Extreme wind fluctuations: joint statistics, extreme turbulence, and impact on wind turbine loads

Hannesdóttir, Ásta; Kelly, Mark; Dimitrov, Nikolay

doi:https://doi.org/10.5194/wes-4-325-2019

Articles | Volume 4, issue 2

https://doi.org/10.5194/wes-4-325-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/wes-4-325-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 4, issue 2

Research article

|

03 Jun 2019

Research article |

| 03 Jun 2019

Extreme wind fluctuations: joint statistics, extreme turbulence, and impact on wind turbine loads

Ásta Hannesdóttir, Mark Kelly, and Nikolay Dimitrov

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Final revised paper (published on 03 Jun 2019)
Preprint (discussion started on 21 Feb 2018)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review', Anonymous Referee #1, 20 Apr 2018
RC2: 'Extreme fluctuations of wind speed for a coastal/offshore climate: statistics and impact on wind turbine loads', Anonymous Referee #2, 16 May 2018
AC1: 'Responses to reviews', Ásta Hannesdóttir, 14 Jul 2018

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Ásta Hannesdóttir on behalf of the Authors (14 Jul 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (02 Sep 2018) by Joachim Peinke

RR by Anonymous Referee #1 (07 Oct 2018)

RR by Anonymous Referee #3 (16 Nov 2018)

Suggestions for revision or reasons for rejection

Review of the manuscript

Extreme wind fluctuations: joint statistics, extreme turbulence, and impact on wind turbine loads

by
Ásta Hannesdóttir, Mark Kelly, and Nikolay Dimitrov

As I will contribute only to the second round of reviews, and most issues have already been addressed, the review will be restricted to remaining issues.

The paper reports on work about an interesting and relevant topic, and is expected to receive considerable interest. The scientific work is in general sound and thorough, and well presented.

There are two remaining issues, which follow two recommendations of referee 1.

First, as stated by referee 1 in issue 9.), the consideration of realistic, non-Gaussian turbulence would improve the results. The paper justifies the usage of Gaussian turbulence fields by citing Berg et
al. (2016), namely their conclusion that difference to non-Gaussian turbulence with respect to wind turbine loads would be insignificant. This cannot be accepted.
While this special conclusion is claimed in the cited paper, the contents and results of Berg et al. (2016) do not support that claim. Moreover, other publications have clearly shown the relevant influence of intermittency, such as [1,2]. There may be, however, many other possible reasons to restrict the investigations to Gaussian turbulence, such as restricting the complexity of the set-up, availability of widely accepted codes, numerical efficiency, etc.

Second, similar to what was stated by referee 1 in issue 8.), a deeper analysis of the measured wind speed time series would be beneficial, namely in terms of higher-order two-point statistics. This can be done by conditional pdfs p(u(t+tau)|u(t)) as suggested by referee 1, or by increment pdfs p(u(t+tau)-u(t)). The relevant time scales tau are those where there is dynamic response of the turbine to turbulence, typically in the range of 1 to 100 s. Relevant literature should be available. The inclusion of the three references to works by Fitzwater, Moon, and Saranyasoontorn (while still helpful for the paper) does not seem to answer the recommendation of referee 1.

With these two issues addressed, I would consider the paper to be ready for publication.

[1] Schottler et al., Wind Energ. Sci. 2, 1-13, 2017
[2] Mücke et al., Wind Energ. 14, 301-316, 2011

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ED: Publish subject to minor revisions (review by editor) (13 Apr 2019) by Joachim Peinke

AR by Ásta Hannesdóttir on behalf of the Authors (01 May 2019) Author's response Manuscript

ED: Publish as is (06 May 2019) by Joachim Peinke

ED: Publish as is (06 May 2019) by Jakob Mann (Chief editor)

AR by Ásta Hannesdóttir on behalf of the Authors (13 May 2019) Manuscript

Short summary

We investigate large wind speed fluctuations from a 10-year period at the Danish coastal site Høvsøre. The most extreme fluctuations are not turbulent but due to larger-scale weather phenomena. We find how these fluctuations impact wind turbines using simulations. The results are then compared to an extreme turbulence model described in the wind turbine safety standards, and it is found that the loads on the different turbine components are not the same as what the standard describes.