Exploring Evolution and Trends: A Bibliometric Analysis and Scientific Mapping of Multiobjective Optimization Applied to Hybrid Microgrid Systems

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors,

Thank you for this interesting bibliometric analysis that would serve as a reference for having a solid knowledge on the current state of play, but also understand future trends and perspective.

The paper is generally well written, except some english typos that I suggest to clean. The methodology is well defined and used (please highlight that the software used is actually an open-source).

The results however should be well described, and the figures well presented (some figures are blur).

The major concern when reading your paper is to understand where is the novelty when comparing your previous paper (reference 11) on the 3 themes: microgrids, renewable energy, and optimisation. As far as you described, the major themes of this paper are also renewable energy, microgrid and multiobjective optimization. MOO is a branch of optimization, you should thus emphasize well why such a specific MOO deserves a special analysis.

please find below some additional comments to enhance the quality of the paper:

- Figure 1: axis name

- Figure 1: what is 'variable' and 'other' renewables?

- Figure 4, 6, 9, 12, 13: blur, please adjust

- equation 5 (line 164): please define the eta letter (efficiency?). Suggest to include a nomeclature table for the paper to help the reader.

 

 

Kind regards

Comments on the Quality of English Language

Please consider a screening of the paper to clean it from typos, some exaples below:

- line 238: probability

- Table 2: AC-generator

- lines 565 to 569: ?

 

Author Response

Dear Reviewer,

We would like to thank you for your valuable feedback and suggestions, which have significantly enhanced the quality of our manuscript. We have amended the manuscript based on your recommendations. Below are the answers to your questions.

Note: Phrases in red indicate reviewers' notes, and phrases in black indicate authors' answers.

 

1. Please highlight that the software used is actually an open-source.1.

We have included this information in Section 2.3.1 of the manuscript, under 'Second phase: Bibliometric analysis.

 

2. The results however should be well described, and the figures well presented (some figures are blur).

We have carefully revised the manuscript to ensure that each theme discussed in the results section is clearly described and its significance in the field is emphasized. Additionally, we have amended all figures to improve their clarity and presentation.

3. The major concern when reading your paper is to understand where is the novelty when comparing your previous paper (reference 11) on the 3 themes: microgrids, renewable energy, and optimisation. As far as you described, the major themes of this paper are also renewable energy, microgrid and multiobjective optimization. MOO is a branch of optimization, you should thus emphasize well why such a specific MOO deserves a special analysis.

This study builds on our previous findings (reference 11) by delving deeper into the application of multi-objective optimization (MOO) in Hybrid Microgrid Systems (HMGSs). We focus on MOO due to its crucial role in effectively balancing the often conflicting objectives of cost, efficiency, and environmental impact within HMGSs. Since our last publication, there has been a noticeable 35% increase in MOO research, underscoring its growing importance. This manuscript not only tracks these developments but also introduces new optimization models and frameworks that address emerging challenges in HMGS design and operation—advancements that were not explored in our previous research. These contributions significantly extend the current understanding and application of MOO, showcasing novel approaches and solutions in the field.

 

Please find below some additional comments to enhance the quality of the paper:

4. Figure 1: axis name

We have updated Figure 1 to include the axis names: 'Year' for the horizontal axis and 'Share of Renewable Electricity Production (%)' for the vertical axis to clarify the data presented.

5. Figure 1: what are 'variable' and 'other' renewables?

In the context of the IEA report, 'variable renewables' specifically refers to solar PV and wind energy combined, due to their dependence on weather conditions which leads to variability in their power output. The category labeled 'other renewables' in Figure 1 includes concentrated solar power (CSP) and geothermal energy.

6. Figure 4, 6, 9, 12, and 13: blur, please adjust.

We have adjusted Figures 4, 6, 9, 12, and 13 to enhance their clarity.

7. Equation 5 (line 164): please define the eta letter (efficiency?). Suggest including a nomenclature table for the paper to help the reader.

To address Equation 5 and the definition of eta ( , we have ensured that each symbol is explicitly defined within the manuscript for clarity. Furthermore, we included an Abbreviation list at the end of Table 6 to define each symbol used. Given the comprehensive nature of this list, adding an additional nomenclature table would be redundant. We believe the measures taken will adequately guide the reader through the manuscript's technical content.

8. Please consider a screening of the paper to clean it from typos, some examples below:

We apologize for the typographical errors in the manuscript, which occurred during the format transition to the journal's template. These errors have been thoroughly reviewed and corrected to ensure the document meets the highest standards of accuracy and clarity. We appreciate your understanding and are committed to maintaining quality in our submissions.

9. Table 2: AC-generator

The term 'AC-generator-motors' in Table 2 corresponds to the theme name as depicted in the strategic diagrams for period 1, illustrated in Figure 12(a).

