the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
From wind conditions to operational strategy: Optimal planning of wind turbine damage progression over its lifetime
Niklas Requate
Tobias Meyer
Rene Hofmann
Abstract. Renewable energies have an entirely different cost structure than fossil fuel-based electricity generation. This is mainly due to the operation at zero marginal cost, whereas for fossil fuel plants, the fuel itself is a major driver of the entire cost of energy. For a wind turbine, most of the materials and resources are spent up front. Over its lifetime, this initial capital and material investment is converted into usable energy. Therefore, it is desirable to gain the maximum benefit from the utilized materials for each individual turbine over its entire operating lifetime. Material usage is closely linked to individual damage progression of various turbine components and their respective failure modes.
Within this work, we present a novel approach for an optimal long-term planning of the operation of wind energy systems over their entire lifetime. It is based on a process for setting up a mathematical optimization problem that optimally distributes the available damage budget of a given failure mode over the entire lifetime. The complete process ranges from an adaptation of real-time wind turbine control to the evaluation of long-term goals and requirements. During this process, relevant deterministic external conditions and real-time controller setpoints influence the damage progression with equal importance. Finally, the selection of optimal planning strategies is based on an economic evaluation. The method is applied to an example for demonstration. It shows the high potential of the approach for an effective damage reduction on different use cases. The focus of the example is to effectively reduce power of a turbine under conditions where high loads are induced from wake-induced turbulence of neighbouring turbines. Through the optimization approach, the damage budget can be saved or spent under conditions where it pays off most in the long-term perspective. This way, it is possible to gain more energy from a given system and thus to reduce cost and ecological impact by a better usage of materials.
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Niklas Requate et al.
Status: final response (author comments only)
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RC1: 'Comment on wes-2022-99', Vasilis Pettas, 22 Nov 2022
The comment was uploaded in the form of a supplement: https://wes.copernicus.org/preprints/wes-2022-99/wes-2022-99-RC1-supplement.pdf
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AC1: 'Reply on RC1', Niklas Requate, 30 Apr 2023
We kindly thank reviewer 1 for the highly detailed and valuable feedback with some clear suggestions how to revise the paper. We will hand in a revised manuscript with a new structure of sections and with reduced text. A detailed reply to each of the comments can be found in the attached pdf. Here, we reply to the comments of both reviewers, because both of them gave similar suggestions how to restructure the paper.
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AC1: 'Reply on RC1', Niklas Requate, 30 Apr 2023
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RC2: 'Comment on wes-2022-99', Anonymous Referee #2, 10 Feb 2023
Summary:
The authors have done a good job for presenting a novel method for operating wind farm, in which
the long-term fatigue consumption and energy production of each turbine are managed individually to reach the objectives. The authors addessed that relevant deterministic
external conditions and real-time controller setpoints influence the damage progression with equal importance.
The authors use case studies/examples to illustrate the conclusions made in the paper, which was somehow effective, as it gave examples of the benefits of the potential applications for equalizing the fatigue
consumption among the turbines and the impact can have on potential economic benefitsGeneral Comments
This is an interesting article with a novel approach to operate wind turbines. It has a complete literature studies, the research question is sufficient, the methods are explained by using good terminology. the topic is relevant to the community.
My major comment is about the clarity of the paper. First of all, it is cumbersome to understand. Secondly, It is too long with a lot of overlapping descritipions which makes it difficult to read. It is a journal paper not a thesis! I suggest that the article needs to be re-organized and decreased the length. Additionally, there are lot of sentences in this paper which state "based on assumption", "we assume". It can be subjective or over simplify the problem, which make your conclusions less concrete and solid. I believe the manuscript should be published only after a major revision by addressing the issues mentioned in this review.Specific comments
Line 167 , ... for setpoints for the real-time ... -> ... for setpoints of the real-time ...
Line 183: means -> ways
Line 208: Even with the explanations in the footnote (2), It is still unclear to me which one is variable and which one is parameter. Because the author only metioned they are separated by semicolon without mentioning which one is in front.
Figure 2. It is not clear to me what do the dash lines represent when I read the figure without trying to look for the explanation in the contexts.
L242: sound?
L248 to L254: I don't think this discussion is relevant to the paper.
L259 - L260: ... The sets X and U will lateron be clearly defined based on the system boundaries ... It is better to describe directly here in order to improve the readability. Beside this, "lateron" should be "later on".Trying to unify the usage of the mathmatical symbol. One example, In equation (1): time increament is represented by Δτ, in L260, you use Δt to denote time increment.
Section 2.2 to 2.4 are similar to section 1.3. The difference is it includes more detailed theoretical description and literature study. So maybe you could merge them and shorten the content?
