Review Reports - Current Challenges in Operation, Performance, and Maintenance of Photovoltaic Panels

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Remarks:

1. The work does not have a scientific character, but only a general technical-economic one.

2. If the title starts with "Current Challenges..." The content should have focused on chapter 4, in my opinion.

3. Case studies or examples from Spain, which is in a good position in Europe, would be more useful. The examples from China ref [128] are not relevant.

4. PV capacities are not measured in MW? What does MVA represent (table 1 and text)?

5. Fig 1 - the title "Built-in relative quantity of the PV capacity in...", to be replaced with Built-in relative increase of the PV capacity

6. in Fig. 4 notations sw, sd, sr... require explanations in the text related to the figure.

7. With the content on pages 4-6, a more suggestive graphic would be a graphic with the frequency of failures, in percentages or number of events over 5 or 10 years of use - panel cracks, delamination of the panels, failures on the electrical components - inverters, transformers, cables etc.

8. Fig. 6 is pointless, not being an installation in the authors' areas.

9. Ref 94 is incomplete.

10. Abbreviations are used and are not explained. What does the abbreviation DSO, TSO represent? Or DER, VPP etc?

11. The conclusions are too general. The important things and the personal contributions of the authors must be emphasized.

12. The article format is not for Energies journal.

Comments on the Quality of English Language

Orthographic faults.

Author Response

Dear Reviewer,

we would like to thank you for your time and valuable comments which helped us to improve the quality of our article. You can find our point-by-point answers to your questions below:

Remarks:

1. The work does not have a scientific character, but only a general technical-economic one.

We extensively reviewed the paper and answered all of the reviewers' comments. We hope these improvements helped to highlight the scientific character of the paper.

2. If the title starts with "Current Challenges..." The content should have focused on chapter 4, in my opinion.

We changed the title to reduce the scope of the paper. Section 4 reviews some AI-based techniques which can increase the PV system's performance and trading; this is a current operation and performance problem. However, we would like to highlight the maintenance problems as well, which consist of many small failures. This is why we organized this information under a separate section.

3. Case studies or examples from Spain, which is in a good position in Europe, would be more useful. The examples from China ref [128] are not relevant.
The example from China was disregarded.

4.PV capacities are not measured in MW? What does MVA represent (table 1 and text)?
Corrected.
5.Fig 1 - the title "Built-in relative quantity of the PV capacity in...", to be replaced with Built-in relative increase of the PV capacity
Corrected.

6. in Fig. 4 notations sw, sd, sr... require explanations in the text related to the figure.
Corrected.

This is an interesting question; however, creating an image needs a more extensive reliability analysis. To resolve this issue, we added the following text to section 2.1:

Many recent papers on reliability analysis have found that a solar farm's reliability is proportional to its size, i.e., smaller solar farms are more reliable. However, after ten years, even these smaller solar parks have reliability approaching zero, i.e. at least one of its main components (e.g. inverter, transformer, solar panels, wiring systems) needs to be replaced at this time

8. Fig. 6 is pointless, not being an installation in the authors' areas.
Figure 6 removed

9. Ref 94 is incomplete.
The author of the reference is corrected.

10. Abbreviations are used and are not explained. What does the abbreviation DSO, TSO represent? Or DER, VPP etc?
DSO, Distributed system operator introduced at the end of the Introduction., Transmission System Operators (TSO)}, DER - distributed energy resources, the abbreviation was removed. VPP - virtual power plant introduced.

11. The conclusions are too general. The important things and the personal contributions of the authors must be emphasized.

The conclusions extended.

12. The article format is not for Energies journal.
ANSWER: The document class changed accordingly to Energies.

Reviewer 2 Report

Comments and Suggestions for Authors

Define acronyms (e.g., PV, ROI, etc.) in the abstract and manuscript. All acronyms should be defined the first time they are used.

Use space after full stop. Use full stop at the end of the sentence.

Use Fig. 1 instead of Fig 1. Same applies for all figures.

No reference to Table 1 in the text.

Rewrite last paragraph of the introductory sector. For example, use “Section 2. Predictive Maintenance of PV Systems describes ….” instead of “The next chapter”.

Please highlight the novelty of the proposed method. In other words, mention clearly the contributions of the paper in the introduction.

Line 133 should be: Fig. 2a shows …. Same applies for the rest of the paper.

Better illustration of the economic and technical importance of problems. Discussion to be added.

Some sentences in the manuscript are not complete - not grammatically correct. Review and re-write.

Comments on the Quality of English Language

Some sentences in the manuscript are not complete - not grammatically correct. Review and re-write.

Author Response

Dear Reviewer,

We would like to thank you for your time and valuable comments which helped us improve our article's quality. You can find our point-by-point answers below; all of the changes are highlighted in blue in the text.

1. Define acronyms (e.g., PV, ROI, etc.) in the abstract and manuscript. All acronyms should be defined the first time they are used.