 

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors,

You conducted very very detailed bibliometric analysis of hybrid microgrids systems primarily focusing on multi-objective optimization (MOO) used to optimize the systems. As the main driving theme, MOO is interconnected with other themes that appear in bibliometric analysisand you address that interconnectivity. The evolution of used MOO techniques over the period from 2010 to 2019 and 2020 to 2023 is also analyzed in details.

On the overall I think that the article is good and worthy of publication. I do have some smaller suggestions.

Lines 39-40 – please verify the percentage of RES that IEA scenarios indicate for 2030. I believe that 80% include all low emission sources including nuclear and unabated fossils. Pure RES is lower.

Line 238 – “Pprobability” should be “Probability”

For Table 2 please clarify the column “Citations count”? The problem is the number of overall citations given in line 650 that does not directly correspond to sum of citations in table 2.

For Table 5 please comment on the relevance of data. The article published in 2013 may have larger number of citations than the article published in 2021, but in 5 years the situation may change. Why not use some kind of yearly rate of citations?

Author Response

Dear Reviewer,

We would like to thank you for your valuable feedback and suggestions, which have significantly enhanced the quality of our manuscript. We have amended the manuscript based on your recommendations. Below are the answers to your questions.

Note: Phrases in red indicate reviewers' notes, and phrases in black indicate authors' answers

1. Lines 39-40 – please verify the percentage of RES that IEA scenarios indicate for 2030. I believe that 80% include all low emission sources including nuclear and unabated fossils. Pure RES is lower.

The correct interpretation, as outlined in the STEPS, is that renewables are expected to account for 80% of the new power capacity added by 2030, with solar PV (SPV) contributing to more than half of this new capacity. The manuscript has been updated to accurately reflect this distinction, and we have ensured that the text now clearly differentiates between new capacity additions and the overall power mix.

 

2. Line 238 – “Pprobability” should be “Probability”

We apologize for the typographical errors in the manuscript, which occurred during the format transition to the journal's template. These errors have been thoroughly reviewed and corrected to ensure the document meets the highest standards of accuracy and clarity. We appreciate your understanding and are committed to maintaining quality in our submissions.

 

3. For Table 2 please clarify the column “Citations count”? The problem is the number of overall citations given in line 650 that does not directly correspond to sum of citations in table 2.

Table 2 presents performance measures for each theme across two periods, including document counts, h-index, centrality, density, and citation count per theme, as analyzed by SciMAT. In contrast, the citation total mentioned in line 650 represents the aggregate number of citations for all 470 documents analyzed in the study. Therefore, the citation counts in Table 2 are theme-specific, while line 650 provides an overall citation figure, encompassing all documents reviewed.

4. For Table 5 please comment on the relevance of data. The article published in 2013 may have larger number of citations than the article published in 2021, but in 5 years the situation may change. Why not use some kind of yearly rate of citations?

Regarding the yearly rate of citations, this metric could indeed provide a more normalized comparison between articles published at different times by reflecting more recent citation trends. Given that our analysis covers 470 documents, applying a yearly rate of citations for each would be a significant undertaking, considering our study is split into two distinct periods (2010-2019 and 2020-2023). For instance, no document from 2010 emerged as a top citation in our findings. In Table 5, which lists the top cited documents, we observe that more recent publications, such as one from 2018 (ref. 32), have quickly accumulated citations compared to older ones from 2012 and 2014 (refs. [33] and [79]). This demonstrates the dynamic nature of citation accrual over time and supports our decision to focus on absolute citations rather than yearly rates, given the scope and scale of our analysis.

 

 

Reviewer 3 Report

Comments and Suggestions for Authors

• - Why is "R" included in the abbreviation "HRESs"?
• - In economically and technically, HRESs emerge as an optimal solution, ensuring energy supply stability when RESs are insufficient. What does "RESs are insufficient" mean in this sentence?
• - Why is it expressed that "The integration of HRESs into the utility grid" has led to the utilization of microgrids (MGs) in the sentence? Explanation is needed on how it led.

There are too many expressions that seem ambiguous and inaccurate. Overall clarification seems necessary for the reader's understanding.

For instance, let's look at TABLE 6, which is written to summarize and explain the content.

What are the criteria for selecting the comparison analysis target papers in TABLE 6? What does "DG" stand for in system components in Ref. [30]? What does it mean to optimize the size of HMGS components in the Objective of optimization? What does "MOSaDE" stand for in Technique Used? The first sentence in Study findings, "Optimization of PV/WT/DG HMGS in Yanbu, Saudi Arabia, showing application in optimizing the system and practical implications," seems to be a fragmented sentence. What does this sentence mean? What does "COE" stand for? What does "HERS" stand for? Comments on Algorithm are comments based on what criteria? On what basis was the expression "very effective" used?

Although tables are meant to summarize and organize content, it seems that this one is not well-organized. There are many ambiguous or omitted expressions, which may leave the reader with many questions and confusion.

There are too many issues to address. It seems that first organizing the content well, and then commenting on the key points would be more feasible.

Comments on the Quality of English Language

Extensive revisions needed for the English language.