Section 3.1: this section title has no relation to the sub-sections. Please consider to modify it.
section 3.11: More information regarding the simulations is needed. The cited reference does not include any technical details. which controller is used?L534: The authors mentioed that the wake effects are covered only through an increase of turbulence intensity. Actually, the wake meandering has even more affects on the fatigue loads on the downstream turbines. Without included the wake mandering make the conclusion less solid.
L544: "bm", what is this? bending moment? so far until L544, this abbreviation is not defined. later the abbreviation appears in table 1.
L544-L545: The correct statement should be the variation of the edgewise bending moment is driven by gravitity loads. The fluctuation of flapwise bending moment is strongly influenced by the turbulence. But the controller setpoints plays a major role. But you did not mention this.
L578: the TI is set to 5%? Is this realistic? According to my knowledge and based on IEC standard, this value should be correlated to the mean wind speed. Why do the authors use a constant value?
L582: You need the reference for FOXES, both the footnotes ③ and the cited paper (Schmidt et al., 2021) that you used do not contain information about this code. Please cite the correct paper.
L583: ... In this case, only a small part of the software is used ... This sentence is not professional and needs to be revised.L610: ‘This is however neglectably small’. I suggest avoiding such qualitative statements and replace with quantitative statements or just don't use. There are similar expressions throughout the paper.
section 4.1: The title of section 4.1 is exactly the same as section 2.2, this time with a bit more information compared to section 2.2, Because only now, it is really linked to a concrete controller design and description. So my suggestion is to re-organize the structure, remove the overlapping and make the paper more concise and readable. For now, it is really difficult to read through. The reader can easily lost their focus. (The same for section 4.2, 4.3 and 4.4, please consider to revise)
Section 4.1: For the derating strategy used in the test wind farm, have you considered the minimun thrust coefficient derating strategy as describle in this reference (Meng et al., 2020: The effect of minimum thrust coefficient control strategy on power output and loads of a wind farm) and what is the results compared to your 3 derating methods? Please clarify this.Some general comment on the formulas: Try to avoid use word abbreviation in the formulas, except for superscript or lowerscript, because it reduces the readability.
L682-685: Diffcult to understand. Please consider to revise the sentences.
L689: is -> are,
L692: "... degree of 5 ..." is this the order of the polynomial? Please clarify this.
Table 2: please clarify the notation that you used in the column of turbulence intensity.
L727-728: "...The load reduction of the edgewise bm directly corresponds to the reduction in rotor speed..." what do you mean? Load reduction (fatigue) of the edgewise can relate to the less fluctuation in rotor speed. But it can not reduce the rotor speed.
L732: In the simulation setup, L578, you have mentioned that the TI is set to 5% for all wind speed, but here it is 11.3% for all wind speed. Probably here, the 11.3% TI is the wake induced turbulent Intensity? Please clarify this.Figure 6, the normalization approach is not clear to me. for example, the power is not normalized by 100% derating case. The normalized loads are also strange. Please check and modified the normalization procedure.
L773-776: " ... Due to the low .... explanation in Sect. 2. ..." This sentence is not understandable. please revise it.
Figure 8: please consider to improve the readability, for example, increase the size of the circle and change the location of the number in the plot.
Table 3: You mentioned " total damage and energy production with reference from turbine 4". Based on my understanding, the values for turbine No.4 should be 1, right? And why the energy production is still with units?
Should not it also be a normalized value? Please clarify this.
Table 4: This table is also not clear to me. very confusing. So this need to be clarified and revised accordingly.figure 9: Please consider to use "probability" to replace "frequency". Because you are discussing the probability distribution of wind condition. Please also check the whole manuscript and change them accordingly if it applys.
L822-826: This statement does not consistent with the figure 9(a), Fig.10(b,c) and Fig. 11(b,c). Please clarify this.
L839-845, 891-895: Those lines are overlapping with other section, e.g. L401 to 405. Please consider to remove them.
Figure 14: Caption: "Annual progression over time for damage energy and profit for multiple optimized planning strategies", what do you mean by "damage energy". I think part of the sentence is misplaced. it should be :"Annual progression over time for damage and energy profit for multiple optimized planning strategies", right?
Section 5: some of the content can be moved to section 4.x where you show the results to make the text flow more smoothly and also increase the readability.
Citation: https://doi.org/10.5194/wes-2022-99-RC2 -
AC2: 'Reply on RC2', Niklas Requate, 30 Apr 2023
We kindly thank reviewer 2 for the highly detailed and valuable feedback with some clear suggestions how to revise the paper. We will hand in a revised manuscript with a new structure of sections and with reduced text. A detailed reply to each of the comments can be found in the attached pdf. Here, we reply to the comments of both reviewers, because both of them gave similar suggestions how to restructure the paper.
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AC2: 'Reply on RC2', Niklas Requate, 30 Apr 2023
Niklas Requate et al.
Niklas Requate et al.
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