Optimal Micro-Siting of Weathervaning Floating Wind Turbines

Round 1

Reviewer 1 Report

This paper presents a novel tool for optimizing floating offshore wind farms based on weathervaning turbines. The problem is solved using the genetic algorithm. Results well support the algorithm.  This paper is very interesting in the nowadays development of offshore wind farms. However the following questions should be addressed

1) Description of genetic algorithm should have more details.

2) missing of important recent literatures from top journals, as some literatures are too old in this paper, such as: https://doi.org/10.1016/j.enconman.2020.112964

https://doi.org/10.1016/j.apenergy.2019.04.084

https://doi.org/10.1016/j.apenergy.2020.115511

3) writing can be further improved. 

 

Author Response

This paper presents a novel tool for optimizing floating offshore wind farms based on weathervaning turbines. The problem is solved using the genetic algorithm. Results well support the algorithm.  This paper is very interesting in the nowadays development of offshore wind farms. However the following questions should be addressed.

We gratefully thank the reviewer for his/her advices and comments. In the following lines, we address the comment that he/she raised.

 

Point 1: Description of genetic algorithm should have more details.

Response 1: Thank you very much for this comment. The description of the genetic algorithm has been described in further detail, explaining the different steps and operations involved in the algorithm. In addition, a flowchart (Figure 3) has been added in order to provide more clarity on the proposed methodology.

 

Point 2: missing of important recent literatures from top journals, as some literatures are too old in this paper, such as:

https://doi.org/10.1016/j.enconman.2020.112964

https://doi.org/10.1016/j.apenergy.2019.04.084

https://doi.org/10.1016/j.apenergy.2020.115511

Response 2: The literature review has been updated by adding the suggested references as well as other current references relevant to the problem addressed in this paper.

 

Point 3: writing can be further improved.

Thank you for this comment. The manuscript has been revised in detail with the aim of improving the written quality, as well as providing greater clarity to the reader on the proposed approach and the results obtained through the research conducted in this paper.

Reviewer 2 Report

This manuscript reports a modeling tool for optimizing floating wind farm design. This optimization tool is developed specifically for weathervaning floating wind turbines, and can serve as a valuable designing tool for several floating wind turbine platform concepts that are currently in study or test phase.

This manuscript is well written, but need some minor revision to address a few points.  They are listed below:

(1) Please provide references for the wind behavior model shown in Eq.(4). Please also explain and provide references for the associated wind behavior model parameters C and K listed in Table 1.

(2) Is the "free-flow speed" u_0 in Eq.(5) different from the "wind speed" u in Eq.(4)?

(3) In Eq.(5), the turbine thrust coefficient C_T is a function of the free-flow wind speed. Please provide the specific model equation of C_T(u_0) for the calculations reported in this manuscript.

(4) What is the parameter d in Eq.(5)?

(5) What is the value of k_losses in Eq.(6) for the calculations reported in this manuscript? Please also provide references to explain how the value is chosen.

(6) Is the "feasible surface" shown by the red lines in Fig.3 related to the "maximum allowed area"? Please provide some discussion. Please also add the definition of the red lines in the caption of Fig.3. Readers should not be required to look for such critical information of the figure in the text.

(7) In Fig.4, why is the result with R_w=328m very different from those in the other three conditions? No clear explanation or discussion is given in the paragraph of Lines 381-401. On Lines 381 and 382, it is stated that "It can be seen that the solutions obtained by the proposed algorithm are virtually identical", which appears to be inconsistent with the results shown in Fig.4.

(8) Why is the "feasible surface" not indicated by the red lines in Fig.7? If it is relevant to the results shown in Fig.7, please add the red lines.

(9) Please correct the typos in the author names of Ref.40 on Line 614.

Author Response

This manuscript reports a modeling tool for optimizing floating wind farm design. This optimization tool is developed specifically for weathervaning floating wind turbines, and can serve as a valuable designing tool for several floating wind turbine platform concepts that are currently in study or test phase.

This manuscript is well written, but need some minor revision to address a few points. 

We gratefully thank the reviewer for his/her positive comments. In the following lines, we address the issues that he/she raised.

Point 1: Please provide references for the wind behavior model shown in Eq.(4). Please also explain and provide references for the associated wind behavior model parameters C and K listed in Table 1.

