Ed.4?

Thank you very much and kind regards,

Sinisa Knezevic

Data format is as follows:

2015-01-01 00:00:00,9.4,43

2015-01-01 00:10:00,9.2,44

2015-01-01 00:20:00,9.3,43

2015-01-01 00:30:00,10.1,41

2015-01-01 00:40:00,10.3,41

I tested it with only 10 records, but it cannot finish with "reading file" message.

No error message comes, but "reading file" continues.

What should I do.

Mitsuru Haraoka

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