Corrected.

2. Use space after full stop. Use full stop at the end of the sentence.

Corrected.

3. Some references were placed after full stop. It was corrected.

Corrected.

4. Use Fig. 1 instead of Fig 1. The same applies to all figures.

Corrected.

5. No reference to Table 1 in the text.

Corrected.

6. Rewrite the last paragraph of the introductory sector. For example, use “Section 2. Predictive Maintenance of PV Systems describes ….” instead of “The next chapter”.

Corrected.

7. Please highlight the novelty of the proposed method. In other words, mention clearly the contributions of the paper in the introduction.

This is a review-type paper, which offers a comprehensive analysis of the existing literature within a field of study, identifying current gaps or problems.

8. Line 133 should be: Fig. 2a shows …. Same applies for the rest of the paper.

Section 2 and Figure 2 are extensively reviewed.

9. Better illustration of the economic and technical importance of problems. Discussion to be added.

We extended the introduction section and section 2 to better illustrate the importance of the problems and some new paragraphs were added to highlight the issues.

10. Some sentences in the manuscript are not complete - not grammatically correct. Review and re-write.

The paper was reviewed by our colleagues, and we hope now we can correct the bugs.

Reviewer 3 Report

Comments and Suggestions for Authors

The paper is interesting and well-written. Anyway, the description of the current challenges in operation, performance, and maintenance of modern PV plants appear to be not exhaustive

First of all, the authors should better cite the papers that are available in the literature on the same subject. For instance, see G. D. Lorenzo, R. Araneo, M. Mitolo, A. Niccolai, and F. Grimaccia, "Review of O&M Practices in PV Plants: Failures, Solutions, Remote Control, and Monitoring Tools," in IEEE Journal of Photovoltaics, vol. 10, no. 4, pp. 914-926, July 2020.

Among the several problems affecting PV modules, the authors should address PID, LID, and degradation, also concerning modern half-cut PERC or TopCon cells.

Then, the authors should better explain the problems that are encountered in devices other than the PV modules, e.g., trackers and inverters.

Finally, they should better explain the potentialities of predictive maintenance in terms of algorithms and devices that must be deployed on the field.

Comments on the Quality of English Language

The paper is easily readable and the English seems to be sound.

Author Response

Dear Reviewer,

we would like to thank you for your time and valuable comments which helped us improve our article's quality. You can find our point-by-point answers below, and all of the changes are highlighted in blue colour in the text.

The paper is interesting and well-written. Anyway, the description of the current challenges in operation, performance, and maintenance of modern PV plants appear to be not exhaustive

ANSWER:

First of all, the authors should better cite the papers that are available in the literature on the same subject. For instance, see G. D. Lorenzo, R. Araneo, M. Mitolo, A. Niccolai, and F. Grimaccia, "Review of O&M Practices in PV Plants: Failures, Solutions, Remote Control, and Monitoring Tools," in IEEE Journal of Photovoltaics, vol. 10, no. 4, pp. 914-926, July 2020.

ANSWER: Thank you for your suggestion. The proposed paper was added to the reference list.

Among the several problems affecting PV modules, the authors should address PID, LID, and degradation, also concerning modern half-cut PERC or TopCon cells.

ANSWER: Thank you for your suggestion, mentioned issues discussed in the text (lines 245-256)

Then, the authors should better explain the problems that are encountered in devices other than the PV modules, e.g., trackers and inverters.

ANSWER: Thank you for pointing out that issue. We believe that adding details regarding inverters and trackers will double the size of the paper. To avoid misunderstanding, we adjusted the title of the manuscript and added a paragraph to the introduction section (lines 66-70)

Finally, they should better explain the potentialities of predictive maintenance in terms of algorithms and devices that must be deployed on the field.

ANSWER: Thank you for your suggestion, mentioned issues discussed in the text (lines 302-356)

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

On page 2 and in the conclusions, MVA appears, as a unit of measure for solar capacity. Is that correct?

Some sentences are long, hard to follow.

The conclusions could still be improved.

Comments on the Quality of English Language

Some sentences are long, hard to follow.

Author Response

Dear Reviewer,

Thank you for your time and feedback, which helped us improve our paper.

You can see our point-by-point answers to your questions and our changes are highlighted in red colour in the text:

On page 2 and in the conclusions, MVA appears, as a unit of measure for solar capacity. Is that correct? Corrected.
Some sentences are long, hard to follow. The text was proofread again. We hope the grammatical changes improved the paper's readability.
The conclusions could still be improved.
We have revised the Conclusions, as well and extended the last paragraph with a new ideas, all of the changes can be seen from line 644 to line 655 in the text.

Reviewer 3 Report

Comments and Suggestions for Authors

The paper can be accepted in its present form. The authors have replied to all the raised comments in a proper manner.

Author Response

Dear Reviewer,

Thank you for your positive feedback.