Wrong Roughness Used In Downscaling EmdConWx: Difference between revisions

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[[Category:windPRO 3.0 Service Pack 3]]
[[Category:windPRO 3.0 Service Pack 3]]
[[Category:windPRO Known Issues-3.0]]
[[Category:windPRO Known Issues-3.0]]
[[Category:windPRO Known Issues]]
[[Category:windPRO Known Issues]]


'''Status:''' Open - part of windPRO 3.0 Service Pack 3
'''Status:''' Closed - part of windPRO 3.0 Service Pack 3


'''Fixed in build:''' 633
'''Fixed in build:''' 633


In time-varying calculations that uses the Scaler for downscaling EmdConWx data there was an error in the meso-scale roughness data used. The default Meso-scale downscaler is supposed to use the minimum roughness data from the meso-scale terrain. However, for EmdConWx data downloaded after the 25th of February 2015 the minimum and maximum roughness was mixed around so that the maximum roughness was used instead.  
For PARK-calculations using the '''Scaler to downscale the EMD-ConWx''' meso scale data we noticed a problem which is fixed in Service Pack 3. The problem is related to the downscaling method only and '''does not affect''' the use of the meso scale data as regular time series as for:
 
* Long-term-correlation via MCP
* creating a wind-index
 
 
In case the data is used for downscaling as time-varying PARK calculation, there is '''no impact''' on the results if
 
* … the data is used at an offshore-site
 
Onshore there is a '''minor impact''' if
 
* … the post calibration factors are determined based on reference WTGs or wind measurements at a similar hub height as the planned WTGs
 
Onshore there may be a '''significant impact''' if
 
* … the post calibration factors are determined based on reference WTGs or wind measurements at considerably different hub height as the planned WTGs
 
 
A considerable height difference would be a differnce of more than 15% between hub height and reference height.
 
We recommend installing windPRO 3.0 Service Pack 3 and inspecting the calculations at which a '''significant''' impact is expected. A new determination of post-calibration parameters must be part of any recalculation (also if only a minor influence is expected).


This problem has been fixed in windPRO 3.0.632 so that it will use the correct roughness regardsless of when the EmdConWx data was downloaded. There are a few things to be aware of:
The degree of the impact is defined by the specific terrain and wind conditions of the site. In case you note considerable differences in your results we recommend inspecting also other projects at similar site conditions although only a '''minor''' impact would be expected according to the above systematic.


* If your project is affected by this (uses downscaling calculations with EmdConWx) the results from the PARK calculations can change significantly (10-20%)
We apologize for the problem and are happy to answer upcoming questions. In case you already use the downscaling method of the EMD-ConWx data and would like to get more details concerning the problem, please contact us via the EMD Hotline Service [mailto:support@emd.dk support@emd.dk]
* If you have a project where you have calibrated your Scaler against measurements or reference turbines you should re-visit this calibration after updating to windPRO 3.0.632
* The actual time series data in EmdConWx is not affected by this. It is only the meso-terrain for EmdConWx that is used in downscaling that is affected. So if you have used EmdConWx data for e.g. MCP it should not be affected.

Latest revision as of 08:57, 3 December 2015


Status: Closed - part of windPRO 3.0 Service Pack 3

Fixed in build: 633

For PARK-calculations using the Scaler to downscale the EMD-ConWx meso scale data we noticed a problem which is fixed in Service Pack 3. The problem is related to the downscaling method only and does not affect the use of the meso scale data as regular time series as for:

  • Long-term-correlation via MCP
  • creating a wind-index


In case the data is used for downscaling as time-varying PARK calculation, there is no impact on the results if

  • … the data is used at an offshore-site

Onshore there is a minor impact if

  • … the post calibration factors are determined based on reference WTGs or wind measurements at a similar hub height as the planned WTGs

Onshore there may be a significant impact if

  • … the post calibration factors are determined based on reference WTGs or wind measurements at considerably different hub height as the planned WTGs


A considerable height difference would be a differnce of more than 15% between hub height and reference height.

We recommend installing windPRO 3.0 Service Pack 3 and inspecting the calculations at which a significant impact is expected. A new determination of post-calibration parameters must be part of any recalculation (also if only a minor influence is expected).

The degree of the impact is defined by the specific terrain and wind conditions of the site. In case you note considerable differences in your results we recommend inspecting also other projects at similar site conditions although only a minor impact would be expected according to the above systematic.

We apologize for the problem and are happy to answer upcoming questions. In case you already use the downscaling method of the EMD-ConWx data and would like to get more details concerning the problem, please contact us via the EMD Hotline Service support@emd.dk

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