Author Response

Dear Reviewer,

We would like to thank you for your valuable feedback and suggestions, which have significantly enhanced the quality of our manuscript. We wish to extend our sincerest apologies for the shortcomings identified in the initial version. We have amended the manuscript based on your recommendations. Below are the answers to your questions.

Note: Phrases in red indicate reviewers' notes, and phrases in black indicate authors' answers.

1. Why “R” is included in the abbreviation "HRESs"?

We've addressed this by differentiating between Hybrid Energy Systems (HESs) and Hybrid Renewable Energy Systems (HRESs). The 'R' in 'HRESs' stands for 'Renewable,' indicating that these systems exclusively use renewable energy sources and storage solutions. In contrast, HESs integrate both renewable and non-renewable energy sources, such as natural gas or diesel, alongside energy storage. [Amended for clarity].

2. In economically and technically, HRESs emerge as an optimal solution, ensuring energy supply stability when RESs are insufficient. What does "RESs are insufficient" mean in this sentence?

In this context, 'RESs are insufficient' means that Renewable Energy Systems (RESs) alone may not consistently meet energy demands due to their dependence on variable environmental conditions, such as reduced solar power on cloudy days or diminished wind energy during calm weather. We've amended the statement for clarity as follows: 'Economically and technically, HESs provide an optimal solution by ensuring energy supply stability when RESs alone are limited by environmental variability. By integrating multiple energy sources, HESs maintain consistent energy availability.'

3. Why is it expressed that "The integration of HRESs into the utility grid" has led to the utilization of microgrids (MGs) in the sentence? Explanation is needed on how it led.

The revised sentence now reads: 'The integration of HESs into the grid necessitates management to maintain operations independently from the main grid as needed. This requirement has paved the way for the utilization of microgrids (MGs), which can operate in two modes: connected to the main grid or in an islanded (independent) mode, ensuring coordinated and controlled energy distribution.' This amendment aims to clarify how the need for independent operational capabilities in HESs directly facilitates the broader use of MGs, enhancing their role in grid management and resilience.

4. For instance, let's look at TABLE 6, which is written to summarize and explain the content. What are the criteria for selecting the comparison analysis target papers in TABLE 6? What does "DG" stand for in system components in Ref. [30]? What does it mean to optimize the size of HMGS components in the Objective of optimization? What does "MOSaDE" stand for in Technique Used? The first sentence in Study findings, "Optimization of PV/WT/DG HMGS in Yanbu, Saudi Arabia, showing application in optimizing the system and practical implications," seems to be a fragmented sentence. What does this sentence mean? What does "COE" stand for? What does "HERS" stand for? Comments on Algorithm are comments based on what criteria? On what basis was the expression "very effective" used?

4.1 In selecting target papers for Table 6, we ensured a diverse representation of research spanning from 2010 to 2023. The chosen papers vary in their focus on different issues, algorithms, and system components, and include some of the most highly cited works, particularly for years with a high volume of publications. This selection strategy covers crucial challenges such as efficiency and scalability, employing a range from traditional to advanced computational methods.

4.2 In response to your queries regarding the specific terms and abbreviations used within Table 6, such as 'DG' for Diesel Generator, 'COE' for Cost of Energy, and 'MOSaDE' for Multi-Objective Self-Adaptive Differential Evolution, please refer to the Abbreviation list provided at the end of the table. This list includes definitions for all such terms, ensuring clarity and aiding in the understanding of the table’s content.

4.3 To optimize the size of HMGS components means to determine the most efficient and cost-effective scale of each component (solar panels, wind turbines, diesel generators, batteries, etc.) within a microgrid, ensuring that it meets energy demands while minimizing costs and environmental impact.

4.4 Comments on algorithms were based on their performance in simulation tests, which include assessments of their efficiency, reliability, and ability to handle complex optimization problems. The expression 'very effective' was used to describe algorithms that consistently produced superior results in terms of cost reduction, energy efficiency, and system stability under varying operational conditions. This assessment is based on the outcomes identified by researchers in their studies, which substantiate the effectiveness of the algorithms used.

5. Although tables are meant to summarize and organize content, it seems that this one is not well-organized. There are many ambiguous or omitted expressions, which may leave the reader with many questions and confusion.

Thank you for your valuable feedback on Table 6. We have revised it to address the concerns raised, considering the complexity of the data and our goal to condense significant information into a concise format. We have clarified specific terms and abbreviations in the table's footnotes to enhance understanding. We believe these changes have improved the table's readability and we are open to further suggestions to refine our presentation.

6. There are too many issues to address. It seems that first organizing the content well and then commenting on the key points would be more feasible.

We appreciate your suggestions and recognize the importance of effectively organizing the content. We are committed to enhancing the clarity and effectiveness of our manuscript accordingly.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you for this revised and enhanced version,

I have no further comments,

Kind regards;

Author Response

Dear reviewer,

Just to thank you for your work.

Best Regards