Reference has been added, as well as a brief explanation of the influence of both parameters on the characterisation of the wind speed behaviour.

 

Point 2: Is the "free-flow speed" u_0 in Eq.(5) different from the "wind speed" u in Eq.(4)?

Response 2: Thank you for pointing out this issue. Indeed both variables represented the same magnitude. The nomenclature has been corrected and standardised in equation (5), using only 'u' to refer to the free-flow wind speed.

 

Point 3: In Eq.(5), the turbine thrust coefficient C_T is a function of the free-flow wind speed. Please provide the specific model equation of C_T(u_0) for the calculations reported in this manuscript.

Response 3: The dependence of the thrust coefficient on speed is a characteristic of the wind turbine that is provided by the manufacturer. This issue has been clarified in the explanatory text of equation (5), as well as a new figure (Figure 5) has been added in the results section which jointly shows the power and thrust coefficient curve for the turbine model analysed in this work.

 

Point 4: What is the parameter d in Eq.(5)?

The parameter d stands for the downwind distance, this has been clarified in the explanatory text below equation (5).

 

Point 5: What is the value of k_losses in Eq.(6) for the calculations reported in this manuscript? Please also provide references to explain how the value is chosen.

Thank you for highlighting this issue. The value of the energy losses factor is given in Table 2. In order to provide greater clarity to the reader, the nomenclature of this parameter has been standardised in this table with respect to the nomenclature defined in equation (6). Also, the relevant references to the typical value of this parameter have been added.

 

Point 6: Is the "feasible surface" shown by the red lines in Fig.3 related to the "maximum allowed area"? Please provide some discussion. Please also add the definition of the red lines in the caption of Fig.3. Readers should not be required to look for such critical information of the figure in the text.

Thank you very much for pointing out this important issue. The proposed approach considers two types of constraints with respect to the deployable area, on the one hand, the maximum area occupied by the wind turbines (including the weathervaning motion) which is a constraint determined by means of a maximum area value (expressed in square kilometres) and, on the other hand, the constraint concerning the boundaries of the plot on which the project can be deployed is also considered. In order to provide greater clarity to the reader, the nomenclature referring to both concepts has been standardised throughout the manuscript, using the term 'maximum area occupied' for the first mentioned constraint and the term 'plot feasible surface' for the second constraint referring to the shape of the plot. Also, the text concerning these two concepts has been reworded throughout the manuscript to provide greater clarity. Finally, as suggested, the definition of the red lines (referring to the plot feasible surface) and the dotted surface (referring to the area occupied) has been added in the caption of Figure 4 (Figure 3 in the previous version of the manuscript).

 

Point 7: In Fig.4, why is the result with R_w=328m very different from those in the other three conditions? No clear explanation or discussion is given in the paragraph of Lines 381-401. On Lines 381 and 382, it is stated that "It can be seen that the solutions obtained by the proposed algorithm are virtually identical", which appears to be inconsistent with the results shown in Fig.4.

Thank you very much again for this important comment. Unfortunately, the result shown in Figure 4 for the case of Rw=328 m was wrong (as it corresponded to a preliminary test result). The figure has been corrected in this new version of the manuscript. The authors sincerely apologise for this issue.

 

Point 8: Why is the "feasible surface" not indicated by the red lines in Fig.7? If it is relevant to the results shown in Fig.7, please add the red lines.

Figure 9 (Figure 7 in the original version of the manuscript) corresponds to the case where the constraint of maximal area occupied is considered (but the constraint concerning the plot feasible surface is not considered). This has been clarified in the new version of the manuscript. Also, in order to enable the reader to better identify the applicable constraint in this case, the dotted surface representing the area occupied by the wind turbine layout has been added in Figure 9.

 

Point 9: Please correct the typos in the author names of Ref.40 on Line 614.

Thank you very much. Identified typos have been corrected.

Reviewer 3 Report

This paper presents a new method to optimize floating offshore wind turbines. The paper is well written and the idea is novel. 

Author Response

This paper presents a new method to optimize floating offshore wind turbines. The paper is well written and the idea is novel.

 We gratefully thank the reviewer for his/her positive comments.